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23-Water Reclamation Facilities Plan
Bozeman Water Reclamation Facilities Plan February 2023 WATER RECLAMATION FACILITIES PLAN BOZEMAN, MT FEBRUARY 2023 I hereby certify that this report was prepared by me or under my direct supervision and that I am a duly registered professional engineer under the laws of the State of Montana. Coralynn Revis, PE Project Manager HDR Engineering, Inc. 2150 Analysis Drive Bozeman, MT 59718 1 2 3 4 5 6 7 8 9 10 Table of Contents Executive Summary.................................................................................... Chapter . Introduction ............................................................................... Chapter . Basis of Planning ...................................................................... Chapter . Flows and Loads ....................................................................... Chapter . Water Quality ............................................................................ Chapter . Effluent Management Plan ........................................................ Chapter . Existing Unit Processes Evaluation ........................................... Chapter . Treatment Upgrade Alternatives ................................................ Chapter . Biosolids Disposal ..................................................................... Chapter . Sidestream Treatment............................................................... Chapter . Capital Improvement Plan ....................................................... This page is intentionally left blank. Bozeman Water Reclamation Facilities Plan Executive Summary | 2022 11 9 4 12 8 6 5 7 10 3 2 1 1. Headworks 2. Primary Clarifers 3. Primary Efuent Pump Station 4. Secondary Clarifers 5. Bioreactor No. 1 6. Bioreactors No. 2 & 3 7. Fermenter & Gravity Thickener 8. Dissolved Air Flotation Thickener 9. UV Disinfection & Outfall 10. Digester Control Building No. 1 11. Digester Control Building No. 2 & Digester No. 3 12.12. Administration/Laboratory Building Overview During the next 20 years, it is anticipated that the City of Bozeman’s population will continue to increase and that efuent discharge standards for nutrients will become more stringent. These two trends represent the primary drivers for this Water Reclamation Facilities Plan. The existing infrastructure of the Water Reclamation Facility (WRF) was evaluated against the projected capacity and regulatory requirements of the 20-year planning period (2020-2040). Recommended upgrades stemming from these requirements are documented in the fnal capital improvements plan (CIP). Recommendations are included for three respective treatment scenarios, as the future of nutrient regulations in Montana remains unclear at this time. The three scenarios encompass a range of possible efuent standards, varying from current regulations to much more stringent. 1 2 3 1 2 3 EAST GALLATIN RIVER SPRINGHILL ROAD MOSS BRIDGE ROAD YEAR 4% GROWTH 2020 53,293 2025 64,839 2030 78,887 2035 95,978 2040 116,772 PARAMETER 2040 FLOW (MGD) Annual Average 14.6 Maximum Monthly Average 17.9 Peak Daily Average 21.2 Peak Hourly 28.4 Capacity Flows and loads for the planning period were projected using Bozeman per capita usage fgures and a projected population growth rate of 4%. Figure 2. Historical Infuent Flows to the WRF Figure 1. Historical and Projected Population 1 2 3 140,000 12.00 ' 120,000 . 10.00 . • . 100,000 ' "a' 8.00 '\. . bO 80,000 ..5 ••• ~ C: 0 6.00 ~ w::: "" 60,000 ....... ro C: Cl) . ::, ::, .. 0.. ;:;::: 0 .E 4.00 a.. 40,000 • 20,000 2.00 0 1985 1995 2005 2015 2025 2035 2045 0.00 Year 1/1/2016 1/1/2017 1/1/2018 1/1/2019 1/1/2020 1/1/2021 Date -+-Historical Population -+-Projected Pop, 4% 1 2 3 PROCESS AREA DESIGN CONDITION CAPACITY AT DESIGN CONDITION 2040 DESIGN FLOW Headworks Parshall Flume Peak Day 32 mgd 21.2 mgd Perforated Plate Infuent Screens Peak Hour 28 mgd 28.4 mgd Coarse Infuent Screens Peak Hour 18 mgd 28.4 mgd Manual Screen Peak Hour 30 mgd 28.4 mgd Grit Removal System Peak Hour 28 mgd 28.4 mgd Primary Treatment Primary Clarifer Basins1 Max Month 10.6 mgd 17.9 mgd Primary Efuent Pumps Peak Hour 28.8 mgd 28.4 mgd & RAS Flows Secondary Treatment BNR Bioreactors Max Month 10.6 mgd 17.9 mgd Secondary Clarifer Basins Max Month 10.6 mgd 17.9 mgd Tertiary Treatment UV Disinfection Peak Hour 16.9 mgd 28.4 mgd Solids, PSL Stream Fermenter2 Average Annual 8.5 mgd 14.6 mgd Thickener2 Average Annual 8.5 mgd 14.6 mgd Solids, WAS Stream RST Max Month 30+ mgd 17.9 mgd Solids Digestion and Disposal Anaerobic Digesters No. 1 and No. 2 Max Month 10.6 mgd 17.2 mgd Anaerobic Digesters No. 1, No. 2 and No. 3 Max Month 17.4 mgd 17.2 mgd Screw Press No. 1 and No. 2 Average Annual 16.5 mgd 14.0 mgd Table 1. Unit Process Capacity Summary 1 - Not all primary clarifers are currently in use at the WRF, and it is not recommended that an additional primary clarifer be constructed at this time despite the capacity analysis indicating that one is needed. 2 - The UFAT system is not currently in use at the WRF, and it is not recommended that an additional thickener or fermenter be constructed at this time despite the capacity analysis indicating that they are needed. 1 2 3 1 2 3 Projected Capacity Defciencies Unit processes that show capacity defciencies by the end of the planning horizon include the following: • Infuent Screen • Primary Efuent Pump Station (PEPS) • Bioreactors • Primary Clarifers • Secondary Clarifers • UV Treatment • Fermenter and Thickener • Digesters • Screw Presses These base capacity upgrades and their associated opinions of probable construction cost (OPCC) are summarized in Table 2. PARAMETER NUMBER OPCC Primary Treatment Additional Infuent Screen 1x $720,000 Additional PEPS Pump 1x $790,000 Secondary Treatment Refurbish Bioreactor #1 Train into 5-Stage 2.0 MG $2,760,000 Construct New Bioreactor #4 Train Adaptive Planning Additional Aeration Blower 1x $890,000 Secondary Clarifers 2 x 85'Ǿ $7,510,000 InDENSE: Hold +20% Solids Inventory InDENSE, 90 SVI $1,430,000 Tertiary Treatment UV Banks 1x $1,270,000 Solids Dewatering and Digestion Rotary Screen Thickener Adaptive Planning Fourth Digester 0.6 MG $4,930,000 Screw Press Upgrade 1x $1,400,000 Additional Screw Press 1x $2,410,000 TOTAL CAPITAL COSTS $24,110,000 Table 2. Base Capacity Upgrades 1 2 3 1 2 3 - - Regulatory Exploring Treatment Scenarios Treatment upgrades will likely be required during the planning period in addition to the base capacity upgrades outlined. These upgrades will be necessary for the WRF to meet future efuent nutrient discharge standards. However, the permitting situation in Montana remains fuid and uncertain. As a result, the WRF must be prepared to meet the treatment requirements stemming from a number of permitting scenarios. • Treatment Scenario 1 levels represent the probable, most lenient efuent nutrient standards that could be expected in a future discharge permit. • Treatment Scenario 2 levels represent the probable, most lenient nitrogen treatment standard and the most stringent phosphorus treatment standard. • Treatment Scenario 3 levels represent the probable most stringent nutrient treatment standards for both phosphorus and nitrogen. PARAMETER TS 1* TS 2* TS 3* Permit TN & TP Limit (mg/L) 6.4/0.27 6.4/0.05 3.0/0.05 Flow (mgd) 14.6 14.6 14.6 WRF UPGRADES COST COST COST Base Capacity Upgrades $24,110,000 $24,110,000 $24,110,000 Construct New Bioreactor #4 Train, 2.3 MG Adaptive Planning Adaptive Planning $10,890,000 Postanoxic Carbon Dosing System, 2500 ppd C $1,000,000 Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) $800,000 $800,000 Tertiary Sand Filtration Adaptive Planning Tertiary Membrane Filtration, 17.9 mgd $52,120,000 $52,120,000 Filter Pump Station, 17.9 mgd Adaptive Planning $1,950,000 $1,950,000 Chem Coag/Dosing, 17.9 mgd $1,500,000 $1,500,000 Total Capital Costs $24,110,000 $80,480,000 $92,370,000 Table 3. Capacity and Regulatory OPCCs *Treatment Scenario 1 2 3 1 2 3 -- - -- - - Capital Improvement Plan Treatment Scenario 1 Table 4. TS 1 Overall Recommended Improvements Recommended Implementation Timeline Begin work by these dates to meet required year. UNIT PROCESS OPCC YEAR REQUIRED Fourth Digester $4,930,000 ASAP Efuent Filtration Study $25,000 2023 UV Capacity Addition $1,270,000 2024 Install InDENSE $1,430,000 2024 Pilot InDENSE $100,000 2024 Construct New Bioreactor #4 Train, 2.3 MG Adaptive Planning Wetland Pilot In Progress Two Secondary Clarifers $7,510,000 2027 Bioreactor No. 1 Upgrade $2,760,000 2027 Aeration Blower $890,000 2027 Screw Press Upgrade $1,400,000 2030 Third Screw Press $2,410,000 2035 Additional PEPS Pump $790,000 2040 Additional Screen $720,000 Adaptive Planning TOTAL $24,235,000 2022 •Fourth Digester Addition •UV Capacity Addition •Wetland Pilot •InDENSE Pilot 2025 •Bioreactor No. 1 Upgrade •Additional Aeration Blower •Two Additional Secondary Clarifers 2033 •Third Screw Press 2040 •End of Planning Period 2028 •Upgrade Screw Press No. 1 •InDENSE and/or Bioreactor 4 2023 •Efuent Filtration Study 2038 •PEPS Pump 1. Additional Infuent Screen 2. Additional Aeration Blower 3. InDENSE 4. PEPS Pump 5. Refurbish Bioreactor #1 Train 6. Secondary Clarifers 7. UV Banks 8. Additional Bioreactor Capacity, Possible 1 2 5 7 8 6 3 4 1 2 3 1 2 3 - - 1. Additional Infuent Screen 2. Additional Bioreactor Capacity, Possible 3. Additional Aeration Blower 4. Membrane Filtration & Pump Station 5. PEPS Pump 6. Refurbish Bioreactor #1 Train 7. Secondary Clarifers 8. Sidestream EBPR 9. UV Banks 10. InDENSE 3 6 4 9 8 7 10 5 2022 •Fourth Digester Addition •UV Capacity Addition •Wetland Pilot •InDENSE Pilot 2025 •Bioreactor No. 1 Upgrade •Additional Aeration Blower •Two Additional Secondary Clarifers 2033 •Third Screw Press 2040 •End of Planning Period 2 1 1 2 3 1 2 3 Capital Improvement Plan Treatment Scenario 2 Table 5. TS 2 Overall Recommended Improvements UNIT PROCESS OPCC YEAR REQUIRED CIP TS 1 Items $24,235,000 As Listed in Table 4 Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) $800,000 - Tertiary Membrane Filtration, 17.9 mgd $52,120,000 - Filter Pump Station, 17.9 mgd $1,950,000 - Chem Coag/Dosing, 17.9 mgd $1,500,000 - TOTAL $80,605,000 Recommended Implementation Timeline Begin work by these dates to meet required year. 2028 •Upgrade Screw Press No. 1 •InDENSE and/or Bioreactor 4 •Tertiary Membrane Filters 2038 •PEPS Pump 2024 •Receive Permit 2023 •Efuent Filtration Study 1. Additional Infuent Screen 2. Aeration Basins 4th Bioreactor 3. Additional Aeration Blower 4. Membrane Filtration & Pump Station 5. PEPS Pump 6. Refurbish Bioreactor #1 Train 7. Secondary Clarifers 8. Sidestream EBPR 9. UV Banks 10. InDENSE 3 6 9 8 2 5 2022 •Fourth Digester Addition •UV Capacity Addition •Wetland Pilot •inDENSE Pilot 2025 •Bioreactor No. 1 Upgrade •Additional Aeration Blower •Two Additional Secondary Clarifers 2033 •Third Screw Press 2040 •End of Planning Period 2028 •Upgrade Screw Press No. 1 •InDENSE and/or Bioreactor 4 •Tertiary Membrane Filters • Additional Bioreactor Capacity • Carbon Addition 2038 •PEPS Pump 2024 •Receive Permit 2023 •Efuent Filtration Study 4 1 10 7 1 2 3 1 2 3 Capital Improvement Plan Treatment Scenario 3 Table 6. TS 3 Overall Recommended Improvements UNIT PROCESS OPCC YEAR REQUIRED CIP TS 1 & 2 Items $80,605,000 As Listed in Tables 4 & 5 Construct New Bioreactor #4 Train, 2.3 MG $10,890,000 - Postanoxic Carbon Dosing System $1,000,000 - TOTAL $92,495,000 Recommended Implementation Timeline Begin work by these dates to meet required year. We practice increased use of sustainable materials and reduction of material use. © HDR, all rights reserved. 0092654 0622 1 2 3 1 2 3 Chapter 1 Introduction 1 Bozeman WRF Facility Plan Update Chapter 1 -Introduction Contents Introduction.......................................................................................................................................1-1 1.1 Facility Plan Update Objectives .............................................................................................1-1 1.2 Facility Plan Update Approach and Organization ..................................................................1-1 i Bozeman WRF Facility Plan Update Chapter 1 - Introduction This page is intentionally left blank. ii 1 Bozeman WRF Facility Plan Update Chapter 1 -Introduction Introduction This document provides an update to the previous Bozeman Wastewater Facilities Plan, which was completed in 2006. This Wastewater Facility Plan Update for the City of Bozeman (City) Wastewater Reclamation Facility (WRF) identifies cost effective means and methods for the WRF to maintain compliance with Montana’s water quality standards as the City continues to grow. A 20-year planning horizon is covered by the facility plan. Various capital improvements and process optimization strategies are recommended, as well as pollutant minimization program elements and long-range permit compliance approaches. The recommendations will be necessary to achieve compliance with Montana water quality standards as Bozeman’s population continues to increase. 1.1 Objectives The objectives of this Facility Plan Update are to prepare a document that meets the requirements of Montana Department of Environmental Quality (MDEQ) regulations, address the capacities and conditions of the various WRF processes and components, and addresses uncertainty regarding nutrient treatment regulations in the State of Montana. 1.2 Historical Facility Improvements The Bozeman WRF was originally constructed in 1970 as a simple secondary treatment plant. The WRF was upgraded to an activated sludge treatment plant in 1982. Final effluent polishing and sludge storage facilities were added soon afterwards. In 1998, two digested sludge storage lagoons were converted into a larger lagoon and sludge storage capacity was increased. In 2002 and 2003, the plant was expanded with the addition of a new primary clarifier and anaerobic digester improvements. The construction of a new secondary clarifier was completed in 2005, as well as improvements to the headworks and aeration facility, and the installation of a new computer based supervisory control and data acquisition system. The WRF was upgraded to a biological nutrient removal (BNR) facility during the Phase I Improvements Project, which lasted from 2008 to 2012. This project consisted of $53 million in improvements that upgraded the WRF to a high performance BNR facility. Included in the improvements were new bioreactors, clarifiers, headworks elements, and UV disinfection. A new Admin/Lab building was also completed during this same timeframe. The new bioreactors were the primary design improvement of the Phase I Improvements project. The bioreactors upgraded the WRF to a 5-Stage Bardenpho design, allowing for biological nitrogen and phosphorus removal without the addition of expensive chemicals. 1.3 Facility Plan Update Organization This facility plan update consists of an executive summary and x chapters. The contents of each chapter are described below. 1-1 Bozeman WRF Facility Plan Update Chapter 1 - Introduction Chapter 1 – Introduction (this chapter) o Describes objectives and outline of the facility plan update. Chapter 2 – Basis of Planning o Establishes the planning constraints and identifies the variables that will impact planning decisions, including population growth. Chapter 3 – Flows and Loads, Monitoring, Sampling and Data Analysis o WRF data for the previous five years is evaluated. Projected flow and loading conditions are developed for the 20-year planning period. Chapter 4 – Long Range Nutrient Water Quality Standards Compliance o Feasible long‐range nutrient WQS compliance scenarios are developed and analyzed based on current regulatory trends. Chapter 5 – Effluent Management Alternatives Development and Analysis o Effluent management alternatives for the WRF are developed and evaluated. Chapter 6 – Existing WRF Facility Major Process Evaluations o The respective capacities of the WRF’s existing liquid and solid stream major process elements are evaluated. Deficiencies are then identified. Chapter 7 – WRF Treatment Capacity Upgrades Alternatives Development and Analysis o Upgrade alternatives for the WRF that meet the needs identified in the preceding chapters are outlined and evaluated. Chapter 8 – Solids Disposal Alternatives Development and Analysis o Final solids disposal options are evaluated that build upon the alternatives selected in Chapter 8. Chapter 9 – Resource Recovery Evaluation and Economic Feasibility Analysis o Potential resource recovery options that could be implemented for nitrogen, phosphorus, methane, and finished sludge are identified and evaluated. Chapter 10 – WRF Capital Improvement Plan o A final capital improvement plan is included for the recommended alternatives. 1-2 Chapter 2 Basis of Planning 2 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning Contents Introduction.......................................................................................................................................2-1 2.1 Study Area..............................................................................................................................2-1 2.2 Population ..............................................................................................................................2-2 2.2.1 Previous Population Projections ...............................................................................2-3 2.2.2 Current Planning Period Population Projections.......................................................2-4 2.3 Climate Change......................................................................................................................2-6 Figures Figure 2-1. 2020 Bozeman Community Plan Planning Area Boundaries..................................................2-2 Figure 2-2. Graph of Population Projections..............................................................................................2-5 Tables Table 2-1. Bozeman Population.................................................................................................................2-3 Table 2-2. Previous Facility Plan Population Projections ..........................................................................2-3 Table 2-3. Population Projection Scenarios...............................................................................................2-4 Table 2-4. Selected Population Projections for Facility Plan .....................................................................2-6 i Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning This page is intentionally left blank. ii 2 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning Introduction The basis of planning establishes the baseline conditions and boundaries for the facility plan development. In this chapter, the study boundary area for the facility plan is defined. Current population trends for the boundary area are then examined and projections are developed for a 20-year planning period, spanning from 2020 to 2040. The population projections outlined in this section are used to develop flow and loading projections in Chapter 3. An overview of projected climate change impacts to the region is also introduced. 2.1 Study Area The study area for this facility plan is the Growth Policy Boundary delineated in the 2020 Bozeman Community Plan. The Growth Policy Boundary extends beyond the current extent of the City of Bozeman (City) limits, and it is anticipated that the area between the two boundaries will be gradually annexed over time by the City. The Community Plan map is shown in Figure 2-1. . 2-1 City of Bozeman Planning Area City Limits Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning Figure 2-1. 2020 Bozeman Community Plan Planning Area Boundaries 2.2 Population US Census Bureau data was used to establish current and historical population figures for the City of Bozeman. Bozeman population since 2010 is shown in Table 2-1. The respective annual growth rate (AGR) for each year is also shown. 2-2 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning Table 2-1. Bozeman Population Year Total Population Annual Growth Rate 2020 53,293 6.95% 2019 49,831 2.88% 2018 48,437 3.26% 2017 46,907 3.81% 2016 45,187 4.29% 2015 43,327 4.07% 2014 41,631 4.67% 2013 39,773 2.96% 2012 38,629 1.45% 2011 38,077 2.14% 2010 37,280 -5.74% Annual growth rates in Bozeman have shown few slowdowns in the years since the Great Recession, with 2010 being the last year that the City experienced negative growth. Annual growth rates were especially high from 2014 to 2016, exceeding a 4.0% AGR during each respective year. Growth rates slowed slightly in the ensuing years, but generally remained well above 3.0%. 2020 saw substantial growth that pushed the City’s population well over 50,000 people for the first time ever. Examining the data from Table 2-1, the average overall AGR for the previous ten years, 2011 to 2020, is 3.81%, and the average overall AGR for the previous five years, 2016 to 2020, stands slightly higher at 4.21%. 2.2.1 Previous Population Projections Bozeman was experiencing high growth rates when the previous facility plan (HDR 2006) was written. Annual growth rates exceeding 6.0% were observed in the two years prior to the completion of the facility plan, and a 5.0% AGR was ultimately used to project future populations for the facility plan planning period. The projected populations from the previous facility plan are shown in Table 2-2. A comparison of these values to the actual population figures from Table 2-1 shows that projected populations were overestimated. Table 2-2. Previous Facility Plan Population Projections Year ----- --- Projected Population Actual Population 2005 34,900 34,983 2010 44,500 37,336 2015 56,800 43,334 2020 72,500 51,287 2-3 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning The 2020 Bozeman Community Plan was also examined during the evaluation of Bozeman population information. Population projections were not a focal point of the Community Plan, but a population projection was included. The Community Plan lists an estimated 2018 population of 48,105, and projects that the City will grow by an estimated 27,000 people by 2045. This gives a projected total population of 75,105 by 2045, and an overall AGR of 1.66%. This population projection appears unrealistically low given the annual growth rates experienced in the City over the last decade and is not considered further. 2.2.2 Current Planning Period Population Projections The 3.81% 10-year average and 4.21% 5-year average annual growth rates were projected through the end of the planning period. A 5.0% extreme growth rate was also projected, as well as a more plausible high growth rate of 4.0%. The resulting population projections are shown in Table 2-3, and a graph of the population projections is shown in Figure 2-2. The various scenarios result in 2040 population projections ranging from 112,494 to 141,402 people. Table 2-3. Population Projection Scenarios Year 3.81% Growth 4.21% Growth 4% Growth 5% Growth 2020 53,293 53,293 53,293 53,293 2025 64,237 65,500 64,839 68,017 2030 77,428 80,503 78,887 86,809 2035 93,329 98,942 95,978 110,792 2040 112,494 121,606 116,772 141,402 -- 2-4 C: 0 ·.:; "' :i 160,000 140,000 120,000 100,000 g-80,000 Q. 60,000 40,000 20,000 ~ Historical Population ~ Projected Pop, 3.23% 1985 1995 ~ Projected Pop, 3.81% 2005 ~ Projected Pop, 4% 2015 Year _.,_Projected Pop, 4.21% ~ Projected Pop, 5% 2025 2035 2045 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning Figure 2-2. Graph of Population Projections 2-5 Bozeman WRF Facility Plan Update Chapter 2 – Basis of Planning The 5.0% AGR from the previous facility overestimated the ensuing populations, and the annual growth rates for the last decade in Bozeman have never reached 5.0%. The 5.0% extreme growth scenario appears unrealistic given these considerations. Additionally, projecting an annual growth rate in the mid 3.0% range, similar to what has been observed during the last decade, provides no margin of conservatism. If growth rates tick upwards from what has been observed, any infrastructure changes could be undersized for the end of the 20-year planning period. Given these considerations, and following conversations with City of Bozeman engineering staff during the Basis of Planning Workshop, the 4.0% high growth scenario was ultimately selected for use in this Facility Plan. The 4.0% AGR provides a comfortable margin of safety over the average growth rates experienced over the preceding five-year and ten-year periods, with the extreme population growth observed in 2020 considered a likely outlier driven by the COVID-19 pandemic. The population projections in Table 2-4 will be used in Chapter 3 to develop future flow and loading projections to the WRF. Table 2-4. Selected Population Projections for Facility Plan Year 4% Growth 2020 53,293 2025 64,839 2030 78,887 2035 95,978 2040 116,772 --- 2.3 Climate Change The Fourth National Climate Assessment published in November 2018 provided a thorough examination of the effects of climate change on the United States (USGCRP 2018). This assessment helps inform decision-makers, utility and natural resource managers, public health officials, emergency planners, and other stakeholders. The National Climate Assessment delineates the country into several regions based on geography and expected climate change impacts. The report discusses the potential effects of climate change on these delineated geographic regions and highlights potential impacts to natural resources and existing infrastructure. Montana and the City of Bozeman fall within the Northern Great Plains Region in the report. The regional summary for the Northern Great Plains notes that, “Future changes in precipitation and the potential for more extreme rainfall events will exacerbate water- related challenges in the Northern Great Plains” (USGCRP 2018). The potential for extreme precipitation events will likely increase in a warming climate, as will the potential for droughts. Such events could affect the operation of the WRF, as well as the regulation of its effluent discharge. These possibilities and potential impacts will be considered during applicable sections later in the Facility Plan. 2-6 Chapter 3 Flows and Loads 3 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Contents Introduction.......................................................................................................................................3-1 3.1 Pretreatment Program Requirements ....................................................................................3-1 3.1.1 Significant Industrial Users........................................................................................3-1 3.2 Historical Influent Conditions..................................................................................................3-3 3.2.1 Influent Flow..............................................................................................................3-3 3.2.2 Historical CBOD ........................................................................................................3-6 3.2.3 Historical TSS............................................................................................................3-9 3.2.4 Historical TP............................................................................................................3-11 3.2.5 Historical TKN .........................................................................................................3-13 3.2.6 Historical Ammonia .................................................................................................3-15 3.2.7 Influent Ratios .........................................................................................................3-16 3.2.8 Water Conservation.................................................................................................3-17 3.3 Projected Influent Conditions ...............................................................................................3-17 3.3.1 Peaking Factors ......................................................................................................3-17 3.3.2 Projected Loadings..................................................................................................3-18 Tables Table 3-1. SIU Contributors to the WRF ....................................................................................................3-2 Table 3-2. Metered Water Usage Makeup.................................................................................................3-3 Table 3-3. Annual Average Influent Flows and Aggregate Per Capita Flow .............................................3-4 Table 3-4. Metered Water Usage...............................................................................................................3-4 Table 3-5. True Per Capita Flows ..............................................................................................................3-6 Table 3-6. Annual Influent CBOD Characteristics .....................................................................................3-7 Table 3-7. Annual Influent TSS Characteristics.........................................................................................3-9 Table 3-8. Annual Influent TP Characteristics .........................................................................................3-11 Table 3-9. Annual Influent TKN Characteristics.......................................................................................3-13 Table 3-10. Annual Influent Ammonia Characteristics.............................................................................3-15 Table 3-11. Influent Wastewater Ratios Compared to Typical Ranges...................................................3-16 Table 3-12. Average Day Peaking Factor Table......................................................................................3-18 Table 3-13. Projected Loadings for Planning Period ...............................................................................3-19 Figures Figure 3-1. Historical Influent Flows to the WRF .......................................................................................3-5 Figure 3-2. Average Influent Flows by Month ............................................................................................3-5 Figure 3-3. Historical Influent CBOD Concentrations to the WRF.............................................................3-7 Figure 3-4. Historical Influent CBOD Loading to the WRF ........................................................................3-8 Figure 3-5. Average Influent CBOD Loading by Month .............................................................................3-8 Figure 3-6. Historical Influent TSS Concentrations to the WRF ..............................................................3-10 Figure 3-7. Historical Influent TSS Loading to the WRF..........................................................................3-10 Figure 3-8. Historical Influent TP Concentrations to the WRF.................................................................3-11 Figure 3-9. Historical Influent TP Loading to the WRF ............................................................................3-12 Figure 3-10. Average Influent TP Loading by Month...............................................................................3-12 i Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-11. Historical Influent TKN Concentrations to the WRF ............................................................3-13 Figure 3-12. Historical Influent TKN Loading to the WRF........................................................................3-14 Figure 3-13. Average Influent TKN Loading by Month ............................................................................3-14 Figure 3-14. Historical Influent Ammonia Concentrations to the WRF ....................................................3-15 Figure 3-15. Historical Influent Ammonia Loadings to the WRF..............................................................3-16 ii Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads This page is intentionally left blank. iii 3 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Introduction This chapter defines the wastewater criteria and future loading projections that will be used to evaluate alternatives and recommendations for the WRF. Historical WRF influent data for the previous five-year period (2016 to 2020) was provided by WRF staff, and the data was evaluated to determine baseline influent conditions. Future conditions were then developed from the baseline conditions in five-year increments for the 20-year planning horizon of 2040. 3.1 Pretreatment Program Requirements The City administers an Industrial Pretreatment Program (IPP) to better regulate influent characteristics to the WRF. IPPs are required under the Clean Water Act for municipal publicly owned treatment works (POTWs) with design flows greater than 5 mgd that receive pollutants from industrial users that could interfere with the operation of the POTW (or are otherwise subject to pretreatment standards). The objectives of the IPP are to: Prevent the introduction of pollutants into the municipal wastewater system which will interfere with or upset the operation of the wastewater treatment plant, or contaminate treatment plant sludge with toxic or hazardous materials Prevent the introduction of incompatible pollutants into the municipal wastewater system and the wastewater treatment plant which may pass through without adequate treatment into receiving waters or the atmosphere Prevent water quality violations resulting from direct discharges into waters of the state, or violations of the Montana Pollution Discharge Elimination System (MPDES) permit for the wastewater treatment plant Improve the opportunity to recycle and reclaim wastewaters and sludges from the system Provide for equitable distribution of the costs of the program Establish and maintain a data base and inspection program sufficient to determine compliance with pretreatment requirements Enhance the efficiency and cost-effective operation of the wastewater system Protect the health and safety of city residents and wastewater system workers Protect the municipal wastewater system and wastewater treatment plant from physical damage 3.1.1 Significant Industrial Users As part of the pretreatment program, the WRF is required to identify any significant industrial users (SIU) that contribute flows to the wastewater system. There are currently five SIUs that contribute flows to the WRF. Flows from all SIUs are summarized in Table 3-1. 3-1 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads The first SIU is Montana State University (MSU), which contributes approximately 430,465 gpd of non-process wastewater. The flow contributions are largely domestic strength waste; however, the waste stream also includes contributions from university laboratories that handle a wide variety of chemical and biological materials, and there are several large-scale commercial kitchens operating on campus. The second SIU is Darigold, which contributes approximately 59,000 gpd of process wastewater flow and 49,287 gpd of non-process wastewater flow. Darigold is a categorical industrial user (CIU) as legally defined under 40 CFR Part 405 - Dairy Products Processing Point Source Category, and has federally imposed pretreatment standards. The third SIU is the Story Mill Landfill, which is a CIU as legally defined in 40 CFR 445 – Landfills Point Source Category. The landfill contributes approximately 110 gpd of condensate and 25 gpd of leachate. The condensate is collected in an underground storage tank and discharged once the tank is full. The leachate is discharged directly to the collection system. The fourth SIU is Finishing Lab LLC, which is a CIU as legally defined in 40 CFR 433 – Metal Finishing Point Source Category. Approximately 1,500 gpd of process flow is contributed by Finishing Lab. The fifth SIU is Spark R&D, which is also a CIU as legally defined in 40 CFR 433. Approximately 1,025 gpd of process flow is contributed by Spark R&D. Table 3-1. SIU Contributors to the WRF SIU Process Flow (gpd) Non Process Flow (gpd) Montana State University -430,465 Darigold 59,000 49,287 Story Mill Landfill 135 - Finishing Lab LLC 1,500 - Spark R&D 1,025 - The City’s MPDES permit prohibits the introduction of the following pollutants into the WRF from any source, including SIUs: Any pollutant which may cause Pass Through or Interference Pollutants which create a fire or explosion hazard Pollutants which will cause corrosive structural damage to the POTW, but in no case discharges with pH lower than 5.0 Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW, or other interference with the operation of the POTW Any pollutant, including oxygen demanding pollutants (e.g. BOD), released in a discharge at a flow rate and/or pollutant concentration which will cause Interference with the POTW Heat in amounts which will inhibit biological activity in the POTW resulting in Interference Petroleum oil, non-biodegradable cutting oil, or products of mineral oil origin in amounts that will cause Interference or Pass Through 3-2 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Pollutants which result in the presence of toxic gases, vapors, or fumes within the POTW in a quantity that may cause worker health and safety problems Any trucked or hauled pollutants, except at discharge points designated by the POTW Any specific pollutant that exceeds a local limitation established by the POTW The SIUs contributing flow to the WRF are not currently known to interfere with plant processes or degrade the quality of the effluent. A breakdown of flow sources to the WRF is shown in Table 3-2. The percentages of total flow were calculated from the City’s metered water usage data from 2016 – 2020. Only the months of December to March were used for this calculation because there is no irrigation during this timeframe, and metered water usage is indicative of what flows are sent to the collection system. Flows from MSU make up approximately 13% of the WRF’s influent flows. Contributions from industrial sources are otherwise negligible. Table 3-2. Metered Water Usage Makeup Flow Category Percent of Total1 Single Family Residential 29.2% Multi-Family Residential 29.5% Commercial 25.0% Industrial 1.7% Government 1.5% Montana State University 12.8% Low Income 0.3% 1 Based on Metered Water Usage from Dec – Mar, 2016-2020 3.2 Historical Influent Conditions Influent flows and loadings to the WRF are discussed and evaluated in this section. Influent flow, carbonaceous biochemical oxygen demand (CBOD), total suspended solids (TSS), total phosphorus (TP), total Kjeldahl nitrogen (TKN), and ammonia are evaluated. These waste constituents are evaluated because they are the parameters currently included in the WRF’s effluent permit limitations. 3.2.1 Influent Flow The annual average day and max month flows to the WRF for 2016 – 2020 are shown in Table 3-3. The average aggregate per capita flows, using the total influent flow to the WRF, are also shown. A graph of influent flows to the WRF is shown in Figure 3-1. Influent flows have generally exhibited steady growth over the 2016 – 2020 timeframe, increasing by a total of 15.6% from 2016 to 2020. This growth is similar to the 17.9% increase in population over the same time period. 3-3 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Table 3-3. Annual Average Influent Flows and Aggregate Per Capita Flow Year Population Annual Avg Day (mgd) Max Month (mgd) Avg Per Capita Flow (gpd) - Average metered water usage for December to March of each year is shown in Table 3-4. For example, flows from 2015-2016 represent flows from December 2015 to March 2016. From 2016 to 2020, average metered flow from single family residential accounts increased by approximately 10.0%, and average metered flow from multi-family residential accounts increased by approximately 17.8%. Average metered usage to all other categories, including commercial and industrial sources, has remained fairly steady over the same time period. Given this information, the observed increases in influent flow are most likely being driven by population growth. Table 3-4. Metered Water Usage ------------ -------------------- 2016 45,187 5.01 5.64 111 2017 46,907 5.22 5.90 111 2018 48,437 6.06 8.88 125 2019 49,831 6.17 8.21 125 2020 53,293 5.79 6.21 109 Average 5.65 6.97 116 Category Year1 and Average Flows (mgd) 2015 2016 2016 2017 2017 2018 2018 2019 2019 2020 Single Family Residential 0.967 0.995 1.003 1.053 1.064 Multi-Family Residential 0.944 0.987 1.038 1.055 1.112 Commercial 0.863 0.860 0.880 0.890 0.849 Industrial 0.053 0.059 0.049 0.079 0.050 Government 0.047 0.047 0.064 0.048 0.047 Montana State University 0.409 0.472 0.419 0.515 0.408 Low Income 0.010 0.010 0.012 0.013 0.013 1 Flows from Dec – Mar 3-4 12.0 ... 10.0 l i t l l -------------------~ ----------------- ---:------1-------------~ ----... -------------~-------------------- : : : A : I I l I I I I I I I J I I I J I 8.0 : : : A : - - - - - - - - - - - - - - - - - - -~ - - - - - - - - - - - - - - - - - - - -:- - - -- - - - - - - - - - - -;- - - - - -·- - - - - - - -i - - - - - - - - - - - - - - - - - - - - I I I I ' ' ' C C) ' ... : i f :ii: 6.0 4.0 ... ' ... ----------------~-------------------~-------------------- 2.0 - - - - - - - - - - - - - - - - - - -... - - - - - - - - - - - - - - - - - - - -1-- --- - - - - - - - - - - - --- -.I,. - - - - - - - - - - - - - - - - - - ---- - - - - - - - - - - - - - - - - - -I I I I I I I I ' ' ' ' ' ' 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 & Influent, Flow 8.00 7.00 6.00 ~ bl) 5.00 E - == 4.00 ..Q L.L. .., 3.00 C: QI ::, .;:::: 2.00 C: 1.00 0.00 ~~ ~..:.., o' ~v 1,.v ~~ \~ ~~ Month Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-1. Historical Influent Flows to the WRF Large spikes in influent flow are evident in the spring of 2018 and the spring of 2019 respectively. These influent flow spikes coincide with periods of high snowmelt runoff and abnormally wet spring weather, indicating that the influent flow spikes are the result of high inflow and infiltration (I&I). In each case, influent flows decreased once the abnormally wet conditions abated and snowmelt concluded. Smaller seasonal spikes during the same timeframe are evident in the other years, and an examination of average monthly influent flow shows that flows are highest in April, May, and June. Average monthly influent flows are shown in Figure 3-2. Figure 3-2. Average Influent Flows by Month 3-5 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads To evaluate how much of the influent flow is comprised of I&I, metered water usage from December to March was once again examined to calculate the expected per capita flow. For example, flows from 2015-2016 represent flows from December 2015 to March 2016. The average aggregate per capita flows from the metered water data are shown in Table 3-5. These per capita flows are considered “true” per capita flows because they omit irrigation and only encompass the flows sent to the collection system. Table 3-5. True Per Capita Flows Year1 Population Average Consumption (gpd) Per Capita Flow (gpd) 2015-2016 43,334 3,262,532 75.3 2016-2017 45,200 3,429,001 75.9 2017-2018 46,951 3,463,566 73.8 2018-2019 48,532 3,652,214 75.3 2019-2020 49,504 3,509,011 70.9 1 Flows from Dec -Mar ----- Based on the information in Table 3-5, the expected per capita flow for Bozeman is closer to 74 gpd. This number is much less than the 117 gpd average of the per capita flows in Table 3-3, and given the seasonal spikes in influent flow (Figure 3-1, Figure 3-2), indicates that there is considerable I&I included in WRF influent flows. As the annual per capita flows in Table 3-5 have remained fairly steady for the preceding five years, the range in per capita flows in Table 3-3 is likely the result of varying I&I volumes to the collection system. These volumes are in turn influenced by annual climatic variation, as evidenced by the influent flow spikes in the spring of 2018 and the spring of 2019, and the accompanying 125 gpd per capita flows in each of those years. The maximum observed per capita flow of 125 gpd from Table 3-3 will be used to project future influent flows in conjunction with the population projections developed in Chapter 2. Using the 125 gpd maximum observed per capita flow from the five preceding years to develop future influent flows will better account for the potential of wet years with high I&I, which could become more frequent due to the effects of climate change. This decision was made in consultation with City of Bozeman engineering staff during the Basis of Planning Workshop, and will result in more conservative flow estimates than using the 117 gpd average per capita flow, or any of the “true” per capita flows. 3.2.2 Historical CBOD The annual average day CBOD concentrations and loadings, including per capita loadings, and the annual max month CBOD concentrations and loadings for 2016 – 2020 are shown in Table 3-6. The respective averages are also shown for each parameter. A graph of influent CBOD concentrations to the WRF can be seen in Figure 3-3, and a graph of influent CBOD loadings can be seen in Figure 3-4. 3-6 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Table 3-6. Annual Influent CBOD Characteristics Year Avg Day (mg/l) Avg Day (lb/d) Max Month (mg/l) Max Month (lb/d) Avg Per Capita Loading (lb/d) 2016 256 10,850 281 11,355 0.24 2017 250 10,967 283 12,059 0.23 2018 220 10,703 282 12,314 0.22 2019 189 9,553 263 11,456 0.19 2020 175 8,542 211 9,833 0.16 Average 218 10,123 264 11,403 0.21 ...I c, E --------------- 600.0 500.0 400.0 300.0 200.0 100.0 ' & -- - -- - - -... ~-- - - -... -- - - - - - - -- - - - ' ' ' 0.0 --------------------------------Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 .&Influent, CBOD Figure 3-3. Historical Influent CBOD Concentrations to the WRF 3-7 • 25,000.0 _ -_ --___ -- - _ -_ --- -_ .I - - - - -_ - - -_ -__ -- -- -_ -1-- -_ -- - ---_ --_ - - _ - --.J. -__ -_ - --- - -- --_ -- - --1-_ -- --- _ -- - --- - -- -- -I I I I . ' . ' ' ' 20,000.0 >, -------------------~ --------------------:-A -----------------;--------------------:--------------------: ... : ... ~ : "' ~ 1/1 :!:! 15,000.0 •: • • • • ' ----------fc •_: ___ • ---------------... : ... ... .: . . 10,000.0 5 000 0 ----------------_ _.J__ _____ • .. ~-~~---__ t __ ------,--------_;._ ___ -------------_, ___ ---·-------------, • ... ...... : -: -: : ~ : : : 0.0 -------------------------------Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 • Influent, CBOD Load 12,000 10,000 -=c-....... :e 8,000 0 0 a:i u 6,000 ... C: a, ::s .;:::: 4,000 C: 2,000 Month Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-4. Historical Influent CBOD Loading to the WRF Average influent CBOD loadings split by month are shown in Figure 3-5. A small decrease in average loading is evident during May, June, and July. This is likely attributable to the lack of Montana State University students in Bozeman during the summer months. Figure 3-5. Average Influent CBOD Loading by Month Influent CBOD concentrations have steadily decreased in recent years, falling by approximately 31.6% from 2016 to 2020. Influent CBOD loadings have also decreased during this timeframe, falling by approximately 21.3%. This observed decrease in 3-8 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads concentrations was discussed with WRF staff, and they believe that a change in their BOD sampling method could account for some of the observed decrease. Part of the difference may be explained by the distinction between the cBOD test, which includes an inhibitor to disallow nitrogenous oxygen demand in the result, and the more traditional BOD test which does not include the inhibitor. No inhibitor was being added to the samples prior to mid-2018. The ratio of BOD (standard BOD test) to cBOD (BOD test with inhibitors) is plant specific and may range from 1.0 to 1.4. The observed decrease in load of 21.3% falls within this possible range of variance between cBOD and BOD in the testing procedures. The average per capita CBOD loading to the WRF of 0.21 lb/d from 2016 to 2020 is less than the 0.27 lb/d per capita CBOD loading used in the previous facility plan. These values are greater than typical BOD5 concentrations from residences in the United States. Typical values average approximately 0.17 lb/capita/day (Metcalf & Eddy). 3.2.3 Historical TSS The annual average day TSS concentrations and loadings, including per capita loadings, and the annual max month TSS concentrations and loadings for 2016 – 2020 are shown in Table 3-7. The respective averages are also shown for each parameter. A graph of influent TSS concentrations can be seen in Figure 3-6, and a graph of influent TSS loading can be seen in Figure 3-7. Table 3-7. Annual Influent TSS Characteristics Year Avg Day (mg/l) Avg Day (lb/d) Max Month (mg/l) Max Month (lb/d) Avg Per Capita Loading (lb/d) 2016 212 8,979 273 11,438 0.20 2017 215 9,426 238 10,475 0.20 2018 184 8,935 232 10,721 0.18 2019 243 12,418 290 14,402 0.25 2020 250 12,098 312 14,687 0.23 Average 221 10,371 269 12,345 0.21 --------------- 3-9 ◄: ◄' ~ 1'11 ' ' ' ' :◄ ' ' ' ' ' ' ' ' ◄ ' ' ' -A!JI.~: .. I ...... "'-I t i ◄◄~:. :1,◄--L----!----+----r--------i---◄~---: : : : ' ◄4, ~~. ◄◄• : ' : ◄ : ◄: :◄ : ' : : : ◄ .: ◄:◄.: : : : jlll : ' ... : : : ' : : ◄: ... ...f..d~.... : 11 : :◄: ◄1~.,. : : ...ii~ ◄ ◄: : ' ◄: ◄ ◄ -I I-I. : ◄ I I ◄..: ◄ I t ◄◄!I ' ' : ' 1• ◄, ◄ ' ' 0 N 0 N C: "' -, a, .... 0 N C: "' -, ----;-----:------ - - --:-•- - - - --:--◄--:- --◄-:----co .... 0 N C: I, C! 0 0 .., I I t I I I I I ◄1 : ◄ : ◄ : : 'ii •◄ ' ' ◄" : I : : ◄<1111 : ' :◄.,... ' ' ' ; .JI~ ... --.... ~ : ' ' ' ~ : : : "' -, t------~ -----~ -----~----~-----,----i----0 N C: ◄ ~~! I , , I " " I , C! C! C! C! C! 0 0 0 0 0 .., 0 .., 0 .., s:t s:t M M N 7/6W ~ ' ~ ' ' ' ' ' .. ◄ : ' ◄: ' ' ' ' "' -, co - -· •◄ 10 l,,,,!,,,,1,,,,N C! C! C! 0 0 0 0 .., 0 N 0 0 .., 0 C: . "' 0 -, II) ~ ~ C: GJ ::, .:: -= ◄ ◄ :.. ◄~ : ◄I l" ◄ ' ' ◄ -·--◄-------, __________ J_________ j----0 0 0 0 on N ◄ ◄~~ 0 0 0 0 c:i N t :◄ ◄ : ◄ 0 0 0 0 on .... ~ep1sqI 0 0 0 0 c:i ◄ ◄: 1 :◄ ' ' ' ◄: ◄ 1111 : ◄◄-~◄◄ ~ I ◄ ◄ ~ ... -~-----◄ ◄◄ ◄ ...... :◄ -~--◄..---◄ :~◄◄ .... ·~ 0 N C: "' -, t N C: "' -, 00 .... 0 N C: "' -, t--0 N C: "' -, <O ~ ,◄;' I ◄ , '~ 0 0 0 0 on 0 C: . "' 0 -, ,::, "' 0 ..J VI VI t-'E GJ ::, .:: -= ◄ Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-6. Historical Influent TSS Concentrations to the WRF Figure 3-7. Historical Influent TSS Loading to the WRF TSS concentrations decreased during 2018, likely due to high I&I, but concentrations have since rebounded to a higher level similar to the preceding years. Influent TSS loading was relatively steady from 2016 to 2018, but increased considerably in 2019. Loading then decreased in early 2020 and remained fairly constant at around 12,000 lb/day for the remainder of the year. The average per capita TSS loading to the WRF of lb/d from 0.21 2016 to 2020 is less than the 0.28 lb/d per capita TSS loading used in the previous facility plan. These values are greater than typical TSS concentrations from 3-10 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads residences in the United States. Typical values average approximately 0.16 lb/capita/day (Metcalf & Eddy). 3.2.4 Historical TP The annual average day TP concentrations and loadings, including per capita loadings, and the annual max month TP concentrations and loadings for 2016 – 2020 are shown in Table 3-8. The respective averages are also shown for each parameter. As no max month concentrations were included in the WRF data set from the City, a max month concentration was calculated by dividing each year’s max month loading value by the respective monthly average flow. A graph of influent TP concentrations can be seen in Figure 3-8, and a graph of influent TP loading can be seen in Figure 3-9. Table 3-8. Annual Influent TP Characteristics Year Avg Day (mg/l) Avg Day (lb/d) Max Month (mg/l) Max Month (lb/d) Avg Per Capita Loading (lb/d) 2016 5.37 224 6.61 273 0.0050 2017 4.95 215 6.07 264 0.0046 2018 4.52 221 5.92 307 0.0045 2019 4.85 246 5.47 291 0.0050 2020 5.19 249 5.73 297 0.0047 Average 4.97 231 5.96 286 0.0047 ..J c, E --------------- 7.0 6.0 5.0 4.0 3.0 2.0 1.0 ' ' I I I I .. -------------------~ ------------..... _ -----~ --& --- -----------~ -----------------· ~------------. ----"' - j. ' j. ,.. '•• j. j. •:• ' j. .: j. • j. .. .. I I I • I ~ j. •• j. :• .: j.: - - - - - - - - - --&- -... - - -~ - - - - - - - - - - - - - - --&-- -~ -- - - - - - - - - - -- - - -- - -~ -- - - - - - - - - - - - - - -- - -~- - - - -•. - - - - - - -- - - ' j. j. &' • j. ' j. j. ' + j. j. ' I .... : I I .. ------------------_ 1 _ ------------------_:_ _ ------------------~ -------------------~-----------· ------- ' ' ' ' ' j. j.& ' j. ' - - - - - - - - - - - - - - - - - - -.I - - - - - - - - - - - - - - - - - - - _._ - - - - - - - - - - - - - - - - - - -J. - - - - - - - - - - - - - - - - - - -...I-- - - - - - - - - - - - - - - - - - - ' ' ' ' ' ' j. ' ' -------------------~ --------------------:--------------------~ --------------------:-------------------- ' ' ' ' ' ' ' ' I I I I --- - --- - --- - --- - -- -I --- - --- - --- - --- - --- -, -- - --- - - - - - -- -- - - - -I - -- - - - - -- -- - - - - - ---I- - - - --- - --- - --- - --- - I I l I I I I I I I I I ' ' ' ' ' ' 0.0 -------------------------------.... Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 & Influent, TP Figure 3-8. Historical Influent TP Concentrations to the WRF 3-11 350.0 300.0 250.0 Ill f! 200.0 I I t I - - - - - - - - - - - - - - - - - - --:- - - - - - - - - - - - - - - - - - - -:-- - - - - - - - - - - - - - - - - - -"!"- - - - - - - - - - - - - - - --:&-:- - -... - - - - - - - - - - -~ - - - -.. .. : : : .. : .. : : .. .. : .... :.. .. .. - - - - - - - - - - - - - - - - ---~ - - - - - - - - - - - - -•- - - - - -~ - - - - - - - - - - - - - -·- -. ~ -.. •-- - - - -.. - - - - - - -i - - - - - - - - - - - - - - - - - -- & ' ....... &' & & ' ...... .... .. .. : .. : .. .. : .. .... .. ... : .. I I & _____ & _ & _______ 1..& ___ .... •-_______ -~ ___________________ 1 _____ & • -__________ : __________ -· ______ _ l • • & • & ......... ' ' 150.0 - - - - - - - - - - - - - - - - - - -.l - - - - - - - - - - - - - - - - - - -• ' - - - - - - - - - - - - - - - - - - -.I. - - - - - - - - - - - - - - - - - - --1-- - - - - - - - - - - - - - - - - - -I t I I I I I I I I I I I I I I ' ' ' ' ' I I I I 100.0 - - - - - - - - - - - - - - - - - --{-- - - - - - - - - - - - - - - - - - -:-- - - - - - - - - - - - - - - - - - -+- - - - - - - - - - - - - - - - - - --:-- - - - - - - - - - - - - - - - - -- I I I I I I I I ' ' ' ' ' ' ' ' ' I I I I 50.0 I I I I --- - -- ---- --- - -- -- -I - - - --- - - --- - - - -- -- - -,--- -- --- - ------ -- - --I -- --- -- - ------- - -- --,--- - ----- - --- - --- --- I t I I I I I I I t I I I I t I ' ' ' ' ' ' 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 & Influent, TP Load 300 250 200 150 100 so 0 1><;\ 1-~ o' i...~ ~1>~ ~fl, ~~ i} fl,<.. rb'-rt- rt-~-> ~-> ~,,}, "?-~ --,v 'i ~ ~ cf' ~ ~ --,1> ~~ "?-.;;j ~q; oc:f ~fl, cf c.f~ '<;'o 'vq; Month Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-9. Historical Influent TP Loading to the WRF Average influent TP loadings split by month are shown in Figure 3-10. A small decrease in average loading is evident during May, June, and July. This is likely attributable to the lack of Montana State University students in Bozeman during the summer months. Figure 3-10. Average Influent TP Loading by Month Influent TP concentrations have remained fairly steady over the preceding five years, and in the range of 4.5 mg/L to 5.5 mg/L. Influent TP loading has generally increased over this period, primarily due to rising influent flows. The average per capita loading of 3-12 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads 0.0047 lb/capita/day is nearly identical to typical residential wastewater concentrations in the United States, which average 0.0046 lb/capita/day (Metcalf & Eddy). 3.2.5 Historical TKN The annual average day influent TKN concentrations and loadings, including per capita loadings, and the annual max month TKN concentrations and loadings for 2016 – 2020 are shown in Table 3-9. The respective averages are also shown for each parameter. As no max month concentrations were included in the WRF data set from the City, a max month concentration was calculated by dividing each year’s max month loading value by the respective monthly average flow. A graph of influent TKN concentrations can be seen in Figure 3-11, and a graph of influent TKN loading can be seen in Figure 3-12. Table 3-9. Annual Influent TKN Characteristics Year Avg Day (mg/l) Avg Day (lb/d) Max Month (mg/l) Max Month (lb/d) Avg Per Capita Loading (lb/d) 2016 41.02 1,710 49.20 2,032 0.038 2017 38.73 1,681 46.43 2,017 0.036 2018 35.95 1,765 44.23 2,294 0.036 2019 36.46 1,849 44.23 2,348 0.037 2020 37.65 1,858 45.03 2,332 0.035 Average 37.96 1,772 45.82 2,204 0.036 --------------- 60.0 50.0 ... : I.. J. .J 40.0 ...J ci E 30.0 : . . : . : . l.& : ' A .& & : & .& : A A . ., . . '. ., ., - _ ... _ .. _ - - - - - - --&-_.,. _ - - - - - - - - - - - -------:---- - - - - - - - - - - - -_._ -~ - - - - - --- - - - - --- - ---~- - - - - - - - - - - - - - - - - - - -I .. I I .. I .. .6. . . . . ' . ' . . . ' . -. : .. .. ... • .. : + ... I .. I I I .. : .. : : : . -- - - - - - - - - - - - - - -- - -~ -- - - --- - - - - - - - -- --- -:-- - - - - - - - - - - - - - -- - --7 - --A--•.A. • -------~----&-- - - - - -- - - - -- - - : ' . .. : ' 20.0 ' ' . ' . ' -- - --- - - - - - - --- - ---1 - - - - - - - - - - - - - - - - - - - • I ' - - --- - - - - - - - --- - - -T- - - - - - - - - - - - - - - - - - -;---- - - - - - - - --- - - - - - - I I I I I I I I I I l I I I I I I I I I I I I I ' ' ' 10.0 ' ' ' -- - - - - - - - - - - - - ---- -.. -- - - - - - - - - - - - - - -- - -_._ - - - - - - --- - - - - - -- - - -J. - --- - --- - - - - ----- - -..1-- - - -- -- - - - - - -- - -- - -' ' ' ' ' ' ' ' ' 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 a Influent, TKN Figure 3-11. Historical Influent TKN Concentrations to the WRF 3-13 2,500.0 2,000.0 "' f! 1,500.0 1,000.0 - - - - - - - - --- - - - - - - - -"t - - --- - - - - - - - - - - - - - --1- --- - - - - - - - - - - -- -- - -1' - - - - - --- - - - - - - - - - - - -1- - - - - - - - - - - - - - - - - ---I I I I I I I I ' ' ' 500.0 - - - - - - - - - - - - - - - - - - -.l - - - --- - - - - - - - - - - - - -_1_ - - - - - - - - - - - - - - - - - - -.l - - - - - - - - - - - - - - - - - - - _,_ - - - - - - - - - - - - - - - - - - -I I I I ' ' ' ' ' ' ' ' ' ' ' ' ' ' 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 .A. Influent, TKN Load 2500 2000 ~ ....... 1500 ::!:! z ::.:: I-... 