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2021.0330.PR0010 2020-10-12 - Basis of Design Report (Liquid) - WRF Ph 2
Water Reclamation Facility – Phase 2 Basis of Design Report Prepared for City of Yelm June 2020 Prepared by June 2020 │ 216-1781-042 Water Reclamation Facility – Phase 2 Basis of Design Report Prepared for City of Yelm 106 2nd Street SE Yelm, WA 98597 Prepared by Parametrix 1019 39th Avenue SE, Suite 100 Puyallup, WA 98374 T. 253.604.6600 F. 1.855.542.6353 www.parametrix.com CITATION Parametrix. 2020. Water Reclamation Facility – Phase 2 Basis of Design Report. Prepared by Parametrix, Puyallup, WA. June 2020. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 CERTIFICATION The technical material and data contained in this document were prepared under the supervision and direction of the undersigned, whose seal, as a professional engineer licensed to practice as such, is affixed below. Prepared by: Scott Weirich Allan Maas, P.E. Robert W. Rohler, P.E. Glen Barcus Douglas M. Berschauer, P.E. Steven A. Wagner, P.E. _____________________________________________ Checked by David Michael Kopchynski, P.E. _____________________________________________ Approved by Brian E. Bunker, P.E. 06/24/2020 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 i TABLE OF CONTENTS 1. INTRODUCTION .................................................................................................................... 1-1 2. PROJECT OVERVIEW ............................................................................................................. 2-1 3. EFFLUENT CRITERIA .............................................................................................................. 3-1 3.1 Outfall Descriptions ...................................................................................................................... 3-1 3.2 Reclaimed Water .......................................................................................................................... 3-1 3.3 Surface Percolation ....................................................................................................................... 3-1 3.4 Power Canal and Nisqually River .................................................................................................. 3-2 3.5 Effluent Water Quality Design Criteria ......................................................................................... 3-2 4. TREATMENT PROCESS ........................................................................................................... 4-1 4.1 General Information ..................................................................................................................... 4-1 4.2 Design Criteria ............................................................................................................................... 4-1 4.2.1 Phased Design ............................................................................................................... 4-1 4.2.2 Flow, BOD, TSS, and TKN Loading Estimates ................................................................ 4-2 4.2.3 Design Concentrations .................................................................................................. 4-3 4.2.4 Design Influent Criteria ................................................................................................. 4-3 4.2.5 A Note on the Effect of Gravity Sewer Connections .................................................... 4-4 4.3 MBR System-Specific Design Criteria ............................................................................................ 4-5 4.3.1 Membrane Sizing .......................................................................................................... 4-5 4.3.2 Process Air Blower Sizing .............................................................................................. 4-5 4.3.3 Effluent TN Requirement .............................................................................................. 4-5 4.4 Treatment System Components Design Criteria .......................................................................... 4-6 5. CIVIL DESIGN ........................................................................................................................ 5-1 5.1 General Information ..................................................................................................................... 5-1 5.2 Design Criteria ............................................................................................................................... 5-1 5.3 Applicable Codes ........................................................................................................................... 5-1 6. STRUCTURAL DESIGN ............................................................................................................ 6-1 6.1 General Information ..................................................................................................................... 6-1 6.2 Design Criteria ............................................................................................................................... 6-1 6.2.1 Structural Loads ............................................................................................................ 6-1 6.2.2 Materials ....................................................................................................................... 6-2 6.3 Applicable Codes ........................................................................................................................... 6-2 7. MECHANICAL DESIGN ........................................................................................................... 7-1 7.1 General Information ..................................................................................................................... 7-1 7.2 Design Criteria ............................................................................................................................... 7-1 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm TABLE OF CONTENTS (CONTINUED) ii June 2020 │ 216-1781-042 7.3 Applicable Codes ........................................................................................................................... 7-1 7.4 Pumps ........................................................................................................................................... 7-2 7.5 Lifting and Hoisting Equipment ..................................................................................................... 7-2 7.6 Piping ............................................................................................................................................ 7-2 7.7 Plumbing ....................................................................................................................................... 7-2 7.8 HVAC ............................................................................................................................................. 7-3 7.9 Corrosion Protection ..................................................................................................................... 7-3 8. ELECTRICAL DESIGN .............................................................................................................. 8-1 8.1 General Information ..................................................................................................................... 8-1 8.1.1 Plant Electrical Distribution .......................................................................................... 8-2 8.1.2 Site Electrical ................................................................................................................ 8-2 8.2 Design Criteria ............................................................................................................................... 8-2 8.3 Applicable Codes ........................................................................................................................... 