1000 C a, ::I .;:::: C 500 0 Month Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-12. Historical Influent TKN Loading to the WRF Average influent TKN loadings split by month are shown in Figure 3-13. A small decrease in average loading is evident during May, June, and July. This is likely attributable to the lack of Montana State University students in Bozeman during the summer months. Figure 3-13. Average Influent TKN Loading by Month From 2016 to 2020, influent TKN concentrations generally remained in the high 30 mg/L range and have exhibited a slight downward trend since 2016. The average per capita 3-14 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads loading of 0.036 lb/capita/day is slightly higher than typical residential wastewater concentrations in the United States, which average 0.029 lb/capita/day (Metcalf & Eddy). 3.2.6 Historical Ammonia The annual average day influent ammonia concentrations and loadings, including per capita loadings, and the annual max month ammonia concentrations and loadings for 2016 to 2020 are shown in Table 3-10. The respective averages are also shown for each parameter. Table 3-10. Annual Influent Ammonia Characteristics Year Avg Day (mg/l) Avg Day (lb/d) Max Month (mg/l) Max Month (lb/d) Avg Per Capita Loading (lb/d) 2016 24.14 1,026 28.08 1,166 0.023 2017 23.05 1,006 24.89 1,221 0.021 2018 19.60 954 27.93 1,283 0.020 2019 22.11 1,137 31.63 1,647 0.023 2020 26.41 1,309 31.84 1,498 0.025 Average 23.06 1,086 28.87 1,363 0.022 --------------- 140.0 120.0 -- - ---- - - - - - - - - - - - -., -- -- - --- - --- -- - -- - --1- - --- -- - - - - - - - - - - - --,. -- - --- - --- -- - -- - -- --,--- -- - - - - - - - - - - - - - - -I I I I I I I I I I I I I I I I : : . : : 100.0 I I I 1 - - - - - - - - - -- - --- - - ---I - - --- --- - --- - - - - - - - -1- - - - --- - - -- - - - - - ----.. - -- --- - --- - - --- - - - --4-- - - - - - -- - - - - - - -- - --I I I I :• : : ' ..I c, 80.0 E -------------------~ --------------------:--------------------~ -----------·"'-----~--------------------: : : :. : : : .. : 60.0 40.0 - - - - - - - - - - - - - - - - - - -~ - - - - - - - - - - - - - - - - - - --i-- - - - - - - - - - - -_£_ - - - -~- - - - - - - - - - - - -\- -~ ~- -~ - - - - - - - - - - - - - - - - - I I I .. • t l : i• • .. : • • & '& ' ' ... ' & & ..... & -_________________ l ___ ------•--------: -------------•--}------..--- --J_ -------- -~- 20.0 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 • Influent, NH3 Figure 3-14. Historical Influent Ammonia Concentrations to the WRF 3-15 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Figure 3-15. Historical Influent Ammonia Loadings to the WRF Influent ammonia concentrations have remained relatively consistent since 2016, and average loadings have increased slightly. The average per capita loading of 0.022 lb/d from 2016 to 2020 is nearly identical to the 0.023 lb/d per capita loading used in the previous facility plan. The per capita loadings are slightly higher than typical residential wastewater concentrations in the United States, which average 0.017 lb/capita/day. Increased sampling variability is evident starting in mid-2019, and this could be the result of different sampling procedures being used by WRF staff. WRF staff report that the existing probes were switched around the time of increased sample variability, and that the replacement probes take longer to stabilize when measuring low influent ammonia concentrations as compared with higher concentration samples. This likely explains the period of high sample volatility, and the trend towards decreasing volatility beginning in mid-2020 as staff has sought to minimize the variability associated with the probes. 3.2.7 Influent Ratios Ratios of influent constituents were examined and compared to typical ratios for influent wastewater parameters. The results are shown in Table 3-11. Table 3-11. Influent Wastewater Ratios Compared to Typical Ranges Ratio Value Typical Range NH3:TKN 0.614 0.6 – 0.7 TKN:CBOD 0.177 0.16 – 0.18 TP:CBOD 0.023 0.02 – 0.03 >, "' 7,000.0 6,000.0 5,000.0 - - - - - --- - --- - - - - - - -.,. --- - - - - --- - - - - - - - - --.--- - - - - - - - - - - - - - - - - -.,. - - - - - - --- - - - - - - - - - --1- - - - - - - - - - --- - - - - - - -I I I I I I I I I I I I I I I I : : . ' : ' ' ' - - - - - - - - - - - - - - - - - - -➔ - - - - - - - - - - - - - - - - - - --1-- - - - - - - - - - - - - - - - - - --+ - - - - - - - - - - - - - - - - - - - -1- - - - - - - - - - - - - - - - - - - -I I I I : : : .. : : : : .. : ~ 4,000.0 I I I I - - - - - - - - - - - - - - - - - - --I - - - - - - - - - - - - - - - - - - --I-- - - - - - - - - - - - - - - - - - --I - - - - - - - - - - - - - - - - - - --I- - - - - - - - - - - - - - - - - - - - :.. I :!= 3,000.0 ' ' I ... .. :• : I : .. _& I I I I ... j. I --- - --- --- --- - - --- -~ - -- -- ----- ----- - -- --:-- - - - - - - - - -- --... - - - - -:--- - -- - -- ---• -----:--.A.- - - - - - - - - - --- - - - 2,000.0 : ; .. I .. .. .. ' : :• • ••t •: • ~ -\ •• --- -- -- - - - - --- -- -- -:- -- -.-- -- --- ----- - - -;--- -- -- - - - - --- -- - -- -,1 _ - --- - -~ - --- _,_ ---- --- - --- --- 1,000.0 0.0 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 • Influent, NH3 Load ---- The influent wastewater ratios for Bozeman are comfortably within the ranges typically observed for influent wastewater. The ratios do not engender any concerns about the 3-16 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads validity of the influent data. Furthermore, all per capita loading values are similar to respective residential American averages, and do not raise concerns. 3.2.8 Water Conservation The City of Bozeman implements a water conservation program that encourages citizens to conserve water and offers cash rebates for upgrading to high efficiency fixtures and sprinkler systems. The water conservation program in Bozeman is an integral part of the City’s water management planning. However, reduced water consumption also has direct and indirect impacts on the characteristics of the influent wastewater and the treatment infrastructure of the WRF. Reducing the relative influent flow to the WRF as the City’s population continues to grow will lead to increased wastewater concentrations of influent compounds. More concentrated wastewater could lead to new compliance challenges, such as increases in total and refractory nitrogen, soluble nonreactive phosphorus, and total dissolved solids (TDS), and increases in the concentrations of toxics and contaminants of emerging concern. Additionally, it may be more difficult to achieve numeric effluent limits as influent concentrations increase. However, the comparison of the respective per capita loadings for CBOD, TSS, and NH3 to the values used in the previous facility plan does not indicate that loading is becoming more concentrated at this time. In the case of CBOD and TSS, per capita loading has decreased since the writing of the previous facility plan. Increased concentrations resulting from water conservation could still become problematic during the planning horizon though, and should be monitored accordingly. 3.3 Projected Influent Conditions Projected influent conditions for the planning period were developed using per capita flows and loads and the respective peaking factors for the various parameters being examined. 3.3.1 Peaking Factors To develop peaking factors, max month and peak day loadings to the WRF were compared to average day loadings to derive max month and peak day ratios. The respective ratios for each influent parameter are shown in Table 3-12, and the average ratios constitute the values used to project peak conditions. No peak day values were available for TN or TP in the City data set. 3-17 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Table 3-12. Average Day Peaking Factor Table Influent Analyte Parameter Year Average 2016 2017 2018 2019 2020 Flow Max Month Peak Day 1.13 1.24 1.13 1.34 1.47 1.84 1.33 1.59 1.07 1.25 1.22 1.45 CBOD Max Month Peak Day 1.05 2.17 1.1 1.96 1.15 2.43 1.2 2.05 1.15 2.75 1.13 2.27 TSS Max Month Peak Day 1.27 2.33 1.11 1.55 1.2 2.08 1.16 1.88 1.21 1.63 1.19 1.89 NH3 Max Month Peak Day 1.14 1.83 1.21 3.79 1.34 5.55 1.45 4.1 1.14 4.85 1.26 4.02 TN Max Month Peak Day 1.19 - 1.2 - 1.3 - 1.27 - 1.25 - 1.24 - ------------------------------------------TP Peak Day - - - - - - Max Month 1.22 1.23 1.39 1.18 1.19 1.24 3.3.2 Projected Loadings The projected influent flow and loadings for CBOD, TSS, NH3, TN, and TP are shown in Table 3-13. Projected influent flows were developed using the 4% population growth projections from Chapter 2, and a 125 gpd per capita flow. The average per capita loadings for each parameter were used to project average future loadings for all other constituents. The average peaking factors from Table 3-12 were multiplied by the average future loadings to project max month and peak day loadings. The peak hourly flow rate was calculated using equation 10-1 from Montana DEQ Circular 2. 3-18 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads Table 3-13. Projected Loadings for Planning Period Year 2025 2030 2035 2040 Annual Average Flow, mgd 14.6 Maximum Monthly Average Flow, mgd 9.9 12.1 14.7 17.9 CBOD, lb/day 15,340 18,664 22,707 27,627 TSS, lb/day 16,403 19,957 24,280 29,541 NH3, lb/day 1,815 2,208 2,687 3,269 TN, lb/day 2,936 3,572 4,346 5,288 TP, lb/day 382 465 566 688 Peak Daily Average Flow, mgd 11.8 14.3 17.4 21.2 CBOD, lb/day 30,889 37,581 45,723 55,630 TSS, lb/day 26,070 31,719 38,591 46,951 NH3, lb/day 5,807 7,066 8,596 10,459 TN, lb/day TP, lb/day Peak Hourly Flow Flow, mgd 17.5 20.6 24.2 28.4 ---- -------- ------------ ---------------- Population 64,839 78,887 95,978 116,772 8.1 9.9 12.0 CBOD, lb/day 13,583 16,526 20,106 24,462 TSS, lb/day 13,764 16,746 20,374 24,788 NH3, lb/day 1,443 1,756 2,137 2,600 TN, lb/day 2,363 2,875 3,497 4,255 TP, lb/day 308 374 455 554 3-19 Bozeman WRF Facility Plan Update Chapter 3 – Flows and Loads References Metcalf & Eddy Inc., et al. Wastewater Engineering: Treatment and Resource Recovery. 5th ed., McGraw-Hill Professional, 2013. 3-20 Chapter 4 Water Quality 4 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Contents Water Quality and Regulatory Requirements...................................................................................4-4 4.1 Regulatory Trends..................................................................................................................4-4 4.2 Permit and Regulatory Issue Summary .................................................................................4-5 4.2.1 Plant Effluent and East Gallatin River Flows ..........................................................4-10 4.2.2 Bacteria ...................................................................................................................4-10 4.2.3 Ammonia-Nitrogen ..................................................................................................4-10 4.2.4 Nitrogen...................................................................................................................4-12 4.2.5 Phosphorus .............................................................................................................4-13 4.2.6 Constituents of Emerging Concern .........................................................................4-13 4.2.7 Human Health Toxics..............................................................................................4-14 4.2.8 Perfluoroalkyl Substances.......................................................................................4-14 4.2.9 PFAS Strategic Roadmap: EPA’s Commitments to Action 2021–2024..................4-15 4.2.10 Temperature............................................................................................................4-16 4.2.11 pH............................................................................................................................4-17 4.3 Surface Water Quality Standards - Beneficial Uses ............................................................4-17 4.4 Surface Water Quality Standards - Criteria..........................................................................4-20 4.4.1 Antidegradation .......................................................................................................4-20 4.4.2 Mixing Zones ...........................................................................................................4-20 4.4.3 Water Quality Standards .........................................................................................4-21 4.4.4 Nutrient Total Maximum Daily Load for the East Gallatin River..............................4-23 4.5 Groundwater Protection .......................................................................................................4-25 4.5.1 General Groundwater Protection Regulations ........................................................4-25 4.6 Site Specific Water Quality Standards .................................................................................4-26 4.6.1 Variances ................................................................................................................4-27 4.6.2 Montana Nutrient Variances....................................................................................4-28 4.6.3 2022 EPA Financial Capability Assessment Guidance...........................................4-32 4.6.4 Nutrient Trading.......................................................................................................4-40 4.7 Nutrient Removal..................................................................................................................4-40 4.7.1 Nitrogen...................................................................................................................4-40 4.7.2 Phosphorus .............................................................................................................4-41 4.7.3 Nutrients: Historical Perspective .............................................................................4-41 4.7.4 Nutrients: Current Regulatory Trends for the East Gallatin River...........................4-45 4.7.5 Nutrients: Future Looking........................................................................................4-47 4.8 Biomonitoring and Whole Effluent Toxicity Testing..............................................................4-50 4.9 Biosolids Management.........................................................................................................4-50 4.10 Air Toxics..............................................................................................................................4-50 4.10.1 The Clean Air Act and Rules for the Control of Air Pollution in Montana................4-50 4.11 Odors....................................................................................................................................4-51 4.12 Virus Control.........................................................................................................................4-52 4.13 Noise ....................................................................................................................................4-52 4.14 Effluent Reclamation and Reuse..........................................................................................4-53 References ...............................................................................................................................................4-54 i Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Tables Table 4-1. Current Bozeman MPDES Discharge Permit Limits.................................................................4-5 Table 4-2: Summary of Anticipated Regulatory and Permitting Issues .....................................................4-6 Table 4-3. Beneficial Uses of the East Gallatin River ..............................................................................4-18 Table 4-4. Water Quality in Montana .......................................................................................................4-21 Table 4-5. Hydraulic Loading Rates in Montana DEQ Circular 2 ............................................................4-26 Table 4-6. Financial Capability Indicators for Bozeman ..........................................................................4-37 Table 4-7. Matrix 1 Information ................................................................................................................4-37 Table 4-8. Lowest Quintile Poverty Indicators for Bozeman....................................................................4-39 Table 4-9. Third Matrix Information..........................................................................................................4-40 Table 4-10. Historical Perspective 2016 to 2020: Influent to Bozeman WRF..........................................4-41 Table 4-11. Historical Perspective 2016 to 2020: Drinking Water Phosphorus Data (mg/L)...................4-42 Table 4-12. Historical Perspective 2016 to 2020: Effluent from Bozeman WRF.....................................4-42 Table 4-13. Historical Perspective 2016 to 2020: Effluent from Bozeman WRF, 95th Percentile............4-43 Table 4-14. Historical Perspective 2016 to 2020: East Gallatin River Water Quality Data .....................4-45 Table 4-15. Current MPDES Permit Nutrient Effluent Limitations ...........................................................4-46 Table 4-16. Current Trends 2020: DEQ Rules and Policies that Could Affect Future Permit .................4-47 Table 4-17. Current Trends 2020: Treatment Technology Capabilities...................................................4-47 Table 4-18. Future Looking 2020 to 2040: Receiving Water Conditions .................................................4-48 Table 4-19. Future Looking 2020 to 2040: Bozeman WRF Planning Scenarios.....................................4-49 Table 4-20. Odorous Compounds Associated with Untreated Wastewater ............................................4-52 Figures Figure 4-1. Effluent Ammonia Daily Concentrations................................................................................4-12 Figure 4-2. Effluent Ammonia Average Monthly Concentrations.............................................................4-12 Figure 4-3. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Nitrogen Concentrations ............................................................................................................................4-43 Figure 4-4. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Nitrogen Loads........4-44 Figure 4-5. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Phosphorus Concentrations ............................................................................................................................4-44 Figure 4-6. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Phosphorus Loads...........................................................................................................................................4-45 ii Bozeman WRF Facility Plan Update Chapter 4 – Water Quality This page is intentionally left blank. iii Bozeman WRF Facility Plan Update Chapter 4 – Water Quality 4 Water Quality and Regulatory Requirements The purpose of this chapter is to identify water quality and regulatory requirements that will drive decisions relating to treatment, effluent management, and biosolids management for the next 20 years. This includes the identification of current permit conditions for effluent discharge. A spectrum of potential regulatory scenarios that could impact the scope and extent of the treatment facilities will be summarized, along with the likely timeframe in which these scenarios would necessitate treatment modifications. These scenarios are in turn used to establish most restrictive and least restrictive ranges for each of the Water Reclamation Facility (WRF) Management Alternatives. 4.1 Regulatory Trends The City of Bozeman (City) discharges treated effluent to the East Gallatin River, which flows to the Gallatin River and then to the Missouri River. The City’s Montana Pollutant Discharge Elimination System (MPDES) permit authorizes the discharge and dictates requirements for the quality of the effluent. The Montana Department of Environmental Quality (Department or DEQ) has regulatory authority and issued the City’s MPDES permit. The permit conditions specify the effluent quality requirements for discharge to the river, which dictate the level of wastewater treatment. Historically, the City has been required to treat its wastewater to an advanced level beyond base secondary treatment to remove nitrogen and phosphorus to meet the discharge requirements for the East Gallatin River. The current permit became effective June 1, 2012 and authorized discharge until midnight, May 31, 2017. In accordance with 40 Code of Federal Regulations (CFR) Section 122.21(d), if a permittee intends to continue an activity regulated by a discharge permit after the expiration date of the permit, then the permittee must apply for and obtain a new permit. The City submitted their discharge application renewal by December 3, 2016, as required by regulations. The permit has since been administratively extended, and it is unknown when DEQ will begin efforts to renew the permit. The effluent discharge limits in the administratively extended permit are shown in Table 4-1. 4-4 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-1. Current Bozeman MPDES Discharge Permit Limits Parameter Units Average Monthly Limit1 Average Weekly Limit1 Maximum Daily Limit1 mg/L 25 40 -Carbonaceous Biological Oxygen Demand (CBOD5) lbs/day 1,072 1,928 - mg/L 30 45 -Total Suspended Solids (TSS) lbs/day 1,083 2,169 - Escherichia coli Bacteria2, 4 No./100ml 126 252 - Escherichia coli Bacteria3, 4 No./100ml 630 1,260 - Total Ammonia, as N mg/L 1.52 -3.15 Oil and Grease5 mg/L --10 lbs/day6 783 -971 Total Nitrogen lbs/day7 864 -1,072 lbs/day6 160 -199 Total Phosphorus lbs/day7 170 -211 Notes: 1. “Average Monthly Limitation” means the highest allowable average of daily discharges over a calendar month, calculated as the sum of all daily discharges measured during a calendar month divided by the number of daily discharges measured during that month. “Average Weekly Limitation” means the highest allowable average of daily discharges over a calendar week, calculated as the sum of all daily discharges measured during a calendar week divided by the number of daily discharges measured during that week. “Maximum Daily Limit” means the maximum allowable discharge of a pollutant during a calendar day. 2. This limitation applies from April 1 through October 31. 3. This limitation applies from November 1 through March 31. 4. Report Geometric Mean if more than one sample is collected in the reporting period. 5. Oil and Grease monitoring is only required when a visible sheen is observed. 6. Effective June 1 through September 30. 7. Effective October 1 through May 31. Other requirements in the permit include the following: Effluent pH shall remain between 6.0 and 9.0. 85% removal requirement for CBOD5 and TSS. There shall be no discharge of floating solids or visible foam in other than trace amounts. There shall be no discharge which causes visible oil sheen in the receiving stream. 4.2 Permit and Regulatory Issue Summary Treatment requirements for the WRF have become more stringent over time and this trend is likely to continue in the future, as suggested by past DEQ assessments of the East Gallatin River in a Total Maximum Daily Load (TMDL). A summary of the regulatory and permitting issues facing the City, as well as the status of each issue and the level of concern regarding the issue, are presented in Table 4-2 based on the MPDES discharge permit limits and related regulatory issues which may influence planning. Issues with a high level of concern 4-5 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality are likely to require action within the 20 year planning period; a moderate level of concern indicates that regulations affect the operation of the treatment facility, but action is not likely to be required in the near future; and a low level of concern indicates that the issue has little effect on the operation of the wastewater treatment facility. Following the table is a discussion of some of the key issues. Table 4-2: Summary of Anticipated Regulatory and Permitting Issues Regulatory Driver/Parameter MPDES Permit Limitations and Issues June 1, 2012 MPDES Permit Limits Importance to Planning Effluent Discharge Flow No, not included High The permit continues to be based on an 8.5 mgd plant effluent flow and seasonal 7Q10 flow for the East Gallatin River. ARM 17.30.635(4) requires, for design of disposal systems, that stream flow dilution requirements be based on the minimum consecutive seven-day average flow which may be expected to occur on the average of once in ten years (7Q10). Additionally, ARM 17.30.1345(2)(a) requires the Department to base permit limitations, standards or prohibitions for POTWs on the facility design flow. This combination of the 7Q10 and the facility design flow represents the design condition upon which the Department develops water quality-based effluent limits (WQBEL). The resulting limits are protective of the receiving water quality when the instream flow is at or above the 7Q10. The 7Q10 established in the permit varied by season; 20 cubic feet per second (cfs) between November and March, and 23 cfs April through October. Permit limits for Carbonaceous Biochemical Oxygen Demand (CBOD) are limited to the following: Average monthly: 25 mg/L and 1,072 lbs/day, and 85% removal. Concentration limit, CBOD Low mass limit Average weekly: 40 mg/L, and 1,928 lbs/day. Total Suspended Solids secondary treatment standards continue: Average monthly: 30 mg/l and Concentration limit, TSS Low1,083 lb/d and 85% removal. mass limit Average weekly: 45 mg/l and 2,169 lb/d. 4-6 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Regulatory Driver/Parameter MPDES Permit Limitations and Issues June 1, 2012 MPDES Permit Limits Importance to Planning The permit limits E. Coli. to the following: Limitation applies from April 1 through October 31 as a geometric mean. Average monthly: 126/100 ml Average weekly: 252/100 ml Geometric mean of Bacteria colonies per Low volume Limitation applies from November 1 through March 31 as a geometric mean. Average monthly: 630/100 ml Average weekly: 1,260/100 ml Oil and Grease Permit includes a maximum daily limit of 10 mg/l Concentration limit Low The permit limits ammonia to the following: Ammonia Nitrogen Concentration limit Medium Maximum daily: 3.15 mg/l Average monthly: 1.52 mg/l The permit limits total nitrogen to the following: Limitation applies from June 1 through September 30. Average monthly: 783 lbs/day. Maximum daily: 971 lbs/day. Mass limit HighTotal Nitrogen Limitation applies from October 1 through May 31. Average monthly: 864 lbs/day. Maximum daily: 1,072 lbs/day. The permit limits total phosphorus to the following: Phosphorus Limitation applies from June 1 through September 30. Average monthly: 160 lbs/day. Maximum daily: 199 lbs/day. Mass limit High Limitation applies from October 1 through May 31. Average monthly: 170 lbs/day. Maximum daily: 211 lbs/day. The permit requires whole effluent toxicity Biomonitoring Yes, included Lowtesting quarterly. 4-7 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Regulatory Driver/Parameter MPDES Permit Limitations and Issues June 1, 2012 MPDES Permit Limits Importance to Planning Biosolids The Permittee shall analyze the treatment Yes, included Moderate facility sludge (biosolids) prior to disposal, for the presence of toxic pollutants listed in 40 CFR 122 Appendix D (NPDES Application Testing Requirements) Table III at least once per year. If the Permittee does not dispose of biosolids during the calendar year, the Permittee shall certify to that in the Pretreatment Annual Report and the monitoring requirements in this paragraph shall be suspended for that calendar year. Pretreatment Requirements The City must sustain its Industrial Yes, included High Pretreatment Program per 40 CFR 403, any categorical pretreatment standards promulgated by the EPA, and any additional requirements imposed by the City as part of its approved pretreatment program or sewer ordinance. Pretreatment reports must be submitted annually. The permit requires an annual analysis to determine whether influent pollutant loadings are approaching the maximum allowable headworks loadings calculated in the permittee’s most recent local limits calculations Monitoring Requirements Multiple parameters have monitoring Yes, included Moderate requirements but no current discharge permit limitations. Data may be used to demonstrate future permit limitations. Odor Control high priority. No specific regulatory requirements apply; subject to local standards. No, not included High Air Emissions Regulations apply to VOCs, H2S, Cl2; but not likely to be considered major sources. Air Toxics No, not included Low Management Plan (RMP) requirements had a compliance deadline of June 21, 1999. Clean Air Act Section 112r Risk Maintenance of good neighbor policy has Aesthetics 4-8 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Regulatory Driver/Parameter MPDES Permit Limitations and Issues June 1, 2012 MPDES Permit Limits Importance to Planning Endangered Species Noise Control Maintenance of good neighbor policy has high priority. No specific regulatory requirements apply; subject to local standards. No, not included Low Visual Appearance Maintenance of good neighbor policy has No, not included High high priority. No specific regulatory requirements apply; subject to local standards. De facto neighborhood standards may dictate acceptable architectural appearance. ESA Listings U.S Fish and Wildlife Service identified the No, not included Low threatened species (Canada Lynx, Grizzly Bear, and Ute Ladies Tresses) in Gallatin County. The National Marine Fisheries Service indicates no threatened or endangered species under its jurisdiction in the East Gallatin River. Other Effluent Reclamation and Reuse DEQ Reuse Regulations and permits are DEQ Reuse HighRegulations required. Effluent reuse may be a management tool for load diversion from the East Gallatin River. Stormwater EPA Phase II Stormwater Permitting MPDES Stormwater MS4 High Permit program has designations for small urban areas with populations of 10,000 or more and includes the City. Regulated small municipal separate storm sewer systems have permits required with the current permit effective January 1, 2017. Stormwater loadings to the East Gallatin River consume shared assimilative capacity. Inflow reduction efforts to reduce peak wastewater loadings increase stormwater loadings and infrastructure requirements. 4-9 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality 4.2.1 Plant Effluent and East Gallatin River Flows For the June 1, 2012 discharge permit, the fact sheet includes seasonal low flows for the East Gallatin River receiving waters for November through March and April through October. The 7Q10 flows are 20 and 23 cfs, respectively. The 7Q10 flows are the lowest seven-day average flow based on a ten-year return interval. The discharge permit is based on an annual average design flow for the WRF of 8.5 mgd. There is a potential that future climatic changes could alter these low flow conditions. Earlier snowmelt and warmer temperatures could result in diminished 7Q10 flows in the East Gallatin River. If the 7Q10 flow decreases in the future, there will be less dilution water available in the river for effluent mixing, which could result in DEQ administering more stringent permit limits. 4.2.2 Bacteria The June 1, 2012 permit includes effluent limitations for Escherichia coli Bacteria (E. coli). The limits apply for seasons from April through October and November through March. There is potential for new requirements based on coliphage for additional virus control to be promulgated by EPA in the future. This possibility is discussed in the Virus Control section. 4.2.3 Ammonia-Nitrogen The June 1, 2012 permit calls for the City to produce an effluent with an average monthly ammonia as nitrogen concentration discharge of 1.52 mg/l. The maximum daily ammonia as nitrogen concentration discharge limit is 3.15 mg/l. Ammonia Nitrogen Standards Issues Water quality criteria for ammonia nitrogen has been evolving, with modifications by EPA in 1984, 1997, and 1998. On December 22, 1999, EPA published new recommended ammonia criteria in the federal register. The 1999 Update of Water Quality Criteria for ammonia contains EPA's most recent freshwater aquatic life criteria for ammonia and reflects recent research and data since 1984. These revisions led to the acute criterion for ammonia being dependent on pH and fish species, and the chronic criterion being dependent on pH and temperature. At lower temperatures, the chronic criterion is also dependent on the presence or absence of early life stages of fish (ELS). The June 1, 2012 permit established effluent limits for ammonia based on a pH of 8.3 and a temperature range from 6.4º C to 13º C. Salmonid fish and fish early life stages are present in the East Gallatin. The other significant revision in the 1999 criteria update is EPA's recommendation of 30 days as the averaging period for the chronic ammonia criterion. EPA recommends the 30Q10 (the lowest thirty-day average flow based on a ten-year return interval) as opposed to the lower 7Q10 flows. EPA also recommends that no 4-day average concentration exceed 2.5 times the chronic criterion. In 2013, EPA published new recommended freshwater ambient water quality criteria for ammonia. The criteria are published in EPA-822-R-13-001, and continue to exist only as 4-10 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality recommended federal water quality criteria. The 2013 criteria take into account data for several sensitive freshwater mussel species that were not included in the previous criteria updates. DEQ is continuing to study the recommended ammonia criteria, and is developing strategy options to accompany the potential future adoption of the revised federal ammonia criteria as state water quality standards. These options were outlined in a DEQ 2016 Triennial Review Response to Comment document, and include: 1. Best management practices to achieve best ammonia, TN and TP removal from wastewater lagoons. 2. Recalculate ammonia criteria for specific aquatic life. 3. Collect better pH and temperature datasets for receiving waters. 4. Understanding mixing zones. 5. Include appropriate compliance schedules in permits. 6. Provide opportunity to request a variance. 7. Review stream classification and designated uses where needed. It is not known when DEQ will adopt the 2013 revised federal ammonia criteria as state standards, but some degree of future adoption is considered likely. The WRF’s ammonia limits under the new criteria were projected for a future 14.6 mgd average design flow. A pH value of 8.3 and a temperature of 14.9° C were taken from the permit fact sheet and used to determine the acute and chronic criterion from the revised 2013 federal criteria when both salmonids and mussels are present. A 10% mixing zone dilution was used for the chronic wasteload calculation, and a 1% mixing zone dilution was used for the acute wasteload allocation. The result of this calculation is a projected AML of 0.56 mg/L and a MDL of 3.12 mg/L, compared to the current permit limits of 1.52 mg/l AML and MDL of 3.15 mg/l. The 1% and 10% mixing zone dilution factors have been applied previously by DEQ for other municipalities, but it’s possible a more favorable dilution factor could be used based on the favorable results of a previous mixing zone study completed for the City. If 25% were used, the AML would increase to 0.63 mg/L and the MDL would increase to 3.83 mg/L. The range between the respective set of values demonstrates that there is considerable latitude in what the ammonia limits would be if the federal criteria is adopted, and why it is important that Bozeman remain engaged in any future limit creation. A graph of daily effluent ammonia concentrations is shown in Figure 4-1, and a graph of monthly average effluent ammonia concentrations is shown in Figure 4-2. Based on the WRF’s recent historical performance, there should be little risk of exceeding the potential maximum daily limit for ammonia, as all measured effluent values fall below the projected MDL value of 3.12 mg/L. However, the potential average monthly limit of 0.56 mg/L, shown as a red dashed line on the figure, could pose a compliance challenge. 4-11 ...J c, E ...J c, E 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Dec 2015 Dec 2016 Dec 2017 Dec 2018 Dec 2019 Dec 2020 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1.EFF NH3 - - - - - - - - - - - - - - - - - - -~ - - - - - - - - - - - - - - - - - - --:- - - - - - - - - - - - - - - - - - - -~ - - - - - - - - - - - - - - - - - - -~ - - - - - - - - --A-- - - - - - - - -' ' ' ' ' ' I I I I - - --- - ---- ---- - -- - -~ ----- -- --- --- - - -----:- -- - -- --------- --- --~ - - -.&- ---- - -- - --- --~ ----- - - - - -------- --- t I I I t I I I : : : .& : ---________________ ! ___ --------_________ : __________ ----------~ .& ____________ .& -- -~-------------------- -- -- --- -- - -- - - - - - --J. --- - - - --------- -- - -_,_ - -- -- -- --- - - - - - - - --.I,. - - - - - --- - ------- -- -.J ----- -- -- -- - --- ----- .& : : : : •• 4 ---------i----~--------t-------------t-------------t----------~- ------------------_ l _ ------------------_:_ ---------------~ --~ -------------------~ --...._ A.. - - - - - - - - - - - - - - : :, : ••• & ~ I & : A •• • & & : I & & :• : •• : : & - - - - -• - - -.£ - - -•- -: - - - - - - .• - - - - - - - - - - -:- - - - - - - - - - - - - -•- - - -I - - - - - - - - - - - - - - - - - - -:- - - - - - - - - - - - - - - - - - - - i, i, i, ' i, i, i, i, ' i, i, • i,• & •: & • ! & •• : I : : & Dec 2015 Dec 2016 Dec 2017 Dec 2018 Dec 2019 Dec 2020 i. EFF NH3 MAVG Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Figure 4-1. Effluent Ammonia Daily Concentrations Figure 4-2. Effluent Ammonia Average Monthly Concentrations 4.2.4 Nitrogen The June 1, 2012 permit requires the City to produce an effluent with an average monthly nitrogen mass discharge of 783 lbs/day from June through September, and 864 lbs/day from October through May. The maximum daily nitrogen mass discharge limits are 971 lbs/day from June through September and 1,072 lbs/day from October through May. 4-12 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality The June 1, 2012 permit does not include nitrogen concentration limits. For reference, at the WRF design flow of 8.5 mgd the permitted mass discharge limits would equate to the following concentrations: average monthly limits of 11.0 mg/l from June through September and 12.2 mg/l from October through May, and maximum daily limits of 13.7 mg/l from June through September and 15.1 mg/l from October through May. 4.2.5 Phosphorus The June 1, 2012 permit calls for the City to produce an effluent with an average monthly phosphorus mass discharge of 160 lbs/day from June through September and 170 lbs/day from October through May. The maximum daily phosphorus mass discharge limits are 199 lbs/day from June through September and 211 lbs/day from October through May. The June 1, 2012 permit does not include phosphorus concentration limits. For reference, at the WRF design flow of 8.5 mgd the permitted mass discharge limits would equate to the following concentrations: average monthly limits of 2.3 mg/l from June through September and 2.4 mg/l from October through May, and maximum daily limits of 2.8 mg/l from June through September and 3.0 mg/l from October through May. 4.2.6 Constituents of Emerging Concern In recent years, a topic of growing public and political interest is the presence of constituents of emerging concerns in public waters. There is no federal statutory or regulatory definition for constituents of emerging concern, but generally refers to unregulated substances detected in the environment that may present a risk to human health, aquatic life, or the environment, and for which scientific understanding of potential risks is evolving. These constituents consist of items such as trace organic compounds, pharmaceuticals, personal care products, endocrine disrupting compounds, micronutrients, and micropollutants. These compounds are often present in wastewater treatment effluent, stormwater, and agricultural runoff. However, treatment facilities do not produce constituents of emerging concern but receive them in their influent flows. Regardless of this distinction, dischargers may still be required to comply with effluent limits for these constituents. DEQ can address constituents of emerging concern using either technology-based or water-quality-based requirements. Technology-based effluent limitations may use national Effluent Limitation Guidelines and Standards (ELGs) or by setting technology-based effluent limits on a case-by-case basis. Water-quality-based limitations are based on water quality criteria. EPA publishes information reflecting the latest scientific knowledge and provides recommendations to DEQ for updating state water quality standards used to inform water-quality-based limitations. However, both methods have multiple challenges to implementation, including a lack of data available to support new or revised ELGs, a lack of data needed to support development of criteria, and the process to update regulations and include such within the state MPDES program. Monitoring data for such constituents would need to be sampled from the facility effluent and a dataset establish before any conclusions could be reached. 4-13 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality 4.2.7 Human Health Toxics A toxic standard or prohibition is established under Section 307(a) of the Clean Water Act for the discharge of toxic pollutants. Human health criteria for toxics based on water and fish consumption continue to evolve and most standards are generally becoming more stringent. The ubiquitous and enduring nature of toxics in the environment, in combination with new laboratory methods with lower detection limits, has resulted in greater reports of detection in many locations across the country. In some cases, human health water quality criteria based on consumption of fish, shellfish, and drinking water, have resulted in very restrictive surface water quality standards in Washington, Oregon, and Idaho. In these instances, there is a potential for very restrictive effluent limitations that may, in some cases, exceed the capabilities of advanced wastewater treatment. Trace organic toxics are ubiquitous and enduring in nature, and new laboratory methods with lower detection limits have resulted in increased reports of detection in many locations across the country. Options for removal of trace organics in wastewater are based on biological decomposition, physical and chemical removal processes, advanced filtration, and advanced oxidation processes. For trace organic compounds found to be present in effluent, a screening level reasonable potential analysis may be used to evaluate the potential need to control the concentration of the compounds in receiving waters by making comparisons to restrictive water quality standards from other locations. One such trace organic compound that poses a concern for the City is Bis(2- Ethylhexyl)Phthalate. There have been several high influent values of Bis(2- Ethylhexyl)Phthalate recorded at the WRF in recent years, and a high effluent value of 7.7 ug/L was measured in 2019 that exceeded reasonable potential for the human health standards documented in DEQ Circular 7. 4.2.8 Perfluoroalkyl Substances Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are fluorinated organic chemicals that are part of a larger group referred to as perfluoroalkyl substances (PFASs) that have been used in industry and consumer products since the 1950s. They are persistent and do not break down in the environment. People are exposed to PFASs through food, disposal of consumer products that contain PFAS, and drinking water. Some PFASs are no longer used, but many products may still contain PFAS, such as: Food-packaging materials Nonstick cookware Stain-resistant carpet treatments Water-resistant clothing Cleaning products Paints, varnishes, and sealants Firefighting foam Some cosmetics 4-14 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality The EPA has issued a health advisory that exposure to PFASs over time may result in adverse health effects. This advisory is based on studies of the effects of PFOA and PFOS on laboratory animals and epidemiological studies of humans. The EPA established a health advisory level of 70 parts per trillion for the combined concentrations of PFOA and PFOS in drinking water. However, the EPA has not set national primary drinking water regulations for PFOA and PFOS but is evaluating PFOA and PFOS as drinking water contaminants in accordance with the Safe Drinking Water Act (SDWA). The EPA announced four actions at a May 22, 2018 PFAS National Leadership Summit. These actions are as follows: They will initiate steps to evaluate the need for a maximum contaminant level for PFOA and PFOS. It will convene federal partners and examine everything known about PFOA and PFOS in drinking water. They are beginning the necessary steps to propose designating PFOA and PFOS as “hazardous substances” through one of the available statutory mechanisms, including potentially CERCLA Section 102. They are currently developing groundwater cleanup recommendations for PFOA and PFOS at contaminated sites and will complete this task by fall 2018. They are taking action in close collaboration with federal and state partners to develop toxicity values for GenX and PFBS. EPA’s comment period closed on January 22, 2019. EPA will consider the comments, revise the draft documents, as appropriate, and then publish final toxicity assessments. 4.2.9 PFAS Strategic Roadmap: EPA’s Commitments to Action 2021– 2024 In October 2021, EPA published a “PFAS Strategic Roadmap” that provides a 4-year timeline of agency-wide actions planned to address PFAS across the environment. These upcoming actions will advance research, remediate contamination, and restrict further environmental release. EPA’s integrated approach to PFAS will account for the full lifecycle of PFAS, their unique properties, the ubiquity of their uses, and the multiple pathways for exposure. The PFAS Roadmap includes actions regulated under the Clean Water Act (CWA), Safe Drinking Water Act (SDWA), Clean Air Act (CAA), and the Toxic Substances Control Act (TSCA). EPA’s Office of Land and Emergency Management will propose to designate certain PFAS as Hazardous Substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in the Spring of 2022 and finalize in the Summer of 2023. EPA will issue an advance notice of proposed rulemaking on various PFAS under CERCLA in the Spring of 2022. Some key actions in the PFAS Roadmap from the EPA Office of Water focused on wastewater management are highlighted as follows: The Effluent Limitation Guidelines Program (ELG) will target landfills and establish effluent guidelines by end of 2022. Effluent Guidelines are national regulatory standards for wastewater discharged to surface waters and municipal sewage 4-15 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality treatment plants. In addition to the nine industrial categories identified in the PFAS Action Act of 2021, EPA expects to complete landfill studies by Fall of 2022 and complete rulemaking by the end of 2022. By the end of 2022, landfills will need to employ pretreatment strategies if surface water or POTW PFAS concentrations exceed established ELGs. o EPA has identified key industries with significant documented discharges that include PFAS production and processing, metal finishing, airports, pulp and paper, landfills, and textile and carpet manufacturing. NPDES permits will address PFAS by Winter 2022. This will result in PFAS monitoring requirements at facilities suspected of containing PFAS. All NPDES permits will require PFAS monitoring and may result in the potential identification of and need for treatment of sources. o EPA plans to publish a Multi-Laboratory Validated Analytical Method for 40 PFAS by the Fall of 2022. Ambient water quality criteria for PFAS will be established in the Winter of 2022 and Fall of 2024. Aquatic life criteria are anticipated in the Winter of 2022 and human health criteria are anticipated by Fall 2024. Wastewater facilities treatment processes may not adequately remove PFAS, which may require modification to address PFAS discharge limitations once standards are established. o EPA plans to monitor Fish Tissue for PFAS from the nation’s lakes and evaluate human biomarkers for PFAS by the Summer of 2022. EPA plans to finalize a list of PFAS for use in Fish Advisory Programs by the Spring of 2023. Finalize PFOA/PFOS biosolids risk assessment by the Winter of 2024. Biosolids are typically landfilled or land applied on agricultural fields. If biosolids contain PFAS, landfilled solids may contribute to landfill leachate PFAS issues. Land applied biosolids may contaminate crops, livestock, groundwater, and surface water. POTWs may be responsible for crop, livestock, and environmental contamination caused by historical biosolid disposal methods. Additional biosolids treatment may be required before disposal. 4.2.10 Temperature The East Gallatin River is subject to B-2 classification standards for temperature. B-2 standards dictate that: A 1ºF maximum increase above naturally occurring water temperature is allowed within the range of 32ºF to 66ºF; within the naturally occurring range of 66ºF to 66.5ºF, no discharge is allowed which will cause the water temperature to exceed 67ºF; and where the naturally occurring water temperature is 66.5ºF or greater, the maximum allowable increase in water temperature is 0.5ºF. A 2ºF per-hour maximum decrease below naturally occurring water temperature is allowed when the water temperature is above 55ºF. A 2ºF maximum decrease below naturally occurring water temperature is allowed within the range of 55ºF to 32ºF. 4-16 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality There is limited temperature monitoring data taken concurrently from both upstream and downstream of the WRF outfall. However, the data available do not show reasonable potential to exceed the B-2 stream criteria for temperature. Continuous upstream temperature monitoring shows that the East Gallatin naturally exceeds 66ºF during the summer months. Additionally, the effluent WRF temperatures generally mirror the ambient upstream temperatures and do not appear to greatly affect temperature in the river downstream of the outfall. 4.2.11 pH The June 1, 2012 permit includes effluent limitations for pH to remain between 6.0 and 9.0. The limits apply year-round. The WRF effluent meets this limitation and is not an issue. The issue is the receiving water and potential influences on pH due to other effluent constituents. Impairment from high pH values in a waterbody are a secondary response to excess nutrient pollution and excessive algal growth. DEQ’s assessment of the East Gallatin River includes the item not supporting pH due to municipal point source discharge (see Section 4.3). DEQ field assessments in the 2000s measured pH from 8.15 to 9.10 indicating impairment. The East Gallatin River TMDL addressed pH based on the linkage between nutrient impairment and pH. Continuous monitoring of pH shows diel cycling. The East Gallatin River TMDL describes diel cycling as occurring in streams with low acid neutralizing capacity and is related to excessive algal growth. The capture of CO2 by photosynthesis removes carbon from the system raising pH levels. Conversely, respiration and decomposition processes lower pH by releasing carbon dioxide which forms carbonic acid and hydroxyl ions. 4.3 Surface Water Quality Standards - Beneficial Uses The East Gallatin originates from tributaries in the Gallatin and Bridger mountains and flows northwestward through the Gallatin Valley to the Gallatin River. The East Gallatin is listed as impaired by DEQ, indicating that it does not fully support beneficial uses. Beneficial use in the State of Montana is defined as the use of water for the benefit of the appropriator, other persons, or the public including but not limited to agricultural, domestic, fish and wildlife, industrial, irrigation, mining, municipal, power, and recreational uses. Beneficial uses are goals and expectations specified in water quality standards for how state surface waters should be able to be used; also referred to as designated uses or designated beneficial uses. Regulatory beneficial uses of the East Gallatin River are outlined in Montana’s Water Quality Standards. The beneficial use classifications and descriptions for the East Gallatin River are shown in Table 4-3. 4-17 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-3. Beneficial Uses of the East Gallatin River Designated Use - Description of Use Aquatic Life and Fishes Growth and propagation of salmonid or non- salmonid fishes and associated aquatic life, waterfowl, and furbearers Per Administrative Rules of Montana, the aquatic life beneficial use includes “fishes and associated aquatic life, waterfowl, and furbearers.” Use classifications distinguish between salmonid and non- salmonid fish species because water quality conditions necessary to sustain these communities varies. The inclusion of the terms “growth and propagation” highlight the need for water quality conditions that support the life cycle stages of organisms so they can not only live and grow but also reproduce and spread. The term “marginal” further stratifies areas where full reproductive capacity does not exist for salmonid fish. The classification states “growth and marginal propagation of salmonid fishes and associated aquatic life, waterfowl, and furbearers. Protection of waterfowl and furbearers promotes consideration of riparian habitat evaluations in water quality assessments. EPA recommends that monitoring for aquatic life use support include measurement of chemical parameters in water and sediment, and the collection of habitat and community level biological data (DEQ, 2006). EPA recommends that states include biological indicators among the core indicators used to assess attainment with aquatic life–based water quality standards (EPA, 2002). DEQ will review biological data when considering the full support of aquatic life use. Some pollutant specific assessment methods contain guidance for evaluating biological data. However, assessors cannot use biological data alone (i.e., direct measures of aquatic life support) to override pollution specific assessment outcomes. DEQ will not list or delist waterbody-pollutant impairments or consider the use fully supported based solely on biological data. If biological data exists, to affirm that the aquatic life use is fully supported, the assessor must ensure that biological data does not indicate non-support. DEQ may consider data and information related to fish consumption (e.g., fish tissue data or fish consumption advisories) when making aquatic life use support determinations. Contact Recreation Bathing, swimming, and recreation Per Administrative Rules of Montana, the recreation beneficial use includes “bathing, swimming, and recreation.” For parameters that are harmful or toxic to human health (e.g., E. coli, harmful algal blooms), the recreation use criteria generally protect “contact recreation” and criteria may distinguish between primary contact recreation (e.g., swimming) and secondary contact recreation (e.g., boating). Other parameters that affect aesthetic or odor qualities may also affect the suitability of waters for recreation use. DEQ may consider data and information related to fish consumption (e.g., fish tissue data or fish consumption advisories) when making recreation use support determinations. 4-18 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Designated Use Description of Use Drinking Water Per Administrative Rules of Montana, the drinking water (Human Health) beneficial use includes “drinking, culinary, and food processing.” Drinking, culinary, and food processing Surface waters are not intended for human consumption without adequate treatment, and use classifications distinguish between the level of treatment necessary for drinking water use (i.e., after convention treatment or after simple disinfection). Circular DEQ-7 provides a basis for assessing human health beneficial use. Many numeric standards in DEQ-7 take into consideration the human exposure pathway of fish consumption, especially for chemicals that bioaccumulate. Agricultural Water Supply The agriculture beneficial use encompasses agricultural water supply for various uses (e.g., livestock watering, irrigation). Criteria and thresholds for parameters may vary depending on the agricultural use being protected (e.g., a threshold for consumption of water by livestock may be more or less stringent than the threshold used to evaluate toxicity to plants via irrigation). - Industrial Water Supply The industrial use encompasses water supply for any industrial uses (e.g., fabricating, processing, cooling). DEQ does not report the use support status for industrial use because, as the least sensitive beneficial use, it is assumed that if a waterbody supports other more sensitive beneficial uses it will also support industrial uses. Notes: DEQ 2020. Beneficial Use Assessment Method for Montana’s Surface Waters. WQPBWQM-001 As required by the Clean Water Act, every two years the State of Montana must report to EPA the water quality status of state waters. In July of 2020, DEQ released the 2020 Integrated Report. The Integrated Report includes both the current conditions of state waters, referred to as the §305(b) list, and a listing of those waters that are impaired, referred to as the §303(d) list. Waters are considered impaired if water quality standards for one or more designated beneficial uses for one or more pollutants are not met. In Montana, these are considered Category 5 waters and constitute the §303(d) list of impaired waters. The 2020 Integrated Report includes the East Gallatin River on the §303(d) list. Three river segments are identified along with pollutants not meeting water quality standards. East Gallatin River, confluence of Rocky and Bear Creeks to MT HWY No. 411 (Spring Hill Rd) (10.7 miles, upstream of the WRF discharge) o Total nitrogen and total phosphorus East Gallatin River, MT HWY 411 to Smith Creek (22.12 miles, includes WRF discharge) o Algae, alteration in stream-side or littoral vegetative covers, flow regime modification, total nitrogen, total phosphorus, and pH 4-19 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality East Gallatin River, Smith Creek to mouth (Gallatin River) (13.54 miles, downstream of the WRF discharge) o Alteration in stream-side or littoral vegetative covers, total nitrogen, total phosphorus, and pH 4.4 Surface Water Quality Standards - Criteria Allowable concentrations of chemical species in surface water are based on the water quality standards necessary to protect the beneficial uses of natural water sources. Montana’s surface water quality standards are discussed in this section, as well as rules pertaining to antidegradation, mixing zones, and variances. 4.4.1 Antidegradation The State of Montana has an Antidegradation Policy in statute MCA 75-5-303 and rule ARM 17.30.701 through 717 that prohibits the degradation of existing water quality when introducing a new use. The policy states that: "Existing water quality" means the quality of the receiving water, including chemical, physical, and biological conditions immediately prior to commencement of the proposed activity or that which can be adequately documented to have existed on or after July 1, 1971, whichever is the highest quality.” “For state waters, existing and anticipated uses and the water quality necessary to protect those uses must be maintained and protected.” (ARM 17.30.705(2)(a)). 4.4.2 Mixing Zones The State of Montana has mixing zone rules (17.30.501) as authorized by section 75-5- 301(4) of the water quality act. Mixing zones are defined in the act as an area established in a permit, or final decision on nondegradation issued by the department, where water quality standards may be exceeded, subject to conditions that are imposed by the department and that are consistent with the rules adopted by the board. Rules governing the granting of mixing zones require that mixing zones granted by the department be specifically identified and that mixing zones have: (a) the smallest practicable size; (b) a minimum practicable effect on water uses; and (c) definable boundaries. The department will determine the applicability of a mixing zone and, if applicable, its size, configuration, and location after assessing information received from the applicant concerning the biological, chemical, and physical characteristics of the receiving water. No mixing zone will be granted if it would threaten or impair existing beneficial uses. The mixing zone rules (17.30.505) states that if a mixing zone at a given level for a parameter would threaten or impair existing beneficial use, discharge limitations will be modified as necessary to prevent the interference with or threat to the beneficial use. If necessary, these modifications may require achieving applicable numeric water quality criteria at the end-of-pipe for the parameter so that no mixing zone will be necessary or granted. A mixing zone study was previously conducted by HDR in 2018. The study determined that the Bozeman WRF discharge completely mixes with the East Gallatin less than 300 feet downstream of the WRF outfall during critical effluent and river flows. The WRF’s 4-20 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality current permit contains a mixing zone for ammonia with a maximum extent of 710 feet downstream. Based on the results, the existing outfall configuration for the WRF appears satisfactory to meet the mixing zone requirement in the permit. 4.4.3 Water Quality Standards The general surface water quality criteria for Montana are adopted to preserve water by protecting, maintaining, and improving the quality and potability of water for public water supplies, wildlife, fish and aquatic life, agriculture, industry, recreation, and other beneficial uses. The standards are adopted to establish maximum allowable changes in surface water quality and to establish a basis for limiting the discharge of pollutants that affect prescribed beneficial uses of surface waters. Specific water quality criteria for protecting the East Gallatin River’s beneficial uses are listed in Table 4-4. Table 4-4. Water Quality in Montana Beneficial Use Regulated Parameter Water Quality Standard Aquatic Life and Fish Sediment No increases are allowed above naturally occurring concentrations of sediment or suspended sediment (except as permitted in 75-5-318, MCA). Biological metrics apply for some pollutant specific Biological communities assessment methods Dissolved oxygen concentration must not be reduced Dissolved oxygen (DO) below the applicable standards given in department Circular DEQ-7 Nutrients Concentrations of carcinogenic, bioconcentrating, toxic, radioactive, nutrient, or harmful parameters may not exceed the applicable standards set forth in Department Circular DEQ-7 and, unless a nutrient standards variance has been granted, Department Circular DEQ-12A. As a result of EPA’s action disapproving DEQ’s general variance rules, DEQ concluded that the non- severability provisions were activated, and thereby eliminated DEQ-12A (Numeric Nutrient Criteria). In response, DEQ agreed to work with stakeholders in a Nutrient Work Group to develop a plan with steps toward using the existing narrative standards to replace the numeric nutrient criteria. In the interim, EPA will continue to use the previous numeric nutrient criteria, until DEQ adopts and EPA approves new rules that are equally scientifically defensible and protective of the applicable designated uses (EPA 2021). If site-specific criteria for aquatic life are adopted using the procedures given in 75-5-310, MCA, the criteria Parameters with shall be used as water quality standards for the numeric aquatic life affected waters and as the basis for permit limits standards (e.g., metals) instead of the applicable standards in Department Circular DEQ-7. 4-21 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Beneficial Use Regulated Parameter Water Quality Standard Contact Recreation Escherichia coli (E. coli) Temperature A 1ºF maximum increase above naturally occurring water temperature is allowed within the range of 32ºF to 66ºF; within the naturally occurring range of 66ºF to 66.5ºF, no discharge is allowed which will cause the water temperature to exceed 67ºF; and where the naturally occurring water temperature is 66.5ºF or greater, the maximum allowable increase in water temperature is 0.5ºF. Habitat n/a Electrical conductivity (EC)n/a Sulfate n/a Turbidity/TSS The maximum allowable increase above naturally occurring turbidity is five nephelometric turbidity units except as permitted in 75-5-318, MCA. pH Induced variation of hydrogen ion concentration (pH) within the range of 6.5 to 8.5 must be less than 0.5 pH unit. Natural pH outside this range must be maintained without change. Natural pH above 7.0 must be maintained above 7.0. Flow alterations n/a Water quality criteria for Escherichia coli are expressed in colony forming units per 100 milliliters of water or as most probable number, which is a statistical representation of the number of organisms in a sample, as incorporated by reference in 40 CFR 136.3(b). The water quality standard for Escherichia coli bacteria (E-coli) varies according to season, as follows: (i) from April 1 through October 31, the geometric mean number of E-coli may not exceed 126 colony forming units per 100 milliliters and 10 percent of the total samples may not exceed 252 colony forming units per 100 milliliters during any 30-day period; and (ii) from November 1 through March 31, the geometric mean number of E-coli may not exceed 630 colony forming units per 100 milliliters and 10 percent of the samples may not exceed 1,260 colony forming units per 100 milliliters during any 30-day period. 4-22 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Beneficial Use Regulated Parameter Water Quality Standard Drinking Water Concentrations of carcinogenic, bioconcentrating, Parameters with (Human Health) toxic, radioactive, nutrient, or harmful parameters may numeric human health not exceed the applicable standards set forth in standards (e.g., metals) Department Circular DEQ-7 Agriculture Electrical conductivity (EC) and Sodium n/a adsorption ratio (SAR) Harmful algal blooms n/a (HABs) Industrial n/a n/a Nutrients (mountain/transitional streams only [assessment methods for wadeable streams]) If numeric nutrient standards become void, which the legislature has directed, then narrative water quality standards contained in ARM 17.30.637 are the standards for total nitrogen and total phosphorus in surface water, State surface waters must be free from substances attributable to municipal, industrial, agricultural practices or other discharges. No wastes may be discharged, and no activities conducted such that the wastes or activities, either alone or in combination with other wastes or activities, will violate, or can reasonably be expected to violate, any of the standards. Harmful algal blooms (HABs) [assessment may also consider benthic algae] n/a Oil & Grease No increases are allowed above naturally occurring concentrations of oils, or floating solids. Aesthetics/Odor n/a 4.4.4 Nutrient Total Maximum Daily Load for the East Gallatin River The Lower Gallatin Planning Area TMDLs and Framework Water Quality Improvement Plan were completed in 2013. The TMDL states: “The City of Bozeman Water Reclamation Facility (WRF) completed an extensive upgrade in fall 2011, in addition to a smaller upgrade completed in November 2007. Existing nutrient loads to the East Gallatin River were calculated using the primary assumption that since October 1, 2011, the WRF is able to treat wastewater to 7.5 mg/L TN and 1.0 mg/L TP. The long-term mean discharge from the facility during the summer period (July 1 – September 30) is 5.39 million gallons per day (MGD) (8.34 cfs). Therefore, the mean continuous nutrient load from the WRF to the East Gallatin River is approximately 336 lbs TN/day and 45 lbs TP/day.” A wasteload allocation is a TMDL term that refers to numeric limits placed on point source discharges of pollution that must be incorporated into NPDES permits. In cases where an EPA-approved TMDL includes a WLA for a point source, either specifically or within a categorical allocation, the permitting authority may make a reasonable potential determination based directly on the fact that an allocation has been established and 4-23 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality assigned to the point source. In this circumstance, it is unnecessary to conduct a separate quantitative reasonable potential analysis during the development of the NPDES permit for that point source, unless there is new information to suggest that the source’s levels of discharge of the pollutant of concern differs significantly from the information used to establish the TMDL WLA. Wasteload allocations in the TMDL were found to have target concentrations that are lower than current limits of technology for treatment of wastewater effluent. MPDES permits provide a regulatory mechanism for implementing the TMDL via the variance process, once nutrient standards are adopted into rule, to address affordability issues and concerns about the limits of treatment technology. The WRF WLAs for TN and TP defined in this TMDL allows phased implementation consistent with the variance process.. DEQ has determined that the East Gallatin River upstream of the WRF exceeds the applicable water quality standards based on application of the TMDL targets and nutrient assessment methodology. This means there is insufficient assimilative capacity in the receiving water for additional nutrient loads above the TMDL target values. The TMDL target values are a numeric translation of the applicable narrative standard. Since these targets are concentrations less than the current limits of treatment technology, the TMDL includes a phased implementation via a variance. The TMDL indicates the WLA will then be set at the current limit of technology or concentration identified from required WRF optimization. This requirement remains until the WRF meets the TMDL WLA or upstream reductions provide assimilative capacity. The EPA recognizes that any TMDL can be revised at any time following due process. A TMDL can be revised upon new data which indicate a revision in the loading capacity (better knowledge of relation between loading and water quality), or deviation from anticipated load reductions. These revisions may be up or down, resulting in less or more control actions needed than originally determined. Some DEQ TMDLs include the statement that TMDLs may be refined as new data become available, land uses change, or as new sources are identified. The regulatory agencies are unlikely to initiate such action. Stakeholders within the watershed would need to petition DEQ and likely fund such an initiative to amend an existing and approved TMDL. NPDES regulations specify that mass based WQBELs are required in permits except when pollutants cannot appropriately be expressed in terms of mass; the applicable standards are expressed in terms of other units; or limits expressed in terms of mass are infeasible. For nutrients, a point source would commonly ask for a seasonal load since nutrients are not toxic and a seasonal averaging period would provide some flexibility in the accounting. The Lower Gallatin TMDL has a WLA that is concentration based; the discharge concentration of TN and TP must be equal or less than the TMDL target concentrations. This has a benefit of allowing loads to increase as the flow increases. However, there is no flexibility with the WRF required to reliably treat to concentrations lower than those in the TMDL. The TMDL refers to this as phased implementation with the variance process being the regulatory mechanism. The regulations give permit writers the discretion to include limits such as concentration-based limits to supplement mass-based WQBELs. NPDES regulations further require that WQBELs be consistent with the assumptions and requirements of any available WLA in a TMDL. 4-24 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality The TMDL states the WLA should be based on the phased implementation concentrations multiplied by the WRF discharge flow at that time (versus the design flow). The CWA states that in the case of POTWs, permit effluent limitations, standards, or prohibitions shall be calculated based on design flow. However, the design flow shall not be inflated or a far future projection, but rather a permitted reasonable measure of near future flows. The TMDL outlines two general paths for developing future WLAs for the WRF: Option 1. WLA is based on the lower value of either the WRF design treatment performance or post 2011 WRF upgrade average discharge concentrations. Option 2. WLA is based on limits of technology or concentration identified from optimization evaluation. In future, follow Option 2 until WRF meets the TMDL WLA or WRF meets the TMDL WLA based on assimilative capacity of the East Gallatin River. The WRF has been optimized for nutrients, but a permit writer could interpret this differently. Coordination with the permit writer to discuss if renewed permit limits will be based on optimized nutrient effluent concentrations will be beneficial. It will also be important to discuss if the permit writer will proceed just with the WLA or will recognize that the TMDL approach is predicated on the variance process. The TMDL suggests eligibility for a variance or phased implementation values under the variance process. Given the long and uncertain regulation of nutrients in the state, it is unclear how a permit writer would proceed and being prepared for the possibility of requesting a variance during the permit renewal process. 4.5 Groundwater Protection Discharge to groundwater is proposed in several of the management alternatives defined in the WRF Management Alternatives Chapter. The following section describes Montana regulations pertaining to effluent groundwater discharge. 4.5.1 General Groundwater Protection Regulations Chapter 122 of Montana DEQ Circular 2 lists standards for the discharge of treated effluent to groundwater via rapid infiltration (RI) systems. RI systems consist of the application of treated effluent to infiltration/percolation (IP) basins or subsurface absorption cells. The use of RI systems for groundwater discharge carries several requirements that could affect the feasibility of groundwater discharge for an entity like the WRF. These include: To proceed with RI discharge, a groundwater discharge permit (MGWPCS) must be obtained from DEQ. It is unknown how a permit writer would consider the TMDL and potential hydrologic connection. The TMDL states, given the groundwater flow direction at the Belgrade WWTP and rapid infiltration percolation beds along with the elevation gradient north of the facility, Ben Hart Creek is the most likely receiving waterbody of the groundwater discharge from the Belgrade WWTP. Belgrade has permit MTX000116 authorizing discharge to ground water. The permit and fact sheet do not address the TMDL. Given recent regulatory development, groundwater hydrologically connected to surface water should be 4-25 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality considered for MPDES surface water permitting rules. DEQ has yet to address this issue. Groundwater monitoring is also required for RI systems. Monitoring wells must be installed near the groundwater discharge, with the number and placement determined by DEQ. Additionally, the RI site location must be protected from flooding and must not be located in the 100-year floodplain of any waterway. The site must also be located a minimum of 500 feet from water supply wells. RI systems must be designed to minimize plugging or other fouling. High quality effluent meeting the following limits is required for subsurface absorption cells: BOD5: < 10 mg/L TSS: < 10 mg/L Turbidity: < 5 NTU Total N: < 5 mg/L The design hydraulic loading rate of an RI system must be directly related to the infiltration, permeability, hydraulic conductivity, and transmissivity of the soil at the proposed site. These parameters must be determined from soils investigations and borings during the design of the RI system. The overall soil permeability should be greater than 0.6 in/hr for a site to be used for infiltration discharge. Hydraulic conductivity must be based on whichever soil layer is found to be the most restrictive at a given site. The design loading rate for an RI system must be based upon the percentages shown in Table 4-5. Table 4-5. Hydraulic Loading Rates in Montana DEQ Circular 2 Test Procedure1 Adjustment Factor for Annual Loading Rate Basin Flooding Test 7 – 10% of minimum measured infiltration rate Air Entry Permeameter & Cylinder Infiltrometers 2 – 4% of minimum measured infiltration rate 1 The methodology for these test procedures are included in the EPA Process Design Manual Land Treatment of Municipal Wastewater Effluents, September 2006 4.6 Site Specific Water Quality Standards The State of Montana allows for and has developed procedures for establishing site- specific surface water quality criteria. These procedures are codified in MCA 75-5-310. Site-specific criteria can be developed for aquatic life if: (1) Notwithstanding any other provisions of this chapter and except as provided in subsection (2), the department, upon application by a permit applicant, permittee, or person potentially liable under any state or federal environmental remediation statute, shall adopt site-specific standards of water quality for aquatic life, both acute and chronic, as the standards of water quality required under 75-5-301(2) and (3). The site-specific standards of water quality must be developed in accordance with the procedures set forth in draft or final federal regulations, guidelines, or criteria. 4-26 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality (2) If the department, based upon its review of an application submitted under subsection (1) and sound scientific, technical, and available site-specific evidence, determines that the development of site-specific criteria in accordance with draft or final federal regulations, guidelines, or criteria would not be protective of beneficial uses, the department, within 90 days of the submission of an application under subsection (1), shall notify the applicant in writing of its determination and of additional procedures that the applicant is required to comply with in the development of site- specific standards of water quality under this section. If there is a dispute between the department and the applicant as to the additional procedures, the board shall, on the request of the department or the applicant, hear and determine the dispute. The board's decision must be based on sound scientific, technical, and available site- specific evidence. 4.6.1 Variances The State of Montana allows for variances from meeting certain water quality standards. These variances may be granted by DEQ consistent with requirements listed in ARM 17.30.661. The department may grant to a permittee a variance from a water quality standard if the department determines in writing that the following conditions are met: (a) The standard is more stringent than the quality of the receiving water; (b) the condition in (a) exists because of anthropogenic contributions of the pollutant to the water body; (c) the condition in (a) cannot reasonably be expected to be remediated during the permit term for which the variance is sought; (d) the discharge to which the variance would apply would not materially contribute to the condition in (a); and (e) one of the demonstrations provided at 40 CFR 131.14(b)(2)(i)(A)(1), which is by this reference adopted and incorporated into this rule, applies. The EPA considers several factors when developing compliance schedules for a community/ municipality to achieve compliance with Clean Water Act (CWA) regulations. EPA’s decision making considers public health, environmental considerations, and a community’s financial capability to meet the obligations. Under 40 CFR 131.10(g), a discharger can demonstrate that obtaining designated uses are not feasible based on: 1. Naturally occurring pollutant concentrations prevent the attainment of the use; or 2. Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State water conservation requirements to enable uses to be met; or 3. Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; or 4. Dams, diversions or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its 4-27 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality original condition or to operate such modification in a way that would result in the attainment of the use; or 5. Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or 6. Controls more stringent than those required by sections 301(b) and 306 of the Act would result in substantial and widespread economic and social impact. 4.6.2 Montana Nutrient Variances Following a number of years of water quality studies and nutrient work group meetings, nutrient criteria discussions in Montana matured to rulemaking in 2014. This followed the passage of two legislative bills providing for water quality variances from numeric nutrient criteria. In 2009, Montana Senate Bill 95 passed and provided for temporary nutrient standards under two conditions: 1) affordability; and 2) limits of treatment technology. In 2011, Montana Senate Bill 367 was passed to provide for nutrient standards variances on a statewide general basis, and also to provide for individual and alternative variances. Larger treatment facilities (flows greater than 1 mgd) were required to meet effluent limits of 1 mg/L TP and 10 mg/L TN based on a monthly average basis. Smaller facilities (flows less than 1 mgd) were required to meet 2 mg/L TP and 15 mg/L TN. In February 2015, EPA approved Montana’s numeric nutrient criteria, general variance, and individual variance provisions. The general variance interim effluent conditions were based on total nitrogen of 10 mg/L and total phosphorus of 1 mg/L. Nutrient Variance Litigation In 2016, the Upper Missouri Waterkeeper (Waterkeeper) sued the EPA over its approval of Montana’s nutrient variance. The lawsuit targeted EPA approval of Montana’s Numeric Nutrient Rule Package and specifically variances, which Waterkeeper asserted violated the federal Clean Water Act and undermined clean water protections for Montana waters. The Waterkeeper’s argument was that variances supplant the numeric standards with weaker, less-protective limits. The Waterkeeper noted that in limited circumstances, EPA can consider a constrained, time-limited variance for very specific reasons and that in some of those instances cost can be a consideration. The Waterkeeper contended that Montana and EPA grossly expanded a very limited regulatory mechanism based on costs to support variances from compliance with numeric nutrient criteria. The Waterkeeper alleged that EPA’s approval of Montana’s numeric nutrient criteria and variance violated the Clean Water Act federal regulations and that EPA’s approval of the variance was arbitrary and capricious. The Federal District Court of Montana issued a ruling that upheld the nutrient variance, but the ruling also confused a number of other issues related to the time of treatment performance requirements under variances. These included the timing for when the Highest Attainable Condition (HAC) condition must be attained with a variance and when ultimate compliance with the in-stream water quality standards must eventually be attained. 4-28 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality In October of 2017, EPA approved the general nutrient variance for 36 Montana dischargers as consistent with the requirements of the Clean Water Act and federal regulations. EPA took no action on the individual variance provisions. The general variance interim effluent conditions expired on July 1, 2017. The general variance interim effluent conditions were revised. For facilities greater than 1 mgd, end-of-pipe requirements reduced effluent concentrations for total nitrogen to 6 mg/L and total phosphorus to 0.30 mg/L. For facilities less than 1 mgd, effluent concentrations were reduced to 10 mg/L of total nitrogen and 1 mg/L of total phosphorus. Lagoons not designed for nutrient removal were specified to maintain long term average performance. In 2019, the Federal District Court ordered that Waterkeeper plaintiff and the defendants including the EPA, DEQ, and intervenors (Treasure State Resources Association of Montana, Montana League of Cities and Towns, National Association of Clean Water Agencies) to meet and confer in good faith to attempt to reach an agreement as to remedies in the lawsuit. The court ruled that DEQ did not act arbitrarily and capriciously when they adopted the variance standard. However, the court found that DEQ did act arbitrarily and capriciously when they set forth a seventeen-year timeline after their first triennial review merely to meet the relaxed criteria of the Current Variance Standard. The Court found it appropriate to seek guidance from the parties as to the timing and scope of the appropriate timeline to achieve prompt compliance with the water quality standards. The court called for a timeline for which attainment of Montana’s Base WQS would be feasible. State Nutrient Legislation Meanwhile, Montana passed legislation that invalidated the numeric nutrient standards. ARM 17.30.660 includes a section that in the event of court rulings or EPA disapproval: If a court of competent jurisdiction declares 75-5-312, MCA, or any portion of that statute invalid, or if the United States Environmental Protection Agency disapproves 75-5-313, MCA, or any portion of that statute, under 30 CFR 131.21, or if rules adopted pursuant to 75-5-313(6) or (7), MCA, expire and general variances are not available, then (1)(e) and all references to DEQ-12A, base numeric nutrient standards and nutrient standards variances in ARM 17.30.201, 17.30.507, 17.30.516, 17.30.602, 17.30.622 through 17.30.629, 17.30.635, 17.30.702, and 17.30.715 are void, and the narrative water quality standards contain in ARM 17.30.637 are the standards for total nitrogen and total phosphorus in surface water, except for the Clark Fork River, for which the standards are the numeric standards in ARM 17.30.631. The state passed a new law based on Senate Bill 358 (SB358) with highlights for the transition of nutrient standards as follows: (1) By March 1, 2022, the department of environmental quality shall adopt rules related to narrative nutrient standards in consultation with the nutrient work group. (2) The rules shall provide for the development of an adaptive management program which provides for an incremental watershed approach for protecting and maintaining water quality, and that: (a) reasonably balances all factors impacting a water body; (b) prioritizes the minimization of phosphorus, taking into account site-specific conditions; and 4-29 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality (c) identifies the appropriate response variables affected by nutrients and associated impact thresholds in accordance with the beneficial uses of the waterbody. (3) In developing the rules in subsection (2), the department shall consider options pertaining to whether the point source is new or existing and whether the receiving water body is considered impaired or unimpaired.” Senate Bill 358 (SB358) also includes a repealer in Sections 9 and 10: Section 9. Repealer. The following sections of the Montana Code Annotated are repealed: 75-5-313. Nutrient standards variances -- individual, general, and alternative. 75-5-314. Confidentiality of base numeric standards and nutrient standards variances. 75-5-319. Compliance schedule for base numeric nutrient standards. Section 10. Repealer. ARM 17.30.660 is repealed. As a result of EPA’s action disapproving DEQ’s general variance rules, DEQ concluded that the non-severability provisions were activated, and thereby eliminated DEQ-12A (Numeric Nutrient Criteria). In response, DEQ agreed to work with stakeholders in a Nutrient Work Group to develop a plan with steps toward using the existing narrative standards to replace the numeric nutrient criteria. In the interim, EPA will continue to use the previous numeric nutrient criteria, until DEQ adopts and EPA approves new rules that are equally scientifically defensible and protective of the applicable designated uses (EPA 2021). EPA’s position is the record contains approved numeric nutrient criteria that cannot now be backstepped and may only be equally replaced. DEQ is challenged with developing new rules that maintain the previous scientific basis behind the numeric nutrient criteria, via a numeric translator for the narrative criterion or other approaches, within the framework of the existing narrative standards. EPA will not approve any proposed rules failing this technical integration and the water quality standards required in the Code of Federal Regulations. The City should anticipate this process will take many years and may not result in less stringent standards than exist today; therefore, the City should continue with proper planning and consideration of alternative approaches to addressing nutrients. The narrative nutrient standards rulemaking process began in 2021 and is on-going. As a result of the removal of the numeric nutrient standards, the state reverted to the narrative nutrient standards. To meet the statutorily required rulemaking deadline of March 1, 2022, draft rules were originally targeted for completion by early November 2021. Six Nutrient Work Group meetings were originally planned, but that meeting plan and schedule have been extended. Ninth Circuit Court of Appeals The defendants in the Waterkeeper lawsuits, including EPA, DEQ and intervenors (Treasure State Resources Association of Montana, Montana League of Cities and Towns, National Association of Clean Water Agencies) appealed the Federal District Court ruling to the US Court of Appeals for the Ninth Circuit. 4-30 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality The Federal District Court issued a Consolidated Order in October 2020 that combined Waterkeeper I (Cause No. CV-16-52) and Waterkeeper II (Cause No. CV-20-27) since they involve the same underlying facts, law, and parties. The federal district court judge issued a stay on February 9, 2021, on the proceedings to await the ruling from the Ninth Circuit Court of Appeals. In 2021, the US Court of Appeals for the Ninth Circuit ruled on the Montana variance case in favor of DEQ and EPA to uphold the nutrient variance. The ruling supports the consideration of compliance costs for a variance, avoids requiring wastewater dischargers to comply with the Highest Attainable Condition (HAC) for effluent quality immediately upon receiving coverage under the variance, and postpones compliance with the in- stream standards until such time that it’s feasible and a compliance schedule is issued. Highlights of the ruling are summarized in the following: Compliance Costs. With regard to allowing the use of compliance costs, the 9th Circuit Court of Appeals agrees that costs can be considered: o “The panel concluded that the EPA’s regulations reasonably interpreted the Clean Water Act as allowing consideration of compliance costs when the agency approves water quality standards and variance requests.” o “We thus conclude that the EPA’s regulations reasonably interpret the Clean Water Act as allowing consideration of compliance costs when the agency approves water quality standards and variance requests.” Timing for Highest Attainable Condition (HAC). With regard to when a discharger must be in compliance with the Highest Attainable Condition (HAC) when operating under a variance, the 9th Circuit Court of Appeals ruled that dischargers do not have to comply with the HAC at the outset of receiving a variance: o “The panel disagreed, and held that the EPA’s variance regulation unambiguously provided that compliance with the highest attainable condition was not required at the outset. The district court did not identify any provision in the EPA’s variance regulation supporting its view that the variance must require compliance with the base water quality standards by the end of the variance’s term. As reflected in the variance at issue here, the EPA’s regulations included numerous features to ensure that dischargers and waterbodies subject to variances continued to improve water quality. The panel concluded that the regulatory framework was consistent with the goals of the Clean Water Act, which as reasonably construed by the EPA, included supporting aquatic life and recreational uses whenever attainable.” o “But those provisions do not state that an individual discharger must be in compliance with the highest attainable condition on day one. Instead, the EPA’s variance regulation unambiguously provides that compliance with the highest attainable condition is not required at the outset.” Time for Compliance with In-stream Standards. With regard to the schedule for compliance with in-stream numeric standards when a discharger must comply 4-31 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality with the Water Quality Based Effluent Limits (WQBELs), the 9th Circuit Court of Appeals ruled that the regulations do not require compliance with the standards by the end of the term of the variance. The court ruled that when compliance with the standards becomes feasible, the state can issue a compliance schedule at that time. o “The district court did not identify any provision in the EPA’s variance regulation supporting its view that a variance must require compliance with the base water quality standards by the end of the variance’s term. We have found nothing in the regulation to support that view either. As just noted, the regulation explicitly states that the term of the variance may last only as long as necessary to achieve compliance with the highest attainable condition—not with the base water quality standards. 40 C.F.R. § 131.14(b)(1)(iv).” o “When attainment of the base water quality standards is feasible within a reasonably foreseeable timeframe, a State may instead use a permit compliance schedule to set a specific deadline by which compliance with the base water quality standards will be achieved. 2022 Earthjustice and Waterkeeper Notice of Intent to Sue On January 11, 2022 Earthjustice and Waterkeeper filed a Notice of Intent to Sue EPA for failure under the Clean Water Act to approve or disapprove Montana’s revised water quality standards in Senate Bill 358. The new lawsuit calls for EPA to intercede over the state Department of Environmental Quality and take control of Montana nutrient standards. 4.6.3 2022 EPA Financial Capability Assessment Guidance On February 16, 2022 EPA issued its proposed 2022 Clean Water Act (CWA) Financial Capability Assessment (FCA) Guidance for public comment. The proposed guidance outlines strategies for communities to support affordable utility rates while planning investments in water infrastructure that are essential for CWA implementation. The Proposed 2022 FCA Guidance describes the financial information and formulas the agency intends to use to assess the financial resources a community has available to implement control measures and timeframes associated with implementation. When finalized, EPA intends for the proposed 2022 FCA to replace the 1997 FCA Guidance to evaluate a community’s capability to fund CWA control measures in both the permitting and enforcement context. The 2022 FCA will also supplement the public sector sections of the 1995 WQS Guidance to assist states and authorized tribes in assessing the degree of economic and social impact of potential WQS decisions. Financial capability is one of many factors EPA considers when developing schedules for implementation of long-term CWA control plans and calls for achieving compliance as soon as practicable. The public health and environmental considerations that EPA assesses when developing CWA implementation schedules include environmental justice and mitigation of environmental and public health impacts in low-income and overburdened communities. EPA also encourages communities to utilize integrated planning and innovative technologies, such as green infrastructure, to achieve compliance 4-32 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality in a timely, flexible, and cost-effective manner. The proposed 2022 Financial Capability Assessment Guidance is intended to standardize EPA’s determination of financial capability to implement control measures required for compliance. Lowest Quintile of Household Income and Poverty Levels The proposed guidance adds consideration of the lowest quintile income and poverty prevalence within a service area to the 1997 FCA Guidance using the Residential Indicator (RI) and the Financial Capability Indicator (FCI). The proposed guidance utilizes dynamic financial and rate models that evaluate the impacts of debt service on customer bills. Additional information, such as a community’s total water costs (i.e., costs for wastewater, stormwater, and drinking water infrastructure investment) may also be submitted and considered when negotiating the length of an implementation schedule for CWA obligations. Funding Sources and Financing EPA plans to work with communities to identify funding sources and financing strategies that can be used to reduce costs over time. The availability of funding should be part of a community’s financial capability assessment where there are poverty concerns. The proposed FCA recommends submittal of a Financial Alternatives Analysis documenting that all feasible steps have been taken to mitigate impacts on the lowest quintile. This step should be a precursor to EPA’s consideration of an extended compliance schedule or water quality standard (WQS) revisions based on poverty considerations. Other Financial Metrics The proposed guidance includes specific instructions for consideration of other metrics which may be considered to support an extended implementation schedule, as follows: 1. Drinking Water Costs a. EPA recognizes that both clean water and drinking water costs are often paid for through charges on a single bill. For this reason, the proposed 2022 FCA more explicitly provides guidance on incorporating a community’s drinking water obligations into an FCA evaluation. 2. Potential Bill Impact Relative to Household Size a. EPA has found that household size impacts the maximum potential bill. As household size increases, monthly water usage increases. One-person households generally use significantly less water, but also have fewer financial resources. Displaying data by household size provides a more nuanced view of the impact of costs based on likely usage. 3. Customer Assistance Programs CAPs) a. Households on fixed or lower incomes, as well as households that face a temporary crisis such as a job loss or illness, may have difficulty paying water and sewer bills. Many utilities have seen an opportunity to meet specific customer needs through developing CAPs. These programs can provide households short-term or long-term reductions through a Bill Discount, Flexible Terms, Lifeline Rate, Temporary Assistance, and Water Efficiency 4-33 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality assistance programs. These programs typically determine eligibility of individual households relative to a percentage of the Federal Poverty Level. 4. Asset Management Costs a. Asset management is a critical foundation for understanding near- and long- term operational and capital needs. A community may provide information on its asset management costs if the community can verify that asset management practices are being implemented. Submission of information verifying asset management practices should allow EPA to confirm that the appropriate asset management costs are being included as part of a community’s FCA. 5. Stormwater Management Costs a. EPA’s continued commitment to Integrated Planning recognizes that many local governments and authorities have increased investments in their stormwater infrastructure through capital projects to rehabilitate existing systems, improve operation and maintenance, reduce impermeable surfaces, make use of green infrastructure, and address additional regulatory requirements. As programs are implemented to improve water quality and attain CWA objectives, many state and local government partners find themselves facing difficult economic challenges with limited resources and financial capability. Submission of stormwater management costs should allow EPA to confirm that the appropriate stormwater costs are included as part of a community’s FCA and provide EPA with the appropriate assurances that those expenditures will be made. 6. Comparisons to National Data a. EPA encourages communities to provide additional financial and demographic information regarding the community’s financial capability to implement compliance obligations or to evaluate water quality standards decisions. Other metrics submitted by a community may include unemployment rates, debt service coverage ratio, debt to income ratio, percent population decline, population trends, state or local legal restrictions on property taxes, other revenue streams, or debt levels. Implementation Schedule The proposed Financial Capability Assessment Guidance calls for a community to consider public health, environmental justice, and environmental impacts in addition to financial capability. Communities should consider the following when developing implementation schedules to construct control measures to meet CWA: 1. Environmental and Public Health Considerations a. Discharges to Sensitive Areas: Sensitive areas include the Outstanding National Resource Waters; National Marine Sanctuaries; waters with threatened or endangered species and their habitat; waters with primary contact recreation; public drinking water intakes and their designated protection areas; and shellfish beds. Giving highest priority to sensitive areas might mean in some cases that discharges to non-sensitive areas would be 4-34 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality addressed later in the implementation schedule than would be the case under a normal engineering and construction schedule. b. Use Impairment: Priority should be given to receiving waters that experience recurring adverse impacts from the community on aquatic life, human health, or aesthetics. Giving highest priority to certain use-impaired waters might mean that discharges to other waters would be addressed later in the implementation schedule than would be the case under a normal engineering and construction schedule. c. Public Health: Reducing exposure to raw sewage should be a priority in any schedule that is negotiated with the community to protect public health. d. Environmental Justice: The guiding principle of environmental justice is the fair treatment and involvement of all people regardless of race, color, culture, national origin, income, and educational levels with respect to the development, implementation, and enforcement of protective environmental laws, regulations, and policies. Communities can use EPA’s EJSCREEN tool when assessing whether there may be environmental justice concerns within their service area, such as areas with: people of color and/or low-income households; potential environmental quality issues; and/or existing environmental quality impairments in an area with demographic factors that suggest the community is sensitive to environmental pollution. 2. Schedule Development a. EPA has developed schedule benchmarks to account for the consideration of the new critical metric, the Lowest Quintile Poverty Indicator LQPI Score. EPA recommends that, absent consideration of Other Metrics, it is financially feasible for communities to implement measures for compliance with the CWA that would have a “medium” impact within 15 years and to implement measures that would have a “high” impact within 20 years. In unusually high impact situations, an implementation schedule up to 25 years may be negotiated with state NPDES and EPA authorities based on consideration of Other Metrics. EPA Request for Public Comment EPA is proposing two simplified options to assess the severity and prevalence of poverty in a community’s service area for consideration. Both options consider the community’s lowest quintile income as benchmarked against the national lowest quintile income, as well as five poverty indicators. EPA’s proposed Option 1 would add a single new metric, the Lowest Quintile Poverty Indicator (LQPI), to be considered with the Residential Indicator (RI) and Financial Capability Indicator (FCI). The LQPI would combine a lowest quintile income element with poverty indicator elements. To ensure that both the severity and prevalence of poverty are reflected in the LQPI metric, EPA would give equal weight to the LQI (50%) and the five poverty indicators (weighted at 10% each for a total of 50%). Under EPA’s Proposed Option 1, RI and FCI would be combined in a matrix to determine an FCA Score. An Initial LQPI Score would be calculated, and adjusted based on a Financial Alternatives Analysis, if appropriate. Finally, 4-35 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality the FCA Score and Final LQPI Score would be combined in the Expanded FCA Matrix to provide the final FCA result. EPA’s proposed Option 2 would add two new metrics, the Lowest Quintile Income Indicator (LQII) and the Poverty Indicator (PI) to be considered with the Residential Indicator (RI) and Financial Capability Indicator (FCI). The LQII is the lowest quintile income metric; and the PI is a separate metric based on the average scores of the five prevalence of poverty indicators. The LQII and PI would be each calculated and combined in a matrix to determine the final FCA result. Bozeman Financial Capability Analysis To determine whether the City of Bozeman is eligible for a variance based on widespread economic and social impact, the 2022 EPA Financial Capability Assessment Guidance was evaluated using current demographic and economic figures for Bozeman. EPA’s proposed Option 1 was used in the analysis. There are several respective matrices and calculations included in the full analysis. The first part of the analysis considers the Residential Indicator (RI) and the Financial Capability Indicator (FCI) from EPA’s prior 1997 FCA Guidance. In the first respective matrix, the RI is compared against the FCI to calculate an overall community burden. The RI calculates the cost per household of a municipality’s wastewater program as a percentage of median household income. The FCI evaluates the overall fiscal health of the municipality by comparing its financial benchmarks to national norms. The RI and FCI results are brought together in the first matrix to determine the burden on the community (high, medium, or low). Bozeman’s sewer rates were used to assess the cost per household. Current monthly sewer rates in 2020 were $19.58 plus $3.28/HCF. Using the 74 gpcd flow calculated in Chapter 3, and 2.17 people per dwelling unit (2015 WWFPU), the average monthly sewer cost for a residential household comes to approximately $41. When compared to the current median household income (MHI) of $55,569, an RI of 0.89% is calculated. The FCI considers a number of financial benchmarks. These benchmarks are shown in Table 4-6, and the footnotes document the respective calculations. Data were taken from the Bureau of Labor Statistic’s most recent figures and from the City of Bozeman Comprehensive Annual Financial Report, for the fiscal year ended June 30, 2020. Bozeman’s score (Strong, Mid-Range, Weak) is highlighted for each indicator. Bozeman scored “Strong” for each financial indicator except MHI, which was “Mid-Range”. This translates to an FCI score of 2.83. 4-36 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-6. Financial Capability Indicators for Bozeman – – ’ – - - Property Tax - - – ’ - ’ The FCI score and RI impact are placed in EPA’s Matrix 1 in Table 4-7 below. The two scores yield a Low Burden for Bozeman. Table 4-7. Matrix 1 Information Indicator Weak (1)Mid Range (2)Strong (3) AAA A (S&P) or BBB (S&P) or BB D (S&P) or Bond Rating 1 Aaa A (Moody’s) or BAA (Moody s) or Ba C (Moody s) or AAA A (Fitch Ratings) BBB (Fitch Ratings) BB D (Fitch Ratings) Overall Net Debt as a Percent of Full Market Below 2%2% 5%Above 5% Property Value 2 Unemployment Rate 3 More than 1 Percentage Point Below the National Average ± 1 Percentage Point of National Average More than 1 Percentage Point Above the National Average Median Household More than 25% Above ± 25% of Adjusted More than 25% Below Income4 Adjusted National MHI National MHI Adjusted National MHI Property Tax Revenues as a Percent of Full Below 2%2% 4%Above 4% Market Property Value 5 Above 98%94% 98%Below 94%Collection Rate 6 Notes: 1 Moody s General Obligation Bond Rating for Bozeman is Aa1 2 0.53% General Obligation Debt: $45.4 million Full Market Value of Property: $8,596,253,775 3 Bozeman Unemployment Rate 3% Below US Average at Time of Writing 4 15.4% Below US Avg Bozeman MHI: $55,569 National MHI: $65,712 5 0.27% Full Market Value of Property: $8,596,253,775 2020 Property Tax Collection: $23,381,671 6 Property Tax Collection Rate:99.32% Residential Indicator Financial Capability Indicator Low Impact Mid-Range High Impact (Below 1.0%) (1.0% to 2.0%) (Above 2.0%) Strong (Above 2.5) Low Burden Low Burden Medium Burden Mid-Range (1.5 to 2.5) Low Burden Medium Burden High Burden Weak (Below 1.5) Medium Burden High Burden High Burden 4-37 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality For the next part of the analysis, the lowest quintile poverty indicator (LQPI) RI is calculated. This portion of the analysis is included as a new addition in the 2022 FCA. Similar to the FCI, the LQPI considers a number of lowest income financial benchmarks. These benchmarks are shown in Table 4-8, and the footnotes document the respective calculations. Data were taken from current US Census Bureau figures. The overall LQPI score for Bozeman is 2.3, indicating Medium Impact. No statistics were available to calculate LQPI #5 for Bozeman, and so this criterion was assumed to be greater than 1% given the large growth experienced in Bozeman in recent years. 4-38 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-8. Lowest Quintile Poverty Indicators for Bozeman Indicator Strong (3) Mid Range (2) Weak (1) Weight Actual Value Score More than 25% More than 25% More than 25% More than 25%±25% of national 16 and Over in Civilian Labor Force6 Score for LQPI #1 2 Average Score for LQPI #2 to #6 (Sum of 2 through 6 divided by 5) 2.6 LQPI #1 Upper Limit of Lowest Quintile Income 1 More than 25% above national LQI ±25%of national LQI More than 25% below national LQI 50% 2 1 LQPI #2 Percentage of Population with Income Below 200% of Federal Poverty Level 2 LQPI #3 Percentage of Population Receiving Food Stamps/SNAP Benefits 3 More than 25% below national value More than 25% below national value ±25%of national value ±25%of national value More than 25% above national value More than 25% above national value 10% 10% 2 3 0.20 0.30 LQPI #4 ±25%of nationalPercentage of Vacant below national above national 10% 2 0.20valueHouseholds4valuevalue LQPI #5 Trend in Household >1%0%-1%<0%10% 3 0.30 Growth5 LQPI #6 Percentage of Unemployed Population below national above national 10% 3 0.30valuevaluevalue 2.3Initial Lowest Quintile Poverty Indicator Score (Sum of two lines above divided by 2) Initial Lowest Quintile Poverty Indicator Benchmarks Low Impact (Above 2.5) Medium Impact (1.5 to 2.5) High Impact (Below 1.5) Medium Impact Notes: 1 Bozeman LQI: $30,955 National LQI: $26,685 2 Bozeman: 26.5% National: 29.8% 3 Bozeman: 4.1% National: 11.4% 4 Bozeman: 11.2% National: 11.6% 5 Unknown, assumed >1% 6 Bozeman: 1.7% National: 3.4% The results of the first two calculations (Table 4-7, Table 4-8) are combined in a final matrix (Table 4-9) to calculate the overall financial burden on Bozeman. At current rates and metrics, Bozeman’s overall financial burden is currently low. For the relative burden to increase, rate increases (that increase the RI) would be required, and/or the financial benchmarks used in the matrices would need to become weaker. 4-39 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-9. Third Matrix Information Final Lowest Quintile Poverty Indicator Score FCA Burden (RI and FCI) Low Burden Low Burden Low Burden Medium Burden Medium Burden Low Burden Medium Burden High Burden High Burden Medium Burden High Burden High Burden Low Burden Medium Burden High Burden However, compliance schedules for CWA obligations are not rigidly set based on a burden designation of low, medium, or high. EPA evaluates financial capability on a continuum and recognizes that the relative burden may not provide the most complete picture of a community’s ability to meet CWA obligations. For example, a community with an RI of 1.1% and a community with an RI of 1.9% would receive different compliance schedules from EPA, even though both RIs fall within the Mid-Range impact zone. In the future, slight rate increases or weakening of financial benchmarks could increase the likelihood that Bozeman receives more generous compliance schedules from the EPA for making infrastructure improvements. 4.6.4 Nutrient Trading Circular DEQ-13 outlines the documentation needed to perform a nutrient load trade within a watershed. In general, upstream trades are encouraged and the wasteload allocation from the respective TMDL must be used. The nearby Riverside Lagoon presents an opportunity for the WRF to receive a nutrient trade credit in their discharge permit. The lagoon has been leaking wastewater to the East Gallatin River for many years, and the area’s wastewater will soon be routed to the WRF for treatment instead. A previous evaluation by HDR determined that the WRF should request a nutrient trade credit of approximately 2.9 lb/day total phosphorus and 14.23 lb/day total nitrogen for treating the Riverside wastewater. The TP trade value is slightly lower than the TMDL allocation (the trade is conservative relative to the TMDL), but it is based on updated information regarding the actual lagoon discharge rate and total phosphorus concentration. While not a large number, 2.9 lb/day TP would be substantial if treatment to the limits of technology is required in a future permit, and the trade value is used in the planning scenarios in Table 4-19. When the calculated trade values were previously discussed with DEQ, DEQ countered with smaller values for both nitrogen and phosphorus. 4.7 Nutrient Removal 4.7.1 Nitrogen Excessive nitrogen concentrations in natural surface water bodies can lead to water quality problems due to the toxicity of ammonia to aquatic biota and the role that nitrogen plays in algae proliferation. Effluent ammonia nitrogen limitations are included in the WRF discharge permit. The current total nitrogen limitations were introduced in the 2006 permit and continue to remain in effect. The 2012 permit fact sheet states that the limits were crafted based upon facility performance, meaning pre 2011, in anticipation of the 4-40 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality completion of a formal TMDL and WLA. As these measures remain in regulatory flux, the existing nutrient limits from the 2012 permit remain unchanged. 4.7.2 Phosphorus Excessive phosphorus concentrations in natural surface water bodies can lead to water quality problems due to the role that phosphorus plays in algae proliferation and the subsequent dissolved oxygen and pH issues the algae growth causes. The current total phosphorus limitations were introduced in the 2006 permit and continue to remain in effect. The 2012 permit fact sheet states that the limits were crafted based upon facility performance, meaning pre 2011, in anticipation of the completion of a formal TMDL and WLA. As these measures remain in regulatory flux, the existing nutrient limits from the 2012 permit remain unchanged. 4.7.3 Nutrients: Historical Perspective Historical nutrient influent data and effluent nutrient performance are examined in this section. Trends for these parameters are evaluated and discussed. Influent Influent data for flow, nutrients, and CBOD are shown in Table 4-10. Nitrogen and phosphorus concentrations at the upper end of the respective observed ranges are about 20 to 30 percent greater than the average respective concentrations. Nutrient loading into the Bozeman WRF varies depending upon the time of day, the day of the week, and the month. Trends in influent loading are discussed in detail in Chapter 3. Table 4-10. Historical Perspective 2016 to 2020: Influent to Bozeman WRF Parameter Average 95th Percentile 99th Percentile Flow (mgd) 5.65 7.53 9.15 Total Nitrogen (mg/L) 37.96 45.62 47.55 Total Phosphorus (mg/L) 4.97 5.98 6.34 Ammonia as N (mg/L) 23.06 38.12 59.80 Carbonaceous Biochemical Oxygen Demand (CBOD) (mg/L) 218 308 395 --- Bozeman’s water supply exhibits high background concentrations of phosphorus. Statistics for the phosphorus concentrations measured at the Bozeman drinking water treatment plant are shown in Table 4-11. The ambient background concentrations for phosphorus in the East Gallatin River are also generally high relative to elsewhere and are understood to be linked to local volcanic geology. The phosphorus concentrations in Bozeman’s treated water supply are lower than in the WRF influent, which includes the addition of wastes, but are greater than those of the receiving water in the East Gallatin which includes water from a variety of sources. Nutrient related receiving water data are shown in Table 4-14. 4-41 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-11. Historical Perspective 2016 to 2020: Drinking Water Phosphorus Data (mg/L) Period Average 95th Percentile 99th Percentile – -- --- June through September 0.145 0.215 0.227 July through September 0.157 0.275 0.359 Period of Record (2018 2019) 0.136 0.215 0.328 Effluent Nutrient related WRF effluent data are shown in Table 4-12. Nitrogen and phosphorus concentrations at the upper end of the respective observed ranges are about 150 to 500 percent greater than the average respective concentrations. Treatment performance can vary widely depending upon influent loading, operations, weather, seasonality, and other factors. Trends relating to seasonality are shown by the monthly 95th percentile statistics in Table 4-13; however, using data from the previous five years integrates changes that have occurred during that period. These changes include extensive development providing additional influent, as well as treatment process changes such as alterations in the solids processing. Visualization of the data over the five years is provided by Figure 4-3 and Figure 4-4 for nitrogen, and by Figure 4-5 and Figure 4-6 for phosphorus. Table 4-12. Historical Perspective 2016 to 2020: Effluent from Bozeman WRF Parameter Average 95th Percentile 99th Percentile Flow (mgd) 5.65 7.53 9.15 Total Nitrogen (mg/L) 6.20 9.97 11.53 Total Phosphorus (mg/L) 0.33 1.12 1.60 Ammonia as N (mg/L) 0.35 1.26 2.07 Nitrate + Nitrite as N (mg/L) 4.56 7.79 8.91 Carbonaceous Biochemical Oxygen Demand (CBOD) (mg/L) 1.96 3.99 5.09 4-42 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-13. Historical Perspective 2016 to 2020: Effluent from Bozeman WRF, 95th Percentile Month Flow (mgd) Total Nitrogen (mg/L) Total Nitrogen (lb/day) Total Phosphorus (mg/L) Total Phosphorus (lb/day) January 5.70 11.5 532 0.74 42 February 5.85 10.9 543 0.98 49 March 7.66 9.9 580 1.22 74 April 9.67 9.2 553 1.35 78 May 8.85 10.4 730 1.42 100 June 7.21 7.5 532 1.04 73 July 6.48 5.2 341 0.16 11 August 5.98 6.4 344 0.31 16 September 6.66 5.9 310 1.12 53 October 6.37 8.1 426 0.72 35 November 6.32 7.8 407 0.69 35 December 5.93 9.3 537 0.37 19 June - September 6.69 6.2 347 0.86 46 October - May 7.90 10.5 555 1.18 68 16 14 12 • 'g; 10 ... .s ~ 0 8 i:.: ~ C: .. ::, iE 6 w 4 2 0 1/1/2016 --------------------- • f • .. • Effluent Flow • Effluent TN • • •• 1 t • • j. • 1/1/2017 1/2/2018 1/3/2019 Date • • • • • • 1/4/2020 • • • •• 14 12 10 -:; ..... 8 00 E z ... ~ C: .. ::, iE w 4 2 0 Figure 4-3. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Nitrogen Concentrations 4-43 16 14 12 'c" 10 bO .s ~ 0 8 u: 1: ., ::, iE 6 w 4 • • • 2 0 1/1/2016 16 14 12 'c" 10 bO .s • ~ 0 8 u: ~ C: ., ::, iE 6 w 4 • 2 • • • , 1/1/2017 • • Effluent Flow • EffluentTN Load • • 1/2/2018 1/3/2019 Date • Effluent Flow • Effluent TP • • • + . ~ • • • ., • .... -· ' .. :~. • • • • I 900 800 700 • I 600 -"C ...... • • ~ 500 -g 0 __, 2 400 I- ~ C: ., ::, iE 300 w f • • 200 • •• 100 0 1/4/2020 • 3 2.5 2 :::. ...... bO .s Q. 1.5 I- ~ C: ., ::, iE w • • 0.5 0 ~ Ji 1\.Jl#i ' ~-------~-------~--~-----~-------~-------~ 0 1/1/2016 1/1/2017 1/2/2018 1/3/2019 1/4/2020 Date Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Figure 4-4. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Nitrogen Loads Figure 4-5. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Phosphorus Concentrations 4-44 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Figure 4-6. Historical Perspective 2016 to 2020: Effluent Flow and Effluent Total Phosphorus Loads Receiving Water The Bozeman WRF is authorized to discharge to the East Gallatin River. Nutrient related receiving water data is shown in Table 4-14. Table 4-14. Historical Perspective 2016 to 2020: East Gallatin River Water Quality Data Parameter Average 75th Percentile 95th Percentile 99th Percentile • Effluent Flow • EffluentTP Load 16 160 • 14 140 • 12 120 • 'c" 10 bO 'c" 100 ~ .s ,:, ~ 0 8 u: .. 0 80 __, Q. 1: I-... ., C ::, ., iE 6 w 60 ::, ~ • • 4 • 40 • • • • ..,, ,s 0 1/1/2016 1/1/2017 1/2/2018 1/3/2019 1/4/2020 Date --- Total Nitrogen (mg/L) 0.330 0.453 0.640 0.640 Total Phosphorus (mg/L) 0.025 0.026 0.046 0.047 Ammonia as N (mg/L) 0.032 -0.050 0.050 Nitrate + Nitrite as N (mg/L) 0.171 -0.420 0.420 Orthophosphorus (mg/L) 0.017 -0.035 0.049 Carbonaceous Biochemical 2.4 -3.00 3.00 Oxygen Demand (CBOD) (mg/L) 4.7.4 Nutrients: Current Regulatory Trends for the East Gallatin River Current regulatory trends for nutrients in the East Gallatin River and Montana are discussed in this section. The current trends provide information about existing nutrient management. Permitting The Bozeman WRF is authorized to discharge under the effluent limitations shown in Table 4-15. The effluent limitations are seasonal with average monthly and maximum 4-45 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality daily load limits. The 2012 permit fact sheet indicates that historical nutrient removal performance (pre WRF upgrade) was the basis for the current permit. The basis for the future permit renewal will be influenced by a number of current DEQ rules and policies, which are summarized in Table 4-16. The East Gallatin River has a nutrient total maximum daily load (TMDL) with a wasteload allocation (WLA) for the Bozeman WRF that is lower than current treatment technology. For reference, treatment technologies and corresponding nutrient reduction concentrations are shown in Table 4-17. The numeric criteria remain in flux, and two options for the WLA were included in the TMDL. It is indicated that Option 2 will be followed in the future, even if Option 1 is exercised during the next permit renewal. Option 1. WLA is based on the lower value of either the WRF design treatment performance or post 2011 WRF upgrade average discharge concentrations. Option 2. WLA is based on limits of technology or concentration identified from optimization evaluation. In future, follow Option 2 until WRF meets the TMDL WLA or WRF meets the TMDL WLA based on assimilative capacity of the East Gallatin River. The low WLAs present a challenge for projecting effluent limitations for the permit renewal. The WRF WLAs for TN and TP in the TMDL assume that a constant effluent concentration will be maintained as flows increase. However, using current nutrient removal performance to justify future limits doesn’t consider that influent flows and concentrations will increase due to ongoing development in Bozeman, and past WRF performance is unlikely to provide an indication for future performance. Table 4-15. Current MPDES Permit Nutrient Effluent Limitations Parameter Period Average Monthly Limit (lb/d) Average Weekly Limit (lb/d) Maximum Daily Limit (lb/d) June 1 – Sept 30 783 971 Total Nitrogen Oct 1 – May 31 864 1,072 -- -- -- -- Total Phosphorus Oct 1 – May 31 170 211 June 1 – Sept 30 160 199 4-46 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-16. Current Trends 2020: DEQ Rules and Policies that Could Affect Future Permit Basis TN (mg/L) TP (mg/L) - – -- – -- -- -- Source: DEQ 2013. Lower Gallatin Planning Area TMDLs & Framework Water Quality Improvement Plan TMDL WLA end of pipe (DEQ 2013) Table 6-3 Nutrient Targets ≤0.300 ≤0.040 TMDL Phased WLA Scenario 2 (DEQ 2013) pg. 6 55 numeric nutrient standards not adopted into rule WRF performance, transitioning to TN limits of technology WRF performance, transitioning to TP limits of technology MCA 75-5-313 Nutrient standards variances individual (3) Case-by case Case-by case MCA 75-5-313 Nutrient standards variances alternate (10) Case-by case capped by current Case-by case capped by current DEQ Memo 10/18/2019 performance performance Intake credits due to the high phosphorus in the drinking water Unknown Unknown Water Pollution Control Advisory Council 1/10/2020 Nutrient Trading Department Circular DEQ-13 Case-by case Case-by case Septic Offset Department Circular DEQ-4 Case-by case Case-by case Table 4-17. Current Trends 2020: Treatment Technology Capabilities Treatment Total Nitrogen (mg/L) Total Phosphorus (mg/L) Typical Municipal Raw Wastewater 25 to 35 4 to 8 Secondary Effluent (No Active Nutrient 20 to 30 4 to 6Removal) Typical Advanced Treatment Nutrient Removal ~10 ~1 (BNR) Enhanced Nutrient Removal (ENR) 4 to 6 0.25 to 0.50 Limits of Treatment Technology 3 to 4 0.03 to 0.07 Typical Instream Nutrient Criteria 0.1 to 0.6 0.010 to 0.050 Source: Clark, et.al., 2010 Nutrient Management: Regulatory Approaches to Protect Water Quality, Volume 1 – Review of Existing Practices. WERF NUTR1R06i 4.7.5 Nutrients: Future Looking It is difficult to foresee future rules and policies, influent loading, and effluent treatment for nutrients. Rule and policy changes, land use changes, loadings from non-point sources, and drought or flow changes from climate change can impact future conditions for nutrient management. Additionally, DEQ’s numeric nutrient standards continue to be the subject of current litigation, which complicates planning efforts considerably. Conditions that could impact the receiving water are shown in Table 4-18. 4-47 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-18. Future Looking 2020 to 2040: Receiving Water Conditions Issue Comments Rules and Policies Changes Pending legal litigation Climate, Drought, Storm Intensity, and Snowmelt Changes affecting Flow General variance and performance not based on local receiving water conditions. Alternative variance could be impacted. General variance and performance not Flow/Land Use/Nonpoint source based on local receiving water conditions. controls/Stormwater Changes affecting Water Quality Alternative variance could be impacted. Given the uncertainty surrounding future nutrient management, scenarios were developed to assess potential permitting outcomes based on the current regulations summarized in Table 4-16. The potential scenarios and outcomes are shown in Table 4-19, and include projected average monthly and max day permitted loads. The equivalent concentrations for these loads at flows of 8.5 mgd and 14.6 mgd are included for reference. The outcomes range from a stringent TMDL wasteload allocation to a favorable site-specific variance. The projected permit limits in the table are used to develop best-case and worst- case nutrient permitting outcomes for the effluent management alternatives discussed in Chapter 5. 4-48 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-19. Future Looking 2020 to 2040: Bozeman WRF Planning Scenarios Condition Scenario TN or TP Flow (mgd) = 8.5 Flow (mgd) = 14.6 Average Monthly Limit Max Day Limit Average Monthly Limit Max Day Limit mg/l CV=0.6 C*1.55 AML lb/day mg/l CV=0.6 C*2.13 MDL lb/day mg/l CV=0.6 C*1.55 AML lb/day mg/l CV=0.6 C*2.13 MDL lb/day ID No Description Regulation Bold is reference value; Italic is computed equivalent Design Conditions 0a 2006 Facility Plan Design capacities as concentrations TN 7.5 11.6 825 7.5 16.0 1,133 n/a TP 1.00 1.55 110 1.00 2.13 151 Existing Conditions 0b Current Permit Effective MPDES Permit Effluent limitations in loads TN 7.1 11.0 783 6.4 13.7 971 n/a TP 1.50 2.26 160 1.30 2.81 199 Highest Effluent Limits 1 Individual Variance (Site specific variance) (previously prepared request) TMDL Variance Scenario 1 (DEQ 2013) p.6-55 numeric nutrient standards adopted into rule MCA 75-5-313 Nutrient standards variances – individual (3) Case-by-Case TN 7.1 11.0 783 6.4 13.7 971 4.1 6.4 783 3.7 8.0 971 TP 0.30 0.47 33 0.30 0.63 45 0.17 0.27 33 0.17 0.37 45 | 2a Performance Cap (with projected performance) Unknown, possible future regulation TN In between In between TP | 2b Performance Cap (at performance) TMDL Variance Scenario 2 (DEQ 2013) p.6-55 numeric nutrient standards not adopted into rule TN 6.3 9.7 687 6.3 13.3 944 3.6 5.6 687 3.6 7.8 944 TP 0.66 1.02 72 0.66 1.40 99 0.38 0.59 72 0.38 0.81 99 | 3 Limits of Treatment Technology Tetra Tech Memorandum 10/21/2016 State of MT WW system nutrient reduction cost estimates TN 4.0 6.2 440 4.0 8.5 640 4.0 6.2 755 4.0 8.5 1,037 TP 0.07 0.11 8 0.07 0.15 11 0.07 0.11 13 0.07 0.14 17 ↓ 4 Assimilative capacity with nutrient trade TMDL WLA end of pipe (DEQ 2013), Options 1 & 2 Table 6-3 Nutrient Targets Nutrient Trading Department Circular DEQ-13 TN 0.3 0.5 33+ 0.3 0.6 45+ 0.3 0.4 54+ 0.3 0.6 75+ TP 0.04@mix 0.065 0.10 7+ 0.065 0.14 10+ 0.053 0.08 10+ 0.054 0.11 14+ Lowest Effluent Limits 5 TMDL wasteload allocation (worse case) TMDL WLA end of pipe (DEQ 2013), Options 1 & 2 Table 6-3 Nutrient Targets TN 0.3 0.5 33 0.3 0.6 45 0.3 0.4 54 0.3 0.6 75 TP 0.04 0.10 4 0.04 0.14 6 0.04 0.06 7 0.04 0.08 10 4-49 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality 4.8 Biomonitoring and Whole Effluent Toxicity Testing Biomonitoring and whole effluent toxicity testing are methods of examining the impact of discharge from wastewater treatment facilities on water quality. Biomonitoring is the use of a biological entity as a detector and its response as a measure to determine environmental conditions. As the regulatory approach shifts from technology based permitting to water quality based permitting, biomonitoring and whole effluent toxicity tests are likely to increase in importance in the permitting and operation of wastewater treatment facilities. These biological tools can be used to develop specific chemical criteria for pollutants not addressed directly in the rules, or to demonstrate a difference between the perceived toxicity of a chemical and the actual toxicity in a specific receiving stream. The City is currently required to follow a program of chronic and acute whole effluent toxicity tests. These tests are included in the MPDES permit requirements to determine if the effluent affects the survival of certain test organisms. Initial definitive tests performed are of Pimephales promelas or Ceriodaphnia dubia. If no toxic effects are seen during the initial test, screening tests continue to be performed quarterly. If a statistically significant difference between the control and the test organisms indicates effluent toxicity, then further tests are performed monthly. 4.9 Biosolids Management Under 40 CFR 122 and 124, future drafts of MPDES permits for publicly owned wastewater treatment facilities treating domestic sludge will include sewage sludge disposal conditions. Regulations regarding biosolids management are outlined in 40 CFR 503 - Standards for the Use or Disposal of Sewage Sludge. Chapter 503 gives general requirements, pollution limits, management practices, operating standards, and monitoring and reporting requirements for land application and surface disposal of biosolids. The disposal of biosolids produced in the treatment process varies from community to community. Regulations regarding general requirements and management practices exclude “sewage sludge sold or given away in a bag or other container for land application” (40 CFR 503.10(e)), and thus would not apply to compost. However, biosolids sold or given away in such a form still must meet the pollutant concentration requirements in section 503.13. The City biosolids is governed by EPA Biosolids General Permit Authorization Number MTG650008. Biosolids management as it pertains to the WRF is discussed in Chapter 8. 4.10 Air Toxics 4.10.1 The Clean Air Act and Rules for the Control of Air Pollution in Montana The emission of air pollutants is regulated under the Clean Air Act, the Clean Air Act Amendments of 1990, and the Rules for Control of Air Pollution in Montana. The Clean Air Act is implemented and enforced by the state with oversight from EPA. Title V of the 4-50 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Clean Air Act requires any major stationary source of air pollution to submit a permit application and conform to certain regulations regarding the control of emissions from the source. The WRF is not regarded as a major source and is not subject to Title V permitting. The Clean Air Act includes national air quality standards for criteria pollutants including nitrous oxides (NOx), volatile organic compounds (VOCs), particulate matter of diameter less than 10 m (PM10), total suspended particulate (TSP), sulfur oxides (SOx), ozone (O3), carbon monoxide (CO), and lead (Pb). Montana does not include VOCs in its list of criteria air pollutants, but instead designates ozone, of which VOCs are often used as potential indicators, and fluorides. Hazardous air pollutants which “present, or may present, through inhalation or other routes of exposure, a threat of adverse human health effects or adverse environmental effects” are also included in section 112(b)(2) of the Clean Air Act. Hazardous air pollutants that may routinely be released from wastewater treatment facilities include hydrogen sulfide (H2S), chlorine, and specific VOCs such as benzene. Other criteria pollutants can be of concern when engine generators are present. Montana requires permit applications to be filed for Tier I sources, which are sources located at major facilities. A facility is defined as the combined sources that emit air pollutants, belong to the same industrial grouping, are located on one or more contiguous or adjacent properties and are owned or operated by the same person or by persons under common control. A facility is considered major if it emits or has the potential to emit 10 tons per year or more of any hazardous air pollutant, 25 tons per year or more of any combination of hazardous air pollutants, or 100 tons per year or more of any air pollutant. Permits must be obtained for the operation of a Tier I facility, or for modification and construction which would cause a facility to qualify as a Tier I facility. 4.11 Odors Odor control is a concern at any wastewater treatment facility, and minimizing odors is essential to the maintenance of a good neighbor policy. No specific regulatory requirements apply to odor control other than nuisance standards. It is possible for foul air to emanate from the plant headworks, preliminary treatment, sludge thickening, anaerobic digestion, solids dewatering, and trickling filters. The most common odor- producing gases are hydrogen sulfide (H2S) and volatile organic compounds. Hydrogen sulfide is formed when anaerobic organisms reduce sulfate to sulfide, producing a characteristic rotten egg odor. Other common odor-producing chemicals are listed in Table 4-20. 4-51 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality Table 4-20. Odorous Compounds Associated with Untreated Wastewater Odorous Compound Chemical Formula Odor Quality Amines CH3NH2(CH3)H Fishy Ammonia NH3 Ammonia Diamines NH2(CH2)4NH2, NH2(CH2)5NH2 Decayed flesh Hydrogen Sulfide H2S Rotten eggs Mercaptans (methyl and ethyl) CH3SH, CH3(CH2)SH Decayed cabbage Mercaptans (butyl and crotyl) (CH3)3CSH, CH3(CH2)3SH Skunk Organic Sulfides (CH3)2S, (C6H5)2S Rotten cabbage Skatole C9H9N Fecal matter Source: Metcalf & Eddy, 1991 While these odorous compounds do not have strong health effects at low concentrations, they can have physical and psychological effects. For this reason, DEQ regulates the emission of odor from wastewater treatment facilities. It is important to note that jurisdictional regulations are often not the driving factor for odor control. Regardless of the loadings to the facilities and local rules, the communities and neighbors are sensitive to odors from wastewater treatment facilities. The control of nuisance odors is an important element in the system’s capital and operating budgets. 4.12 Virus Control The current standard measure of virus control for wastewater treatment plant effluent is the E. coli limit given in the facility’s MPDES permit. Limits are based on the water quality protection criteria presented in the discussion on the effluent discharge permit. Bacteria are used as an indicator species for virus control due to the lack of an easily implementable analytical method to test for the presence of infectious viruses. Virus control is a concern for the protection of beneficial uses. Since viral monitoring is technologically limited, the probability of stricter viral monitoring requirements for wastewater treatment plants is based on the probability of the development of an easily implementable viral monitoring technique. If such a method is approved for use in wastewater laboratories in the future, it is likely that an effluent limit on infectious viruses will be included in future MPDES permits. 4.13 Noise Regulations pertaining to noise are not likely to be a concern in future modifications to, or construction of, wastewater treatment facilities. Regardless of regulations, it is important that the WRF work with the surrounding community to manage noise levels and maintain a positive relationship with nearby neighbors. 4-52 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality 4.14 Effluent Reclamation and Reuse Many states recognize the value of treated municipal wastewater as a non-potable water source. Reclaimed water has been used to serve agricultural needs, as industrial process water, and for non-potable services in large business complexes. Switching from potable to non-potable water for industrial uses can be very expensive, due to the need for retrofitting an existing facility with dual piping for potable and non-potable water. However, if the savings in potable water is large enough or if the system is part of a new construction project, water reuse can meet both water conservation and pollution abatement needs. Currently, there are no federal regulations directly governing water reuse practices in the United States. Water reuse regulations have, however, been developed by many states. These regulations vary considerably from state to state. Some states, such as Arizona, California, Florida, Oregon, Texas, and Washington have developed regulations that strongly encourage water reuse as a water resources conservation strategy. These states have developed comprehensive regulations specifying water quality requirements, treatment processes, or both for the full spectrum of reuse applications. The objective is to derive the maximum resource benefits of the reclaimed water while protecting the environment and public health. Montana Circular DEQ-2 contains current reuse regulations for the state. Detailed information regarding effluent reuse rules is included in Chapter 5. 4-53 Bozeman WRF Facility Plan Update Chapter 4 – Water Quality References PFAS Strategic Roadmap: EPA’s Commitments to Action 2021–2024, United States Environmental Protection Agency, 2021. Proposed 2022 Clean Water Act Financial Capability Assessment Guidance, United States Environmental Protection Agency, 2022. 4-54 Chapter 5 Effluent Management Plan 5 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Contents Introduction.......................................................................................................................................5-1 5.1 Effluent Management Alternatives .........................................................................................5-1 5.1.1 Surface Water Discharge ..........................................................................................5-1 5.1.2 Shallow Groundwater Discharge...............................................................................5-4 5.1.3 Non-Potable Reuse ...................................................................................................5-4 5.2 Effluent Management Alternatives .........................................................................................5-8 5.2.1 Alternative 1a. Discharge to East Gallatin Surface Water ........................................5-8 5.2.2 Alternative 1b. Seasonal Land Application & Irrigation .............................................5-9 5.2.3 Alternative 1c. Shallow Groundwater Discharge.....................................................5-12 5.2.4 Alternative 1d. Aquifer Recharge ............................................................................5-15 5.2.5 Alternative 1e. Wetland Treatment..........................................................................5-16 5.2.6 Alternative 2. West End Discharge to Belgrade......................................................5-18 5.2.7 Alternative 3. City of Bozeman West End Satellite Treatment Facility ...................5-20 5.2.8 OPCC Summary......................................................................................................5-22 5.3 Alternatives Treatment Table ...............................................................................................5-22 References ...............................................................................................................................................5-24 Figures Figure 5-1. Map of Landmarks in WRF Vicinity .........................................................................................5-1 Figure 5-2. Potential Pipeline to Facilitate Alternative 1b ........................................................................5-10 Figure 5-3. Example IP Basins on WRF Site...........................................................................................5-14 Figure 5-4. Example Constructed Wetland on WRF Site ........................................................................5-18 Figure 5-5. Area of Wastewater Flows to be Routed to the Belgrade WWTP for Treatment..................5-19 Figure 5-6. Area of Wastewater Flows to be Routed to the Satellite WWTP for Treatment....................5-21 Tables Table 5-1. Montana Reclaimed Water Classifications ...............................................................................5-5 Table 5-2. Allowable Uses of Reclaimed Water.........................................................................................5-5 Table 5-3. Advantages and Disadvantages of Alternative 1a....................................................................5-9 Table 5-4. Potential Land Application Areas for WRF Effluent................................................................5-10 Table 5-5. Advantages and Disadvantages of Alternative 1b..................................................................5-12 Table 5-6. IP Basin Acreage Summary....................................................................................................5-13 Table 5-7. Advantages and Disadvantages of Alternative 1c..................................................................5-15 Table 5-8. Advantages and Disadvantages of Alternative 1d..................................................................5-16 Table 5-9. Wetland Treatment Sizing and Summary...............................................................................5-17 Table 5-10. Advantages and Disadvantages of Alternative 1e................................................................5-18 Table 5-11. West End Flows....................................................................................................................5-19 Table 5-12. Pros and Cons of Alternative 2 .............................................................................................5-20 Table 5-13. Advantages and Disadvantages of Alternative 3..................................................................5-22 Table 5-14. Effluent Management Alternatives' OPCC Summary...........................................................5-22 Table 5-15. WRF Management Alternatives Nutrient Treatment Projections..........................................5-23 i Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan This page is intentionally left blank. ii 5 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Introduction Feasible alternative effluent management options for the Bozeman WRF are presented in this chapter, including surface water discharge, shallow groundwater discharge, and various effluent non‐potable reuse discharge options. Risks, assumptions, data gaps, limitations, regulatory processes, and opinions of probable construction cost are provided for each alternative. Information pertaining to regulatory drivers and the basis of design will build upon the material presented in Chapter 4. A general map of landmarks in the WRF area pertaining to this chapter is shown in Figure 5-1. Figure 5-1. Map of Landmarks in WRF Vicinity 5.1 Effluent Management Alternatives Effluent management alternatives discussed in this Chapter include: Discharge to surface water Shallow groundwater discharge Non-potable reuse 5.1.1 Surface Water Discharge WRF effluent is currently discharged to the East Gallatin River through a surface water outfall. The East Gallatin River is subject to low flows and high nutrient levels, both of which harm its designated beneficial uses. If more stringent nutrient discharge standards 5-1 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan are mandated by Montana Department of Environmental Quality (DEQ), it may become technologically and economically impractical for the WRF to continue discharging to the East Gallatin. Preliminary TMDL considerations for the East Gallatin River look to reduce the amount of nutrients that the facility is capable of discharging to the river. If upstream nutrient concentrations were to exceed the TMDLs, the WRF may not be allowed to discharge any nutrients to the East Gallatin. These conditions make other effluent management options economically attractive and possibly necessary. However, the WRF currently supplies approximately 33 percent of the instream flow to the East Gallatin River during periods of low flow. The effluent water is vital to both downstream water users and aquatic life. If the WRF were to remove the effluent from the river in favor of one of the other effluent management alternatives discussed, this removal will likely harm cold-water aquatic life since low flows typically result in increased water temperature. Any removal of flow may also prompt legal challenges from water rights holders downstream of the WRF. The Montana Department of Natural Resources and Conservation (DNRC) previously addressed this issue in 1996 as it pertained to the City of Deer Lodge. The Montana DNRC examined the issue of “what, if any, administrative approval by the DNRC must the City of Deer Lodge obtain before it proceeds to land apply its sewage effluent for treatment rather than discharging it into the Clark Fork River as it has historically done.” Upon reviewing the previous case law, the DNRC issued Final Order No. 97514-76G, the Deer Lodge Order, with the following key findings: “[T]he treatment of sewage by a municipality is as much a part of its municipal use of water as anything else that is done with it.” DNRC agrees with the holding of the Wyoming Supreme Court in Wyoming Hereford Ranch, in that as part of their municipal water right, a city may treat their water in a manner that “even totally consumes it, without objection or interference to downstream demands for that water.” Because “sewage effluent” is specifically included in the definition of “water” in Montana’s Water Use Act (MCA § 85-2-102(24)(2007)), a downstream potential user may apply for a beneficial use permit to appropriate the sewage effluent, “but it will be up to the appropriator to properly convey the water [sewage effluent] to its place of intended use – the DNRC will not insist that the sewage effluent be returned to the River by the city…” The DNRC’s ruling in the Order is summarized as follows: A municipality is not required to obtain either a new water use permit or a change authorization, nor is it required to obtain permission from DNRC in any manner, to switch from surface water discharge of its sewage effluent to land treatment. This ruling applies even if the municipality land applies the effluent outside the boundaries of the defined place of use of the underlying water right (e.g., outside the municipal boundary), so long as the sewage effluent is not intended to be used for a new beneficial use (e.g., irrigation). DNRC’s Order specifically addresses situations where a municipality owns the water rights for the municipal use, and intends to either land apply it within its defined boundary (within the place of use defined for the underlying water right), or intends to land apply it 5-2 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan outside its defined boundary, so long as the effluent is not used for irrigation or any other beneficial use. Therefore, so long as a municipality’s sewage treatment situation meets the following criteria, the municipality may fall within the narrow ruling of the DNRC’s Order: 1. The municipality owns the water rights for the municipal use (owns the underlying water rights), and either; a. The change to land application or other sewage treatment method that would result in more (if not all) of the water being consumed as compared to the existing treatment method, would occur entirely within the place of use defined for the underlying water right (within the defined boundaries of the municipality) whether or not the new treatment method resulted in further beneficial use of the water (such as irrigation of with the effluent), or b. The change to land application or other sewage treatment method would result in more (if not all) of the water being consumed as compared to the existing treatment method, would occur outside the place of use defined for the underlying water right (outside the defined boundaries of the municipality), so long as the treatment method was not intended to result in a new beneficial use of the water (such as irrigation with the effluent). The DNRC’s declaratory ruling is essentially an interpretation of the statutory definition of “Beneficial Use,” specifically, whether or not treatment of sewage effluent by the City of Deer Lodge is considered to be included in the “beneficial use” of their water right for “municipal” purposes. Because the declaratory ruling addressed a question of law (interpretation of a statute), but was narrowed to the specific set of facts regarding the City of Deer Lodge’s water rights and sewage treatment, DNRC’s resulting Order is considered a Quasi-Judicial ruling. Montana courts must “take judicial notice” of the Order. As a Quasi-Judicial ruling, the Deer Lodge Order is binding between DNRC and the City of Deer Lodge, but is essentially binding to all potentially affected parties within Montana’s court system. Therefore, if another municipality with similar facts and circumstances as Deer Lodge was to change to land application of its effluent (or reduce the return flow of their effluent to a significant degree), it would likely have two options: 1. Proceed directly with its change in effluent treatment without requesting authorization from DNRC or any court, and if it were later challenged by a downstream appropriator it could use the Deer Lodge Order as persuasive authority in arguing its case in court. While this option likely has a good chance of success, any differences in its facts and circumstances as compared to Deer Lodge can open the door to make the earlier Deer Lodge Order less applicable and thus less persuasive to the court. 2. Prior to changing its effluent treatment, the municipality can seek its own declaratory ruling, relying on the Deer Lodge Order as precedent for DNRC to rule in accordance with the earlier Order. This option has a high likelihood of a favorable ruling by DNRC. However, potentially affected parties are afforded the opportunity to argue against the ruling in a DNRC hearings process, and to appeal the new order to district court (just as potentially affected parties were afforded these opportunities in the Deer Lodge Order). As in the above option, if the new, favorable order were 5-3 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan challenged by a downstream appropriator the municipality can use both the Deer Lodge Order and the new order as persuasive authority in arguing its case in court, and would likely have a good chance of success. In summary, even though the Deer Lodge Order is not considered an agency “rule” and is not considered “binding” authority in a Montana court, it likely carries substantial “persuasive” authority in a court and is considered precedential with respect to future DNRC rulings. The City may wish to attempt to modify existing state law and/or propose new legislation which would strengthen the existing Order while removing vagueness and ambiguity. The primary advantage of continuing to discharge to surface water is the existing infrastructure already facilitates this approach. Even if another effluent management option were to be implemented, the existing infrastructure should be maintained as a feasible backup discharge option and the City’s surface water discharge permit should be continued. 5.1.2 Shallow Groundwater Discharge Groundwater discharge offers an effluent management approach which removes the WRF discharge from the East Gallatin River. Treated water is conveyed to constructed infiltration/percolation (IP) basins where it infiltrates into the subsurface and enters the groundwater system. Nearby sampling data suggests the groundwater and surface waters are disconnected in the area of the IP basins on the WRF property. This separation is beneficial from a nutrient standpoint, as the WRF would likely be subject to less stringent discharge limitations compared to discharging directly to the East Gallatin River. The area of existing IP basins is shown in Figure 5-1. However, additional investigation is required to definitively determine the surface water- groundwater interaction in the area. If it is determined that the groundwater below the IP basins is hydrologically connected to the East Gallatin surface water, then the primary advantage of this effluent management option is eliminated. Such a connection likely results in surface water nutrient limits being applied to the groundwater discharge. Montana DEQ Circular 2 contains regulations for IP basins and subsurface absorption cells, and these rules are discussed in Chapter 4. 5.1.3 Non-Potable Reuse Reclaiming the WRF’s effluent for non-potable reuse provides a water supply for a variety of beneficial uses while also benefitting the City’s permitting situation by reducing nutrient loading to the East Gallatin. In order to use reclaimed wastewater, effluent must be treated to sufficient levels, monitored and/or stored to ensure protection of public health, and distributed to users in a safe and reliable distribution system. Reclaimed water falls under several treatment classifications, and abbreviated descriptions of these classifications are summarized in Table 5-1. A full description of the classifications can be found in Attachment A. The treatment classification ultimately determines how reclaimed wastewater can be used. 5-4 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-1. Montana Reclaimed Water Classifications Description Class A 1 Class A1 Class B 1 Class B Class C Total nitrogen below 5 mg/l? Yes No Yes No No Notes: 1 Reclaimed Class A typically includes secondary treatment, plus flocculation/sedimentation, filtration, and disinfection. Reclaimed water can be used for irrigation, aquifer recharge, and various commercial and industrial uses. The amount of treatment and disinfection that is required varies depending on the intended use. Allowable uses for reclaimed water, based on the respective reclamation class, are shown in Table 5-2. These uses assume application greater than the respective agronomic uptake rates of the receiving crops, where noted. For many crops, lower classes of effluent can still be applied, but only at or below the agronomic uptake rate. Table 5-2. Allowable Uses of Reclaimed Water A 1 A B 1 B C Sod, Ornamental Plants for Commercial Use, and Pasture to Which Milking Cows or Goats Have Access YES NO YES NO NO NO Drip or Subsurface Irrigation of Nonfood Crops (greater than agronomic rate) * Trees YES NO YES NO NO NO Spray Irrigation of Food Crops (greater than agronomic uptake rate) * Food Crops Which Undergo Physical or Chemical Processing Sufficient to Destroy All Pathogenic Agents YES NO YES NO NO NO Drip or Subsurface Irrigation of Food Crops (greater than agronomic uptake rate) * NO YES Root Crops YES NO NO NO NO NO Landscape Irrigation (greater than agronomic uptake rate) * Restricted Access Areas (e.g., Cemeteries YES NO YES NO NO NOand Freeway Landscapes) 1-)~ ----- ----- ------ Can be applied to publicly accessible areas? Yes Yes No No No Can be applied to areas with restricted access? Yes Yes Yes Yes Yes Agronomic rate required for exemption from groundwater discharge permit? No Yes No Yes Yes Disinfection to 2.2 CFU/100 mL? Yes Yes Yes Yes No Allowable Uses of Reclaimed Water Class of Reclaimed Water D Spray Irrigation Nonfood Crops (greater than agronomic uptake rate) * Trees and Fodder, Fiber, and Seed Crops YES NO YES NO NO NO Food Crops Where There is No Reclaimed wastewater Contact with Edible Portion of Crop (e.g. orchards, vineyards) YES NO NO NO 5-5 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Allowable Uses of Reclaimed Water Class of Reclaimed Water A 1 I II --+----+-----+-------t- ------------------------------------ ------ A B 1 B C D Unrestricted Access Areas (e.g., Golf Courses, Parks, Playgrounds, School Yards YES NO NO NO NO NO and Residential Landscapes) Impoundments Landscape Impoundments YES NO NO NO NO NO Restricted Recreational Impoundments YES NO YES NO NO NO Unrestricted Recreational Impoundments YES NO NO NO NO NO Animal & Fish Operations Fish Hatchery Basins (with discharge permit) YES YES YES NO NO NO Zoo Operations and Animal Shelter Wash Down Water (discharge to sewer) YES YES YES YES NO NO Decorative Fountains (discharge to sewer) YES YES NO NO NO NO Decorative Fountains (discharge to groundwater) YES NO NO NO NO NO Jetting and Flushing of Sanitary Sewer YES YES YES YES YES NO Street Cleaning and Washing Operations Street Sweeping, Brush Dampening YES YES YES YES YES NO Sidewalks and Parking Lot Washing, Spray YES NO YES NO NO NO Dust Control and Soil Compaction/Consolidation Unpaved road dust control, road construction compaction, backfill consolidation around YES YES YES YES YES NO pipelines (Not Drinking Water lines) Fire Fighting and Fire Protection Systems Dumping from Aircraft YES YES YES YES YES NO Hydrants or Sprinkler Systems in Buildings YES YES NO NO NO NO Toilet and Urinal Flushing YES YES NO NO NO NO Washing Aggregate and Concrete Batching Operations (no discharge) YES YES YES YES YES NO Industrial Uses Aerosols not created (e.g. heat pumps, YES YES YES YES YES NOboilers) (non-discharging recirculation type) Aerosols or other mist created (e.g., cooling towers, forced air evaporation, or spraying) YES YES NO NO NO NO Aquifer Recharge Controlled Surface or Subsurface Addition to Replenish the Aquifer ** YES NO NO NO NO NO Aquifer Injection 5-6 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Allowable Uses of Reclaimed Water Class of Reclaimed Water A 1 A B 1 B C D Direct Injection into Aquifer for Purpose of Enhancing a Water Right or Allocation ** YES NO NO NO NO NO Indirect Potable Reuse Intentional Return of Reclaimed Wastewater to Augment Raw Water Supplies *** YES YES YES YES NO NO Stream flow Augmentation Fisheries Support, or Recreational Enhancement with Unrestricted Access *** YES YES YES YES NO NO Snow Making Restricted Access - designed for discharge to groundwater YES NO YES NO NO NO Unrestricted Access - such as ski slopes *** YES NO NO NO NO NO ------The WRF’s effluent currently meets the requirements for Class B-1, and it can be used for a number of land application and irrigation purposes in areas of restricted public access. Such eligible areas in Bozeman include places like the Springhill Sod Farm and freeway landscapes along I-90. Irrigation is typically seasonal and occurs during the summer months when irrigation demand is highest. Discharge to surface water would continue during the winter months. Reclaimed water can also be used along the East Gallatin River or other riparian areas for the creation of wetlands. Reuse in this area would augment the amount of water uptake by riparian plants from the East Gallatin. Wetland creation also provide additional habitat for birds, plants, and other wildlife. The use of reclaimed water near the East Gallatin River would need to be reviewed and approved by the Montana DEQ due to the surface water discharge requirements, as surface water discharge limits may still be applied. Other potential uses worth considering include urban irrigation and aquifer recharge. Urban irrigation involves the use of reclaimed water as an irrigation supply for golf courses, school grounds, parks, and other areas of unrestricted public access. However, in order to use reclaimed effluent for aquifer recharge or urban irrigation, the WRF effluent would need to meet class A-1 treatment requirements which require implementing effluent filtration. Effluent filtration is used to remove suspended solids which do not settle in the clarification process, and enhances downstream disinfection processes by increasing the clarity of the effluent and the resulting UV transmittance properties. Effluent filtration also complements future phosphorus removal processes by removing filterable particulate matter containing phosphorus. There are many types of filters available, and selection of the most appropriate type of filtration depends on whether very low nutrient targets must be met, whether Class A-1 reclaimed water is needed, or both. 5-7 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan 5.2 Effluent Management Alternatives The effluent management options of surface water discharge, groundwater discharge, and non-potable reuse were used to create Bozeman specific alternatives. These alternatives include centralized and decentralized approaches. Alternatives that continue to collect wastewater for treatment at the WRF are considered centralized treatment approaches, and alternatives that collect wastewater for treatment at facilities in addition to the WRF are considered decentralized treatment approaches. Different effluent discharge options are considered for centralized treatment in Alternatives 1a through 1e. Alternatives for decentralized treatment are considered in Alternative 2 and Alternative 3, and include routing sewer flows on the west end of Bozeman to the Belgrade WWTP, or constructing a City of Bozeman owned satellite treatment plant to service the future west side of the City. An opinion of probable construction cost (OPCC) was prepared for each respective alternative, where applicable. The OPCCs presented are Class 5 and are representative of a planning level project phase, and each OPCC carries a 30 percent contingency unless otherwise noted. 5.2.1 Alternative 1a. Discharge to East Gallatin Surface Water Alternative 1a assumes that wastewater continues to be collected at the WRF for treatment and discharged to the East Gallatin. In this alternative, the WRF continues to serve as the principal collection and treatment facility for the City of Bozeman. The primary advantage of this alternative is that the existing infrastructure at the WRF can continue to be utilized and built upon, minimizing the costs associated with capacity upgrades to meet the 20-year planning period design conditions (i.e. maximizes use of existing infrastructure). The primary disadvantage of this approach is that the East Gallatin River is subject to a TMDL allocation for nitrogen and phosphorus. The TMDL limits the nutrient load the WRF can discharge to the East Gallatin, and costly treatment upgrades are likely required to meet future nutrient limits for surface water discharge. The regulatory uncertainty surrounding the future of nutrient limits on the East Gallatin poses a significant planning challenge and makes it difficult to assess the future viability of continuing to discharge effluent to the East Gallatin. Climate change also complicates future discharge to surface water by changing the ambient conditions of the receiving water. It is anticipated that warmer temperatures in the future could exacerbate low flow conditions in the East Gallatin and increase water temperature. Regulatory standards that derive limits from ambient water temperature and pH, such as the proposed federal ammonia criteria, also become more stringent under these circumstances. Lower instream flows also reduce available mixing capacity in the river and would likely lead to more stringent discharge limits. The overall advantages and disadvantages of continuing to discharge to surface water are shown in Table 5-3. 5-8 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-3. Advantages and Disadvantages of Alternative 1a Advantages Disadvantages Existing infrastructure facilitates this approach and maximizes use of existing investments Benefits local water right holders Do not need to add additional infrastructure to send water elsewhere Subject to more stringent future effluent nutrient limits Regulatory uncertainty Effluent makes up large portion of low flow volume resulting in more stringent nutrient limits Likely to require significant future effluent treatment upgrades Climate change could negatively affect the characteristics of the receiving water by reducing stream flow 5.2.2 Alternative 1b. Seasonal Land Application & Irrigation Alternative 1b assumes that wastewater continues to be centrally collected at the WRF for treatment, but that some of the effluent is seasonally land applied and/or used for irrigation. Land application would take place during the summer months when more stringent nutrient regulations are in place on the East Gallatin River. Discharge to the East Gallatin surface water would continue during the remainder of the year. The aptness of a given location for land application depends on its proximity to the WRF and the amount of effluent that can be applied. These two criteria limit the number of locations and uses that can realistically accept effluent for reuse and land application. Given these considerations, land application of effluent at the Springhill Sod Farm, the Riverside Golf Course, and the Beck-Jones Canal provide the greatest benefit. The WRF’s Class B-1 effluent can be applied at the Sod Farm and Beck-Jones Canal without any major treatment upgrades. However, to apply at the nearby Riverside Golf Course will require significant upgrades at the WRF to meet Class A or A-1 reuse standards. The inlet to the Beck-Jones Canal is located adjacent to the WRF property, and is noted on the map in Figure 5-1. It flows to the northwest and the water is used for irrigation. The Beck-Jones water users have a water right to 3.45 cfs (2.2 mgd). Discharging reclaimed water to the Beck-Jones Canal provides a low cost, highly effective, alternative discharge location which reduces nutrient loading to the East Gallatin River. Discharging effluent to the canal essentially takes the place of the canal’s East Gallatin water right, and so there would be no net loss in flow from the river. The Springhill Sod Farm is located approximately two miles north of the WRF, and draws water from the Beck-Nelson-Flannery Ditch. The Ditch is an East Gallatin irrigation canal and is noted on the map in Figure 5-1.. As such, any reuse water sent to the Sod Farm does not result in a net loss of flow in the river. An analysis was performed by Confluence Consulting for Trout Unlimited in 2019 that determined the Sod Farm had the capacity to accept 1.79 mgd from May 11th – September 22nd (McEldowney 2019). The Riverside Golf Course is located immediately north of the WRF on the other side of the East Gallatin. The golf course owners have indicated in recent conversations with the City that they are not interested in accepting effluent reuse flow. However, given the 5-9 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan physical proximity of the course to the plant it is in the best interest of the City to continue pursuing an agreement with Riverside Golf Course. An analysis was performed by Confluence Consulting for Trout Unlimited in 2019 that determined the golf course had the capacity to accept 0.713 mgd from May 11th – September 22nd (McEldowney 2019). A pipeline network would need to be constructed to deliver effluent to the Beck-Nelson- Flannery Ditch and the golf course. The pipeline will need to be 1,000 to 1,500 feet long to reach the Beck-Nelson-Flannery Ditch and a total of 3,000 feet long to reach the golf course, depending on the path taken. This potential pipeline route is shown on Figure 5-2. Figure 5-2. Potential Pipeline to Facilitate Alternative 1b Flows to the three entities discussed are summarized in Table 5-4. Table 5-4. Potential Land Application Areas for WRF Effluent Application Required Class Projected Reuse Volume (mgd) Springhill Sod Farm B-1 1.791 Beck-Jones Canal B-1 2.202 Riverside Golf Course A or A-1 0.7131 Total -4.70 1 (McEldowney 2019) 2 Beck-Jones East Gallatin Water Right 5-10 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Numerous other discharge locations exist in the surrounding area, but the effort and capital improvements required to deliver reclaimed water to myriad of smaller applications outweighs the benefits. A full breakdown of all potentially viable options by user group can be found in Attachment B. Typically, effluent storage must be provided in sufficient volume to cover daily irrigation use patterns. This storage provides a reservoir as irrigation water usage is typically not constant throughout the day and is usually higher during the morning and evening hours. Storage can be provided in the form of an artificial pond on the WRF property and be constructed with a clay or geosynthetic liner to limit infiltration. However, such a storage facility will not be required at the WRF because effluent can be discharged directly to the Beck-Jones Canal and to the golf course’s irrigation pond. A Class 5 opinion of probable construction cost (OPCC) was estimated for the pipeline and required appurtenances. The OPCC came to approximately $2.5 million, and assumes that two pipelines would be constructed, one to the Beck-Jones Canal and one to the Riverside Golf Course. It is also assumed that two pumps would be purchased, no storage ponds would be constructed, and that no class specific (i.e. treatment upgrade to meet Class A-1 requirements) would be installed. The primary advantage of this alternative is that it allows the City to continue utilizing the existing infrastructure at the WRF, but alleviates some of the regulatory uncertainty involved with discharging to surface water during the summer months. By taking some of the WRF effluent out of the river during the summer months, the WRF would be in a much stronger position to comply with possibly more stringent future discharge limitations. Such an approach entails smaller capital expenditures than upgrading the plant’s nutrient treatment capability to meet stringent seasonal surface water limits. The primary disadvantage of this alternative is that it requires stakeholder agreements between the City and the landowners or entities that accept the effluent for land application. Agreements between multiple stakeholders are required for this alternative to be feasible. The Riverside Golf Course has previously shown strong disinterest to the prospect of accepting effluent reuse. The Beck-Jones Canal and Sod Farm have similarly shown disinterest when the prospect of effluent reuse was previously proposed. However, increased usage stress on the East Gallatin and the prospect of lower summer flows due to climate change could push effluent reuse as a more attractive option to independent stakeholders who have water rights on the East Gallatin. Additionally, the WRF’s effluent can currently only be applied to areas of restricted public access. The WRF must be upgraded to meet Class A or A-1 reuse standards in order for the effluent to be land applied in areas of unrestricted public access such as the golf course. As previously discussed in regard to Alternative 1a, there are also potential issues associated with removing flow from the East Gallatin River. This could lead to litigation from downstream water rights holders. A summary of the overall advantages and disadvantages of using reclaimed wastewater for reuse via land application and irrigation is shown in Table 5-5. 5-11 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-5. Advantages and Disadvantages of Alternative 1b Advantages Disadvantages • Offset non-potable irrigation water demand • Reduces nutrient loading to surface water during summer months • Lower cost if using as B-1 water (i.e. no additional treatment is required) • Partnerships required with individual stakeholders • Likely not feasible to discharge entirety of effluent through land application • Only usable during warmer, summer months • Need to upgrade effluent treatment to meet Class A or A-1 requirements for public access applications • Potential challenges associated with removing effluent from East Gallatin 5.2.3 Alternative 1c. Shallow Groundwater Discharge Alternative 1c assumes that wastewater continues to be collected at the WRF for treatment but that the effluent is discharged to shallow groundwater via IP basins west of the plant. The functional premise of IP basins is that they infiltrate wastewater effluent into the shallow groundwater aquifer. The IP basins at the WRF were originally constructed to provide nitrogen removal and are not currently in use. Some of the area encompassed by the IP basins is now occupied by other infrastructure, including the Davis Lane Lift Station. The ability of an IP basin to effectively discharge into groundwater is dependent on three main soil characteristics: porosity, permeability, and hydraulic gradient. Porosity is defined as the volumetric proportion of the amount of void space in the soil structure. Permeability represents the hydraulic connectivity of the pore spaces within the soil, and the hydraulic gradient is the amount of force being placed on the water to push it through the soil (or pressure head). The infiltration rate must ultimately be at least 1 foot per day or higher for infiltration to be feasible based on the land area available. The depth to the groundwater is also a key factor that governs the determination of the allowable sustainable infiltration rate. A feasibility study and physical soil investigation is required to definitively quantify these characteristics in the IP basin soils and determine how much effluent can be discharged. Without a definitive groundwater investigation of the IP basin area, it is unknown whether groundwater discharge on the WRF property is feasible. Absent a site-specific soils investigation, the hydraulic conductivity range from the City of Bozeman Groundwater Investigation report was used (Rotar 2017). The report estimated the hydraulic conductivity of the soil in the vicinity of the WRF to be approximately 25 ft/day to 400 ft/day. This large range of possible values makes it difficult to assess the feasibility of this alternative. There is approximately 26 acres of total unused IP basin space at the WRF that can theoretically be used for groundwater discharge, depending on the hydraulic conductivity of the soil and whether the groundwater affects surface water in this area. Regulations state that 4 to 10 percent of the hydraulic conductivity can be used when calculating the required discharge area, translating to 2.5 – 40 ft/day based on the cited range of values. Regulations also require that an adequate drying period be accommodated, which necessitates having redundant cells. If a loading application period of 1 day is used 5-12 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan during the summer months, then a cycle drying period of 4 – 5 days is required. This entails the construction of a minimum of 5 – 6 infiltration basins to allow for the required drying cycle period to be completed between application periods. Based on these requirements, 8 – 132 acres is needed to discharge the maximum month flow of 17.9 MGD during the summer months. This information is summarized in Table 5-6. Table 5-6. IP Basin Acreage Summary Hydraulic Conductivity Maximum Required Basins Required Acreage 2.5 ft/day 6 8 acres 40 ft/day 6 132 acres This preliminary analysis suggests the WRF may have adequate available land area to discharge to groundwater for the maximum month condition, but this is contingent upon the soil possessing a hydraulic conductivity of approximately 125 ft/d or greater. Regardless, the City should maintain their surface water discharge to maintain the long- term viability of the utility in its current location, and the use of the groundwater discharge should be considered an additional option for ensuring an economical way to meet permitting requirements and managing the total volume of the WRF effluent. For this alternative, WRF effluent is pumped a short distance to the IP basins. The existing IP basins require rework to meet the required acreage and number of cells, and each cell needs extensive piping installations. A Class 5 OPCC was prepared for this alternative, and assumes that 8 – 25 acres of land would be renovated for subsurface discharge, two pumps installed, and the existing piping from the WRF to the cells is reused. The OPCC range came to approximately $6.3 - $18.4 million, due to the range of possible required acreages. A figure depicting the IP acreage corresponding to a hydraulic conductivity of 200 ft/day is shown on Figure 5-3 as an example. 5-13 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Figure 5-3. Example IP Basins on WRF Site If the hydraulic conductivity dictates that more than ~25 acres of land is required to discharge to groundwater, then this alternative becomes impractical due the high cost of land acquisition in the Gallatin Valley. Additionally, there are few large, vacant plats of land available within a short distance of the WRF and consequently the effluent would likely need to be pumped for several miles to a discharge location. Given these considerations, shallow groundwater discharge of WRF effluent at an alternate location is likely not practical. In summary, the primary advantage of this alternative is that groundwater discharge can offset nutrient loading to East Gallatin surface water. This is especially beneficial if the WRF is capped at current nutrient loading. Additionally, the nutrient discharge limits for a groundwater permit are typically more lenient than for a surface water permit. The use of a groundwater discharge enables the City to switch their effluent discharge to the East Gallatin River from month to month based upon river flows and regulatory requirements. Infiltration into the soil also acts as a final barrier for bacteria and viruses, and provides some tertiary treatment. The primary disadvantage of this alternative is uncertainty. While it is likely that the nutrient discharge limits are more lenient for a groundwater discharge in the near term, this is not certain and could change in the future. This negates the primary advantage of discharging to groundwater. Nearby sampling data suggests that the groundwater and surface waters are disconnected in the area of the existing IP basins, but further investigation is required to confirm this. If it were determined the groundwater and East 5-14 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Gallatin surface water was hydrologically connected in this area, then surface water discharge standards would still apply. A low hydraulic conductivity also renders this alternative unfeasible, as anything less than 125 ft/d will be impractical due to the amount of available land on the WRF property. A summary of the overall advantages and disadvantages of groundwater discharge is shown in Table 5-7. Table 5-7. Advantages and Disadvantages of Alternative 1c Advantages Disadvantages Remove some or all nutrient loading to Potential litigation for removing effluent from surface water East Gallatin Replenish groundwater supply Further investigation into local groundwater conditions required Potentially less stringent nutrient discharge limits Groundwater permitting conditions could change Existing IP basins can facilitate discharge 5.2.4 Alternative 1d. Aquifer Recharge Groundwater is increasingly viewed as a valuable and finite resource, and over drafting an aquifer can have detrimental impacts. An aquifer recharge program can sustain surrounding groundwater levels with a high-quality source of replenishment. Alternative 1d assumes that wastewater continues to be collected at the WRF for treatment but that the effluent be discharged to the shallow groundwater aquifer. This alternative largely resembles Alternative 1c, but higher levels of wastewater treatment are required for specific aquifer recharge as compared with a generic groundwater discharge. The effluent reuse rules require Class A-1 wastewater for aquifer recharge. This requires the WRF effluent to be treated to a very high level, and the need for tertiary treatment upgrades to meet Class A-1 standards. The primary advantage of this alternative is that the subsurface aquifer can be recharged, which helps supplement the natural groundwater supply. This alternative takes the WRF effluent out of the East Gallatin entirely, which is beneficial if the WRF is capped at current nutrient loading. The primary disadvantage of this alternative is that it carries high risk and uncertainty, similar to Alternative 1c. The difference being that higher levels of treatment are required to discharge, possibly including treatment for perfluoroalkyl substances (PFASs) and other contaminants of emerging concern (CECs) in addition to the requirements for Class A-1 effluent. These additional considerations are not included in the OPCC, as they are not part of the infrastructure to facilitate aquifer recharge. However, these treatment costs are considered in the full present worth and alternatives analyses in Chapter 7. Consequently, the OPCC range is similar to Alternative 1c or approximately $6.3 - $18.4 million, due to the range of possible required acreages and additional treatment. A summary of the overall advantages and disadvantages of groundwater discharge via aquifer recharge are shown in Table 5-8. 5-15 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-8. Advantages and Disadvantages of Alternative 1d Advantages Disadvantages Remove some or all nutrient loading to High costs to upgrade WRF to meet surface water treatment requirements Replenish groundwater supply Potential litigation for removal of effluent from East Gallatin River Potentially less stringent nutrient discharge limits Property acquisition for infiltration Permitting uncertainty 5.2.5 Alternative 1e. Wetland Treatment Alternative 1e assumes that wastewater continues to be collected at the WRF for treatment but that the effluent passes through wetland treatment before ultimate discharge to the East Gallatin River. This process can be used to polish effluent before its ultimate discharge to the East Gallatin, or can potentially be permitted as a second discharge outfall. Either way, tertiary wetland treatment may be incorporated into the treatment process at the WRF in the near future because an installation is in the process of being piloted there. Once this pilot project is complete the desirability and effectiveness of this alternative will be easier to evaluate. It is important to recognize that while constructed wetlands can effectively remove BOD and TSS, significant removal of nitrogen and phosphorous is typically attributed to solids removal and/or carbon-fueled biological removal. Nitrification and denitrification are the primary nitrogen removal mechanisms in constructed wetlands, and the effectiveness depends on the amount of available carbon, relative presence of open water, and vegetated zones in the wetland. Similarly, phosphorus removal in constructed wetlands is accomplished primarily by plant uptake, making it seasonal in nature for cold climates. Some phosphorous removal can be accomplished through sorption to filter media but effectiveness may deteriorate with time as the media becomes saturated. The removal effectiveness of each is also closely tied to the hydraulic retention time and nutrient- treatment-specific recycle and recycle rates. If the WRF wishes to move forward with a wetland treatment system following the pilot study, either a vertical flow or horizontal flow wetland treatment system could be constructed. Vertical flow wetlands can treat approximately 15 to 20 percent of total nitrogen (TN), and can treat about 10 to 20 percent of TP. Vertical flow wetlands are carbon limited and performance can decrease over time. Horizontal flow wetlands can typically remove slightly more TN than vertical flow wetlands, before background concentration (buildup of base TN over time) limits treatment. They can treat 10 to 20 percent of TP, primarily through sorption, but this performance can also decrease over time. Horizontal flow wetlands have historically been used more often for tertiary treatment and can generally accomplish better nutrient removal under the right circumstances than vertical flow wetlands. However, vertical flow wetlands have more operational flexibility to design recycle rates and loading around nutrient treatment goals. A summary of projected wetland sizing and performance abilities is shown in Table 5-9. . 5-16 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-9. Wetland Treatment Sizing and Summary Design Year Type Minimum Size (acres) Limiting Factor Nutrient Treatment Ability 2020 Vertical Flow Treatment Wetland 2.7 Area restricted by biological (BOD/COD) loading restrictions. Can treat about 15-20% of TN. Can treat about 10-20% of TP primarily through sorption. Performance can decrease over time. 2020 Horizontal Flow Treatment Wetland 4.1 Area restricted by biological (BOD/COD) loading restrictions. Can treat down to 1 mg/L TN before background concentration (buildup of base TN over time) limits treatment. Can treat 10-20% of TP primarily through sorption. Performance can decrease over time. 2040 Vertical Flow Treatment Wetland 4.4 Area restricted by biological (BOD/COD) loading restrictions. Can treat about 15-20% of TN. Can treat about 10-20% of TP primarily through sorption. Performance can decrease over time. 2040 Horizontal Flow Treatment Wetland 16.1 Area restricted by biological (BOD/COD) loading restrictions. Can treat down to 1 mg/L TN before background concentration (buildup of base TN over time) limits treatment. Can treat 10-20% of TP primarily through sorption. Performance can decrease over time. An OPCC was prepared for a 16.1 acre horizontal flow treatment wetland. This OPCC came to approximately $4.52 million, and includes pumping and pipes to the area of the existing IP basins, extensive earthwork, and the purchase of aquatic plants. A figure depicting the wetland is shown on Figure 5-4. 5-17 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Figure 5-4. Example Constructed Wetland on WRF Site The primary advantage of this alternative is that the wetland can provide tertiary treatment of the WRF effluent for minor capital costs and minimal maintenance. The level of treatment provided will be better understood after the pilot project is completed. The disadvantage of this alternative is that constructing the wetlands requires land on the WRF property that may preclude the construction of necessary upgrades in the future. It is also unclear how DEQ will permit the wetland treatment system. A summary of the overall advantages and disadvantages of tertiary wetland treatment is shown in Table 5-10. Table 5-10. Advantages and Disadvantages of Alternative 1e Pros Cons Low capital cost Treatment levels for tertiary treatment are currently unknown Low maintenance Unknown how DEQ will permit the wetland Utilizes a natural system treatment Allows for educational opportunities Will occupy space on property originally planned for future upgrades 5.2.6 Alternative 2. West End Discharge to Belgrade Alternative 2 assumes that wastewater flows west of Davis Lane are routed to a new sewer interceptor and transported to the Belgrade WWTP for treatment. The Belgrade 5-18 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan WWTP is currently permitted to discharge effluent to groundwater, and the groundwater permit has less stringent nutrient limits than for discharging to the East Gallatin. The approximate flows that can be diverted to Belgrade are provided in Table 5-11. These are the projected flows for the future Gooch Hill and Hidden Valley Lift Stations, as outlined in the 2015 Wastewater Collection Facilities Plan Update. A map depicting the general area to be routed to Belgrade for treatment is shown on Figure 5-5. Table 5-11. West End Flows Average Design Flow Rate Peak Hour Design Flow Rate 4.4 mgd 8.1 mgd Figure 5-5. Area of Wastewater Flows to be Routed to the Belgrade WWTP for Treatment The City of Bozeman is currently participating in a wastewater regionalization feasibility study with City of Belgrade and Gallatin County to further analyze this decentralized/regional alternative in further detail. This includes an evaluation of how much effluent the groundwater near Belgrade can accept, the routing of the sewer to the Belgrade WWTP, and what other supporting infrastructure is required. The study will also consider how this alternative impacts existing, planned lift stations identified in the City of Bozeman’s existing wastewater collection facility plan.. An OPCC for this alternative was developed at a price of approximately $76.8 million, and includes infrastructure improvements to construct 4.4 mgd of additional treatment capacity at the Belgrade WWTP. The OPCC does not include any sewer interceptor or other supporting infrastructure necessary to transfer wastewater from northwest Bozeman to Belgrade. This OPCC is primarily based off the reported costs of Belgrade’s 5-19 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan recent WWTP upgrade, which added roughly 2 MGD of increased capacity for $40 million. The $40 million dollar cost was scaled using the rule of six-tenths cost estimating relationship and includes a 20% contingency. A 20% contingency was used rather than a 30% contingency because the cost is directly scaled from a recent upgrade at the WWTP. The primary advantage of this alternative is that it reduces new loadings to the Bozeman WRF, and in turn allows the facility to maintain its current performance for a longer period of time. This is especially beneficial if the WRF is capped at its current nutrient loading in a future discharge permit. A number of septic systems in the area can also be connected to the new sewer interceptor, which offers the potential to obtain nutrient trading credits. The primary disadvantage of this alternative is the transfer of flow to a separate entity. An interlocal agreement between Bozeman and Belgrade is required, and negotiations are needed to establish what extent each municipality assumes for risks to permit compliance and responsibility for any potential violations. Another disadvantage of this alternative is that Belgrade’s discharge permit could change, which eliminates the currently beneficial groundwater nutrient limits. A summary of the overall advantages and disadvantages of Alternative 2 are shown in Table 5-12. Table 5-12. Pros and Cons of Alternative 2 Advantages Disadvantages Helps maintain current WRF performance as loads increase Less stringent nutrient discharge limits due to groundwater discharge City of Bozeman does not need to pursue their own ground water permit No additional treatment infrastructure at the Bozeman WRF Interlocal agreement required Belgrade groundwater permit is subject to change Risk of ownership of permit compliance Required infrastructure changes that otherwise do not benefit Bozeman WRF Not be positioned well if Belgrade permit changes 5.2.7 Alternative 3. City of Bozeman West End Satellite Treatment Facility Alternative 3 takes a similar approach to Alternative 2, except that flows on the west side of the City are routed to a new satellite treatment facility owned by the City of Bozeman. The size of the satellite treatment facility is the same as previously shown in Table 5-11. In order to facilitate this alternative, land would need to be acquired for the treatment plant and a groundwater discharge permit obtained. A map showing the general area to be treated by the satellite plant is shown on Figure 5-6. 5-20 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Figure 5-6. Area of Wastewater Flows to be Routed to the Satellite WWTP for Treatment A Class 5 OPCC was estimated for this alternative, with costs totaling approximately $73.6 million. Recent observed costs for other similarly sized treatment facilities in the Montana were used to develop the cost estimate. It was assumed that land will be required for groundwater discharge, that IP basins are constructed, and that a 4.4 mgd package treatment facility will be installed. It was assumed that 7 acres of land is needed for a price of $150,000 per acre, which is the approximate average cost per acre for large, listed lots at the time of report. Some cost savings could likely be realized by constructing a new package facility rather than upgrading an existing installation, and so the OPCC is slightly less than that of Alternative 2. This alternative holds many of the same advantages as Alternative 2. A decentralized approach involving multiple treatment facilities reduces the overall loading to the Bozeman WRF and helps to maintain the WRF’s current effluent nutrient loading for a longer period of time. Constructing a new treatment facility also allows the City to explore other discharge options, such as discharging to shallow groundwater. The primary disadvantage of this alternative is regulatory uncertainty. Acquiring a discharge permit for the satellite facility involves negotiations with DEQ and creates the potential for an unfavorable permit outcome. This alternative also results in large capital investments to construct and design the new satellite treatment facility. A summary of the overall advantages and disadvantages of Alternative 3 is shown in Table 5-13. . 5-21 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-13. Advantages and Disadvantages of Alternative 3 Pros Cons Reduce pumping costs Capital and O&M costs - 5.2.8 OPCC Summary The OPCCs for each respective alternative are summarized in Table 5-14. OPCCs represent the projected costs to implement the discharge alternatives, and do not include the costs for associated treatment. Table 5-14. Effluent Management Alternatives' OPCC Summary Effluent Management Alternative OPCC 1a –Discharge to East Gallatin - 1b – Seasonal Land App & Irr $2.5 million 1c – Shallow Groundwater Discharge $11.4 - $18.4 million1 1d – Aquifer Recharge $11.4 - $18.4 million1 1e – Wetland Treatment $4.5 million 2 – West End Flows to Belgrade $76.8 million 3 – West End Flows to Satellite Plant $73.6 million1 1 If discharge to groundwater is feasible. Possible less stringent groundwater permit Additional operations Owned and operated by the City of Unknown permit risks Bozeman Negotiation with DEQ in permitting the existing outfall 5.3 Alternatives Treatment Table The projected nutrient permitting conditions described in Chapter 4 were used to develop best-case and worst-case treatment criteria for each alternative. This information is shown in Table 5-15. The treatment criteria in Table 5-15 is used in subsequent chapters to develop treatment alternatives. The costs of these treatment alternatives are combined with the management alternative specific costs to produce final recommendations and an implementation roadmap contingent on the final outcome of Montana’s reworked nutrient regulations. 5-22 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Table 5-15. WRF Management Alternatives Nutrient Treatment Projections Alternative Description Treatment Location Discharge Location Flows (mgd) Group No. 1 Most Lenient Treatment Scenario Group No. 2 Lenient TN, Stringent TP Group No. 3 Worst Case Treatment Scenario TN (mg/l) TP (mg/l) TN (mg/l) TP (mg/l) TN (mg/l) TP (mg/l) Discharge to Alternative 1a Bozeman WRF East Gallatin Surface Water 14.6 6.4 0.27 6.4 0.05 3Surface Water Alternative 1b Seasonal Land Application Bozeman WRF East Gallatin Surface Water, Summer ~10.6 8.9 0.37 8.9 0.05 3 0.05 Bozeman WRF East Gallatin Surface Water, Winter 14.6 6.4 0.27 6.4 0.05 3 0.05 Bozeman WRF Summer Land Application1 ~4 8.9 0.37 8.9 0.05 3 0.05 Alternative 1c Shallow Groundwater Discharge Bozeman WRF Shallow Groundwater 14.6 7.5 0.27 --3 0.05 Alternative 1d Wetland Discharge Bozeman WRF WRF Wetland 14.6 6.4 0.27 --3 0.05 Alternative 1e Aquifer Recharge Bozeman WRF Aquifer 14.6 ----3 0.05 Alternative 2 West End to Belgrade Belgrade WWTP Shallow Groundwater 4.4 ------ Bozeman WRF East Gallatin Surface Water 10.2 9.2 0.39 9.2 0.05 3 0.05 Alternative 3 COB West End Satellite Plant Satellite Treatment Plant Shallow Groundwater 4.4 7.5 1 --7.5 1 Bozeman WRF East Gallatin Surface Water 10.2 9.2 0.39 9.2 0.05 3 0.05 1 Varying levels of treatment could be required depending on the intended use and the agronomic uptake rate of the receiving crop. See discussion in Chapter 5. 0.05 ll ll IJ ---- --------------------------- 5-23 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan References McEldowney, Richard. Confluence Consulting, 2019, Initial Review of the Potential for Reclaimed Water Land Application at the Riverside Country Club Golf Course and the Springhill Sod Farm. Rotar, Michael. RESPEC & New Fields, 2017, City of Bozeman Groundwater Investigation. 5-24 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Attachment A. Reclaimed Water Classifications Reclaimed Wastewater Classifications and Associated Treatment Requirements A-1 Class A-1 reclaimed wastewater must, at all times, be oxidized, coagulated, filtered and disinfected, as described below or defined in this section. Class A-1 reclaimed wastewater that is treated to the standards below is exempt from ground water permit requirements pursuant to ARM 17.30.1022. Following treatment, Class A-1 reclaimed wastewater effluent quality should have approximately 10 mg/L or less of BOD and TSS. To achieve the turbidity requirements for Class A-1 reclaimed wastewaters, a treatment process that incorporates coagulation, flocculation, sedimentation and filtration is typically required. See Section 111 (Clarification Processes) for the required design standards. Class A-1 reclaimed wastewater must be disinfected such that the median number of total coliform organisms, in the wastewater after disinfection, does not exceed 2.2 colony forming units (CFU) per 100 milliliters, as determined from the bacteriological results of the last seven days for which analyses have been completed and such that the number of total coliform organisms does not exceed 23 CFU per 100 milliliters in any sample. Class A-1 reclaimed wastewater has the quality of effluent such that all constituents meet Montana nondegradation requirements prior to application, allowing it to be applied to land at rates that exceed the agronomic uptake rate. Specifically, total nitrogen must not exceed 5.0 mg/L at any time. Per MCA 75-5-410, reclaimed wastewater proposed for aquifer recharge or injection purposes must meet, at a minimum, secondary treatment, as defined in 40 CFR Part 133, and Level II treatment for the removal of nitrogen. For aquifer recharge proposals, the effluent quality must meet either primary drinking water standards or non-degradation requirements at the point of discharge. For aquifer injection proposals, the effluent quality must meet the more stringent of either the primary drinking water standards or the nondegradation requirements at the point of discharge. Soil aquifer treatment (infiltration/percolation basins) may not be considered in meeting these requirements. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include: continuous turbidity analysis with recorder, weekly total coliform analysis, and biweekly total nitrogen analysis. Weekly disinfectant residual analysis if chemical disinfection is being utilized. A Class A reclaimed wastewater must, at all times, be oxidized, coagulated, filtered and disinfected, as described below or defined in this section. Following treatment, Class A reclaimed wastewater effluent quality should have 10 mg/L or less of BOD and TSS. To achieve the turbidity requirements for Class A reclaimed wastewaters, a treatment process that incorporates coagulation, flocculation, sedimentation and filtration is typically required. See Section 111 (Clarification Processes) for the required design standards. Class A reclaimed wastewater must be disinfected such that the median number of total coliform organisms in the wastewater after disinfection does not exceed 2.2 colony forming units (CFU) per 100 milliliters, as determined from the bacteriological results of the last seven days for which analyses have been completed, and such that the number of total coliform organisms does not exceed 23 CFU per 100 milliliters in any sample. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include: continuous turbidity analysis with recorder, weekly total coliform analysis, and monthly total nitrogen analysis. Weekly disinfectant residual analysis if chemical disinfection is being utilized. 5-25 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Reclaimed Wastewater Classifications and Associated Treatment Requirements B-1 Class B-1 reclaimed wastewater must, at all times, be oxidized, settled and disinfected, as described below or defined in this section. Class B-1 reclaimed wastewater that is treated to the standards below is exempt from ground water permit requirements pursuant to ARM 17.30.1022. Class B-1 reclaimed wastewater must be disinfected such that the median number of total coliform organisms in the wastewater after disinfection does not exceed 2.2 colony forming units (CFU) per 100 milliliters, as determined from the bacteriological results of the last seven days for which analyses have been completed, and the number of total coliform organisms does not exceed 23 CFU per 100 milliliters in any sample. Class B-1 reclaimed wastewater has the quality of effluent such that all constituents meet Montana nondegradation requirements prior to application, allowing it to be applied to land at rates that exceed the agronomic uptake rate. Specifically, total nitrogen must not exceed 5.0 mg/L at any time. Per MCA 75-5-410, reclaimed wastewater proposed for aquifer recharge or injection purposes must meet, at a minimum, secondary treatment, as defined in 40 CFR Part 133, and Level II treatment for the removal of nitrogen. For aquifer recharge proposals, the effluent quality must meet either primary drinking water standards or nondegradation requirements at the point of discharge. For aquifer injection proposals, the effluent quality must meet the more stringent of either the primary drinking water standards or the nondegradation requirements at the point of discharge. Soil aquifer treatment (infiltration/percolation basins) may not be considered in meeting these requirements. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include weekly total coliform analysis and bi-weekly total nitrogen analysis. Weekly disinfectant residual analysis if chemical disinfection is being utilized. B Class B reclaimed wastewater must, at all times, be oxidized, settled and disinfected, as described below or defined in this section. Class B reclaimed wastewater must be disinfected such that the median number of total coliform organisms in the wastewater after disinfection does not exceed 2.2 colony forming units (CFU) per 100 milliliters, as determined from the bacteriological results of the last seven days for which analyses have been completed, and the number of total coliform organisms does not exceed 23 CFU per 100 milliliters in any sample. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include weekly total coliform analysis and monthly total nitrogen analysis. Weekly disinfectant residual analysis if chemical disinfection is being utilized. * C Class C reclaimed wastewater must, at all times, be oxidized, settled and disinfected, as described below or defined in this section. Class C reclaimed wastewater must be disinfected such that the median number of total coliform organisms in the wastewater after disinfection does not exceed 23 colony forming units (CFU) per 100 milliliters, as determined from the bacteriological results of the last seven days for which analyses have been completed, and the number of total coliform organisms does not exceed 240 CFU per 100 milliliters in any sample. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include monthly total coliform and monthly total nitrogen analysis. Weekly disinfectant residual analysis if chemical disinfection is being utilized. D Class D reclaimed wastewater must, at all times, be oxidized and settled, as described below or defined in this section. Disinfection will typically not be required for Class D reclaimed wastewater; however, proximity to areas of public access or habitation may dictate that disinfection be provided in order to protect public health. The minimum monitoring level required during periods of use (including prior to seasonal startup, if applicable) must include: monthly total nitrogen analysis. 5-26 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Attachment B. Potential Areas for Irrigation Reuse Application/User Potential Irrigation Reuse (gpd) Potential Irrigation Reuse (MGD) Local Government Use Christie Fields 19,500 0.02 City Cemetery 90,200 0.091 City Valley Medical Center 6,200 0.006 County Courthouse 4,500 0.005 City Shops 4,200 0.004 County Fairgrounds 3,700 0.004 Fairground Barn 2,500 0.003 Government Use Subtotal 130,800 0.133 School Use Montana State University 161,000 0.161 Irving School 4,500 0.005 Hawthorne Elementary 4,200 0.004 Longfellow Elementary 2,800 0.003 Whitter Elementary 3,000 0.003 Central Offices 1,000 0.001 Chief Joseph Middle School 500 0.001 School Use Subtotal 177,000 0.178 Private Beck-Jones Canal 2,230,000 2.23 Springhill Sod Farm 656,986 0.657 Bridger Creek Golf Course 186,000 0.186 Valley View Golf Club 186,000 0.186 Story Mill 80,000 0.08 Harvest Creek Park 51,000 0.051 Riverside Golf Course 261,918 0.262 Cashman Nursery 26,000 0.026 Lawson's Greenhouse 21,000 0.021 Langohr's Flowerland 30,000 0.03 Bridger Gardens 15,000 0.015 Brentwood Park 15,000 0.015 Valley Commons 2,000 0.002 ------------- 5-27 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan Private Subtotal 3,760,904 3.761 City of Bozeman Open Space East Gallatin Recreation Area 113,000 Bozeman Pond 26,000 WRF Property 354,000 Bronken Park 136,000 Sport Complex 73,000 Langohr Gardens 51,000 Lindley Park 49,000 Cattail Creek 43,000 Kirk Park 39,000 Rose Park 36,000 Valley Unit 30,000 W. Babcock/Aashiem Field 20,000 Christie Fields 19,000 Cooper Park 15,000 Westfield Park 15,000 Valley West 14,000 0.014 Headlands Park 12,000 0.012 Sandan 11,000 0.011 South Side Park 10,000 0.01 North Grand Fields 10,000 0.01 Bogert Park 9,000 0.009 Centennial Park 9,000 0.009 Baxter Square 8,000 0.008 Beall Park 8,000 0.008 Jarrett Park 6,000 0.006 Walton Homestead 4,000 0.004 North Meadows 3,000 0.003 Sacajawea Park 1,000 0.001 Creekside Park 1,000 0.001 City of Bozeman Open Space Subtotal 1,125,000 1.126 Miscellaneous DOT-Rest Area 13,000 0.013 State Grazing Allotment 356,000 State-Ag Allotment 79,000 City of Bozeman-Ag Land 282,000 0.356 0.079 0.282 ---------------------------------~~ 0.11 0.03 0.354 0.136 0.073 0.051 0.049 0.043 0.039 0.036 0.03 0.02 0.019 0.015 0.015 5-28 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan FWP-Grazing Allotment 179,000 0.179 State-Commercial Park 65,000 0.065 I-90 ROW 209,000 0.209 Miscellaneous Subtotal 1,183,000 1.183 Total 6,376,704 6.381 A map showing a selection of the largest and/or most feasible potential application sites is presented in Figure B-1. 5-29 Figure B-1 Potential Areas for Irrigation Reuse • Canal Intake Effluent Availability (GPO) ->SOOk -250-S00k LJ 150-250k L 50-150k CJ 10-S0k Name Be(k•Jones Canal Flow Capacity (GPD) 2,230,000 Bridger Creek Golf Course Bronken Park Cashman Nursery or, Cemetery 186,000 136,000 26,000 90,200 DOT Rest Area 13,000 East Gallatin Recreational Area 113,000 Harvest Creek Park 51,000 1·90 ROW 209,000 langohr Gardens Lindley Park Montana State University Riverside Golf Course Sports Complex Sp1inghill 5od Farm Stcry Mill Valey View Golf Course WRF Prc,perty 51,000 49,000 161,000 261,918 73,000 656,986 80,000 186,000 354,000 0 Bozeman WRF Facility Plan Update Chapter 5 – Effluent Management Plan 5-30 Chapter 6 Existing Unit Processes Evaluation 6 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Contents Introduction.......................................................................................................................................6-1 6.1 Recent WRF Upgrades ..........................................................................................................6-1 6.2 Overview of Existing Process Elements.................................................................................6-1 6.2.1 Hydraulic Capacity Analysis......................................................................................6-9 6.2.2 Headworks (Screening and Grit Removal)..............................................................6-12 6.2.3 Primary Clarifiers.....................................................................................................6-13 6.2.4 Primary Effluent Pump Station................................................................................6-14 6.2.5 BNR Bioreactors......................................................................................................6-15 6.2.6 Aeration Blowers .....................................................................................................6-18 6.2.7 Secondary Clarifiers................................................................................................6-19 6.2.8 RAS/WAS Systems .................................................................................................6-20 6.2.9 Thickening ...............................................................................................................6-21 6.2.10 UV Disinfection........................................................................................................6-24 6.2.11 Anaerobic Digestion ................................................................................................6-25 6.2.12 Biosolids Dewatering...............................................................................................6-27 6.3 Capacity Summary ...............................................................................................................6-28 Tables Table 6-1. WRF Flow and Loading Design Criteria from Phase I Improvements Upgrade.......................6-2 Table 6-2. Projected Loadings for Planning Period ...................................................................................6-2 Table 6-3. WRF Headworks Design Conditions ......................................................................................6-12 Table 6-4. Primary Clarifier Design Conditions........................................................................................6-14 Table 6-5. PEPS Design Conditions........................................................................................................6-15 Table 6-6. WRF Bioreactor Design Conditions........................................................................................6-17 Table 6-7. Blower System Design Conditions..........................................................................................6-19 Table 6-8. Secondary Clarifier Design Conditions...................................................................................6-20 Table 6-9. RAS/WAS System Design Conditions....................................................................................6-21 Table 6-10. Thickening System Design Conditions .................................................................................6-23 Table 6-11. UV System Design Conditions..............................................................................................6-25 Table 6-12. Digester Design Conditions ..................................................................................................6-26 Table 6-13. Screw Press Operating Information......................................................................................6-27 Table 6-14. Capacities of Existing Unit Processes ..................................................................................6-29 Table 6-15. Projected Years for Completion of Required Upgrades .......................................................6-30 Figures Figure 6-1. Overview of Current WRF Layout............................................................................................6-4 Figure 6-2. Existing Process Flow Diagram I.............................................................................................6-6 Figure 6-3. Existing Process Flow Diagram II............................................................................................6-7 Figure 6-4. Existing Process Flow Diagram III...........................................................................................6-8 Figure 6-5. WRF Primary Clarifiers Water Surface Elevations ..................................................................6-9 Figure 6-6. WRF Main Hydraulics Water Surface Elevations ..................................................................6-10 i Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Figure 6-7. WRF Headworks Water Surface Elevations..........................................................................6-11 Figure 6-8. Bioreactor Process Basin Arrangements ..............................................................................6-16 Figure 6-9. WRF 5-Stage Bardenpho Process Schematic ......................................................................6-17 ii Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation This page is intentionally left blank. iii 6 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Introduction This chapter describes the existing major process elements at the Bozeman Water Reclamation Facility (WRF). The relative capacities of major unit process elements are discussed and evaluated against the WRF’s 2040 flow and loading projections. Projects completed at the WRF since the previous facility plan in 2006 are also discussed. An overview of plant process flow is first provided, with more detailed breakdowns of the various process elements included in the subsequent sections. 6.1 Recent WRF Upgrades Several projects and upgrades have been completed at the WRF since the previous facility plan was finalized in 2006. The largest and most important amongst these projects was the Phase I Improvements, which lasted from 2008 to 2012. This project consisted of $53 million in improvements that upgraded the WRF to a high performance biological nutrient removal (BNR) facility. Included in the improvements were new bioreactors, secondary clarifiers, headworks elements, primary effluent pumping, RAS/WAS pumping, UFAT upgrades, and UV disinfection. A new Admin/Lab building was also completed during this same timeframe. The new bioreactors were the primary design improvement of the Phase I Improvements project. The bioreactors upgraded the WRF to a 5-Stage Bardenpho design, allowing for enhanced biological nitrogen and phosphorus removal without the addition of expensive chemicals. Solids handling capabilities at the WRF were also upgraded during the Digester Control Building Project at a cost of approximately $6.0 million, which lasted from 2010 to 2014. Solids digestion, thickening, and dewatering were all upgraded during this phase of the project. Several small works improvements projects have been completed since 2017. These improvements included cleaning of the digesters and installation of a new digester mixer and new membrane roof on Digesters 1, 2, and the control building. The clarifier launders were replaced with fiberglass reinforced plastic (FRP) and a natural gas jockey boiler was added. These small works improvements were completed at a cost of approximately $900,000. Ongoing projects at the WRF include an expansion to the existing Solids Handling Building and improvements to the existing pretreatment (old headworks) facility. As part of this expansion, a new dewatering screw press was installed in the Solids Handling Building and a new conveyor system was installed in the loadout bay. A 5/8-IN bar screen was added in the Pretreatment Building upstream of the Headworks to remove larger screenings. Cost for these improvements totaled approximately $2.9 million. 6.2 Overview of Existing Process Elements The Bozeman WRF is a high performing 5-Stage Bardenpho BNR facility located adjacent to the East Gallatin River. The existing WRF infrastructure is currently sized for the flow and loading design criteria outlined in Table 6-1, and has a rated capacity of 8.5 6-1 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation mgd. The projected flow and loading conditions for the 20-year planning period is shown in Table 6-2. Table 6-1. WRF Flow and Loading Design Criteria from Phase I Improvements Upgrade Criteria Value Units Design Flows Annual Average, 2015 8.5 mgd -------- ------ ---- -------------------- Max Month, 2015 10.6 mgd Peak Daily, 2015 12.7 mgd Peak Hourly, 2015 16.9 mgd Annual Average, 2025 13.9 mgd Max Month, 2025 17.4 mgd Peak Daily, 2025 20.8 mgd Peak Hourly, 2025 25.4 mgd Design Influent Loads CBOD (Max Month, 2015) 17,600 lb/day TSS (Max Month, 2015) 19,100 lb/day NH3 (Max Month, 2015) 1,950 lb/day CBOD (Peak Daily, 2015) 26,000 lb/day TSS (Peak Daily, 2015) 29,400 lb/day NH3 (Peak Daily, 2015) 2,810 lb/day Table 6-2. Projected Loadings for Planning Period Year 2025 2030 2035 2040 Population 64,839 78,887 95,978 116,772 Annual Average Flow, mgd 8.1 9.9 12.0 14.6 CBOD, lb/day 13,583 16,526 20,106 24,462 TSS, lb/day 13,764 16,746 20,374 24,788 NH3, lb/day 1,443 1,756 2,137 2,600 TN, lb/day 2,363 2,875 3,497 4,255 TP, lb/day 308 374 455 554 Maximum Monthly Average Flow, mgd 9.9 12.1 14.7 17.9 CBOD, lb/day 15,340 18,664 22,707 27,627 TSS, lb/day 16,403 19,957 24,280 29,541 6-2 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Year 2025 2030 2035 2040 NH3, lb/day 1,815 2,208 2,687 3,269 TN, lb/day 2,936 3,572 4,346 5,288 566 688 Peak Daily Average TN, lb/day TP, lb/day Peak Hourly Flow Flow, mgd 17.5 20.6 24.2 28.4 -------- ---------------- TP, lb/day 382 465 Flow, mgd 11.8 14.3 17.4 21.2 CBOD, lb/day 30,889 37,581 45,723 55,630 TSS, lb/day 26,070 31,719 38,591 46,951 NH3, lb/day 5,807 7,066 8,596 10,459 The Bozeman WRF is made up of the following main process elements: Headworks Primary Clarifiers Primary Effluent Pump Station (PEPS) Gravity Thickeners/Fermentation BNR Bioreactors Secondary Clarifiers RAS/WAS Systems UV Disinfection Anaerobic Digestion Biosolids Thickening Biosolids Dewatering An overview of the current WRF layout is provided in Figure 6-1. Detailed discussions of each of the main process elements are included in the subsequent sections. 6-3 1. Headworks 2 Primary Clarifiers 3. Primary Effluent Pump Station 4. Secondary Clarifiers 5. Bioreactor No. l 6. Bioreactors No, 2 & 3 Fermenter & Gravity Thickener 8. Dissolved Air Flotation Thickener 9. UV Disinfection & Outfall 10. Digester Control Building No. 1 11. Digester Control Building No. 2 & Digester No. 3 12. Administration/Laboratory Building Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Figure 6-1. Overview of Current WRF Layout 6-4 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation The general process flow through the WRF is as follows. Influent flow to the WRF enters the Headworks Building where it passes through 6-mm perforated plate screens that remove inorganic debris and trash. Flow continues to the Primary Clarifiers, where organic solids are settled from the primary clarifier influent. Settled solids, i.e. primary sludge, are pumped by the primary sludge pumps to the Sludge Fermenter and Thickener, which together comprise the plant’s UFAT process. A return stream rich in volatile fatty acids (VFAs) is provided by the UFAT process, which supplements phosphorous removing bacteria and denitrifying bacteria in the Bioreactors, enhancing the existing BNR process. However, the WRF currently sees adequate phosphorus removal without the use of UFAT, and so current plant operation is simply to thicken the primary sludge and not to ferment it, the overflow is still sent to the bioreactor via the Primary Effluent Pump Station (PEPS). After thickening, sludge is pumped by the thickened sludge pumps to the Digesters where it is broken down into smaller volumes and biogas is produced. Digested sludge is ultimately sent on to the dewatering process, and the resulting cake is sent to disposal and composting at the Logan Landfill. After primary clarification, primary clarifier effluent flows to the primary effluent pump station, where it is pumped to the Bioreactors. The Bioreactors consist of a series of cells where nutrients and biological oxygen demand, along with other contaminants, are removed from the process flow. Effluent from the Bioreactors then flows to the Secondary Clarifiers, where the remaining organic solids are settled and a clear secondary effluent is produced that is suitable for tertiary treatment. The secondary clarifier effluent flows to UV Disinfection before being discharged to the East Gallatin River. Settled solids from the Secondary Clarifiers, i.e. return activated sludge (RAS), is pumped back to the Bioreactors to maintain proper microbial populations. Some of the RAS is also wasted, and the waste activated sludge (WAS) is pumped to the dissolved air flotation thickener (DAFT) and rotary screen thickener (RST). The thickened WAS is then combined with the thickened primary sludge stream and moves on to the digestion process. The existing overall plant process flow schematics are shown on Figure 6-2, Figure 6-3, and Figure 6-4. Dashed lines indicate assumed future additions. 6-5 FIGURE 6-2. 2 3 4 5 6 7 8 DRAIN 010 DRAIN PEPS WETWELL D VORTEX GRIT REMOVAL, lYP 2 C Pl -----Pl RAS HEADWORKS SC A (FROM PEPS) SC 014 (FROM BIOREACTOR N0.2) NEW INFLUENT DIVERSION a: PSC I I I I I I I BSC ,,., I I I -'- ~ > 0 ►!:Q ABI ABI PAER 2 AB1 EFF ANT 2 RAS 2 SZ2 ,,- AER 28 ~SC AER2A I AB EFF003 TO SCL AB EFF004 TO SCL ~RAS FROM ~SCL B ABI ~RAS FROM ~SCL AB EFF ~SL PUMP, lYP 3 VFA PSL I I I: I ~F=R=O_M__o_u_1_:-=._A-J~~~)>---------------------L--_--_-_-_-_-_--_-_-_-_--_-_-_-_-_--_"________j~~FA~__________J ◊~◊? ◊~◊ 006 TO ◊~◊ UFAT A D 005 D PROJECT MANAGER D. HARMON DESIGNED BY M. BENISCH PROCESS FLOW DIAGRAM -ICity of Bozeman WRFDRAWN BY MORRISON CHECKED BY Phase 1 MAIERLE, INC. Hl~ Improvements Project,.._,,._,_. HOR Enginel!ring, Inc. 7/2008 REVISED PERMIT SUBMITTAL SET SHEETa 1" 2" IFILENAME IOOOOG1 O.dwg6/2008 PERMIT SUBMITTAL SET I1--lBozeman1ISSUE DATE DESCRIPTION PROJECT NUMBER 000000000060746 Montana 2008 -I I SCALE INONE 0000G10 2 3 4 5 6 7 8 DEWATERING PUMP \ TO PEPS<'--__oo_s_ __,1----------11 ◊ ~◊1---...J > DSECONDARY 009 SCUM TO '-----DAFT WAS PUMP, lYP 2 \ ~ ~·7◊~◊ TO DAFT~◊f--@--i ◊ ◊~◊ AB EFF TO SCL 003 AB EFF TO SCL 004 RAS TO AB 1 012 IRAS TO AB 1 012 I MORRISON ... __MAIERLE, INC. HOR Engineering, Inc::. -6/2008 PERMIT SUBMITTAL SET ISSUE DATE DESCRIPTION ~r---@--i◊ ~r---@--i◊ ~r---@--i◊ RAS RAS RAS PROJECT MANAGER D. HARMON DESIGNED BY M. BENISCH DRAWN BY CHECKED BY PROJECT NUMBER 000000000060746 ~----------------7 I II I I -<- SCL 5 - B INFLUENT SPLIT BOX AB EFF AREATION BASIN EFFLUENT SPLIT BOX I ~ ◊ f L Bozeman, Montana FROM FLITURE '>' EFFLUENT FILTERS I I I I I I SE UV DISINFECTION City of Bozeman WRF Phase 1 Improvements Project 0 M 2008 B A FIGURE 6-3.PROCESS FLOW DIAGRAM -II SHEET2· FILENAME OOOOG11.dwg SCALE NONE 0000G11 C 2 3 4 5 6 7 8 DRAIN 7 D PRESSATEl ◊ ~ FROM WASSTATION PUMP 001 C -'-◊ ,l◊H H SECONDARY SCUM ... SLUDGE 0 GRINDER ... fZ DS i;_sL (BYPASS) l B FROM PSL ♦ STATION PUMP~◊006 ""\ ' i • TSN;;r,-~~- /::/ A I ◊♦ TSN TSN TO PE PUMP013 STATIONt ----1FPSL ___/ c·ty FIGURE 6-4.SOLIDS FLOW DIAGRAM, of Bozeman WRF MORRISON Phase 1 ~~c. Improvements Pro·ject HOR Engineering. Inc. 0 ,. OOOOGl 2.dwg P""""'1Bozeman, Montana 2008 0000G12 ... ... ... ts g g 00 0 N ... ... g g ... 0\ ... g 00 ... 0\ ... 0 Starting water surface elevation (4602.78) +-----+-----+-----o---+-----+-----+-------< 54 in PE (4603.59) 48 in PE (4604.01) 42 in PE (4604.26) 36 in PE (4604.64) 30 in PE (4605.16) 24 in PE (4605.81) Primary Clarifier Launder (4606.35) Primary Clarifier Weirs (4606.74) PCS to Splitter ( Phase 3) (4609.39) t ~ OJ nl' ~ ~ ol' (') (!) m ii, < OJ g. ~ ~ ,J Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation 6.2.1 Hydraulic Capacity Analysis A hydraulic capacity analysis using the projected 2040 peak hour flow was performed on the existing WRF liquid stream using the Visual Hydraulics program. Dimensions and elevations were determined from WRF record drawings. A Visual Hydraulics model was created for the headworks, primary clarifiers, and bioreactors. The model did not indicate that any process elements would become submerged at future flows, through the 20-year planning period, except for elements of the bioreactors, which are designed to be submerged. Graphical representations of the water surface elevations can be seen in the following figures for the headworks, primary clarifiers, and the overall WRF hydraulics. Figure 6-5. WRF Primary Clarifiers Water Surface Elevations 6-9 Starting water surface elevation (4596.7) Outfall Weir (4602.16) Pressue Line (4602.9) Parshall Flume (4602.98) UV System (4604.96) From UV to Collection Box (4605.53) From Collection Box to 30 in Reducer (4606.26) From 30 in Reducer to 24 in Reducer (4606.56) From 24 in Reducer to SC6/8 (4606.69) Clarifier Launder (half of one clarifier) (4608.79) SC6/8 Clarifier Weirs (4609.73) From SC6/8 to Splitter Box (4610.64) Splitter Box Weir for SC6/8 (4611.59) From Splitter to BNR2 (4613.52) From BNR2 to BNR3 (4614.39) From BNR3 to BNR4 (4614.8) From BNR4 to BNRS (4614.93) Bioreactor Outlet Weir (4614.95) Weirl ( PstAr to PstAx) (4614.97) Orificel ( PstAr to PstAx) (4614.98) Weir2 (PstAx to MnAr) (4615) Orifice2 (PstAx to MnAr) (4615.01) Mid-Channel Outlet (4615.03) Mid-Channel (4615.05) Mid-Channel Inlet (4615.07) Weir3 ( MnAr to Swing) (4615.09) Orifice3 (MnArto Swing) (4615.11) Weir4 (Swing to MnAx) (4615.13) Orifice4 (Swing to MnAx) (4615.15) Weirs (MnAx to An) (4615.17) Orifices ( MnAx to An) (4615.19) Bioreactor Inlet Weirs (4615.21) Open Channel (4615.21) Bio reactor Splitter Gate (4615.99) ,,. V, 00 V, ,,. V, lD 0 ,,. V, lD V, ~ ,,. ~ 0 " ' ,,. ~ V, \ \ ,,. cr, .... 0 \ ,,. cr, .... V, ◄ ◄ ► ► l i ,,. g) 0 t ~ OJ ~ !€ iil' r, (1) m 1,' < ~ 5· ~ Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Figure 6-6. WRF Main Hydraulics Water Surface Elevations 6-10 .p. s IV Starting water surface elevation (4608.4) From Splitter Box to Flume (Phase 3) (4608.7) lnfluet Parshall Flume (4609.4) From Flume to Inlet Box (Phase 3) (4609.77) From Inlet Box to Headworks (4610.27) Grit Chamber Effluent Channel (4610.31) Grit Chamber Influent Tube (4610.53) Headworks Channel (4610.55) Screen Head lot (4612.2) Screen Influent Channel (4612.21) Transfer Channel (4612.23) Old Headworks Channel (4612.28) Plant lnflue nt 1 (4613.15) Plant Influent 2 (4616.04) Plant lnflue nt 3 (4618.68) .p. .p. .p. s s s .p. a, (X) 0 ◄ .p. a, .... 0 ► .p. a, .... IV \ ► .p. a, .... .p. \ .p. a, .... a, .p. a, .... (X) \ I\ '\.. ~ .p. a, IV 0 t ~ OJ (b -, Vl C: -, ii1' n (1) m ii, < ~ o· ~ ~ ,J Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Figure 6-7. WRF Headworks Water Surface Elevations 6-11 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation 6.2.2 Headworks (Screening and Grit Removal) Raw wastewater enters the WRF at the Headworks Building, where it flows through one of two perforated plate screens with 6-mm openings. An additional coarse screen, with 3/8-in openings, was installed in 2022. This new screen is rated for 18 mgd and will be used to alleviate excess loading on the existing perforated plate screens. Trash material caught on the surfaces of the screens are transported out of the influent channel for removal. Screenings material is removed from the surfaces of the screens by a rotating brush and spray water, and the material is eventually discharged to a dumpster. Normal operation is for one perforated screen to be in use while the second perforated screen remains on standby. Each perforated screen is designed for a peak flow of 14 MGD. After the perforated plate screens, wastewater flows to the upper portion of one of two grit removal basins. Normal operation is for one grit basin to be in use while the second grit basin remains on standby. Each grit chamber is sized for a peak flow of 14 MGD and minimum flow of 2.5 MGD. Organic material remains in suspension at all flow rates in the grit basins while grit settles to the bottom, where it is then pumped to a grit washer. The grit is eventually discharged to a dumpster by an inclined screw conveyor. Following grit removal, influent flow passes through a Parshall flume and then flows to the Primary Clarifiers. Design conditions for the existing headworks process elements are summarized in Table 6-3. The perforated plate influent screens and the grit removal system are both currently sized to meet a 28 mgd peak day flow. The Parshall flume is capable of measuring flows up to approximately 32 mgd. These capacity ratings are the respective manufacturer rated capacities. Table 6-3. WRF Headworks Design Conditions Criteria Value Units Perforated Plate Influent Screens -- --- Number of Units 2 - Channel Width 4.0 ft Peak Hydraulic Capacity (ea) 14 mgd Screen Opening Size 6 mm Coarse Screen Number of Units 1 - Channel Width 3.5 ft Peak Hydraulic Capacity (ea) 18 mgd Screen Opening Size 3/8 in Manual Screen Number of Units 1 - Channel Width 4.0 ft 6-12 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Criteria Value Units Peak Hydraulic Capacity (ea) 30 mgd Screen Opening Size 0.75 in Grit Removal System Number of Units 2 - Type Vortex Basins - Diameter 12 ft Peak Hydraulic Capacity (ea) 14 mgd Grit Pumping Number of Units 3 (2 operating) - Type Recessed Impeller - Capacity (ea) 250 gpm Screenings Washing Number of Units 2 - Type Washer/Compactor - Grit Washing Number of Units 2 - Type Classification/Washing - Capacity (ea) 250 gpm Flow Metering ----- - -- Number of Units 1 - Type Parshall Flume - Throat Width 36 in Peak Hydraulic Capacity (ea) 32 mgd 6.2.3 Primary Clarifiers There are currently three circular center feed primary clarifiers at the WRF. The primary clarifiers (PCL) begin the process of separating organic solids from the influent flow. Organic solids are settled in the primary clarifiers, and the primary sludge (PSL) is pumped by the primary sludge pumps to the thickening process. The primary sludge pumps are controlled by VFDs and each pump is rated at 10 hp and 250 gpm. Primary clarifier effluent flows to the Primary Effluent Pump Station (PEPS) where it is pumped to the Bioreactors. There are also two pumps which convey primary scum from the Primary Clarifiers. One pump serves both PCLs No. 1 and No. 2, and the other serves PCL No. 3 exclusively. Primary Clarifiers are sized on the basis of surface overflow rate. Surface overflow rate is calculated as the clarifier influent flow rate, including any plant recycle streams, divided 6-13 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation by the total tank area within the outer walls, including the area of the effluent collection troughs within the outer walls. Suspended solids are captured in the clarifier if the settling velocity is greater than the average overflow rate. The Primary Clarifiers at the WRF have a design overflow rate of 1,064 gpd/ft2 at their original max design month flow of 10.6 mgd. Design conditions for the Primary Clarifiers are summarized in Table 6-4. Table 6-4. Primary Clarifier Design Conditions Criteria Value Units Primary Clarifiers Number of Units 3 - Diameter 65 ft Type Circular Center Feed - Sidewater Depth 8 ft Surface Area (ea) 3,318 ft2 Overflow Rate (Max Month 2015) 1,064 gpd/ft2 Primary Sludge Pumps --- - - Number of Pumps 3 - Type Vortex - Capacity (ea) 250 gpm Primary Clarifier Scum Pumps Number of Pumps 2 - Clarifiers 1 & 2 Capacity (ea) 100 gpm Clarifier 3 Capacity (ea) 200 gpm 6.2.4 Primary Effluent Pump Station The Primary Effluent Pumping Station (PEPS) receives effluent flow from the Primary Clarifiers, RAS from the secondary clarifiers, and the VFA stream from the Unified Fermentation and Thickening (UFAT) process. Flow from the PEPS is pumped to the Bioreactors. The PEPS has three vertical turbine pumps, each equipped with a VFD, that handle the combined primary clarifier effluent and RAS flow. Each pump has a capacity of 14.4 mgd. There is room in the building for the future installation of a fourth pump. Flow from the pumps is discharged through magnetic flow meters and then to the bioreactors. The total current pumping capacity with one pump out of service is 28.8 mgd. Design conditions for the existing PEPS elements are summarized in Table 6-5. 6-14 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-5. PEPS Design Conditions Criteria -- - - - Units Value Primary Clarifier Effluent Pumps Number of Units 3 - Type Vertical turbine - Peak Hydraulic Capacity (ea) 14.4 mgd Return Flow Pumping 100% Max Month Flow - Primary Clarifier Effluent Flow Metering Type Magnetic - Number of Units 2 at 30", 1 at 20" - Capacity (ea) 2 at 500 - 13,000 1 at 500 - 4,000 gpm Primary Scum Pump Type Submersible Non-Clog - Number of Units 1 each Capacity 133 gpm Drain Pump Type Sump - Number of Units 2 each Capacity (ea) 70 gpm 6.2.5 BNR Bioreactors Three Bioreactor Basins comprise the BNR process at the Bozeman WRF. Bioreactor Basin No. 1 consists of an anaerobic zone followed by four aeration cells that operate in a phased nitrification/denitrification (PNDN) mode. The anaerobic zone is used for biological phosphorus removal, but it can be bypassed if biological phosphorus removal is not required. Flow travels in a clockwise direction from Cell 1 to combine with flow from Cell 2 and continues on through Cells 3 & 4 to secondary clarification. Cells 3 & 4 provide additional nitrification. Bioreactors No. 2 & No. 3 are each 5-Stage Bardenpho BNR facilities. Each bioreactor consists of an Anaerobic Zone, Anoxic Zone 1, Swing Zone 1, Aerobic Zone, Post- Anoxic Zone, and Post-Aerobic Zone having volumes of 0.15 MG, 0.24 MG, 0.24 MG, 0.76 MG, 0.16 MG, and 0.03 MG respectively. A graphical representation of the PNDN and 5-Stage Bardenpho process basin arrangements is shown in Figure 6-8. 6-15 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Bioreactor Basin #3 Bioreactor Basin #2 Bioreactor Basin #1 Anaerobic Zone Bioreactor Basin #1 MLR Secondary Clarifiers Anaerobic Zone Anaerobic Zone Post-Aerobic Zone Post-Aerobic Zone Anoxic Zone Anoxic Zone Aerobic Zone Aerobic Zone Post-Anoxic/Swing Zone Post-Anoxic/Swing Zone Air On/OFF Aerobic Zone Aerobic Zone RAS WAS To DAF PE From Primary Clarifiers PNDN Process ML ML PE ML To UV Disinfection Stop Gate Swing Zone Swing Zone Baffle Anaerobic Bypass MLR Gravity Flow NC Figure 6-8. Bioreactor Process Basin Arrangements The 5-Stage Bardenpho process at the Bozeman WRF generally works in the following manner: Primary clarifier effluent, which is combined with RAS stream, is sent to the anaerobic zone of each bioreactor. Phosphorus is released during anaerobic conditions, and is subsequently taken up by microbial growth requirements during aerobic conditions. The second zone of the bioreactor is anoxic, and is where nitrates from the aerobic mixed liquor recycle are denitrified to nitrogen gas. A portion of the anoxic zone operates as a swing aerobic zone for process flexibility. In the aerobic zone of the bioreactor, influent ammonia is converted to nitrate and the remaining BOD is stabilized. The previously released phosphorus is also taken up by microbial growth. To further reduce total nitrogen, a post anoxic zone follows the aerated zone. 6-16 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation The fifth zone is a small post-aeration zone which is used to strip nitrogen bubbles and raise the dissolved oxygen concentration of the process flow prior to secondary clarification. A schematic of the 5-Stage Bardenpho process is provided on Figure 6-9. VFA's ANX AER I I I I I ANX AER : MLR : •------------------------~ RAS ------- ------- SCL Figure 6-9. WRF 5-Stage Bardenpho Process Schematic The WRF Bioreactors are currently sized to meet a 10.6 mgd max month flow. Overall design conditions for the bioreactors are summarized in Table 6-6. Table 6-6. WRF Bioreactor Design Conditions Criteria Value Units Bioreactor No. 1 (PNDN) Anaerobic Cell Depth 20 ft Anaerobic Cell Dimensions (w x l) 34 x 38 ft Anaerobic Cell Volume 0.19 mg Number of Aerobic Tanks 4 - Aerobic Cell Depth 20 ft Aerobic Cell Dimensions (w x l) 55 x 55 ft Aerobic Cell Volume (ea) 0.45 mg Aerobic Zone Volume (total) 1.81 mg Bioreactors No. 2 and No. 3 (5-Stage Bardenpho) Anaerobic Zone Depth 20 ft Anaerobic Zone Dimensions (w x l) 34 x 30 ft Anaerobic Zone Volume (ea) 0.15 mg Anoxic Zone Depth 20 ft Anoxic Zone Dimensions (w x l) 34 x 48 ft Anoxic Zone Volume (ea) 0.24 mg Swing Zone Depth 20 ft Swing Zone Dimensions (w x l) 34 x 48 ft Swing Zone Volume (ea) 0.24 mg Aerobic Zone Depth 20 ft Aerobic Zone Dimensions (w x l) 34 x 150 ft Aerobic Zone Volume (ea) 0.76 mg 6-17 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Criteria Value Units Post Anoxic Zone Depth 20 ft Post Anoxic Zone Dimensions (w x l) 34 x 31 ft Post Anoxic Zone Volume (ea) 0.16 mg Post Aerobic Zone Depth 20 ft Post Aerobic Zone Dimensions (w x l) 34 x 6 ft Post Aerobic Zone Volume (ea) 0.03 mg Bioreactor No. 1 (Process Criteria) CBOD Loading 5,280 lbs/day Anaerobic Zone HRT 1.4 hrs Aerobic Zone HRT 13.5 hrs MLSS 3,600 mg/l Bioreactor No. 2 and No. 3 (Process Criteria) CBOD Loading 6,160 lbs/day Anaerobic Zone HRT 1 hrs Anoxic Zone HRT 1.5 hrs Swing Zone HRT 1.5 hrs Aerobic Zone 5 hrs Post Anoxic Zone 1 hrs Post Aerobic Zone 0.2 hrs MLSS 3,600 mg/l Bioreactor No. 1 Air Distribution Requirements Air Flow (Max Month) 6,000 scfm ------------ -------------- Bioreactor No. 2 and No. 3 Air Distribution Requirements Swing Zone Air Flow (Max Month) 1,270 scfm Aerobic Zone Air Flow (Max Month) 3,410 scfm Post Aerobic Zone Air Flow (Max Month) 100 scfm 6.2.6 Aeration Blowers Four turbo blowers, each rated at approximately 4,800 cfm, provide process air to the Bioreactors. One of the blowers is designated as a standby. All of the blowers discharge into a common header outside the Blower Building. The blowers operate in a lead, lag, lag, standby fashion. The function of the blower control system is to maintain a setpoint pressure in the header providing an adequate air supply to the bioreactors. The blower control will turn blowers ON/OFF and vary the blower(s) motor speed to maintain the pressure setpoint. As header pressure increases above the setpoint, the control will reduce the speed of the blower(s) and turn blowers OFF as needed to return to the setpoint. At least one blower will remain in operation unless the operator manually overrides the control loops. As header pressure falls below 6-18 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation the setpoint, the control will increase the blower(s) speed and turn blowers ON as needed to return to the setpoint. Blower speed is matched when more than one blower is in service. Table 6-7 provides a summary of the blower capacity. Table 6-7. Blower System Design Conditions Criteria Value Units Number of Units 4 - Type Turbo - Blower Capacity 11,500 scfm Discharge Pressure 10 psig ------6.2.7 Secondary Clarifiers Effluent from the Bioreactors flows to the Secondary Clarifiers. The purpose of secondary clarification is to remove readily settleable solids. Settled solids are pumped back to the Bioreactors as RAS to maintain sufficient activated sludge concentrations. A portion of the RAS is wasted as WAS and is thickened and sent on to the Digesters. The Secondary Clarifiers ultimately produce a clear effluent that is sent on to UV Disinfection. There are six Secondary Clarifiers at the WRF. Secondary Clarifiers No. 1 through No. 4 are 65-FT in diameter and were not upgraded during the Phase I Improvements. Secondary Clarifiers No. 5 and No. 6 are 85-FT in diameter and were constructed as part of the Phase I Improvements Project. Mixed liquor enters beneath the clarifiers and is discharged within the center well. Non-potable water is sprayed in the center well for foam control. The clarifier drive sludge sweep pushes thickened sludge to a sump located near the center column. The scum sweep pushes floating scum to the scum beach where it is deposited in a scum pit. Scum pumps remove scum from the pit and pump scum to the digester. Secondary effluent overflows the peripheral weir of the secondary clarifier and drains to UV disinfection. The two critical factors in secondary clarifier design are the surface overflow rate and the solids loading rate. The surface overflow rate is the rate of flow leaving the clarifier divided by the clarifier surface area. The overflow rate is thus the average upward velocity of effluent leaving the clarifier. Suspended solids will be captured in the clarifier if their settling velocity is greater than the average overflow rate. The solids loading rate is also important in determining the clarifier capacity. The solids loading rate is the total mass rate of suspended solids entering the clarifier divided by the tank cross-sectional area. The total mass rate to the clarifier is the sum of the tank effluent flow rate and the tank underflow, or RAS pumping rate, times the MLSS concentration. A safety factor is typically applied to the clarifier design that takes into consideration variations in design loading, settleability, and other variables. The Secondary Clarifiers were designed to meet a 10.6 mgd max month flow. Design conditions for the secondary clarifiers are summarized in Table 6-8. 6-19 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-8. Secondary Clarifier Design Conditions Criteria Value Units Secondary Clarifiers 5 & 6 Diameter (ea) 85 ft Side Water Depth (ea) 15 ft Surface Area (ea) 5,674 sf Secondary Clarifiers 1, 2, 3 & 4 ------ Diameter (ea) 65 ft Side Water Depth (ea) 12 ft Surface Area (ea) 3,318 sf RAS Flow (Max Month 2015) 10.6 mgd MLSS (Max Month 2015) 3,600 mg/l Hydraulic SLR (Max Month 2015) 861 gpd/ft2 HRT (Max Month 2015) 2.79 hrs SLR (Max Month 2015) 25.85 lbs/ft2/day Secondary Clarifiers 5 & 6 Dewatering Pump Number of Pumps 1 - Non-Clog Type -Centrifugal Capacity 3,400 gpm Secondary Clarifiers 1, 2, 3 & 4 Dewatering Pump Number of Pumps 1 - Non-Clog Type -Centrifugal Capacity 2,800 gpm 6.2.8 RAS/WAS Systems The RAS/WAS system is comprised of RAS Building 1 and RAS/WAS Building 2. In RAS Building 1, return activated sludge flows from the bottom of Secondary Clarifiers No. 1 through No. 4 to a common header pipe where the RAS is transported to the PEPS. Each RAS control valve has a dedicated flowmeter. Modulating ball valves and magnetic flowmeters provide proportional or fixed flow to achieve a determined flow setpoint. The control of RAS in RAS/WAS Building 2 is the same as in RAS Building 1, but the receiving flow is from Secondary Clarifiers No. 5 and No. 6. The WAS pumps pump WAS from Secondary Clarifiers No. 3 – No. 6 to the DAFT and/or the RST for thickening. RAS/WAS Building 2 has been setup for future Secondary Clarifiers 7 and 8. Design conditions for the RAS/WAS pumping system are summarized in Table 6-9. 6-20 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-9. RAS/WAS System Design Conditions Criteria Value (each) Units SCL No. 1 & No. 2 Number of Pumps 2 - ------ - Type Rotary Lobe - Capacity (ea) 35 gpm SCL No. 3 & No. 4 Number of Pumps 1 - Type Progressive - Cavity Capacity (ea) 35 gpm Number of Pumps 1 - Type Rotary Lobe - Capacity (ea) 35 gpm SCL No. 5 & No. 6 Number of Pumps 2 - Type Rotary Lobe - Capacity (ea) 100 gpm 6.2.9 Thickening The thickening equipment at the WRF consists of a dissolved air flotation thickener (DAFT) and rotary screen thickener (RST) for thickening the WAS, and a fermenter and thickener for thickening the PSL. The DAFT is currently not in operation and is at the end of its useful life. The RST can treat 50-100 gpm and produce 5-8 percent solids. The primary advantage of using drum screens is the ability to eliminate debris carryover. Debris remain inside the screen until discharge. The DAFT is not currently in use at the WRF, and only the RSTs are used for thickening the WAS. The existing RSTs have adequate capacity to treat the WAS stream resulting from 30 mgd influent flows. The PSL fermenter and thickener can work in conjunction as a UFAT process. The purpose of the Unified Fermentation and Thickening (UFAT) process is to provide volatile fatty acids (VFAs) to phosphorous removing bacteria and denitrifying bacteria in the Bioreactors. The UFAT process is a patented fermentation and thickening process requiring two tanks, one for fermentation and one for thickening. Both tanks contain thickener/sludge collection mechanisms. Sludge from the Primary Clarifiers is pumped to the Fermentation Tank and allowed to settle in anaerobic conditions. Settled sludge is withdrawn at rates that ensure adequate sludge detention for VFA production. The supernatant overflows the weir and is combined with the sludge before the mixture enters the thickener. Combining the supernatant with the sludge elutriates VFAs and strips micro gas bubbles, thereby improving settling characteristics in the thickener. The 6-21 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation thickened sludge is pumped to the digesters by the TPSL pumps. The thickener supernatant, rich in VFAs, is sent to the Bioreactors. The UFAT process is a "one-pass" system where sludge age is controlled by the depth of the sludge blanket in the fermenter. The maximum sludge age is limited by the maximum depth and solids concentration of the sludge blanket. The hydraulic retention time is a function of the tank volume and influent flow. Since it is a "one-pass" system, no sludge is returned from the thickener to the fermenter. Primary sludge enters the 48-FT diameter fermenter through the bottom of the unit and discharges within the center well. The fermenter mechanism pushes thickened sludge to a sump located near the center column. The sludge is pumped to the thickener through the fermented primary sludge pumps. The scum sweep pushes floating scum to the scum beach where it is deposited in a scum pit. The scum is pumped to the digester through the fermenter scum pumps. Fermenter supernatant overflows the peripheral weir and normally drains to the thickener or alternately to the plant influent or the primary effluent pump station. An operator manually adjusts valves for the selected supernatant location. Fermented primary sludge is pumped to the gravity thickener by the fermented primary sludge pump. The fermented primary sludge pumps are constant speed with on/off timers that are set based on a control strategy as selected by the operator. Each pump is rated at 15 hp and 100 gpm. Primary sludge enters the 35-FT diameter thickener through the side of the unit and discharges within the center well. The existing sludge sweep pushes thickened sludge to a sump located near the center column. Thickener supernatant overflows the peripheral weir and normally drains to the primary effluent pump station. Thickened primary sludge is pumped to the digesters by the thickened primary sludge pumps. The thickened primary sludge pumps are constant speed with on/off timers that are set based on a control strategy as selected by the operator. The control strategies include sludge bed depth, flow, or manual. Each pump is rated at 15 hp and 100 gpm. However, the UFAT system is not currently in operation at the WRF. The Bioreactors currently exhibit strong phosphorus removal without being supplemented by the VFA stream, and consequently the WRF is bypassing the fermenter at this time. The thickener and fermenter are currently sized to thicken the PSL stream resulting from an average annual influent flow of 8.5 mgd. Design conditions for the thickening equipment and pumps are summarized in Table 6- 10. . 6-22 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-10. Thickening System Design Conditions Criteria Value Units Thickener Type Gravity - -- - - - -- ----- Diameter 35 ft Side Water Depth 10.25 ft Surface Area 962 ft2 Fermenter Type Gravity, UFAT - Diameter 48 ft Side Water Depth 24.5 ft TPSL Pumps Number of Pumps 2 - Type Rotary Lobe - Capacity (ea) 100 gpm Fermented PSL Pumps Number of Pumps 2 - Type Rotary Lobe - Capacity (ea) 100 gpm DAFT Type Dissolved Air Flotation - Diameter 30 ft Side Water Depth 8.25 ft Surface Area 707 ft2 Number of Air Supply Compressors 2 - Rotary Screen Thickening Number of Units 2 - Type Horizontal Rotary Screen - Capacity (ea) 80 gpm Feed Solids Concentration 2% - Recycle Pumping Number of Pumps 2 - Type Centrifugal - Capacity (ea) 520 Gpm Thickener Overflow Return Pumping Number of Pumps 3 - Type Non-Clog Centrifugal - 6-23 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Criteria Value Units Capacity (ea) 2 at 300 1 at 650 gpm Polymer Feed Capacity 24 lb/day Float Thickened Sludge Pumping Number of Pumps 2 - Type Progressive Cavity Capacity (ea) 36 gpm Settled Sludge Pumping Number of Pumps 1 - Type Air Operated Diaphragm Capacity (ea) 150 gpm -----6.2.10 UV Disinfection Effluent from the Secondary Clarifiers then flows to the UV Building for disinfection. Secondary Clarifier effluent flows into a distribution box and passes into two UV channels within the UV Building. The UV Building is a temperature controlled, self-framing metal building system. The UV system is a horizontal, open channel, gravity flow, low pressure- high intensity system with 48 lamps per bank located in each UV channel, providing a dosage of 35,000 microWatts-second/square centimeter. There are 192 lamps currently installed. The two channels are redundant, with each being designed for an average flow of 8.5 MGD. After UV disinfection, flow passes into a control structure, through an effluent measurement Parshall flume, and finally through a 42-IN pipe to the plant reaeration outfall structure. Flow is ultimately discharged to the East Gallatin River. The UV system is controlled (flow paced) by the sum of flow signals from the effluent flume and the discharge to the I/P Beds or plant influent flow. The equipment is capable of turning on and off banks and varying the intensity of the banks based on flow. An automatic cleaning system contains wipers that reduces fouling of UV lamps. Wipers clean all modules in a bank simultaneously. The cleaning system can be adjusted to operate automatically as frequently as once every 2 hours or operated manually. A portable davit crane removes UV modules from the channel which can then be placed on maintenance racks, located on the western wall of the UV Building, for lamp cleaning and maintenance purposes. The current UV system has adequate capacity to treat a 16.9 mgd peak hour flow. Design conditions for the UV system are summarized in Table 6-11. 6-24 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-11. UV System Design Conditions Criteria Value Units Basin Dimensions 50 x 112 ft Side Water Depth 6.1 - 7.9 ft Volume 328,000 gal UV Transmittance 65% 254 nm UV Dose 35,000 µWatt-sec/cm2 Number of Lamps 192 - ----6.2.11 Anaerobic Digestion Anaerobic digestion is the process by which organic material from the Bioreactors and Primary Clarifiers is decomposed and stabilized by microorganisms, in the absence of oxygen. The process reduces the feed solids volume and mass, and produces biogas (consisting primarily of methane and carbon dioxide). Sludge temperature must be maintained within the range of 90-100 Deg F for optimum process performance and to meet Class B biosolids standards. There are three digesters at the WRF. Digester No. 3 can act as a sludge storage facility or as a digester. The mode of its operation is determined solely by what set points the operator has chosen for recirculation, mixing and heating. When acting as a sludge storage tank, the feed to Digester No. 3 consists of digested sludge from Digesters No. 1 and No. 2. A level indicating element within Digester No. 3 detects the sludge level. When Digester No. 3 is used as a digester, the digested sludge is mixed, recycled and its temperature is maintained by the heat exchanger for the production of biogas and the destruction of solids. The feed to Digester No. 3 consists of TPSL, scum, and TWAS, which are combined and mixed in the digester feed pipes. The flow control valve is controlled by the SCADA system to feed whichever combination of digesters are on service. Currently, Digesters No. 1 and No. 2 are operated as digesters and Digester No. 3 is operated as a sludge storage facility, although some digestion does occur in Digester No. 3. Digesters No. 1 and No. 2 have a combined capacity to treat the solids stream resulting from a 10.6 mgd max month flow. Design conditions for the three digesters are summarized in Table 6-12. 6-25 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-12. Digester Design Conditions Criteria Value Units Digester No. 1 Diameter 50 ft ----------- - - Side Water Depth 28.5 ft Effective Sludge Volume 56,000 ft3 Effective Gas Volume 3,900 ft3 Number of Mixers 2 - Type of Mixing Vertical Draft Tube - Mixing Capacity (ea) 7,500 gpm Digester No. 2 Diameter 35 ft Side Water Depth 27 ft Effective Sludge Volume 26,000 ft3 Effective Gas Volume 2,100 ft3 Number of Mixers 2 - Type of Mixing Vertical Draft Tube - Mixing Capacity (ea) 3,500 gpm Digester No. 3 Diameter 58 ft Side Water Depth 31 ft Effective Sludge Volume 81,904 ft3 Effective Gas Volume 10,568 ft3 Number of Mixers 1 - Type of Mixing Axial Propeller - Mixing Capacity (ea) Upper – 100,000 Lower – 65,000 gpm Sludge Heating System Number of Boilers 2 - Boiler Type Firebox - Capacity 1 at 2.2 MBH 1 at 4.7 MBH - Number of Heat Exchangers 3 - Heat Exchanger Type External Spiral - Capacity (ea) 1.3 MBH 6-26 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation 6.2.12 Biosolids Dewatering The dewatering system at the WRF consists of two screw presses located in Digester Control Building No. 2. Digested sludge from Digester No. 3 is sent to the dewatering system by the dewatering feed pump located in the basement of the Digester Control Building. The feed line includes a flow meter and flow control valve (FCV) so that any desired flow rate can be fed. From the flow control valve, the sludge passes through dedicated flocculation tanks where the sludge is mechanically mixed with conditioning chemical. From the flocculation tank, conditioned sludge flows to the screw press units through a short gravity pipe. The Bozeman WRF is equipped with two screw presses that dewater digested sludge. Screw Press No. 1 is currently installed and is in operation at the WRF. It has a design solids loading rate of 333 lb/hr. Screw Press No. 2 has been purchased by the City and was installed in 2022. It has a design solids loading rate of 575 lb/hr. Dewatered sludge is loaded via a conveyor system to trucks in the loadout bay. Operating information for the two screw presses and the transfer pumps is summarized in Table 6-13. Table 6-13. Screw Press Operating Information Criteria Value Units Screw Press No. 1 gpm Estimated Cake Solids ≥20% Capture Rate ≥90% Average Wash Water Requirement 26 gpm at 60 – 75 psi Screw Press No. 2 Manufacturer HUBER Technology Model No. Q-Press 800.2 Tag Number 1200-SPR-02 57.5 gpm Estimated Cake Solids 16-25% Capture Rate ≥95% Average Wash Water Requirement1 150.6 gph at 72.5 psi Digested Sludge Transfer Pumping Number of Pumps 2 - Type Progressive Cavity - ---- ----- Manufacturer HUBER Technology Model No.ROTAMAT Screw Press RoS 3 Tag Number 1200-SPR-01 Hydraulic Loading Rate 33.3 Solids Loading Rate 333 lb/hr Hydraulic Loading Rate Solids Loading Rate 575 lb/hr 6-27 Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Criteria Value Units Capacity (ea) 75 gpm ------- Dewatering Feed Pumping Number of Pumps 1 - Type Vortex - Capacity (ea) 400 gpm Thickened Digested Sludge Pumps Number of Pumps 4 - Type Rotary Lobe - Capacity (ea) 100 gpm Dewatered Cake Hopper Number of Units 1 - Volume 300 ft3 1 Wash water cycle runs at 39.6 gpm for 152 seconds. Typical applications experience 1-4 cycles per hour. 6.3 Capacity Summary The existing capacities of the various unit processes were calculated as an influent flow to allow for the identification of capacity deficiencies. These respective capacities are shown in Table 6-14, and the accompanying design flow at projected 2040 conditions is also provided. Process elements that are not projected to meet 2040 capacity requirements are highlighted red. Process elements that are projected to meet design conditions but will require redundancy to meet regulatory requirements are highlighted orange. Unit processes that show capacity deficiencies by the end of the planning horizon include the primary clarifiers, bioreactors, secondary clarifiers, UV disinfection system, the PSL thickening system, and the digesters. The projected years that the associated upgrades and/or new units would be needed by are shown in Table 6-15. Capacity upgrade alternatives for these processes are evaluated in Chapter 7. 6-28 Table 6-14. Capacities of Existing Unit Processes Process Area Design Condition Current Influent Flow at Design Condition3 Existing Capacity at Design Condition Capacity Used at Current Design Flow 2040 Design Flow Headworks 28.4 mgd Parshall flume Peak Hour 12.7 32 mgd 40% 21.2 mgd Perforated Plate Influent Screens Peak Hour 12.7 28 mgd 45% 28.4 mgd Coarse Influent Screens Peak Hour 12.7 18 mgd 71% 28.4 mgd Manual Screen Peak Hour 12.7 30 mgd 42% 28.4 mgd Grit Removal System Peak Hour 12.7 28 mgd 45% 28.4 mgd Primary Treatment Primary Clarifier Basins1 Max Month 7.0 10.6 mgd 66% 17.9 mgd Primary Effluent Pumps Peak Hour and RAS Flow 12.2 28.8 mgd 42% 28.4 mgd & RAS Secondary Treatment BNR Bioreactors Max Month 7.0 10.6 mgd 66% 17.9 mgd Secondary Clarifier Basins Max Month 7.0 10.6 mgd 66% 17.9 mgd 16.9 mgd 75% 28.4 mgd Thickener2 Average Annual 5.7 8.5 mgd 66% 14.6 mgd Solids, WAS Stream Max Month 7.0 Solids Digestion and Disposal Tertiary Treatment UV Disinfection Peak Hour 12.7 Solids, PSL Stream Fermenter2 Average Annual 5.7 8.5 mgd 66% 14.6 mgd RST 30+ mgd 23% 17.9 mgd Anaerobic Digesters No. 1 and No. 2 Max Month 7.0 10.6 mgd 66% 17.2 mgd Anaerobic Digesters No. 1, No. 2 and No. 3 Max Month 7.0 17.4 mgd 40% 17.2 mgd Screw Press No. 1 and No. 2 Average Annual 5.7 16.5 mgd 34% 14.0 mgd 1 Not all primary clarifiers are currently in use at the WRF, and it is not recommended that an additional primary clarifier be constructed at this time despite the capacity analysis indicating that one is needed. Discussion of this recommendation is included in Chapter 7. 2 The UFAT system is not currently in use at the WRF, and it is not recommended that an additional thickener or fermenter be constructed at this time despite the capacity analysis indicating that they are needed. Discussion of this recommendation is included in Chapter 7. 3 Average current influent flows taken from Table 3-3 in Chapter 3. Current peak hour flow approximated by using Bozeman’s 2020 population of 51,287 and peaking equation 10-1 from Montana Circular DEQ-2. Bozeman WRF Facility Plan Update Chapter 6 – Existing Unit Processes Evaluation Table 6-15. Projected Years for Completion of Required Upgrades Required Upgrade Projected Year Needed Bioreactor No. 1 Upgrade 2027 New Secondary Clarifier 2027 UV Capacity Addition 2024 New Digester 2022 New Screw Press 2030 6-30 Chapter 7 Treatment Upgrade Alternatives 7 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Contents Introduction.......................................................................................................................................7-1 7.1 Review of Drivers ...................................................................................................................7-1 7.1.1 Capacity Drivers ........................................................................................................7-1 7.1.2 Regulatory Drivers.....................................................................................................7-2 7.2 Capacity Driven Upgrades and Alternatives ..........................................................................7-4 7.2.1 Influent Screen ..........................................................................................................7-4 7.2.2 PEPS Pump ..............................................................................................................7-5 7.2.3 Bioreactors ................................................................................................................7-5 7.2.4 Primary Clarifiers.......................................................................................................7-8 7.2.5 Secondary Clarifiers..................................................................................................7-8 7.2.6 UV Disinfection Capacity...........................................................................................7-9 7.2.7 Fermenter and Thickener..........................................................................................7-9 7.2.8 Anaerobic Digestion ..................................................................................................7-9 7.2.9 Rotary Screen Thickener (RST)..............................................................................7-13 7.2.10 Screw Press ............................................................................................................7-13 7.2.11 Capacity Summary and Recommendations............................................................7-13 7.3 Regulatory Driven Upgrades and Alternatives .....................................................................7-15 7.3.1 Treatment Technologies .........................................................................................7-15 7.3.2 Alternative 1a – Discharge to East Gallatin Surface Water ....................................7-19 7.3.3 Alternative 1b – Seasonal Land Application ...........................................................7-20 7.3.4 Alternative 1c – Discharge to Shallow Groundwater...............................................7-21 7.3.5 Alternative 1d – Tertiary Wetland Treatment ..........................................................7-22 7.3.6 Alternative 1e – Aquifer Recharge ..........................................................................7-23 7.3.7 Alternative 2 – Discharge to Belgrade.....................................................................7-24 7.3.8 Alternative 3 – Bozeman Owned Satellite Plant .....................................................7-25 7.3.9 Regulatory Driven Alternatives Analysis .................................................................7-26 7.3.10 Regulatory Summary and Recommendations ........................................................7-30 Tables Table 7-1. Projected Loadings for Planning Period ...................................................................................7-1 Table 7-2. WRF Management Alternatives Nutrient Treatment Projections..............................................7-3 Table 7-3. Bioreactor vs. InDENSE Alternatives Weighted Ranking Criteria ............................................7-7 Table 7-4. InDENSE vs. Bioreactor Alternatives Scoring ..........................................................................7-8 Table 7-5. Existing Primary Clarifiers at Future Overflow Rates ...............................................................7-8 Table 7-6. Secondary Clarifier Overflow Rates..........................................................................................7-9 Table 7-7. Secondary Clarifier Solids Loading Rates ................................................................................7-9 Table 7-8. Biosolids Disposal Figures, 2020............................................................................................7-11 Table 7-9. Solids Handling Present Worth Analysis ................................................................................7-11 Table 7-10. Solids Handling Alternatives Ranking Criteria......................................................................7-12 Table 7-11. Solids Handling Alternatives Matrix ......................................................................................7-12 Table 7-12. Capacity Required Upgrades, 14.6 mgd Average Annual Flow...........................................7-14 Table 7-13. Capacity Required Upgrades, 10.2 mgd Average Annual Flow...........................................7-15 Table 7-14. Effluent Management Alternative 1a OPCCs .......................................................................7-19 Table 7-15. Effluent Management Alternative 1b OPCCs .......................................................................7-20 Table 7-16. Effluent Management Alternative 1c OPCC .........................................................................7-21 i Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-17. Effluent Management Alternative 1d OPCC .........................................................................7-22 Table 7-18. Effluent Management Alternative 1e OPCC .........................................................................7-23 Table 7-19. Effluent Management Alternative 2 OPCCs .........................................................................7-24 Table 7-20. Effluent Management Alternative 3 OPCCs .........................................................................7-25 Table 7-21. Effluent Management Alternatives Ranking Criteria.............................................................7-26 Table 7-22. Treatment Scenario 1 Effluent Management Alternatives Matrix .........................................7-27 Table 7-23. Treatment Scenario 2 Effluent Management Alternatives Matrix .........................................7-28 Table 7-24. Treatment Scenario 3 Effluent Management Alternatives Matrix .........................................7-29 Table 7-25. Recommended Improvements, Treatment Scenario 1.........................................................7-31 Table 7-26. Recommended Improvements, Treatment Scenario 2.........................................................7-33 Table 7-27. Recommended Improvements, Treatment Scenario 3.........................................................7-35 Figures Figure 7-1. Location of Future Influent Screen ..........................................................................................7-5 Figure 7-2. Gravity Selective Wasting Pilot Schematic..............................................................................7-6 Figure 7-3. InDENSE System at RW Hite WWTP, Denver, CO ................................................................7-7 Figure 7-4: S2EBPR Versus Traditional Mainstream Anaerobic Zone....................................................7-18 Figure 7-5. Treatment Scenario 1 Recommended Improvements Implementation Timeline..................7-31 Figure 7-6. Treatment Scenario 1 Recommended Improvements Shown on WRF Site.........................7-32 Figure 7-7. Treatment Scenario 2 Recommended Improvements Example Implementation Timeline.......................................................................................................................................7-33 Figure 7-8. Treatment Scenario 2 Recommended Improvements Shown on WRF Site.........................7-34 Figure 7-9. Treatment Scenario 3 Recommended Improvements Example Implementation Timeline.......................................................................................................................................7-35 Figure 7-10. Treatment Scenario 3 Recommended Improvements Shown on WRF Site .......................7-36 ii Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives This page is intentionally left blank. iii 7 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Introduction This chapter presents and evaluates treatment capacity upgrade alternatives for both the liquid and solid stream unit processes at the Bozeman WRF. Information from the preceding chapters is synthesized to identify and recommend alternatives that meet the projected treatment and capacity requirements for the 20-year planning period. Flow and loading projections are taken from Chapter 3, projected treatment standards are taken from Chapters 4 and 5, and existing unit process capacity information is taken from Chapter 6. 7.1 Review of Drivers Upgrades at the Bozeman WRF during the planning period are largely driven by the need for increased capacity to service a growing population and the need for increased treatment performance to meet increasingly stringent effluent nutrient standards. A summary of these two primary drivers is presented in this section. As the future nutrient standards and permit conditions remain unknown at this time, three possible scenarios are examined respectively. 7.1.1 Capacity Drivers The need for increased plant capacity is a primary driver of WRF upgrade requirements during the planning period. Projected influent flows and loads for the planning period were developed in Chapter 3. These projections are shown in Table 7-1. The WRF capacity will need to be increased to treat a 14.6 mgd average annual flow and a 17.9 mgd max month flow by the end of the planning period. Table 7-1. Projected Loadings for Planning Period Year 2025 2030 2035 2040 Annual Average Maximum Month Flow, mgd 9.9 12.1 14.7 17.9 ---- -------- ------------ Projected Population 64,839 78,887 95,978 116,772 Flow, mgd 8.1 9.9 12.0 14.6 CBOD, lb/day 13,583 16,526 20,106 24,462 TSS, lb/day 13,764 16,746 20,374 24,788 NH3, lb/day 1,443 1,756 2,137 2,600 TN, lb/day 2,363 2,875 3,497 4,255 TP, lb/day 308 374 455 554 CBOD, lb/day 15,340 18,664 22,707 27,627 TSS, lb/day 16,403 19,957 24,280 29,541 NH3, lb/day 1,815 2,208 2,687 3,269 TN, lb/day 2,936 3,572 4,346 5,288 7-1 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Year 2025 2030 2035 2040 TP, lb/day 382 465 566 688 Peak Day Flow, mgd 11.8 14.3 17.4 21.2 CBOD, lb/day 30,889 37,581 45,723 55,630 TSS, lb/day 26,070 31,719 38,591 46,951 NH3, lb/day 5,807 7,066 8,596 10,459 TN, lb/day ---- TP, lb/day ---- Peak Hour Flow, mgd 17.5 20.6 24.2 28.4 ---- ----------------7.1.2 Regulatory Drivers Treatment upgrades are likely required during the planning period for the WRF to meet future effluent nutrient standards. However, the permitting situation in Montana remains fluid and uncertain. As discussed in Chapter 4 and Chapter 5, the WRF must be prepared to meet the treatment requirements stemming from a number of permitting scenarios. As part of this preparation, various effluent management alternatives were outlined in Chapter 5. Projected nutrient permit limits for these alternatives, ranging from least stringent to most stringent, are shown in Table 7-2. The Scenario 1 treatment levels represent the probable, most lenient effluent nutrient standards that could be expected in a future discharge permit. In this treatment scenario, the WRF’s current mass based effluent limits would be extended into the future. The Scenario 2 treatment levels represent the probable most lenient nitrogen treatment standard and the most stringent phosphorus treatment standard. This would be the case if Bozeman were to be issued an individual variance that held their nitrogen limit at current standards while stipulating stringent phosphorus removal to the limits of technology. The Scenario 3 levels represent the probable most stringent nutrient treatment standards for both phosphorus and nitrogen. This would be the case if Bozeman was required to treat both nutrients to the limits of treatment technology. The reworked nutrient regulations that are ultimately adopted by the State of Montana will play a significant role in determining which management alternative provides the best path forward. However, it is unknown when these new regulations will be finalized. To prepare for the range of outcomes outlined in Table 7-2, alternative packages will be crafted for each of the effluent management alternative treatment conditions. 7-2 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-2. WRF Management Alternatives Nutrient Treatment Projections Effluent Management Alternative Description Treatment Location Discharge Location Flows (mgd) Group No. 1 Most Lenient Treatment Scenario Group No. 2 Lenient TN, Stringent TP Group No. 3 Worst Case Treatment Scenario TN (mg/l) TP (mg/l) TN (mg/l) TP (mg/l) TN (mg/l) TP (mg/l) Discharge to Alternative 1a Bozeman WRF East Gallatin Surface Water 14.6 6.4 0.27 6.4 0.05 3Surface Water Alternative 1b Seasonal Land Application Bozeman WRF East Gallatin Surface Water, Summer ~10.6 8.9 0.37 8.9 0.05 3 0.05 Bozeman WRF East Gallatin Surface Water, Winter 14.6 6.4 0.27 6.4 0.05 3 0.05 Bozeman WRF Summer Land Application1 ~4 8.9 0.37 8.9 0.05 3 0.05 Alternative 1c Shallow Groundwater Discharge Bozeman WRF Shallow Groundwater 14.6 7.5 0.27 --3 0.05 Alternative 1d Wetland Discharge Bozeman WRF WRF Wetland 14.6 6.4 0.27 --3 0.05 Alternative 1e Aquifer Recharge Bozeman WRF Aquifer 14.6 ----3 0.05 Alternative 2 West End to Belgrade Belgrade WWTP Shallow Groundwater 4.4 ------ Bozeman WRF East Gallatin Surface Water 10.2 9.2 0.39 9.2 0.05 3 0.05 Alternative 3 COB West End Satellite Plant Satellite Treatment Plant Shallow Groundwater 4.4 7.5 1 --7.5 1 Bozeman WRF East Gallatin Surface Water 10.2 9.2 0.39 9.2 0.05 3 0.05 1 Varying levels of treatment could be required depending on the intended use and the agronomic uptake rate of the receiving crop. See discussion in Chapter 5. 0.05 ll ll ll ---- --------------------------- 7-3 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.2 Capacity Driven Upgrades and Alternatives The total treatment capacities and redundancy needs of each unit process were established in Chapter 6. Unit processes that show capacity deficiencies by the end of the planning horizon include the following: Influent Screen Primary Effluent Pump Station (PEPS) Bioreactors Primary Clarifiers Secondary Clarifiers UV Treatment Fermenter and Thickener Digesters Screw Presses The majority of the capacity deficiencies do not require an alternatives analysis, as the capacity deficiencies can be addressed by installing additional unit process capacity. However, multiple alternatives were identified for some of the unit processes, where applicable. These unit processes consist of the bioreactors and the digesters. Adaptive planning is recommended for some unit processes in cases where analysis indicates additional capacity is needed, generally towards the end of the planning period, but in reality such improvements may be unnecessary. In such cases, improvements should only be made if the respective unit processes demonstrate a clear need for additional capacity. 7.2.1 Influent Screen An additional influent screen will be required to provide redundant capacity. The OPCC for the installation of a new influent screen is $720,000. Adaptive planning should be used to determine when to install the redundant screen capacity, as the WRF has adequate capacity to meet projected flows for most of the planning period. The new screen should be installed in the second channel of the Pretreatment Building (Old Headworks Building). The location of the future screen is shown on the drawing in Figure 7-1. It is adjacent to the new screen installed in 2021. 7-4 EXISTING HEADWORKS BUILDING PLAN -I ___ J I I ~,,,, .... "'"" I I I I I L--- Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Figure 7-1. Location of Future Influent Screen 7.2.2 PEPS Pump The existing PEPS pumps have a firm capacity of 28.8 mgd. The RAS flow from the bioreactors is also handled by the PEPS pumps. An additional pump is required to be installed to maintain an adequate firm capacity capable of handling the RAS flows as well as the future influent flows. There is space in the building for a fourth pump to be installed. The OPCC for the installation of a new PEPS pump is $790,000. The PEPS pump is projected to be required in 2040. 7.2.3 Bioreactors Additional bioreactor capacity is required to meet future flows during the planning period. It is recommended that existing Bioreactor No. 1, which is not currently in use, be upgraded to the same 5-Stage Bardenpho process as the other bioreactors. However, additional bioreactor capacity is still required by the end of the planning period. To accommodate this capacity, a fourth bioreactor can be constructed or InDENSE, an intensification process that employs selective wasting, can be implemented. 7-5 . -· -....... ---·-· ------. ------. ---...... --. ·-----· -·-, Screen Gravity Selective: Wisting Plant11NF - Screen w AO AO l l Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Fourth Bioreactor A fourth bioreactor can be constructed with a volume of approximately 2.2 million gallons. The OPCC for the bioreactor is approximately $10.4 million. InDENSE Gravity selective wasting was first introduced at a small treatment plant in Austria with the goal of retaining anammox granules in a mainstream deammonification trial. It quickly resulted in a drop in sludge volume index (SVI) which since has been replicated at several facilities. It provided an effective way to control SVI and promoted the establishment of a more granulated activated sludge, the latter of which however requires an anabolic zone with a high food to microorganism (F/M) ratio. The inDENSE process utilizes hydrocyclones sized for specific WAS flow ranges. The standard modules are equipped with four hydrocyclones. The gravity selection occurs by retaining the heavier particles with the hydrocyclone (similar to grit removal with hydrocyclones), and once the desired SVI range is achieved the number of hydrocyclones in operation can be reduced and managed going forward. Based on experiences from other facilities, 1 to 3 months are needed to establish the full effect of the process. While the hydrocyclones have been shown to improve sludge settleability, the improved settleability may not translate into lower clarifier effluent TSS. However, other results suggest the phosphorus content in the remaining effluent solids is lower than in the wasted solids because the heavier flocks with stored phosphorus are captured. The pilot process schematic can be seen on Figure 7-2, and a photo of an example installation can be seen on Figure 7-3. Figure 7-2. Gravity Selective Wasting Pilot Schematic 7-6 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Figure 7-3. InDENSE System at RW Hite WWTP, Denver, CO The InDENSE process likely will reduce the amount of additional bioreactor capacity required as the bioreactor can be operated at a greater mixed liquor concentration, and in the best-case scenario, possibly negate the need for a fourth bioreactor entirely. Bioreactor Improvement Alternative Evaluation The two bioreactor improvement alternatives were evaluated in a weighted alternatives matrix that employed the criteria and weightings in Table 7-3. These criteria were selected and weighted by City of Bozeman personnel during the Final Alternatives Workshop 1. OPCCs were developed for InDENSE and for constructing a fourth bioreactor with 2.4 million gallons of capacity to match existing. The OPCC for InDENSE resulted in a cost of $1.43 million and the OPCC for the bioreactor of $10.4 million. Table 7-3. Bioreactor vs. InDENSE Alternatives Weighted Ranking Criteria Criteria Description Relative Weighting Growth Management Flexibility Ability to accommodate future changes in growth by adjusting infrastructure/processes. 41% Risk and Uncertainty Amount of uncertainty associated with the alternative. A high scoring alternative reduces risk and uncertainty. 20% Ease of Implementation Alternative is compatible with existing facilities. Land/ROW is available to construct any new infrastructure. 20% Minimize Capital Costs Minimize capital costs of new infrastructure changes. 11% Minimize Operational Costs Minimize operational costs associated with alternative. E.g., electricity, chemicals, labor, etc. 7% 7-7 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Each alternative was scored against each weighted criteria by applying a descriptive score, (i.e., very low, low, moderate, strong, very strong) depending on the alternative’s suitability to the criteria. Based on the descriptive scoring, a numerical score was applied to each alternative for the criteria. Higher scores indicate greater suitability to the relative criteria. The relative weighting of each criterion was then applied to produce the final cumulative scores for each alternative. The results of the scoring are shown in Table 7-4. It was determined that Alternative 1, pilot and implement InDENSE, will be carried forward and recommended as a result of the analysis. InDENSE piloting will need to be completed by 2024 to allow adequate time for full scale installation, or the construction of additional bioreactor capacity if the piloting is unsuccessful. Table 7-4. InDENSE vs. Bioreactor Alternatives Scoring Ranking Criteria Alternative 1 (InDENSE) Score Alternative 2 (Fourth Bioreactor) Score 7.2.4 Primary Clarifiers The existing primary clarifiers provide 9,954 SF of total surface area. Projected overflow rates at the future design flows were calculated, and this information is presented in Table 7-5. Table 7-5. Existing Primary Clarifiers at Future Overflow Rates Parameter Growth Management Flexibility 58%42% Risk and Uncertainty 38%63% Ease of Implementation 63%38% Minimize Capital Costs 70%30% Minimize Operational Costs 58%42% Final Weighted Score 58 44 Rate (mgd) Resultant Overflow Rate (gpd/ft2) Typical Design Overflow Rate (gpd/ft2) Average Flow 14.6 1,467 1,000 Peak Hourly Flow 28.4 2,853 1,500 – 3,000 The projected overflow rates at the future average day design flows exceed the typical design overflow rates. However, not all three of the primary clarifiers at the WRF are currently in use. Consequently, the clarifiers currently operate at similar overflow rates to those projected at the future flow rates. Given the satisfactory current performance, no additional primary clarifiers are recommended to be constructed. 7.2.5 Secondary Clarifiers The existing secondary clarifiers provide 24,620 SF of total surface area. Projected overflow rates at the future design flows were calculated, as well as projected solids loading rates using a 75 percent RAS rate and a 3,600 mg/L MLSS. This information is presented in Table 7-6 and Table 7-7. The analysis found that the existing secondary clarifiers are undersized and required additional capacity by the end of the planning 7-8 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives period. Based on this, a two new secondary clarifiers will be required to meet future flows/loads. Two additional secondary clarifiers of identical surface area as SC 5 and SC 6, 5,674 SF respectively, will be required to maintain proper overflow and solids loading rates. The OPCC for the construction of two new secondary clarifiers is approximately $7.51 million. The secondary clarifiers are projected to be required by 2027. Table 7-6. Secondary Clarifier Overflow Rates Number of Secondary Clarifiers Parameter Flow Rate (mgd) Resultant Overflow Rate (gpd/ft2) Typical Overflow Rate (gpd/ft2) 6, Current Peak Hourly Flow 28.4 mgd 1,150 900 8, Future Peak Hourly Flow 28.4 mgd 790 900 Table 7-7. Secondary Clarifier Solids Loading Rates Number of Secondary Clarifiers Parameter Solids Loading Rate (lb/d) Resultant Solids Loading (lb/d/ft2) Typical Solids Loading (lb/d/ft2) 6, Current Peak Day Solids Loading, 75% RAS 1,114,000 45 35 8, Future Peak Day Solids Loading, 75% RAS 1,114,000 31 35 7.2.6 UV Disinfection Capacity Additional UV disinfection capacity is required to meet the projected flows at the end of the planning period. The existing UV banks have expansion capacity for an additional 96 lamps, which increases the treatment capacity to 25.4 mgd. It is recommended that this additional capacity be installed, and adaptive planning is recommended before installing further lamps to the projected 2040 peak hour flow of 27.5 mgd. The OPCC for expanding the UV banks is $1.27 million. The additional UV capacity is projected to be required by 2024. 7.2.7 Fermenter and Thickener The primary sludge thickening equipment at the WRF consists of a fermenter and a thickener. The two respective unit processes can operate in conjunction as a unified fermentation and thickening (UFAT) process, but the system is not currently in use. The capacity analysis in Chapter 6 found these unit processes required additional capacity, but since they are not currently in use, no changes are recommended. 7.2.8 Anaerobic Digestion Additional anaerobic digestion capacity in the form of a fourth digester is required to maintain an adequate biosolids hydraulic retention time (HRT) of 15 days and to provide operational redundancy and flexibility for biosolids storage to support dewatering and final cake production. Alternatively, the TWAS stream could be directly dewatered 7-9 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives without digestion, which negates the need for an additional digester. However, a TWAS storage tank is required for this operating strategy. Digesting only primary sludge improves volatile solids destruction and the dewaterability of the digested solids, but also increases foul odors and could require the undigested TWAS be covered during storage and transportation. It is also uncertain whether the Logan Landfill would accept undigested TWAS. Such a process alteration requires additional solids dewatering equipment, supporting infrastructure, and increases disposal and transportation costs due to the increase in sludge volume, but significant capital cost savings are realized by not constructing a new digester. Based on this, the following two alternatives were evaluated: Alternative 1 – Construct Fourth Anaerobic Digester Alternative 2 – Directly dewater and dispose TWAS without Digestion O&M costs were calculated for each of the solids alternatives. These costs were based on expenses reported by WRF operations staff, and include line items for power, digester heating, polymer addition, magnesium hydroxide addition, sludge hauling, and sludge landfill disposal. All costs were scaled to the projected sludge production over the course of the 20-year planning period. Costs for power consumption initially include existing WRF equipment and increase to include costs for power from the planned screw press and digester capital improvements. Current biosolids disposal costs and figures were provided by the City of Bozeman. Disposal data and are summarized in Table 7-8. The City indicated that $100,000 was spent on hauling biosolids during 2020, and the landfill charged a flat rate of $7 per ton of biosolids. This rate translated to a monthly tipping fee of approximately $3,300, which the City reported was typical. Based on the provided information, the current annual disposal costs (hauling costs and tipping fees) for the WRF’s biosolids amounts to approximately $140,000. These costs do not include labor costs, and a labor rate of $30 per hour for two persons was added to calculate comparable present worth costs between Alternative 1 and Alternative 2. 7-10 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-8. Biosolids Disposal Figures, 2020 Month Solids Scaled at Landfill (Tons) Truckloads Average Tons per Truckload Avg Tons per Day (Total T per # Haul Days) Dry Weight at 17% Solids (Tons) ------- - January 504 50 10.1 19.4 85.7 February 390 41 9.5 18.6 66.3 March 573 52 11.0 22.0 97.4 April 490 40 12.3 24.5 83.3 May 556 51 10.9 22.2 94.5 June 435 46 9.5 19.8 74.0 July 540 52 10.4 20.8 91.8 August 475 50 9.5 18.3 80.8 September 482 50 9.6 19.3 81.9 October 431 52 8.3 16.6 73.3 November 387 48 8.1 16.1 65.8 December 470 51 9.2 18.1 79.9 Total 5,733 583 --975 Average 478 49 9.9 19.6 81 A present worth analysis was conducted for the two alternatives, and opinions of probable construction cost (OPCCs) were developed. Alternative 1 includes capital costs for a new digester, approximately $4.93 million. Alternative 2 includes capital costs for odor control improvements, approximately $500,000, and WAS infrastructure improvements to implement the process change, approximately $1.0 million. Additionally, both alternatives require an upgrade for Screw Press No. 1 and the installation of an additional screw press during the planning period. These costs are included in the capital costs for both alternatives, and they total approximately $3.8 million. The results of the cost analysis are summarized in Table 7-9. Table 7-9. Solids Handling Present Worth Analysis Alternative OPCC Average Annual O&M Costs 20 Year Present Worth Cost Alternative 1. Fourth Digester $8,740,000 $1,130,000 $26,520,000 Alternative 2. Directly Dewater TWAS $5,310,000 $1,280,000 $25,450,000 The two alternatives were then evaluated in a weighted alternatives matrix that employed the criteria and respective weightings in Table 7-10. These criteria were weighted by City personnel during the Final Alternatives Workshop 1. The scoring and final results are tabulated in Table 7-11. 7-11 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-10. Solids Handling Alternatives Ranking Criteria Criteria Description Relative Weighting Growth Management Flexibility Ease of Implementation Ability to accommodate future changes in growth by adjusting infrastructure/processes. Alternative is compatible with existing facilities. Land/ROW is available to construct any new infrastructure. 35% 24% Minimize Capital Costs Risk and Uncertainty Odor Minimize capital costs of new infrastructure changes. Amount of uncertainty associated with the alternative. A high scoring alternative reduces risk and uncertainty. Amount of foul odor associated with alternative. A high scoring alternative minimizes foul odor to the extent possible. 13% 13% 8% Minimize Operational Costs Minimize operational costs associated with alternative. E.g., electricity, chemicals, labor, etc. 6% Table 7-11. Solids Handling Alternatives Matrix Criteria Alternative 1 (Fourth Digester) Score Alternative 2 (Dewater TWAS without Digestion) Score Growth Management Flexibility 50% 50% Ease of Implementation 58% 42% Minimize Capital Costs 42% 58% Risk and Uncertainty 70% 30% Odor 88% 13% Minimize Operational Costs 63% 38% Final Weighted Score 59 46 Alternative 1, construct a fourth digester, was selected as the recommended alternative as a result of this analysis. While some cost savings can be realized if Alternative 2 was employed, the odor produced by this process change and the uncertainty regarding whether the Logan Landfill will accept the undigested sludge make this alternative untenable. Design and construction of the new digester should begin as soon as possible. 7-12 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.2.9 Rotary Screen Thickener (RST) There are two RSTs currently in use at the WRF. An additional unit may be required during the planning period to maintain firm capacity, but adaptive planning should be utilized before installing an additional unit because each respective RST can provide 50- 100 gpm of thickening capacity for the WAS stream. Consequently, one unit can likely continue to meet thickening needs. 7.2.10 Screw Press Additional dewatering capacity is required to meet the capacity requirements during the 20-year planning period. It is anticipated the existing Screw Press No. 1 will need to be replaced with a larger capacity unit by approximately 2030, and that an additional screw press installation is required by approximately 2035 to provide adequate redundancy. The additional screw press installation will likely require an expansion of the Solids Handling Building at the WRF. The OPCC for the screw press upgrade is approximately $1.40 million and the OPCC for the additional screw press is approximately $2.41 million. The existing screw press upgrade is projected to be required by 2030 and the additional third screw press is projected to be required by 2035. 7.2.11 Capacity Summary and Recommendations The recommendations to address capacity during the planning period are shown in Table 7-12. The projected OPCCs for the respective upgrades are also shown. The capacity related upgrades shown in Table 7-12 are sized to meet the projected flows at the end of the planning period. These upgrades are included as a single OPCC line item for Effluent Management Alternatives 1a – 1e in the subsequent sections. 7-13 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-12. Capacity Required Upgrades, 14.6 mgd Average Annual Flow Estimated Cost Parameter Number and OPCC - - $720,000 $790,000 Estimated Cost $2,760,000 $7,510,000 $1,430,000 Estimated Cost $1,270,000 Estimated Cost $1,400,000 Preliminary/Primary Treatment Number Additional Influent Screen 1x Additional PEPS Pump 1x Secondary Treatment Number Refurbish Bioreactor No. 1 Train into 5-Stage Bardenpho 2.0 MG Construct New Bioreactor No. 4 Train Adaptive Planning Additional Aeration Blower 1x $890,000 Construct Secondary Clarifiers 2 x 85'Ǿ InDENSE: Hold +20% Solids Inventory InDENSE, 90 SVI Tertiary Treatment Number UV Disinfection 1x Solids Dewatering and Digestion Number Rotary Screen Thickener Adaptive Planning Construct Fourth Digester 0.6 MG $4,930,000 Screw Press Upgrade 1x Additional Screw Press 1x $2,410,000 Total Capital Costs $24,110,000 Effluent Management Alternative 2 and Alternative 3 represent decentralized treatment approaches, and only require the WRF to treat an average annual flow of 10.2 mgd at the end of the planning period. Consequently, less capacity related upgrades are required for these two alternatives than what is shown in Table 7-12. Capacity related upgrades required to meet the 10.2 mgd condition are shown in Table 7-13. These capacity related upgrades are included as a single OPCC line item for Effluent Management Alternative 2 and Alternative 3 in the subsequent section. 7-14 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-13. Capacity Required Upgrades, 10.2 mgd Average Annual Flow Parameter Number and OPCC Secondary Treatment Number Estimated Cost Refurbish Bioreactor No. 1 Train into 5-Stage Bardenpho 2.0 MG $2,760,000 Additional Aeration Blower 1x $890,000 Construct Secondary Clarifiers 1 x 85'Ǿ $3,760,000 InDENSE: Hold +20% Solids Inventory InDENSE, 90 SVI $1,000,000 Tertiary Treatment Number Estimated Cost UV Disinfection 1x $1,270,000 Solids Dewatering and Digestion Number Estimated Cost Rotary Screen Thickener Adaptive Planning - Construct Fourth Digester 0.6 MG $4,930,000 Screw Press Upgrade 1x $1,400,000 Additional Screw Press 1x $2,410,000 Total Capital Costs $18,420,000 7.3 Regulatory Driven Upgrades and Alternatives As noted previously, it is unknown when Montana’s new nutrient regulations will be finalized. Depending on how the new regulations affect the WRF’s discharge permit, it may be preferable to implement one of the effluent management alternatives introduced in Chapter 5. Projected treatment requirements for each of these alternatives are outlined in Table 7-2. As part of the evaluation of these alternatives, opinions of projected construction costs (OPCCs) were developed for each respective effluent management alternative and treatment scenario. Capital improvements generally consist of the items identified in Table 7-12, any discharge specific infrastructure needed to facilitate the effluent alternative, and any additional treatment infrastructure required to meet the projected discharge standards of the respective treatment scenario. A 20-year present worth calculation was conducted for each alternative, and accounts for labor, power consumption, chemical addition, biosolids disposal, and general maintenance in addition to the capital costs. The projected costs are then considered in a wider alternatives matrix that incorporates other ranking criteria. 7.3.1 Treatment Technologies The projected effluent nutrient limits for some of the effluent management alternatives may require additional technologies be installed, or process changes be made for the limits to be met. These treatment specific technology upgrades are in addition to the capacity upgrades outlined in Section 8.2. Descriptions of the respective technologies and process changes needed are summarized in this section. 7-15 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Effluent Filtration It is anticipated the effluent discharge limits in Treatment Scenarios 2 and 3 (Table 7-2) generally require effluent filtration to be installed to meet the phosphorus limit. Effluent filtration complements biological phosphorus removal processes by removing filterable particulate matter containing phosphorus. There are many types of filters available for consideration, and selection of the most appropriate type of filtration will be linked to the ultimate need within the effluent management strategies selected and whether very low nutrient targets must be met, whether only Class A reclaimed water is needed, or both. Selection of the final effluent filtration option should be carefully linked to the effluent management strategies and the treatment process plan. The filtration technologies listed below provide a representation of the major types of filter technologies available: Traveling Bridge Sand Media Filters Traveling Bridge Fabric Media Filters Compressible Media Filters Continuous Backwash Sand Filters Cloth Media Disc Filters Deep Bed Mono-Media Filters Traveling Bridge Sand Media Filters. Traveling bridge filters utilize shallow (approximately 16 IN) granular media beds configured in long, narrow basins, typically 16 FT x 100 FT maximum width and length. A motorized bridge, located above the water in each filter basin, is equipped with backwash pumps. As the bridge travels the length of the filter, the filter is backwashed. The recommended hydraulic loading rate for this type of filter is 2 gpm/SF at average flow and not greater than 5 gpm/SF at maximum day flow. Traveling Bridge Fabric Filters. Traveling bridge fabric media filters are long and narrow. The filter media consists of large hollow tubes covered with fabric media. The tubes are submerged and run parallel to each other over the long dimension of the filter basin. Hydraulic loading rates can be as much as 3.2 gpm/SF at annual average flow. Compressible Media Filters. A unique filter media is used in compressible media filters, 1-1/4 IN synthetic fiber balls. A moveable plate with a motor actuator compresses the media to a depth of 30 IN in preparation for operation. Flow is upward at hydraulic loading rates up to 30 gpm/SF. Because the hydraulic loading rate is over six times higher than that of granular media filters or fabric media filters, the footprint space for compressible media filters is smaller than for other filtration alternatives. When backwashing is required, the moveable plate is raised to decompress the media. Low pressure air is used to scour the media. Continuous Backwash Filters. Continuous backwash filters use a deep (generally 40 IN or more) granular media bed. Upflow and downflow configurations are available from various manufacturers. Continuous backwashing is accomplished by pumping media from the bottom of the filter to the top with an air lift pump. The pumping action is used to 7-16 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives scrub the media. The hydraulic loading rate at annual average flow would be 3.4 gpm/SF. Cloth Media Disc Filters. Cloth media filters consist of several disc shaped frames, approximately 7 FT in diameter by 4 IN thickness, covered with cloth filter media and mounted on a hollow shaft. The entire disc assembly is submerged and backwash on each disc occurs by rotating the discs with reversed flow. Loading rates of up to 6 gpm/SF have been accepted nationally. Deep Bed Mono Media Filters. Deep bed mono media filters are similar in configuration to many of the filters used in potable water treatment plants. Granular media is supported on an underdrain collection system and the direction of flow is downward. Filter media is typically about 72 IN thick. The filters are backwashed by pumping water from a clearwell or contact basin into the underdrain, reversing the direction of flow. Compared with other filtration alternatives, backwash flows are considerably higher for this technology. Membrane Filters. Membrane filtration systems are continuing to increase in popularity for municipal wastewater treatment systems due to the processes ability to provide a high-quality effluent which meets reclaimed water standards. Membrane pore size is small enough (0.1 to 0.4 um) such that all bacteria and some viruses are filtered from the effluent as they cannot pass through the membrane. In order to protect the membranes from fouling, fine screening is required upstream of the membranes. Typically, membrane manufacturers require 2 to 3 mm fine screening. Applying a low vacuum to the membrane modules pulls water through the membranes and pumps the filtered water to the next process step. Effluent Filtration Evaluation. Selection of the most appropriate type of filtration is dependent on the regulatory requirements and intended use. In this case, the purpose of the filters is to remove effluent nutrients, phosphorus specifically, in order to comply with stringent effluent limitations as low as TP < 0.05 mg/L. Tertiary membrane filters are the most suitable type for this application because they provide excellent phosphorus removal, and an OPCC line item is included for effluent management alternatives where filtration is projected to be required. The OPCC for tertiary membrane filtration is approximately $52.1 million, and the OPCC for a filter pump station is approximately $1.95 million. However, it is recommended that a filtration technology study be conducted to definitively size and select the required filter. A filtration study is included in the overall capital improvements table at the end of this chapter. Supporting infrastructure in the form of a filter pump station will be required if membrane filtration is installed. Sidestream Enhanced Biological Phosphorus Removal Sidestream enhanced biological phosphorus removal (S2EBPR) is an emerging design modification for EBPR that was previously also called RAS fermentation because it relies on fermenting RAS to generate the necessary volatile fatty acids (VFA) for biological phosphorus removal. The sidestream anaerobic zone (RAS fermentation zone) receives 10 to 15 percent (1.5 mgd) of the total RAS flow and is a supplemental carbon source (about 11,000 lbs COD/d). In this case the carbon source will be either a small fraction of primary sludge or primary sludge fermentate (initial model assumes 8,300 lbs/d of primary sludge) in a reactor with a hydraulic retention time (HRT) of approximately 24 7-17 ANR To PCE Ill j Ill Aeration I I I I l---------------------RAS ANR Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives hours. This design insulates the EBPR from diurnal variation of the VFA supply and preserves influent carbon for denitrification thus permitting higher nitrogen removal rates within the same anoxic volume, which again improves EBPR by reducing RAS nitrates. While RAS nitrates are less of a concern in S2EBPR (long HRT) any nitrate still must be denitrified before anaerobic conditions can establish. Figure 7-4 shows the reactor arrangement compared with a traditional mainstream anaerobic zone. Traditional Mainstream Anaerobic Zone Sidestream Anaerobic Zone (S2EBPR) Figure 7-4: S2EBPR Versus Traditional Mainstream Anaerobic Zone Anaerobic zones in traditional BNR designs are often not truly anaerobic because RAS and primary effluent introduce nitrates and dissolved oxygen, hence weakening anaerobic conditions. In a complete mixed tank this manifests itself in oxidation-reduction potential (ORP) levels that often don’t drop to levels that sustain a truly fermentative environment. In a plug flow configuration, some of the “anaerobic” zone volume does not contribute to the anaerobic mass fraction as it is lost to aerobic oxidation with residual oxygen and denitrification. EBPR performance in traditional BNR designs is also dependent on favorable influent carbon-to-phosphorus ratios. In the absence of such favorable conditions, EBPR performance is less reliable, may require chemical polishing, and generally limit stable operation by perpetually changing the plant phosphorus mass balance, its fraction of recoverable phosphorus in the struvite production facility influent, and phosphorus returned with the plant drain. The benefits of S2EBPR are the inverse to the disadvantages of the transitional EBPR design. One benefit is the ability to reach a high anaerobic mass fraction without requiring a very large anaerobic zone because the RAS fermentation or S2ENPR zone only contains RAS with a TSS concentration roughly three time higher than in a mainstream anaerobic zone. Another more nuanced benefit is phosphorus-accumulating organism (PAO) biodiversity. Different environments will select for different organisms. The S2EBPR zone constantly maintains very deep anaerobic. Tetrasphaera for instance have been shown to exercise diverse metabolism in deep anaerobic conditions (ORP less than -150 mV). Tetrasphaera is able to uptake higher forms of readily biodegradable COD (rbCOD) and ferment it into VFA which is available to all PAOs. Thus a biodiverse PAO population is able to grow on more diverse substrates and ultimately generate more PAO biomass. The net effect is a PAO population which is biodiverse and which exist in a higher proportion of the biomass. This in turn increases the overall phosphorus uptake capacity of the sludge. 7-18 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives It is projected that S2EBPR will be required to meet the effluent TP limits in Treatment Scenarios 2 and 3. An OPCC of approximately $800,000 was calculated for S2EBPR, and this cost is included as a line item for effluent management alternatives needing to meet Treatment Scenario 2 and/or Scenario 3 values. Post-Anoxic Carbon Dosing In order to comply with lower effluent TN limits outlined in Treatment Scenario 3 (Table 7-2), an increase in the volume of the WRF post-anoxic zone is needed, as well as direct carbon dosing. Carbon dosing can be generic compounds like methanol, proprietary products like MicroC, or other high carbon sources like brewery waste. Given the volatile nature of methanol, MicroC or a brewery waste source provides a safer carbon source for storage and handling. An OPCC of approximately $1.0 million was calculated for the carbon dosing infrastructure, and this line item OPCC is included for effluent management alternatives that must meet Treatment Scenario 3 standards. 7.3.2 Alternative 1a – Discharge to East Gallatin Surface Water For Alternative 1a, effluent continues to be discharged to the East Gallatin River. Required infrastructure for implementing Alternative 1a for the three respective treatment scenarios is shown in Table 7-14. At the projected treatment conditions for Scenario 1, conventional literature suggests that tertiary sand filtration are required to ensure adequate phosphorus removal. However, since the WRF currently meets this effluent phosphorus concentration without the use of filters, it is recommended the City refrain from installing filters until there is clear evidence that they must do so to continue meeting the discharge limitation. Table 7-14. Effluent Management Alternative 1a OPCCs Parameter Treatment Scenario 1 Treatment Scenario 2 Treatment Scenario 3 Permit TN & TP (mg/L) 6.4/0.27 6.4/0.05 3.0/0.05 Flow (mgd) 14.6 14.6 14.6 WRF Upgrades Estimated Cost Estimated Cost Estimated Cost Base Capacity Upgrades $24,110,000 $24,110,000 $24,110,000 Construct New Bioreactor #4 Train, 2.3 MG Adaptive Planning Adaptive Planning $10,890,000 Post-Anoxic Carbon Dosing System, 2500 ppd Carbon --$1,000,000 Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) -$800,000 $800,000 Tertiary Membrane Filtration, 17.9 mgd -$52,120,000 $52,120,000 Filter Pump Station, 17.9 mgd -$1,950,000 $1,950,000 Chem Coag/Dosing, 17.9 mgd -$1,500,000 $1,500,000 Total Capital Costs $24,110,000 $80,480,000 $92,370,000 Avg Annual O&M $1,680,000 $2,110,000 $2,150,000 20-Year Present Worth Cost $47,570,000 $110,010,000 $122,520,000 7-19 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.3 Alternative 1b – Seasonal Land Application For Alternative 1b, a portion of the effluent is land applied during the summer months with the remainder continued to be discharged to the East Gallatin River. Required infrastructure for implementing Alternative 1b for the three respective treatment scenarios is shown in Table 7-15. At the projected treatment conditions for Scenario 1, conventional literature suggests that tertiary sand filtration is required to provide adequate phosphorus removal. However, since the WRF currently meets this effluent phosphorus concentration without the use of filters, it is recommended the City refrain from installing filters until there is clear evidence that they must do so to continue meeting the discharge limitation. Alternative specific infrastructure includes a pipeline to the Springhill Sod Farm and Riverside Golf Course, as well as pumps. Table 7-15. Effluent Management Alternative 1b OPCCs Parameter Treatment Scenario 1 Treatment Scenario 2 Treatment Scenario 3 Permit TN & TP (mg/L) 6.4/0.27 6.4/0.05 3.0/0.05 Flow (mgd) 14.6 14.6 14.6 WRF Upgrades Estimated Cost Estimated Cost Estimated Cost Base Capacity Upgrades $24,110,000 $24,110,000 $24,110,000 Construct New Bioreactor #4 Train, 2.3 MG Adaptive Planning Adaptive Planning $10,890,000 Post-Anoxic Carbon Dosing System, 2500 ppd Carbon --$1,000,000 Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) -$800,000 $800,000 Tertiary Membrane Filtration, 17.9 mgd -$52,120,000 $52,120,000 Filter Pump Station, 17.9 mgd -$1,950,000 $1,952,000 Chem Coag/Dosing, 17.9 mgd -$1,500,000 $1,500,000 Management Alternative OPCC OPCC OPCC Land Application Infrastructure $2,520,000 $2,520,000 $2,515,000 Total Capital Costs $26,630,000 $83,000,000 $94,890,200 Avg Annual O&M $1,750,000 $2,170,000 $2,210,000 20-Year Present Worth Cost $50,990,000 $113,440,000 $125,940,000 7-20 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.4 Alternative 1c – Discharge to Shallow Groundwater For Alternative 1c, the effluent is discharged to shallow groundwater via infiltration/percolation (IP) cells on the WRF property. Required infrastructure for implementing Alternative 1c is shown in Table 7-16. Alternative specific infrastructure includes the construction of IP cells on the WRF property, as well as the associated pumps and piping. A range of costs is provided, consistent with the range of potential required discharge areas discussed in Chapter 5. Table 7-16. Effluent Management Alternative 1c OPCC WRF Upgrades Estimated Cost $24,110,000 Adaptive Planning Estimated Cost $11,800,000 – $18,400,000 Avg Annual O&M 20-Year Present Worth Cost $60,490,000 - $67,110,000 Parameter Treatment Scenario Permit TN & TP (mg/L) 7.5/0.27 Flow (mgd) 14.6 Base Capacity Upgrades Construct New Bioreactor No. 4 Train, 2.3 MG Management Alternative IP Cells & Supporting Infrastructure Total Capital Costs $35,910,000 - $42,510,000 $1,760,000 7-21 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.5 Alternative 1d – Tertiary Wetland Treatment For Alternative 1d the effluent is discharged to a constructed wetland on the WRF property. The wetland provides tertiary treatment, and for the purpose of analysis it is assumed that no effluent filtration is required because of the benefits provided by the wetland. Required infrastructure for implementing Alternative 1d is shown in Table 7-17. There is only one treatment scenario for Alternative 1d because it is unknown how DEQ would permit the wetland discharge. Alternative specific infrastructure includes the construction of a 16 acre horizontal flow wetland, as well as the associated pipes and pumps. Table 7-17. Effluent Management Alternative 1d OPCC Parameter Permit TN & TP (mg/L) Flow (mgd) WRF Upgrades Base Capacity Upgrades Construct New Bioreactor No. 4 Train, 2.3 MG Management Alternative Horizontal Flow Wetland Total Capital Costs Avg Annual O&M 20-Year Present Worth Cost Treatment Scenario 6.7/0.28 14.6 Estimated Cost $24,110,000 Adaptive Planning Estimated Cost $4,520,000 $28,630,000 $1,800,000 $53,750,000 7-22 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.6 Alternative 1e – Aquifer Recharge For Alternative 1e the effluent is discharged to the local aquifer with the intention that it can later be extracted by a new municipal well. High levels of treatment to Class A-1 standards is required to discharge effluent for this purpose. Required infrastructure for implementing Alternative 1e is shown in Table 7-18. There is only one treatment scenario for Alternative 1e, and it is to a very high level consistent with the current reuse rules in Montana. Alternative specific infrastructure includes the construction of IP cells on the WRF property, as well as the associated pumps and piping. A range of costs is provided, consistent with the range of potential required discharge areas discussed in Chapter 5. Table 7-18. Effluent Management Alternative 1e OPCC Estimated Cost $24,110,000 $10,890,000 $1,000,000 $800,000 $52,120,000 $1,950,000 $1,500,000 Estimated Cost $11,800,000 – $18,400,000 $104,170,000 - $110,770,000 Avg Annual O&M 20-Year Present Worth Cost $135,440,000 - $142,060,000 Parameter Scenario 3b Permit TN & TP (mg/L) 3.0/0.05 Flow (mgd) 14.6 WRF Upgrades Base Capacity Upgrades Construct New Bioreactor #4 Train, 2.3 MG Post-Anoxic Carbon Dosing System, 2500 ppd Carbon Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) Tertiary Membrane Filtration, 17.9 mgd Filter Pump Station, 17.9 mgd Chem Coag/Dosing, 17.9 mgd Management Alternative IP Cells & Supporting Infrastructure Total Capital Costs $2,230,000 7-23 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.7 Alternative 2 – Discharge to Belgrade For Alternative 2 a portion of future influent flow to the WRF from the western edge of the City is diverted to the Belgrade WWTP for treatment. Required infrastructure for implementing Alternative 2 is shown in Table 7-19. Alternative specific infrastructure includes the construction of an addition at the Belgrade WWTP to accommodate the flows. Table 7-19. Effluent Management Alternative 2 OPCCs Parameter Scenario 1c Scenario 2c Scenario 3c Permit TN & TP (mg/L) 9.4/0.39 9.4/0.05 3.0/0.05 Flow (mgd) 10.2 10.2 10.2 --- - - - - WRF Upgrades Estimated Cost Estimated Cost Estimated Cost Base Capacity Upgrades $18,420,000 $18,420,000 $18,420,000 Construct New Bioreactor #4 Train, 1.6 MG Adaptive Planning Adaptive Planning $7,580,000 Post Anoxic Carbon Dosing System, 1800 ppd Carbon $900,000 Sidestream Enhanced Biological Phosphorus Removal, 0.2 MG $400,000 $400,000 Tertiary Membrane Filtration, 12.3 MGD $37,270,000 $37,270,000 Filter Pump Station, 12.3 mgd $1,400,000 $1,400,000 Chem Coag/Dosing, 12.3 mgd $1,000,000 $1,000,000 Management Alternative Estimated Cost Estimated Cost Estimated Cost Belgrade WWTP Capacity Addition $76,750,000 $76,750,000 $76,750,000 Total Capital Costs $95,170,000 $135,240,000 $143,720,000 Avg Annual O&M $3,170,000 $3,420,000 $3,510,000 20-Year Present Worth Cost $140,190,000 $183,960,000 $193,730,000 7-24 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.8 Alternative 3 – Bozeman Owned Satellite Plant For Alternative 3 a portion of future influent flow to the WRF from the western edge of the City is diverted to a satellite treatment facility, owned and operated by the City of Bozeman, for treatment. Required infrastructure for implementing Alternative 3 is shown in Table 7-20. Alternative specific infrastructure includes the construction of a satellite treatment facility, the acquisition of land to facilitate groundwater discharge, and the construction of IP cells on the acquired property. Table 7-20. Effluent Management Alternative 3 OPCCs Parameter Scenario 1c Scenario 2c Scenario 3c Permit TN & TP (mg/L) 9.4/0.39 9.4/0.05 3.0/0.05 Flow (mgd) 10.2 10.2 10.2 --- - - - WRF Upgrades Estimated Cost Estimated Cost Estimated Cost 10.2 mgd Base Capacity Upgrades $18,420,000 $18,420,000 $18,420,000 Construct New Bioreactor #4 Train, 1.6 MG Adaptive Planning Adaptive Planning $7,580,000 Post Anoxic Carbon Dosing System, 1800 ppd Carbon $900,000 Sidestream Enhanced Biological Phosphorus Removal, 0.2 MG $400,000 $400,000 Tertiary Membrane Filtration, 12.3 MGD $37,270,000 $37,270,000 Filter Pump Station, 12.3 mgd Adaptive Planning $1,400,000 $1,400,000 Chem Coag/Dosing, 12.3 mgd $1,000,000 $1,000,000 Management Alternative Estimated Cost Estimated Cost Estimated Cost Westside Satellite WWTP $73,620,000 $73,620,000 $73,620,000 Total Capital Costs $92,040,000 $132,110,000 $140,590,000 Avg Annual O&M $3,170,000 $3,420,000 $3,510,000 20-Year Present Worth Cost $137,060,000 $180,830,000 $190,590,000 7-25 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.9 Regulatory Driven Alternatives Analysis The effluent management alternatives were analyzed in a weighted matrix during Final Alternatives Workshop II. The weighting criteria consisted of the parameters in Table 7-21. The respective weightings were selected by City personnel during the workshop. Table 7-21. Effluent Management Alternatives Ranking Criteria Criteria Description Relative Weighting Growth Management Flexibility Ability to accommodate future changes in growth. Alternatives that can be easily adjusted to accommodate future growth score higher. 32% Regulatory Acceptance The alternative is acceptable to regulatory agencies. Required permits can be obtained. Alternatives for which permitting is simple and can be obtained score higher. 22% Minimize Capital Costs Capital costs exclusive to management alternative. Alternatives that minimize their respective capital costs score higher. 16% Environmental Stewardship Effluent from alternative protects the environmental quality of the receiving body. Alternatives that go beyond statutory requirements to protect natural resources score higher. 12% Risk and Uncertainty Amount of uncertainty associated with the alternative. Alternatives with high levels of risk and uncertainty score lower. 7% Ease of Implementation Alternative is compatible with existing facilities. Land/ROW is available to construct any new infrastructure. Alternatives that are easier to implement score higher. 7% Ease of Maintenance Amount of maintenance required for new infrastructure or process changes. Alternatives that require minimal maintenance score higher. 4% The alternatives were evaluated in a weighted alternatives matrix that employed the criteria and respective weightings in Table 7-21. The scoring and final results for each treatment scenario are tabulated in Table 7-22, Table 7-23, and Table 7-24. 7-26 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-22. Treatment Scenario 1 Effluent Management Alternatives Matrix Alternative Respective Criteria Scores Growth Management Flexibility Regulatory Acceptance Minimize Capital Costs Environmental Stewardship Risk and Uncertainty Ease of Implementation Ease of Maintenance Final Weighted Score 1a. Discharge to East Gallatin Surface Water 21 18 29 13 23 24 17 70 1b. Seasonal Land Application 9 18 23 18 3 10 17 49 1c. Discharge to Shallow Groundwater 15 13 16 13 10 17 10 48 1d. Tertiary Wetland Treatment 15 8 23 18 16 17 17 51 1e. Aquifer Recharge 9 13 3 13 10 10 10 34 2. Discharge to Belgrade 15 13 3 13 23 10 10 43 3. Bozeman Owned Satellite Plant 15 18 3 13 16 10 17 47 7-27 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-23. Treatment Scenario 2 Effluent Management Alternatives Matrix Alternative Respective Criteria Scores Growth Management Flexibility Regulatory Acceptance Minimize Capital Costs Environmental Stewardship Risk and Uncertainty Ease of Implementation Ease of Maintenance Final Weighted Score 1a. Discharge to East Gallatin Surface Water 21 18 16 13 23 24 17 64 1b. Seasonal Land Application 9 18 16 18 3 10 17 48 1c. Discharge to Shallow Groundwater 15 13 23 13 10 17 10 51 1d. Tertiary Wetland Treatment 15 8 29 18 16 17 17 54 1e. Aquifer Recharge 9 13 10 13 10 10 10 37 2. Discharge to Belgrade 15 13 3 13 23 10 10 43 3. Bozeman Owned Satellite Plant 15 18 3 13 16 10 17 47 7-28 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-24. Treatment Scenario 3 Effluent Management Alternatives Matrix Alternative Respective Criteria Scores Growth Management Flexibility Regulatory Acceptance Minimize Capital Costs Environmental Stewardship Risk and Uncertainty Ease of Implementation Ease of Maintenance Final Weighted Score 1a. Discharge to East Gallatin Surface Water 21 18 11 13 23 24 17 60 1b. Seasonal Land Application 9 18 11 18 3 10 17 44 1c. Discharge to Shallow Groundwater 15 13 26 13 10 17 10 51 1d. Tertiary Wetland Treatment 15 8 33 18 16 17 17 54 1e. Aquifer Recharge 9 13 11 13 10 10 10 37 2. Discharge to Belgrade 15 13 4 13 23 10 10 43 3. Bozeman Owned Satellite Plant 15 18 4 13 16 10 17 47 7-29 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives 7.3.10 Regulatory Summary and Recommendations Alternative 1a was determined to be the highest scoring alternative in all three treatment scenario alternatives matrices. Alternative 1d was determined to be the second highest scoring alternative in all three treatment scenario alternatives matrices, and the relative difference in score between the two alternatives decreased in Scenarios 2 and 3 as more stringent effluent limitations spurred greater capital costs for discharging to surface water. The increase in capital costs reduced the score of Alternative 1a. However, there remains high uncertainty regarding Alternative 1d, including what level of tertiary treatment can be achieved with the wetland and how DEQ would permit such an addition to the WRF. The completion of the wetland pilot at the WRF should provide greater clarity regarding the wetland’s treatment performance and the Alternative’s true feasibility. The recommended improvements are outlined in Table 7-25, and are shown on an implementation timeline on Figure 7-5. The implementation year generally precedes the year required for each item. Improvements are consistent with Treatment Scenario 1 of Table 7-14, but a line item is included for piloting InDENSE in addition to the full InDENSE OPCC. A small line item is also included for an effluent filtration study. These two items are included so that they can be budgeted in the CIP plan. Improvements are shown on a site graphic on Figure 7-6. If a future permit is issued during the planning period that encompasses the nutrient effluent standards of either Treatment Scenario 2 or Scenario 3, the additional improvements shown in Table 7-26 and Table 7-27 should be implemented, respectively. These improvements are also shown on example implementation timelines with a permit issue date of 2024 on Figure 7-7 and Figure 7-9, respectively. The permit issue date of 2024 is given for example purposes only. Implementation should proceed as needed to be in compliance with the applicable permit requirements. Treatment Scenario 2 and Scenario 3 site improvements are shown on Figure 7-8 and Figure 7-10, respectively. 7-30 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-25. Recommended Improvements, Treatment Scenario 1 Unit Process OPCC Year Required Fourth Digester $4,930,000 ASAP Effluent Filtration Study $25,000 2023 UV Capacity Addition $1,270,000 2024 Pilot InDENSE $100,000 2024 InDENSE $1,430,000 2024 Construct New Bioreactor #4 Train, 2.3 MG -Adaptive Planning Wetland Pilot -In Progress Two Secondary Clarifiers $7,510,000 2027 Bioreactor No. 1 Upgrade $2,760,000 2027 Aeration Blower $890,000 2027 Screw Press Upgrade $1,400,000 2030 Third Screw Press $2,410,000 2035 Additional PEPS Pump $790,000 2040 Additional Screen $720,000 Adaptive Planning Total $24,235,000 2023 2028 2038 • Effluent Filtration Study • Upgrade Screw Press No. 1 • PEPS Pump • lnDENSE and/or Bioreactor 4 2022 ..__-~□ 2025 2033 2040 • Fourth Digester Addition • Bioreactor No. 1 Upgrade • Third Screw Press • End of Planning Period • UV Capacity Addition • Additional Aeration Blower • Wetland Pilot • Two Additional Secondary Clarifiers • lnDENSE Pilot Figure 7-5. Treatment Scenario 1 Recommended Improvements Implementation Timeline 7-31 ,. 2. 5. 6. 8. Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Figure 7-6. Treatment Scenario 1 Recommended Improvements Shown on WRF Site 7-32 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-26. Recommended Improvements, Treatment Scenario 2 Unit Process OPCC Year Required Table 8-25 Items $24,235,000 As Listed in Table 8-25 Sidestream Enhanced Biological Phosphorus Removal, 0.4 MG (+0.2 MG) $800,000 - Tertiary Membrane Filtration, 17.9 mgd $52,120,000 - Filter Pump Station, 17.9 mgd $1,950,000 - Chem Coag/Dosing, 17.9 mgd $1,500,000 - Total $80,605,000 Q 2024 I • Receive Permit 2023 • Effluent Filtration Study 2028 • Upgrade Screw Press No. 1 • lnDENSE and/or Bioreactor 4 •Tertiary Membrane Filters 2022 ---'4U2025 • Fourth Digester Addition • Bioreactor No. 1 Upgrade • UV Capacity Addition • Additional Aeration Blower • Wetland Pilot • Two Additional Secondary Clarifiers • lnDENSE Pilot 2038 • PEPS Pump 2033 2040 • Third Screw Press • End of Planning Period Figure 7-7. Treatment Scenario 2 Recommended Improvements Example Implementation Timeline 7-33 1. 2 3. 4. 6. 7. Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Figure 7-8. Treatment Scenario 2 Recommended Improvements Shown on WRF Site 7-34 Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Table 7-27. Recommended Improvements, Treatment Scenario 3 Unit Process OPCC Year Required As Listed in Table 25 Table 25 & Table 26 Items $80,605,000 & Table 26 Construct New Bioreactor #4 Train, 2.3 MG $10,890,000 - Postanoxic Carbon Dosing System $1,000,000 - Total $92,495,000 2024 • Receive Permit 2023 • Effluent Filtration Study 2028 • Upgrade Screw Press No. 1 • In DENSE and/or Bioreactor 4 • Tertiary Membrane Filters • Additional Bioreactor Capacity • Carbon Addition 2022 L...---<J 2025 • Fourth Digester Addition • Bioreactor No. 1 Upgrade • UV Capacity Addition • Additional Aeration Blower • Wetland Pilot • Two Additional Secondary Clarifiers • in DENSE Pilot 2038 • PEPS Pump 2033 2040 •Thi rd Screw Press • End of Planning Period Figure 7-9. Treatment Scenario 3 Recommended Improvements Example Implementation Timeline 7-35 ,. 2 3. 4. 6. 7. Bozeman WRF Facility Plan Update Chapter 7 – Treatment Upgrade Alternatives Figure 7-10. Treatment Scenario 3 Recommended Improvements Shown on WRF Site 7-36 Chapter 8 Biosolids Disposal 8 Contents Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Introduction.......................................................................................................................................8-1 8.1 Biosolids Regulatory Review..................................................................................................8-1 8.1.1 Title 40 CFR, Part 503 Overview ..............................................................................8-1 8.1.2 Application of the Rule ..............................................................................................8-1 8.1.3 Pathogen Reduction Alternatives..............................................................................8-2 8.1.4 Vector Attraction Reduction ......................................................................................8-4 8.1.5 Monitoring..................................................................................................................8-5 8.2 Regulatory Trends and Drivers for Biosolids Management ...................................................8-6 8.2.1 Pathogen Re-growth and Reactivation .....................................................................8-7 8.2.2 Microconstituents of Concern.................................................................................... 8-8 8.2.3 PFAS .........................................................................................................................8-9 8.2.4 Other Considerations ................................................................................................8-9 8.2.5 Summary of Biosolids Drivers .................................................................................8-10 8.3 WRF Biosolids Management................................................................................................8-10 8.3.1 Biosolids Disposal Alternatives ...............................................................................8-10 8.3.2 Alternatives Evaluation............................................................................................8-15 8.3.3 Summary and Recommendation.............................................................................8-17 Tables Table 8-1. Alternatives for Meeting Part 503 Class B Pathogen Requirements........................................8-2 Table 8-2. Site Restrictions for Class B Biosolids Application ...................................................................8-3 Table 8-3. Alternatives for Meeting Part 503 Class A Pathogen Requirements........................................8-4 Table 8-4. Options for Meeting Vector Attraction Requirements ...............................................................8-5 Table 8-5. Frequency of Monitoring Required by Part 503 Regulations....................................................8-6 Table 8-6. Biosolids Disposal Figures for Calendar Year 2020...............................................................8-11 Table 8-7. Present Worth Analysis ..........................................................................................................8-16 Table 8-8. Status Quo vs. WRF Compost Facility Alternatives Weighted Ranking Criteria ....................8-16 Table 8-9. Status Quo vs. WRF Compost Facility Alternatives Scoring ..................................................8-16 Figures Figure 8-1. ASP Compost Facility in Hamilton, MT .................................................................................8-12 Figure 8-2. Solar Greenhouse Biosolids Drying ......................................................................................8-14 i Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal This page is intentionally left blank. ii 8 Introduction Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal This chapter provides an overview of biosolids regulations and trends in the industry. Disposal options specific to the Bozeman WRF are then considered and evaluated consistent with the outlined rules and regulations. The final biosolids disposal alternatives consist of maintaining the status quo of composting biosolids at the Logan Landfill or composting biosolids on site at the WRF. 8.1 Biosolids Regulatory Review 8.1.1 Title 40 CFR, Part 503 Overview In response to the Clean Water Act Amendments of 1987, the EPA published Title 40 of the Code of Federal Regulations (CFR), Part 503 Standards for the Use or Disposal of Sewage Sludge on February 19, 1993. The sewage sludge/biosolids standards, commonly referred to as Part 503 Rule or Part 503, became effective on March 22, 1993.The Part 503 Rule is a complex, risk based assessment of potential environmental effects of pollutants that may be present in biosolids. The EPA subsequently published A Plain English Guide to the EPA Part 503 Biosolids Rule (Appendix B) in September 1994 to help end users interpret and implement the rule. The Part 503 Rule regulates pollutant and pathogen concentrations as well as vector attraction reduction (VAR). The guideline defines biosolids as Class A or Class B, depending on the potential level of pathogens. Class A biosolids must meet strict pathogen standards and can be used with no restrictions, while Class B biosolids can meet less stringent pathogen requirements, with application restricted to crops with limited human and animal exposure. Biosolids in both classes must meet VAR requirements. The WRF currently produces Class B biosolids. 8.1.2 Application of the Rule As defined in 40 CFR 503.1(b)(1), the Part 503 Rule “applies to any person who prepares sewage sludge, applies sewage sludge to the land, or fires sewage sludge in a sewage sludge incinerator and to the owner/operator of a surface disposal site.” Furthermore, a person is defined as an individual, association, partnership, corporation, municipality, State or Federal agency, or an agent or employee thereof. A preparer is a person who generates or derives a material from biosolids (i.e., change the quality of biosolids). (Plain English guide). The Part 503 Rule applies to biosolids applied to agricultural and non-agricultural land, biosolids placed in or on surface disposal sites, and biosolids that are incinerated. Biosolids that are landfilled or used as a cover material at a landfill are subject to federal requirements in 40 CFR Part 258. The general provisions of the Part 503 Rule provide basic requirements for biosolids applied to land including pollutant limits, management practices, operational standards and monitoring, record keeping, and reporting. 8-1 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal 8.1.3 Pathogen Reduction Alternatives Pathogenic organisms are defined in 40 CFR 503.31 as “disease-causing organisms. These include, but are not limited to, certain bacteria, protozoa, viruses, and viable helminth ova.” As mentioned previously, two classes of biosolids are defined by EPA that can be land applied, Class A and Class B. Class A biosolids have stringent limits for pathogens and can be used without any additional public contact restrictions. Class B biosolids may have low levels of pathogens and restrictions are imposed on public access and crop harvesting after land application. Those restrictions are described in the following sections. Class B biosolids are discussed first as they are more commonly produced. Class B Biosolids Class B biosolids are the predominant class of biosolids produced in the US (USEPA, 1999; NEBRA, 2007). Common treatment technologies, such as aerobic and anaerobic digestion, are used at many municipal wastewater treatment plants to inactivate the vast majority of potential pathogens in biosolids. However, the biosolids are not considered “pathogen-free,” and EPA requires that specific management practices be employed to protect the public. Class B biosolids must also meet the same vector attraction reduction requirements as Class A biosolids. Class B biosolids must meet one of several pathogen destruction alternatives included in Table 8-1. Table 8-1. Alternatives for Meeting Part 503 Class B Pathogen Requirements Alternative Description Alternative 1 Meet monitoring requirements for fecal coliform (geometric mean fecal coliform density must be less than 2 million coliform forming units (CFU) or most probable number (MPN) per gram of biosolids) Alternative 2 Employ a Process to Significantly Reduce Pathogens (PSRP) Alternative 3 Employ a process equivalent to a PSRP PSRPs include the following: Anaerobic digestion between 15 days at 35°C (95°F) to 60 days at 20°C (68°F). Aerobic digestion between 40 days at 20°C (68°F) to 60 days at 15°C (59°F). Air drying for at least 3 months. Composting o Temperature of the sludge must be 40°C (104°F) or higher for at least five days. For four hours of that period the temperature must be 55°C (131°F) or higher. Lime stabilization o pH of the sludge must be raised to 12 for at least two hours and must remain above 11.5 for 24 hours. Alternative 3 for Class B biosolids requires approval of the EPA or state regulatory agency. The regulating authority makes the decision on whether or not a process should be considered as equivalent to a PSRP. Both equivalent processes and PSRPs must meet specified pathogen requirements, as well. 8-2 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Biosolids treatment must include a method for reducing the attraction of vectors. Alternatives depend on the method of treatment and include 38 percent volatile solids (VS) destruction, and a specific oxygen uptake rate of less than 1.5 mg oxygen/ hour/ gram total solids. Meeting the 38 percent VS destruction criteria for VAR is usually easily achieved during anaerobic digestion due to the high efficiency of the process. Management practices are required to limit public and animal contact after Class B biosolids are applied and to allow natural processes to further inactivate potential pathogens. The management practices for Class B biosolids are in addition to the general management requirements specified in Subpart A of the Part 503 regulations and are summarized in Table 8-2. Table 8-2. Site Restrictions for Class B Biosolids Application Land/Crop Characteristic Regulatory Criteria (State and Federal) Land with a high potential for public exposure Public access restricted for 1 year after biosolids application Land with a low potential for public exposure Public access restricted for 30 days after biosolids application Food crops, feed crops or fiber crops Not harvested for 30 days after biosolids application Food crops with harvested parts that touch the biosolids/soil mixture and are totally above the land surface (e.g., melons, cucumbers) Not harvested for 14 months after biosolids application Food crops with harvested parts below the land surface (e.g., root crops such as potatoes, carrots, radishes) Not harvested for 20 months after biosolids application Animal grazing on a site Restricted for 30 days after biosolids application Turf placed on land with high potential for public exposure or a lawn unless otherwise specified by the permitting authority Restricted for 1 year after biosolids application Class A Biosolids Class A pathogen reduction requirements include fecal coliforms of less than 1,000 most probable number (MPN) per gram Total Solids (TS) of biosolids or Salmonella of less than 3 MPN per 4 grams TS. Alternatives for meeting Class A pathogen requirements are shown in Table 8-3. Option 1, thermal treatment, means a specific time-temperature requirement must be met as specified by the Part 503 Rule regulations. All biosolids particles processed using this alternative must be subjected to the EPA specified time-temperature regime, which means that batch or plug flow processing must be employed. Continuous flow processes with a detention time on, or above, the time-temperature curve are not acceptable. 8-3 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Table 8-3. Alternatives for Meeting Part 503 Class A Pathogen Requirements Option Biosolids Treatment Description Option 1 Thermally treated, i.e., biosolids must meet specific time- temperature requirements depending on solids concentration. Option 2 High pH-high temperature, e.g., lime stabilization followed by air drying. Option 3 Other Processes. Sampling is required. Option 4 Unknown Processes. Sampling is required. Option 5 Process to Further Reduce Pathogens (PFRP) Option 6 Process equivalent to PFRP. Requires approval of EPA’s Pathogen Equivalency Committee. Option 2, the high pH-high temperature process, is defined as the biosolids having the following three conditions: A pH of greater than 12 for at least 72 hours, Retaining the temperature of the biosolids above 52°C for at least 12 hours while the pH is above 12, and Air drying to over 50 percent solids after the 72-hour period of elevated pH Class A biosolids requirements for Options 3 and 4 rely on enteric virus and helminth ova testing, which can be expensive and time-consuming, typically four weeks for helminth ova testing and two weeks or longer for enteric viruses. There are also a limited number of accredited laboratories capable of performing these analyses. Processes to Further Reduce Pathogens (PFRPs) to produce Class A biosolids include composting, heat drying, heat treatment, thermophilic aerobic digestion (also known as autothermal thermophilic aerobic digestion or ATAD), beta ray irradiation, gamma ray irradiation, and pasteurization. New processes not specified by the EPA can be considered equivalent to a PFRP. The permitting authority, generally the Pathogen Equivalency Committee (PEC) of the EPA, is responsible for determining if a process is equivalent. Although the State of Montana still allows the use of Options 3 and 4, the EPA is considering eliminating their use to achieve Class A. Many states have already eliminated the testing to achieve Class A. The PEC is notoriously slow in considering new PFRP Equivalency and budget cuts to the EPA only increases the likelihood that new processes would not be approved. 8.1.4 Vector Attraction Reduction Vectors, such as rodents and insects, are attracted to putrescible organic matter and can facilitate disease transmission by transmitting pathogens to humans. Federal biosolids regulations require that certain standards be met to reduce how much vectors are attracted to biosolids. Vector attraction reduction (VAR) requirements for Class A biosolids are the same as for Class B requirements. 8-4 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal The EPA outlines 12 options in the Part 503 Rule for meeting the VAR requirements (Table 8-4). Options 1 through 8 and Option 12 are designed to reduce the attractiveness of biosolids to vectors. Options 9 through 11 prevent direct contact between vectors and biosolids. In general, pathogen reduction must be achieved prior to, or at the same time, as vector attraction reduction for biosolids to be considered Class A. Problems with pathogen regrowth led EPA to include this provision. Table 8-4. Options for Meeting Vector Attraction Requirements Option - Description Option 1 Meet 38 percent reduction in volatile solids content.1 Demonstrate vector attraction reduction with additional Option 2 anaerobic digestion in a bench-scale unit. Demonstrate vector attraction reduction with additional Option 3 aerobic digestion in a bench-scale unit. Meet a specific oxygen uptake rate (SOUR) for Option 4 aerobically digested biosolids. Use aerobic processes at greater than 40C for 14 days Option 5 or longer. Option 6 Alkali addition under specified conditions. Dry biosolids with no unstabilized solids to at least 75 Option 7 percent solids. Dry biosolids with unstabilized solids to at least 90 Option 8 percent solids. Option 9 Inject biosolids beneath the soil surface. Incorporate biosolids into the soil within 6 hours ofOption 10 application to or placement on the land. Cover biosolids placed on a surface disposal site with Option 11 soil or other material at the end of each operating day. (Note: Only for surface disposal.) Alkaline treatment of domestic septage to pH 12 or Option 12 above for 30 minutes without adding more alkaline material. Source: 40 CFR 503.33 1. Meeting the 38 percent VS destruction criteria is commonly achieved during anaerobic digestion due to the high efficiency of the process. 8.1.5 Monitoring Microbiological monitoring for either fecal coliforms or Salmonella is required for all biosolids. For Class A biosolids, each sample analyzed must meet the requirements, not just the average of several samples. Requirements must be met at the time of use or disposal, at the time the biosolids are prepared for sale or give away in a bag or other container for land application, or at the time the biosolids or material derived from the biosolids (e.g. compost) is prepared to meet the requirements in Part 503. Monitoring requirements vary by the size of the wastewater utility and the method of sludge processing. Table 8-5 summarizes the required frequency of monitoring for all biosolids under Part 503, which depends on the quantity produced by a utility in a given year. 8-5 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Table 8-5. Frequency of Monitoring Required by Part 503 Regulations Amount of Biosolids per 365 day Period Minimum Frequency Dry Metric Tons Dry English Tons Once per year 0 – 290 0 – 320 Once per quarter 290 – 1,500 320 – 1,654 Once per 60 days 1,500 – 15,000 1,654 – 16,540 Once per month 15,000 or greater 16,540 or greater Reprint of Table 3-4 from USEPA, 2003 1 metric ton = 1.1 English tons 8.2 Regulatory Trends and Drivers for Biosolids Management Political divisions and conflicts have emerged over the management of biosolids around the US, particularly in California, Virginia, and Pennsylvania. Local ordinances have been passed banning either Class B or all biosolids land application. More organized opposition to current biosolids management practices is compelling utilities to apply biosolids in more remote areas or process solids more extensively in order to manage biosolids in alternative ways. A document published in November of 2018 by the EPA Office of Inspector General (OIG) has highlighted several potential challenges in the biosolids industry, due to the undetermined impacts of unregulated pollutants in municipal biosolids. This report summarizes the findings of an audit performed on the EPA’s regulation and control of land application of biosolids. The OIG concluded the EPA’s controls over biosolids for land application were incomplete, and introduced a concern that human health and the environment may not be fully protected. They identified 352 pollutants, including pharmaceuticals, steroids, hormones, and flame retardants, present in biosolids that are currently unregulated due to a lack of data. Of those 352 pollutants, 61 were designated as acutely hazardous, hazardous, or priority pollutants in various programs. There were a number of deficiencies in the EPA’s biosolids program identified in the report to support their findings: Reduced staff and resources in the biosolids program causes difficulties in effectively addressing weaknesses within the program. Insufficient data is present to fully understand the health and environmental impacts of biosolids for land application, particularly in regards to the 352 unregulated pollutants present in biosolids. Additional information needed includes human health and ecological toxicity values, exposure data, pollutant concentrations, environmental fate and transport properties, mobility mechanisms, and bioaccumulation data. EPA continues to monitor for 9 regulated contaminants in biosolids, but no new pollutants have been identified in 20 years. The EPA’s website, biosolids labels, and public documents display a lack of transparency with regards to the uncertainties of the safety of biosolids for land application. Although EPA’s website has modified its safety statement to point 8-6 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal out the need for additional research, it does not explicitly state that biosolids cannot be proven safe for the public and environment until this research is completed. Additional information and data is required to provide comprehensive guidance for controlling and preventing potential risks to workers handling Class B biosolids. Pollutant distribution via biosolids runoff is not well tracked or regulated. There is concern that commonly used household chemicals that are transferred to WWTPs may end up in local surface waters via runoff, in agricultural soils, and in aquatic life. Although this report highlights the deficiencies in the EPA’s biosolids program, as well as the need for repairs and improvements, it is careful to emphasize that there is no data indicating that biosolids are actively harmful to human health or the environment; rather, the objective of this document is to point out that there is insufficient data and research available to rule out every possibility of potential harm to the public and environment via land application of biosolids. Therefore, the report provides recommendations for closing that data gap, and regulating land application of biosolids more thoroughly, including but not limited to: Issue guidance concerning what new technologies are allowable options or alternatives for biosolids pathogen reduction. Issue updated and consistent guidance on allowable and correct biosolids fecal coliform sampling practices. Modify EPA’s website to include a statement that until the required research concerning unregulated pollutants found in biosolids is complete, the safety of biosolids cannot be guaranteed. These recommendations have a few implications: first, updated pathogen reduction and fecal sampling practices are likely to change in the next 5 to 10 years. Particularly, the report states that there are issues with Option 3 and Option 4, referenced earlier (Table 8-3), for Class A pathogen reduction. Processes that are not already established as PFRPs may have to undergo stricter regulations and reevaluation by the EPA to pass Class A standards. Furthermore, if new rules are implemented for biosolids classification, costs of disposal for Class A or Class B biosolids may rise, meaning a process that reduces the total solids leaving the plant would provide an even greater cost benefit. Lastly, clarifying the EPA’s website to state that the safety of biosolids cannot be guaranteed will likely cause some pushback towards land application of biosolids by residents. This could limit the City’s ability to land apply biosolids in the future; however, public outreach to educate residents on the benefits of land application of biosolids may help to ease public concerns. Parameters that may be regulated under new biosolids rules are discussed in the subsequent sections. 8.2.1 Pathogen Re-growth and Reactivation Recent research by the Water Environment Research Foundation (WERF) has shown that fecal coliform, the indicator organism commonly used for pathogens, sometimes reactivates and/or re-grows after mechanical dewatering of solids. This has occurred with 8-7 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal a variety of anaerobic digestion processes, both Class B and Class A. Research is ongoing to further understand the mechanisms and causes of this phenomenon. Research to date has shown that high solids centrifuges have the greatest potential to reactivate/re-grow fecal coliform. This research could ultimately lead to changes in the regulatory requirements surrounding dewatering. Pathogen content in compost and compost like products are of concern in a number of parts of the country. Local Enforcement Agencies (LEA) and other regulatory agencies are being forced to require additional monitoring and provide additional scrutiny at sites. This not only adds cost to the overall management of the biosolids, but also potentially opens the facility to negative public reactions and third-party lawsuits. 8.2.2 Microconstituents of Concern The presence of trace organic chemicals (TOrCs) in municipal biosolids in the U.S. has received considerable attention by the public and scientific community over the last several years. Of particular concern is whether the presence of TOrCs in biosolids results in significant risks to public health and the environment upon land application. While the EPA has evaluated the risks associated with dioxins present in biosolids- amended soils, to date, no other TOrCs or those of emerging concern have been subjected to complete risk assessments. However, there are a growing number of studies being published every year that address the occurrence, mobility, persistence, bioaccumulation, toxicity, and microbial impacts of biosolids-borne TOrCs in soils. As more scientific data becomes available on this subject it is likely that the EPA will start regulating TOrCs that poses clear ecological and human health risk. Recent studies have found that some TOrCs can leach from fields, particularly when the applied biosolids are not dewatered. Specifically, steroid hormones have recently been shown to have the potential for runoff after heavy rainfall. However, other TOrCs (e.g., polybrominated diphenyl ethers, synthetic musks, and some steroidal chemicals) were shown to have low leaching potential. The persistence of biosolids-borne TOrCs in soils is a result of many processes, but biodegradation is generally considered the dominant process. Environmental factors such as pH, moisture content, metal cations, temperature, and bacterial cell concentration all can affect biodegradation rates. Biodegradation rates of steroidal chemicals are favorably impacted by the presence of biosolids, increased temperatures, and adequate (but not excessive) water content in soils. Unfortunately, degradation data for many TOrCs are not yet available for soils and biosolids-amended soils. Bioaccumulation of some of the TOrCs has been documented, but few studies examined bioaccumulation and bioavailability specifically in biosolids-amended soils. Some TOrCs (tetracycline antibiotics, antimicrobials, fluoroquinolones, and synthetic musks, brominated flame retardants) can accumulate in a variety of plants including grass, green onions, cabbage, corn, alfalfa, lettuce, radish, zucchini, and carrots. Studies have shown that bioaccumulation of TOrCs in animals, particularly invertebrates such as earthworms, is also possible. Several studies have indicated that many of the TOrCs found in biosolids can be significantly reduced in concentration if the biosolids are being treated by a combined anaerobic and aerobic digestion process. It is also likely that many TOrCs will be 8-8 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal degraded during aerobic production of Class A biosolids created from composting. A selected list of high priority trace organic chemicals present in biosolids include the following compounds: Brominated Flame Retardants Perflourochemicals (PFCs) - Surface Coatings Pharmaceuticals and Personal Care Products (PPCPs) o Antimicrobials o Antibiotics o Musks Plasticizers - Bisphenol A (BPA) Steroidal Chemicals-Natural and Synthetic hormones Surfactants Nanoparticles - antibacterial/antifungal agents 8.2.3 PFAS Regulatory trends pertaining to perfluoroalkyl substances (PFASs) were discussed in Chapter 4. Some of the trends are likely to affect biosolids disposal. EPA’s PFAS Strategic Roadmap includes a plan to finalize PFOA/PFOS biosolids risk assessment by the Winter of 2024. If biosolids contain PFAS, landfilled solids may contribute to landfill leachate PFAS issues. Land applied biosolids also may contaminate crops, livestock, groundwater, and surface water. POTWs may be responsible for crop, livestock, and environmental contamination caused by historical biosolid disposal methods. Additional biosolids treatment may be required before disposal depending on the final results of the risk assessment. 8.2.4 Other Considerations Regulatory trends in Europe sometimes portend the future direction of programs in America. In Europe, public perception related to risks of biosolids land application has resulted in greater focus on energy recovery/combustion technologies such as incineration, cement kilns, and gasification. Recently, however, the EPA under the Clean Air Act, designated Sewage Sludge as a “Solid Waste”. This action, as well as litigation from environmental groups, forced the Sewage Sludge Incinerator (SSI) Rule to change the monitoring and emission control Maximum Achievable Control Technology (MACT) standards from Rule 112 Standards to Rule 129 Standards. Rule 129 Standards are considerably more stringent. This led to a series of meetings, letter writing campaigns and ultimately a lowering of some of the emission limits and lessening of some of the monitoring whereby facilities with SSIs can achieve compliance. The regulations will lead to modifications in most cases and it will be expensive but they will be able to continue to operate. Because some of these SSI facilities still do not consider these rule changes to be reasonable or appropriate; NACWA is initiating litigation. 8-9 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal The interpretation of these rule changes is also causing concern from the wastewater community. First, even though not intended by the EPA, the rule could apply to all combustion of sewage sludge, biosolids and biosolids products which, if enforced, could bring all use of digester gas under new rules and standards. Second, if sludges and biosolids are classified as a solid waste, public perception on whether they should be land applied may shift. 8.2.5 Summary of Biosolids Drivers The future will likely bring both substantial challenges to, and attractive opportunities for, biosolids management. A continuation of substantial existing pressures, along with the emergence of new ones, presents serious challenges to biosolids management likely resulting in the loss, severe restriction and/or increased cost of management options. This includes the persistence of public perception concerns driven by odors, in combination with more emergent public health concerns (such as microconstituents), as well as the emergence of new regulatory actions such as the SSI rule and managing the phosphorus component of biosolids consistent with agronomic rates. However, substantial opportunities also exist for new and expanded biosolids management. The opportunity is largely tied to the repositioning of biosolids as a community resource too valuable to waste in the context of renewable energy needs, urban sustainability interests, population growth, soil depletion, and technology improvements. These important and substantial societal trends can equate to a compelling opportunity to reposition the biosolids management and product discussions to overcome entrenched negative positions and perceptions and recognize biosolids as a resource too valuable to waste. 8.3 WRF Biosolids Management The WRF currently produces Class B biosolids. The WRF’s primary sludge (PSL) stream and waste activated sludge (WAS) stream both undergo anaerobic digestion. The digested sludge is then dewatered with a screw press and conveyed to the load out bay in the solids handling building. The dewatered cake is hauled to the Logan Landfill where it is composted and then disposed of by placing as landfill cover. Full descriptions and evaluations of the WRF’s biosolids unit processes are included in Chapter 6. Alternatives for the construction of a fourth digester and the direct dewatering of undigested thickened WAS (TWAS) were considered respectively in Chapter 7, and the construction of a new digester was selected. This section evaluates the WRF’s current biosolids disposal practices and other disposal alternatives that could be implemented. 8.3.1 Biosolids Disposal Alternatives A variety of biosolids disposal alternatives are considered in this section, and consist of the following: Alternative 1. Landfill Disposal/Maintain Current Operating Plan Alternative 2. Construct On-Site Composting Facility Alternative 3. Agricultural Land Application Alternative 4. Silvicultural Fertilization 8-10 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Alternative 5. Disturbed Land Reclamation/Rehabilitation Alternative 6. Incineration Alternative 7. Solar Greenhouse Biosolids Drying with Supplemental Heat Only Alternatives 1 and 2 were carried forward for a full analysis. The remainder of the alternatives were dismissed without being carried forward. All alternatives considered are discussed in this section. Alternative 1. Landfill Disposal/Maintain Current Operating Plan Alternative 1 assumes the current operations of trucking biosolids from the WRF to the Logan Landfill for composting is continued. Current biosolids disposal costs and figures were provided by the City of Bozeman. This data is summarized in Table 8-6. The City indicated that $100,000 was spent on hauling biosolids during 2020, and the landfill charged a flat rate of $7 per ton of biosolids. This rate translated to a monthly tipping fee of approximately $3,300, which the City reported was typical. Based on the provided information, the current annual disposal costs (hauling costs and tipping fees) for the WRF’s biosolids amounts to approximately $140,000. The costs in Table 8-6 do not include labor costs, and a labor rate of $30 per hour for two persons was added to calculate comparable present worth costs between the alternatives. Table 8-6. Biosolids Disposal Figures for Calendar Year 2020 Month Solids Scaled at Landfill (Tons) Truckloads Average Tons per Truckload Avg Tons per Day (Total T per # Haul Days) Dry Weight at 17% Solids (Tons) - -- -- -- -- -- -- - January 504 50 10.1 19.4 85.7 February 390 41 9.5 18.6 66.3 March 573 52 11.0 22.0 97.4 April 490 40 12.3 24.5 83.3 May 556 51 10.9 22.2 94.5 June 435 46 9.5 19.8 74.0 July 540 52 10.4 20.8 91.8 August 475 50 9.5 18.3 80.8 September 482 50 9.6 19.3 81.9 October 431 52 8.3 16.6 73.3 November 387 48 8.1 16.1 65.8 December 470 51 9.2 18.1 79.9 Total 5,733 583 --975 Average 478 49 9.9 19.6 81 Alternative 2. Construct On-Site Composting Facility In an aerated static pile (ASP) method of composting, dried biosolids are mixed with woodchips and placed in piles. The piles are kept aerobic through a perforated pipe beneath the compost piles. After several weeks of composting, the aerated static piles 8-11 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal are taken down and screened to separate the wood chips from the compost. The woodchips are stored and reused, while the compost is placed in curing piles for a minimum of 30 days and up to 6 months in the winter. For Alternative 2, an ASP compost facility would be constructed at the WRF to convert the biosolids to a Class A fertilizer product. The compost product produced at the facility can be used for a wider variety of applications and with less restrictions than the Class B biosolids currently produced. The on-site compost system is sized to handle the 2040 average dry solids loading rate of 58 cubic yards per day. The complete system consists of approximately 40 aerated static piles with additional piles for backup capacity, eight curing piles, one compost mixer, a biofilter, one compost screen, odor control, and an open air building constructed over the aerated static piles. Finally, the composting system includes the collection and disposal of leachate from the aerated static and curing piles, the biofilter, and moisture trapped in the blower piping. An example photo of a covered ASP facility in Hamilton, MT is shown in Figure 8-1. Figure 8-1. ASP Compost Facility in Hamilton, MT The new composting facility requires a minimum of 5 acres of land. However, a larger plot of land may realistically be required to ensure proper spacing of the piles and usability of the facility. The WRF has adequate available land to construct the facility in the existing IP cells, but this precludes this space from ever being used for groundwater discharge, wetland discharge, or other uses. An opinion of probable construction cost (OPCC) for the construction of an ASP compost facility is approximately $8.3 million, and an additional OPCC for odor control improvements is $500,000. 8-12 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Alternative 3 – Agricultural Land Application Agricultural land application is one of the largest markets for biosolids, particularly in states with high agricultural activity. Stabilized Class B biosolids are applied to row or field crops for the purpose of fertilization. The nitrogen, phosphorus, iron, and other trace nutrients in biosolids increase crop yields and reduce the need for inorganic fertilizers. Cake biosolids also add moisture to agricultural soils and improve tilth. However, biosolids application cannot exceed the agronomic rate and nitrogen uptake capacity of the respective receiving crop or vegetation. As defined in 40 CFR 503: “Agronomic rate is the whole sludge application rate (dry weight basis) designed: To provide the amount of nitrogen needed by the food crop, feed crop, fiber crop, cover crop, or vegetation grown on land; and To minimize the amount of nitrogen in the sewage sludge that passes between the root zone of the crop or vegetation grown on the land to the groundwater.” Excess nitrogen applied to land can result in nitrate contamination of groundwater. The agronomic rate must be determined by considering total and available nitrogen in the biosolids and the expected yield of the crop or vegetation. There is not a clear agricultural application in the immediate vicinity of the WRF that would accept the WRF’s biosolids as fertilizer, and while the agronomic rate will depend on the receiving crop, even a beneficial uptake capacity will require several thousand acres to fully apply the amount of biosolids currently being produced (Table 8-6). This alternative is not considered further as a result. If circumstances change and a local entity is interested in using the WRF’s biosolids for fertilizer this alternative could be reconsidered, but it is unlikely the entirety of the WRF’s biosolids could be land applied locally. Alternative 4 – Silvicultural Fertilization Similar to agricultural fertilization, forested lands can be fertilized with Class B biosolids to increase tree yields and growth. Typically, fertilization is limited to harvested land, new starts, and young trees due to difficulties with applying biosolids to more mature forests. Access, terrain, and slopes are key issues when applying biosolids in forests. Similarly to Alternative 3 however, there is no clear silvicultural operation in the immediate area where the WRF’s biosolids could be applied. This alternative is not considered further as a result. Alternative 5 – Disturbed Land Reclamation/Rehabilitation Lands disturbed by natural disasters or industrial activities, such as mines and gravel pits, often lack the topsoil to support vegetation. These areas are good candidates for biosolids application and can be rehabilitated. Biosolids can provide topsoil to support vegetation, stabilize slopes, prevent erosion, and potentially restore ecosystems depending on the level of disturbance that has taken place. Since there is not an immediate need for this work in the immediate vicinity of the WRF this alternative is not considered further. If circumstances change and a land reclamation need emerges this alternative could be considered. 8-13 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Alternative 6 – Incineration Incineration is combustion at high temperatures in the presence of oxygen. The organic portion of biosolids can be combusted, which is approximately 70 to 85 percent of the solids. The organic portion is removed and the material left is inert inorganic ash. The ash is typically disposed of in a landfill, but can be recycled in construction materials such as concrete. Typically, undigested solids are combusted as digestion reduces the heat energy value of the solids, decreases the dewaterability of the solids, and increases costs for processing. Federal air emission requirements for sewage sludge incinerators include limits on heavy metals, carbon monoxide or total hydrocarbons, and other organic compounds. There are also required management practices such as temperature and instrument maintenance and operating conditions for air pollution control equipment. This alternative is not considered further due to the foul odors that would be generated, as minimizing such odors is a primary goal of the WRF. Alternative 7 – Solar Greenhouse Biosolids Drying with Supplemental Heat Biosolids drying with greenhouses is a well-established technology, but biosolids drying with a solar greenhouse and supplemental heat is a newer technology that is entering the biosolids stabilization market. This technology involves sending dewatered cake to a greenhouse for storage and additional drying. Evaporation of liquid within the dewatered solids occurs by atmospheric interaction and also by the heated floor slab. The curved solar panels concentrate heat on the water tubing that runs along the center of the panels, which sends the water to an insulated tank for storage. This water is recirculated through concrete slabs to heat the biosolids, and a windrow machine is used to intermittently turn over solids. The manufacturer of this technology, Heat2Hydro, claims that the process can reliably produce Class A biosolids. A depiction of the process is shown in Figure 8-2. Figure 8-2. Solar Greenhouse Biosolids Drying The benefits of this alternative include: Low energy usage Environmentally friendly 8-14 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Smaller footprint than traditional composting The challenges associated with this technology include: High capital costs Odor release/odor control issues Not a proven technology Not included by EPA in processes equivalent to a PFRP for Class A biosolids There are zero full-scale facilities that are currently operational. HDR was able to visit a pilot scale unit in Surprise, Arizona, but there is no performance data and credibility to be obtained from an existing full-scale system. Since the solar panels are not photovoltaic panels, but simply reflect and concentrate light on water tubes running through the center of the panel’s curvature, the panels require direct sunlight to effectively heat the water. This means the technology does not work if it’s even partially cloudy outside. If it’s a cloudy day and the water for the heated slab cannot be heated with solar panels, there is no designed backup plan. The system would likely require a backup boiler than can send hot water to the thermally insulated tank. There would likely be portions of the year in which this system would rely heavily on the backup boiler, which significantly reduces the energy-savings benefit of this alternative. The technology has no established greenhouse design, which causes significant unknowns in its suitability for Montana weather, costs, durability, and robustness. The manufacturer stated the heated floor is typically constructed from concrete. This brings up concerns that the pad will undergo significant damage and spalling due to constant heating and freezing. Additionally, there is no prepared solution to address fouling on top of the pad, or fouling of the heated water tubes throughout the inside of the pad. For the reasons listed above, this alternative was eliminated from further consideration. 8.3.2 Alternatives Evaluation A 20-year present worth evaluation was conducted for the two remaining alternatives, and the costs are summarized in Table 8-7. O&M costs include all those that would be required for composting on site and composting at the Logan Landfill, respectively. For onsite composting, O&M items include labor, electricity, and the general maintenance costs associated with operating the facility. For composting at the Logan Landfill, labor, hauling and disposal costs are included. All costs were scaled to the projected sludge production over the course of the 20-year planning period. The analysis found that the cost savings from operating a composting facility onsite would not offset the capital costs of constructing the ASP facility. 8-15 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal Table 8-7. Present Worth Analysis Alternative 1. Logan Landfill Composting Alternative 2. WRF Compost Facility Parameter - The two alternatives were then evaluated in a weighted alternatives matrix that employed the criteria and respective weightings in Table 8-8. These criteria were weighted by City of Bozeman personnel during the Final Alternatives Workshop 1. The scoring and final results are tabulated in Table 8-9. Table 8-8. Status Quo vs. WRF Compost Facility Alternatives Weighted Ranking Criteria Criteria Description Weighting Capital Costs $8,780,000 Average Annual O&M $560,000 $450,000 20-Year Present Worth Cost $8,700,000 $15,950,000 Growth Management Flexibility Ease of Implementation Minimize Capital Costs Risk and Uncertainty Ability to accommodate future changes in growth. Alternatives that can be easily adjusted to accommodate future growth score higher. Alternative is compatible with existing facilities. Land/ROW is available to construct any new infrastructure. Alternatives that are easier to implement score higher. Capital costs exclusive to management alternative. Alternatives that minimize their respective capital costs score higher. Amount of uncertainty associated with the alternative. Alternatives with high levels of risk and uncertainty score lower. 35% 24% 13% 13% Odor Amount of foul odor associated with alternative. A high scoring alternative minimizes foul odor to the extent possible. 8% Minimize Operational Costs Minimize operational costs associated with alternative. E.g., electricity, chemicals, labor, etc. 6% Table 8-9. Status Quo vs. WRF Compost Facility Alternatives Scoring Criteria Alternative 1 Status Quo Score Alternative 2 WRF Compost Facility Score Growth Management Flexibility 42 58 Ease of Implementation 90 10 Minimize Capital Costs 90 10 Risk and Uncertainty 63 38 Odor 88 13 Minimize Operational Costs 30 70 Final Weighted Score 66 37 8-16 Bozeman WRF Facility Plan Update Chapter 8 – Biosolids Disposal 8.3.3 Summary and Recommendation Alternative 1, maintaining composting at the Logan Landfill, scored much higher than Alternative 2 and was selected as the recommended alternative as a result of this analysis. While some operational cost savings are realized if Alternative 2 was employed, especially as disposal volumes increase further in the planning period, the odor produced by composting onsite and the high capital costs do not render Alternative 2 attractive at this time. 8-17 Chapter 9 Sidestream Treatment 9 Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment Contents Introduction.......................................................................................................................................9-1 9.1 Previous Planning Efforts .......................................................................................................9-1 9.2 Resource Recovery Alternatives............................................................................................9-2 9.2.1 No Sidestream Removal ...........................................................................................9-3 9.2.2 Sidestream Struvite Formation..................................................................................9-3 9.2.3 Sidestream Brushite Formation.................................................................................9-6 9.3 Alternatives Analysis ..............................................................................................................9-7 9.3.1 Alternative 1 - Continued Dosing of Mg(OH)2 ...........................................................9-7 9.3.2 Alternative 2 - MagPrex.............................................................................................9-8 9.3.3 Alternative 3 - Ostara ................................................................................................9-8 9.3.4 Alternative 4 - CalPrex ..............................................................................................9-9 9.3.5 Summary and Recommendations...........................................................................9-10 Figures Figure 9-1. 5-Stage Bardenpho Process with Anammox Schematic.........................................................9-1 Figure 9-2. Nutrient Recovery Hierarchical Breakdown.............................................................................9-3 Figure 9-3. Dosing Mg(OH)2 Process Schematic......................................................................................9-4 Figure 9-4. MagPrex Process Schematic ..................................................................................................9-4 Figure 9-5. OSTARA Process Schematic..................................................................................................9-5 Figure 9-6. CalPrex Process Schematic ....................................................................................................9-7 Tables Table 9-1. Alternative 1 Maintain Status Quo Present Worth Analysis .....................................................9-8 Table 9-2. Alternative 2 MagPrex Present Worth Analysis........................................................................9-8 Table 9-3. Alternative 3 Ostara Present Worth Analysis ...........................................................................9-9 Table 9-4. Alternative 4 Modified CalPrex Present Worth Analysis.........................................................9-10 i Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment This page is intentionally left blank. ii 5-Stage Barden SCL Pm'Oty El ,----- -------------------~ RAS Anammox Equ azauon 9 Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment Introduction The purpose of this chapter is to evaluate resource recovery options for reducing nutrient recycle that can be implemented at the Bozeman WRF as part of sidestream treatment. The analysis will consider the capital improvements necessary to implement the alternatives as well as their relative economic feasibilities and size/layout. 9.1 Previous Planning Efforts A sidestream treatment technical memorandum (TM) was previously prepared for the City by HDR in December 2016. Options for the sidestream treatment of the dewatering screw press recycle stream were examined in the TM, as the recycle stream has a high ammonia loading that negatively impacts the bioreactor nutrient removal process. Sidestream processes that were examined in the TM include Paques ANAMMOX, ANITA-Mox, and bio-augmentation. The Anammox process was considered because it could be used to efficiently remove nitrogen from the solids dewatering sidestream. In the process, partial nitrification is followed by ammonium oxidation and reduction by Anammox bacteria. The “short cut” ammonia conversion allows for reduced oxygen demand and carbon required compared to traditional nitrification-denitrification. Two Anammox reactor configurations were examined: (1) a continuously fed bioreactor with recycle (PAQUES ANAMMOX), or (2) a continuously fed moving bed bioreactor (MBBR) (Anita-Mox). Figure 9-1 below shows how the Anammox process would be inserted into the overall treatment configuration. Figure 9-1. 5-Stage Bardenpho Process with Anammox Schematic Paques ANAMMOX is a proprietary nitrogen removal system that utilizes Annamox bacteria. The system involves an equalization tank, a separator, and a treatment tank. External recycle is required to maintain minimum velocities across the separator. The bioreactor is continuously fed and aerated and equipped with a biomass retention system. The growth of the biomass is controlled to utilize granular biomass formation. 9-1 Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment The granular biomass is recycled, separated, and retained to maintain the biomass density required. The ANITA-Mox system is an Anammox moving bed biofilm reactor (MBBR) from Kruger/Veolia. The MBBR is a continuous flow, non-clogging biofilm reactor containing moving media. The biomass in the ANITA-Mox reactor is grown on AnoxKaldnes polyethylene media that is suspended in the water. The system is known to remove up to 90 percent of ammonia and does not require an external carbon source. Nitrification and Nitrification-Denitrification (NDN) were the two bio-augmentation options evaluated. Both options utilize a complete mixed activated sludge process that requires aeration. Unless alkalinity is added, only about half of the recycle ammonia can be converted during nitrification, and unless an external carbon source is used, denitrification cannot occur. Following the evaluation of these sidestream treatment options, it was recommended the use of the ANITA-Mox option be further explored for implementation in the existing DAFT Building. The purpose of this chapter is to revisit the alternatives, evaluate new technologies which have come into the market and determine which sidestream treatment alternative provides the City the greatest long-term benefit. 9.2 Resource Recovery Alternatives There are a variety of technologies and specialized processes available to remove and recover resources (i.e. nutrients) from the wastewater treatment process. These technologies are primarily geared towards phosphorus removal, as phosphorus is a finite resource whose recovery and reuse has become increasingly important as naturally occurring deposits are depleted. Depending on the process and technology that is used, the recovered phosphorus product can hold monetary value and be beneficially used for a number of applications including as a high value fertilizer. Additionally, recovering phosphorus from the wastewater treatment process offers several important operational benefits including decrease of struvite formation/buildup, reducing required plant maintenance, and lower effluent TP concentrations. Since 2016, removal and/or recovery alternatives have been further improved. This chapter discusses the most viable alternatives including: No sidestream removal Maintaining the status quo of dosing magnesium hydroxide Implement the MagPrex process (not included in original evaluation) Implement the Ostara process (not included in original evaluation) Implement the CalPrex process (not included in original evaluation) These options broadly fall under two categories: sidestream struvite formation and sidestream brushite formation. A visual representation of this categorization can be seen on Figure 9-2. 9-2 Current Operation Evaluated Alternatives Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment Figure 9-2. Nutrient Recovery Hierarchical Breakdown Nutrient Removal Alternatives No Sidestream Removal No Sidestream Removal Sidestream Struvite Formation Mg(OH)2 Dosing to Digester MagPrex w/ Product Recovery MagPrex w/out Product Recovery Ostara Centrate Recovery Ostara w/ WASSTRIP Sidestream Brushite Formation Classic CalPrex w/ SPR Modified Calprex w/ SPR 9.2.1 No Sidestream Removal This alternative is defined as the operation of the BNR system when there is no sidestream chemical dosing or any specific sidestream nutrient removal process. In this context, the recycled ammonia and phosphate concentrations from anaerobic digestion process result in influent concentrations higher than current operation since the current operation includes dosing magnesium hydroxide (see Figure 10-3). Given that current operation already includes a sidestream removal process, there is no desire on the part of the City of Bozeman to return to doing no sidestream removal at all. As such, this alternative is not evaluated further. 9.2.2 Sidestream Struvite Formation MagPrex and Ostara are both vendor-supplied technologies which remove sidestream phosphorus in the form of struvite (MgNH3PO4·6H2O). The current approach of dosing magnesium hydroxide to Anaerobic Digester No. 3 also precipitates struvite in the sidestream and therefore belongs in this grouping of sidestream nutrient removal alternatives. The alternatives of continued dosing of magnesium hydroxide, MagPrex, and Ostara are discussed in this section. Dosing of Mg(OH)2 to Digester 3 An alternative for maintaining status quo operations at the WRF is included to allow for comparisons to the other options. This alternative doses Mg(OH)2 to Digester 3 to create struvite prior to dewatering. The digested sludge is then dewatered with the struvite crystals contained within it, which decreases the potential for struvite buildup in other plant processes and reduces phosphorus recycle to the front of the treatment process. WRF staff report they currently spend approximately $85 per day for Mg(OH)2, which equates to roughly $5 per wet ton of digested sludge per day. 9-3 voo~Grit - Vortex Grit INF Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment Figure 9-3. Dosing Mg(OH)2 Process Schematic Precipitation of struvite in this manner has been attainable due to the steep sloped floors of the digesters, mixing system, and sludge withdrawal systems which allow struvite crystals to remain suspended within the sludge matrix rather than settling out and solidifying on the bottom of the tanks. Significant knowledge development occurred to make Mg(OH)2 dosing reliable at the facility, and since the initial knowledge hurdle this operation strategy has been very effective at removing sidestream phosphorus. MagPrex MagPrex is a patented sludge optimization and phosphorus recovery process manufactured by Centrisys CNP (formerly known as AirPrex). MagPrex precipitates struvite in the sludge stream after anaerobic digestion but prior to dewatering. The crystallization reaction is most effective at a pH of 8.6. In the MagPrex system, the crystals are either removed in the sludge or MagPrex can supply a classifier which separates the crystals from the sludge prior to dewatering. Separating the crystals offers an opportunity for phosphorus recovery. The precipitation of struvite after anaerobic digestion but prior to dewatering typically improves the dewaterability of digested sludge, since phosphate released via anaerobic digestion is precipitated out immediately prior to dewatering. An overview of the treatment process with MagPrex is shown on Figure 9-4. Figure 9-4. MagPrex Process Schematic 9-4 Vortex Grit INF Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment This process is similar to the existing method of dosing Mg(OH)2 to the Digester, since struvite is formed within the sludge matrix. However, the MagPrex process optimizes struvite formation by: 1) Boosting the pH level by aerating the reactor, thereby off-gassing CO2, and 2) Adding magnesium chloride to drive the crystal formation. The addition of a classifier on the solids stream enables separation of struvite crystals from the sludge matrix. Ostara Process For the Ostara process, thickened primary sludge and thickened waste-activated sludge are sent to anaerobic digestion. The anaerobically digested sludge is dewatered and the Ostara process recovers phosphorus and ammonia in the form of struvite from the digested sludge dewatering centrate. The technology uses an upflow conical reactor to hydraulically select for struvite crystals formed at a pH of approximately 8.6. The Ostara technology often makes use of a WAS fermentation step to further release the stored polyphosphate accumulated by the PAOs in an EBPR system prior to anaerobic digestion. The P-released WAS is then dewatered or thickened and the filtrate or subnatent from that unit can be sent to the Ostara crystallization system for boosted phosphorus recovery. Ostara licenses the unit process as part of the overall nutrient recovery system and calls the process WASSTRIP. In this arrangement, phosphate is diverted from the anaerobic digesters, limiting the struvite formation potential in the digesters and achieving some dewatering benefit. Dewatered anaerobic sludge is either landfilled or composted, and overflow from the Ostara process is returned to the front of the plant. Struvite is recovered from the Ostara process and can be sold as a fertilizer. Dewaterability is likely be improved to some degree by Ostara since phosphate is diverted from anaerobic digestion via the WASSTRIP process. An overview of the treatment process with Ostara is shown on Figure 9-5. Figure 9-5. OSTARA Process Schematic 9-5 Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment 9.2.3 Sidestream Brushite Formation Brushite is a phosphorus-rich fertilizer formed by calcium and phosphate (CaHPO4·2H2O). CalPrex is the only brushite precipitation process currently supplied in the municipal WRF market and is manufactured by Centrisys CNP. CalPrex uses calcium hydroxide to precipitate phosphorus in the form of brushite at a pH of approximately 6.5, and then separates the crystals from the liquid using plate settlers and a centrifuge. The process requires some form of acid phase digestion or similar fermentation-type process (stored phosphate release or SPR) to solubilize stored phosphorus prior to anaerobic digestion. The crystallization reaction occurs upstream of anaerobic digestion. The CalPrex process can complement BNR facilities especially well because it captures phosphorus upstream of the digesters, reducing the potential for struvite buildup. The acid phase digestion component (or fermentation unit) also creates a carbon-rich recycle stream that can improve nitrogen removal in the bioreactors. Additionally, dewaterability of the biosolids improves because soluble phosphorus is precipitated prior to dewatering.1 CalPrex A CalPrex arrangement at the WRF would remove phosphate from the WAS stream as brushite and the WAS would be directly dewatered and disposed of without being anaerobically digested. Waste activated sludge would be sent to the RSTs and the thickened WAS is sent to an SPR process to release phosphate. A portion of gravity thickener overflow would be routed to the SPR tank to encourage full release of stored phosphate. The SPR process lowers the pH, produces some additional volatile fatty acids (VFAs), and releases stored phosphorus. The SPR stream would then be dewatered and the filtrate (or supernatent) sent to the CalPrex reactor to precipitate phosphorus in the form of brushite. About 90 percent of soluble phosphorus is precipitated during this process. The precipitated phosphorus is then collected, dewatered completely, and thermally dried. Overflow from the CalPrex process returns to the front of the plant. An overview of the treatment process with CalPrex is shown on Figure 9-6. 1 It is known that soluble phosphate (PO4-P) in the anaerobic digester sludge stream decreases the relative dewaterability of anaerobically digested sludge. Two mechanisms have been proposed to explain this. One theory is that higher dissolved phosphate concentrations in sludge produces a divalent cation bridging effect. The other theory is that dissolved phosphate in the sludge increases stored water connected with protein and polysaccharide (EPS) components. Either way, dissolved phosphate in the sludge is known to increase the stored water content and decrease the dewaterability of sludge. 9-6 Vortex Grit PCL SCL J, I I ! : -DIG 1-2 I I I TPSL -1 I I ______ I I -1 -...1----I DIG3 •---I I --------, ScrewPress :_______ .i """" _____________ _ c-- WAS Disposal -~ Disposal Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment Figure 9-6. CalPrex Process Schematic 9.3 Alternatives Analysis The capital improvements required to implement each of the respective resource recovery technologies are discussed in this section. Vendor proposals for projects similar in size and scope to Bozeman were obtained to estimate opinions of probable construction cost (OPCC). Revenue from recovered product and O&M costs were also estimated from these proposals to calculate a 20-year present worth cost for each option. O&M costs are scaled to account for the increase in biosolids volume over the course of the planning period. The recommended biosolids related capital improvements from Chapter 7 are carried forward and included in the present worth analysis for each alternative to allow for clear comparisons to the status quo. 9.3.1 Alternative 1 - Continued Dosing of Mg(OH)2 There are no additional resource recovery capital costs required to maintain the status quo and continue dosing Mg(OH)2. The recommended capital improvements from Chapter 7 are carried forward and included in the present worth analysis. The results are summarized in Table 9-1. 9-7 Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment Table 9-1. Alternative 1 Maintain Status Quo Present Worth Analysis Parameter Alternative 1 Status Quo Solids Dewatering and Digestion Number OPCC Rotary Screen Thickener Adaptive Planning - Fourth Digester 0.6 MG $4,930,000 Screw Press Upgrade 1x $1,400,000 Additional Screw Press 1x $2,410,000 Total Capital Costs $8,740,000 --- Avg Annual O&M $1,130,000 20-Year Present Worth Cost $24,220,000 9.3.2 Alternative 2 - MagPrex The capital cost for installing a MagPrex process at the WRF is estimated to be approximately $2.48 million. Revenue from the recovered struvite product is estimated to average approximately $12,000 per year over the 20-year planning period. Costs are shown in Table 9-2. Table 9-2. Alternative 2 MagPrex Present Worth Analysis Parameter Alternative 1 Status Quo Alternative 2 MagPrex Solids Dewatering and Digestion Number OPCC Number OPCC Rotary Screen Thickener Adaptive Planning -Adaptive Planning - Fourth Digester 0.6 MG $4,930,000 0.6 MG 4,928,000 Screw Press Upgrade 1x $1,400,000 1x 1,403,000 Additional Screw Press 1x $2,410,000 1x 2,412,000 Nutrient Recovery Technology Number OPCC Number OPCC MagPrex --1x $2,480,000 Total Capital Costs $8,740,000 $11,220,000 Avg Annual O&M $1,130,000 $1,090,000 20-Year Present Worth Cost $24,220,000 $26,150,000 9.3.3 Alternative 3 - Ostara The capital cost for installing an Ostara process with WASSTRIP is estimated to be approximately $1.73 million. Revenue from the recovered struvite product is estimated to average approximately $30,000 per year over the 20-year planning period. Costs are shown in Table 9-3. 9-8 Bozeman WRF Facility Plan Update Chapter 9 – Sidestream Treatment Table 9-3. Alternative 3 Ostara Present Worth Analysis Parameter Alternative 1 Status Quo Alternative 3 Ostara Solids Dewatering and Digestion Number OPCC Number OPCC Rotary Screen Thickener Adaptive Planning -Adaptive Planning - Fourth Digester 0.6 MG $4,930,000 0.6 MG 4,928,000 Screw Press Upgrade 1x $1,400,000 1x 1,403,000 Additional Screw Press 1x $2,410,000 1x 2,412,000 Nutrient Recovery Technology Number OPCC Number OPCC Ostara Pearl --1x $880,000 Ostara WASSTRIP --1x $850,000 Total Capital Costs $8,740,000 $10,470,000 Avg Annual O&M $1,130,000 $1,080,000 20-Year Present Worth Cost $24,220,000 $25,250,000 9.3.4 Alternative 4 - CalPrex The capital cost for installing a CalPrex process at the WRF is estimated to be approximately $2.5 million, with an additional $2.0 million in supporting infrastructure also required. Revenue from the recovered brushite product is estimated to average approximately $17,000 per year over the 20-year planning period. In this arrangement, WAS would not be digested and no additional digester would be constructed. This would maximize phosphorus removal and minimize capital costs. However, this alternative possesses the same drawbacks that come with the current operation of not digesting WAS that were previously discussed in Chapter 7, namely odor and higher O&M costs. OPCCs are shown in Table 9-4. 9-9 Bozeman WRF Facility Plan Update Chapter 9 - Sidestream Treatment Table 9-4. Alternative 4 Modified CalPrex Present Worth Analysis Parameter Alternative 1 Status Quo Alternative 4 Modified CalPrex --- Solids Dewatering and Digestion Number OPCC Number OPCC Rotary Screen Thickener Adaptive Planning -Adaptive Planning - Fourth Digester 0.6 MG $4,930,000 -- Screw Press Upgrade 1x $1,400,000 1x $1,400,000 Additional Screw Press 1x $2,410,000 1x $2,410,000 Nutrient Recovery Technology Number OPCC Number OPCC CalPrex --1x $2,540,000 P-Release Tank System --1x $1,500,000 WAS Infrastructure --1x $540,000 Total Capital Costs $8,740,000 $8,400,000 Avg Annual O&M $1,130,000 $1,340,000 20-Year Present Worth Cost $24,220,000 $26,750,000 9.3.5 Summary and Recommendations The present worth costs of all the resource recovery alternatives exceeded the present worth cost of the status quo alternative (dosing Mg(OH)2). Additionally, since the WRF already effectively removes struvite by dosing Mg(OH)2 there are not strong process benefit offered by any of the alternatives at this time that isn’t already being addresses. Given the economic calculations, and that the WRF currently does not have any strong drivers that make this technology necessary, it is recommended the WRF continue with status quo operations of dosing Mg(OH)2. 9-10 Chapter 10 Capital Improvement Plan Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan Contents 10 Introduction.....................................................................................................................................10-1 10.1 CIP Plan ...............................................................................................................................10-1 10.2 EconH2O...............................................................................................................................10-1 10.3 Financial Planning Considerations.......................................................................................10-2 10.3.1 Funding Sources .....................................................................................................10-3 10.3.2 Grant Programs.......................................................................................................10-3 10.3.3 Financing Sources...................................................................................................10-5 Figures Figure 10-1. EconH2O Control Menu ......................................................................................................10-2 Tables Table 10-1. Recommended Treatment Improvements, Scenario 1.........................................................10-1 i Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan This page is intentionally left blank. ii Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan 10 Introduction The recommended improvements described in Chapter 7 are used to outline a capital improvement plan (CIP) schedule in this chapter. This chapter also presents financial planning considerations for the wastewater utility CIP. 10.1 CIP Plan The recommended improvements as outlined in Chapter 7 are summarized in Table 10-1. The recommended improvements are for Treatment Scenario 1 and represent the probable, most lenient effluent nutrient standards that could be expected in a future discharge permit. Table 10-1. Recommended Treatment Improvements, Scenario 1 Econ H2O ID Unit Process Improvement Estimated Construction Cost (2022 dollars) Required Fiscal Year 1 Additional Screen $720,000 Adaptive Planning 2 Additional PEPS Pump $790,000 FY 38 3 Bioreactor No. 1 Upgrade $2,760,000 FY 25 4 Pilot inDENSE $100,000 FY 22 5 Two Secondary Clarifiers $7,510,000 FY 25 6 Aeration Blower $890,000 FY 25 7 UV Capacity Addition $1,270,000 FY 22 8 Screw Press Upgrade $1,400,000 FY 28 9 Third Screw Press $2,410,000 FY 33 10 Fourth Digester $4,930,000 FY 22 11 Filtration Study $25,000 FY 23 12 Install inDENSE $1,430,000 FY 28 10.2 EconH2O A capital improvement planning database was established for Bozeman to track the proposed CIP schedule in accordance with the three treatment scenarios previously discussed. This tool is called EconH2O and exists in Microsoft Excel. EconH2O functions as a planning tool, reflecting permitting uncertainty by offering the ability to change things like the year the discharge permit is received, the number of years to comply, and the Treatment Scenario (1, 2, or 3). Additionally, EconH2O applies the input annual escalation to report the CIP schedule in the desired year of expenditure dollars. The overall EconH2O control menu is shown in Figure 10-1, demonstrating the options provided in the tool. 10-1 Scenario Definition ACTIVE SCENARIO Scenario 1 Ma 1u ly Change Project Schedules PROJECT CO.ST ASSUMPTIONS: Set costs to input ,or modeled:.!=l=np=u=t ====~ Set all ecosts t o: Use Most Likely Estim.,.. Set all cost curves to: LS_tr_ai"-gh_t-L_in_e ___ ,.._. (if}· Funding Strategy ESCALATION RATES BASE RATES Input I pu1 FUNDING SOURCES BONDS (All In Covg) ...... . WIFIA ............... . .SRF ................. . Interest Rate: PERMIT ASSUMPTIONS: ,-----, Year permit is received 2023 ,.. ! Years to comply: ... Set Set REVENUES Input Coverage: Repai,ment Term: Deferral: 0 years ... 5 Years ... !Year ... RESERVES ......... . Clicic. o !np t Reserves Up date Model Export Results Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan Figure 10-1. EconH2O Control Menu The actual date when improvements will be required could vary depending on the actual pace of growth within the service area and any issuance of an updated discharge permit. EconH2O can be updated to reflect these changes should they occur. 10.3 Financial Planning Considerations The effective implementation of a comprehensive facility plan is dependent upon developing a financial plan which can be supported by the utility, will meet State and local regulatory requirements, and provides the flexibility to deal with unforeseen changes. It is recommended that the City undertake a full financial planning effort to consider rate tolerances, revenue smoothing strategy, continuing to maximize growth share recovery, alternative funding mechanisms, O&M expenses, and debt service in support of a balanced, implementable CIP. 10-2 Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan 10.3.1 Funding Sources For the purposes of this report, funding and financing are two different terms. Financing is a method of paying for infrastructure, such as long-term borrowing. Debt service payments on a revenue bond (i.e., the financing method) must be paid from a funding source (e.g., rates, impact fees, etc.). While the list below is not exhaustive, it does provide the most probable outside funding sources available to the City for its capital improvements. User Fees/Rates. The most basic funding source available to the City is user charges or wastewater rates. For a wastewater utility, the rates are typically composed of a water meter charge and a consumption charge based on usage. The rate funding portion of the capital plan should be equal to or greater than annual depreciation expense. The utility will need to increase this amount, as feasible, over time. Impact Fees. Impact Fees are a one-time fee imposed upon new development as a condition of development. The purpose of impact fees is to either reimburse existing customers for the investment made in wastewater infrastructure capacity to support development, or to finance future wastewater capital infrastructure projects that create expanded capacity. Other Miscellaneous Funding. In addition to the above funding sources, there are also a variety of other funding sources, but typically of a much lesser extent. These other funding sources may take the form of property taxes, voter approved sales taxes, special fees and charges, and interest earnings on reserves. 10.3.2 Grant Programs The wastewater utility projects identified as part of the City’s capital improvement planning process are generally eligible for financial assistance from numerous State or Federal grant programs. Most grant programs require preparation of a Preliminary Engineering Report to support the proposed application. ARPA. The American Rescue Plan Act of 2021 (PUB. L. NO 117-2 SEC 602 (c)(1)(d)) provides state and local aid to make necessary investments in water and sewer infrastructure. The 67th Montana Legislature passed HOUSE BILL 632 which directed the federal funds available under the American Rescue Plan Act for use in Montana. Section 1 – Section 5 address how the federal funds will be distributed to necessary water and sewer infrastructure projects. Montana made these funds available in 2021 and 2022, however it is unclear if future funds will be available. Grants. A very limited funding source that may be available is grants. The advantage of grants is that they do not need to be re-paid. Unfortunately, grants have become increasingly rare and for financial planning purposes should not be relied upon as a funding source unless they are already secured. Grant programs usually entail a competitive process of project evaluation which prioritizes public health need, public safety, environmental degradation, and financial need. Projects primarily to support new growth do not compete well for grant funding. Among the grant programs are the following: 10-3 Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan Montana Coal Endowment Program (MCEP). This program, formally known as the Treasure State Endowment Program (TSEP) is a state-funded program administered by the Montana Department of Commerce that is designed to help address the "affordability" of local infrastructure projects by providing grants to lower the cost of constructing public facilities. Grants up to $750,000 are available and grant applications are ranked on several criteria including the threat to public health and safety, the appropriateness of the proposed technical solution, financial need, and public support. The grants require a 1 to 1 match in the form of other grants, cash or loans. Applications are generally due in May of even numbered years with grant approval occurring in the following legislative session. If approved, the grant money becomes available after July 1 the same years as the legislative session. Planning grants are also available from this program. Montana Renewable Resource Grant and Loan Program (RRGL). The RRGL program, which is administered by the Montana Department of Natural Resources and Conservation (DNRC) typically funds projects that conserve, manage, develop, and/or preserve Montana’s renewable resources. The RRGL program provides both grant and loan funding for public facility and other renewable resources. Projects are ranked based on the benefit to natural resources (e.g. reduction of pollution to a water body as a result of implementing a new treatment process). Grants up to $125,000 are available and there is no specific match requirement. The application deadline, approval and availability of funds matches the Montana Coal Endowment Program. Community Development Block Grant Program (CDBG). This grant program is administered by the Montana Department of Commerce. All CDBG applications must document that at least 51 percent of the non-administrative funds requested for a CDBG project are clearly designed to meet the needs for low and moderate-income families. The CDBG program has a maximum limit of $500,000 per project. Having a high percentage of low and moderate-income people in the community and the presence of a high potential health threat helps a community compete for a CDBG grant. Good local involvement in the planning process also helps grant competitiveness. Applications are made to this program on an annual basis. Planning grants for engineering and grant preparation expenses are also available from the CDBG Program. Federal State and Tribal Assistance Grant (STAG). This source of funding is derived from a special line item appropriation from Congress and is typically earmarked for wastewater pollution control projects, although other types of projects have been funded. Application can be submitted annually and generally consist of a simple request to the congressional delegation including a fact sheet regarding project need, costs, readiness to proceed, etc. The program is administered by the Montana Department of Environmental Quality (MDEQ), similar to the old EPA Construction Grants program. STAG grants will typically require a non-federal match. FEMA Building Resilient Infrastructure Communities Program. The program replaced the current FEMA pre-disaster hazard mitigation program. The program aims to redirect the federal focus toward research-supported, proactive investment in community resilience; more importantly reducing risk to at least one of a community’s infrastructure and lifelines – safety & security; food, water, shelter; health & medical; energy (power & fuel); communications; transportation; hazardous materials. States have different deadlines; the Montana Hazard Mitigation Office should be consulted for specific 10-4 Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan application requirements and deadlines. FEMA continues to establish State/territory allocations as well as funding through a national competition for mitigation projects. 10.3.3 Financing Sources The potential financing sources for a wastewater utility are varied. Given a solid foundation of rate funding, a wastewater utility has the ability to issue long-term debt to finance a variety of capital infrastructure projects. Provided below is a detail of some potential financing sources for the wastewater utility. Revenue Bonds. Revenue bonds pledge the revenues of the utility to repay the debt. Revenue bonds are a very viable source of financing for a wastewater utility. The issuance of a revenue bond requires the utility to maintain their rates at a sufficient level to assure repayment of the bonds. As a part of the issuance process, the bond documents contain rate covenants that require the utility to meet minimum debt service coverage (DSC) ratio. The debt service coverage ratio is a financial ratio (test) of the amount of funds available to pay for debt service, after first meeting all operating costs. General Obligation (G.O.) Bonds. G.O. bonds are similar to revenue bonds but have some distinct differences. First, G.O. bonds are typically backed by property taxes. The bonds are typically authorized by a vote of the people. Utilities typically do not use G.O. bonds due to the voting requirement, but in addition, most cities prefer to reserve their G.O. bonding capacity for other municipal projects that are not enterprise fund related. Special Improvement Districts. A special improvement district (SID) is a group of property owners that agree to pay for specific improvements that benefit them directly. The utility typically issues a form of long-term debt, and the property owners are assessed a property tax or assessment to repay the loan. This financing option is used most often when an improvement will clearly benefit only select properties, and not provide overall benefits to the entire system. Montana Wastewater and Drinking Water State Revolving Fund (SRF) Loan Programs. Montana communities and water and sewer districts use SRF loans to repair or build wastewater and drinking water systems. Growing communities need low-interest loans to make additions and improvements to their water and wastewater infrastructures to accommodate new housing and businesses, especially in oil and gas drilling areas. Federal grant money combined with state match funds create the low-interest loan programs Repaid or “Recycled” funds go back into the programs to fund loans DNRC and the Montana Department of Environmental Quality co-administer the SRF programs. DEQ provides support and guidance to the technical side of the projects and DNRC provides the financial support. Wastewater SRF legislation was passed in 1989. The program provides loans and loan forgiveness for community wastewater treatment projects Intercap Loan Program. The Montana Board of Investments of the Montana Department of Commerce (MDOC) administers this loan program which is available to communities for paying for capital improvements. The INTERCAP Program is a low cost, variable-rate program that lends money to Montana local governments, state agencies 10-5 Bozeman WRF Facility Plan Update Chapter 10 – Capital Improvement Plan and the university system for the purpose of financing or refinancing the acquisition and installation of equipment or personal and real property and infrastructure improvements. The Board of Investments issues tax-exempt bonds and loans the proceeds to eligible borrowers. In addition to long-term financing, INTERCAP is an excellent source for interim financing. The loan term is up to 10 years or the useful life of the project. The funding is always available and is not subject to a funding cycle. Maximum loan amount per project depends on borrower’s legal debt authority. EPA Water Infrastructure Finance and Innovation Act. The WIFIA program provides long-term, low-cost supplemental loans for regionally and nationally significant water and wastewater projects. Overseen by the Environmental Protection Agency (EPA), the WIFIA program was authorized in 2014 and is gaining traction as an innovative way to finance and deliver critical infrastructure projects. Primary benefits of the program include repayment deferral, up to 5 years after substantial completion of a project, customized repayments based on phasing in of rate increases, and early certainty on loan interest rates. Capital expenditures from all project phases are eligible costs and project eligibility aligns with the State Revolving Fund Loan programs. 10-6