8-3 9. INSTRUMENTATION AND CONTROL DESIGN ......................................................................... 9-1 9.1 General Information ..................................................................................................................... 9-1 9.2 Design Criteria ............................................................................................................................... 9-1 9.3 Applicable Codes ........................................................................................................................... 9-1 9.4 Remote Monitoring and Communications ................................................................................... 9-1 9.5 Security Alarm ............................................................................................................................... 9-2 10. CHEMICAL FEED BUILDING .................................................................................................. 10-1 10.1 Description and Functions .......................................................................................................... 10-1 10.2 Design Criteria ............................................................................................................................. 10-1 10.2.1 Magnesium Hydroxide ................................................................................................ 10-1 10.2.2 Supplemental Carbon ................................................................................................. 10-1 10.2.3 Hypochlorite ............................................................................................................... 10-2 10.2.4 Other ........................................................................................................................... 10-2 10.3 Decisions Required...................................................................................................................... 10-2 11. CONTROL BUILDING EXPANSION ........................................................................................ 11-1 11.1 Description and Functions .......................................................................................................... 11-1 11.2 Additional Design Criteria ........................................................................................................... 11-1 11.3 Decisions Required...................................................................................................................... 11-1 12. HEADWORKS ...................................................................................................................... 12-1 12.1 Description and Functions .......................................................................................................... 12-1 12.2 Design Criteria ............................................................................................................................. 12-1 12.3 Additional Information ............................................................................................................... 12-1 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm TABLE OF CONTENTS (CONTINUED) June 2020 │ 216-1781-042 iii 13. EXISTING SBR TANKS – GENERAL REHABILITATION ............................................................. 13-1 13.1 Description and Functions .......................................................................................................... 13-1 13.2 Additional Design Criteria ........................................................................................................... 13-1 13.3 Decisions Required...................................................................................................................... 13-1 14. PROCESS EQUIPMENT AND MODIFICATIONS ...................................................................... 14-1 14.1 Description and Functions .......................................................................................................... 14-1 14.2 Additional Design Criteria ........................................................................................................... 14-1 14.3 Decisions Required...................................................................................................................... 14-1 15. PROCESS AIR DIFFUSER REPLACEMENT ............................................................................... 15-1 15.1 Description and Functions .......................................................................................................... 15-1 15.2 Additional Design Criteria ........................................................................................................... 15-1 15.3 Decisions Required...................................................................................................................... 15-1 16. CONVERSION OF EXISTING SBR PROCESS TO MBR PROCESS ................................................ 16-1 16.1 Description and Functions .......................................................................................................... 16-1 16.2 Additional Design Criteria ........................................................................................................... 16-1 16.3 Decisions Required...................................................................................................................... 16-2 17. DISINFECTION SYSTEM ........................................................................................................ 17-1 17.1 General ........................................................................................................................................ 17-1 17.2 Additional Design Criteria ........................................................................................................... 17-1 17.3 Other ........................................................................................................................................... 17-1 18. PUMP STATIONS ................................................................................................................. 18-1 18.1 Description and Functions .......................................................................................................... 18-1 18.1.1 Plant Drain Pump Station ........................................................................................... 18-1 18.1.2 Sludge Pump Station (Existing Plant Drain and Sludge Pump Station) ....................... 18-1 18.1.3 Intermediate Pump Station ........................................................................................ 18-1 18.1.4 Reject Water Pump Station ........................................................................................ 18-2 18.1.5 Waste Activated Sludge (WAS) Pump Station ............................................................ 18-2 18.2 Additional Design Criteria ........................................................................................................... 18-2 18.3 Decisions Required...................................................................................................................... 18-2 19. ELECTRICAL BUILDINGS AND SERVICE ENTRANCE ................................................................ 19-1 19.1 Description and Functions .......................................................................................................... 19-1 19.1.1 Main Electrical Building Service Entrance .................................................................. 19-1 19.1.2 Standby Generator ..................................................................................................... 19-1 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm TABLE OF CONTENTS (CONTINUED) iv June 2020 │ 216-1781-042 19.1.3 Main Electrical Building Automatic Transfer Switch .................................................. 19-1 19.1.4 Main Electrical Building 480V Switchgear .................................................................. 19-1 19.1.5 Main Electrical Building Motor Control Center .......................................................... 19-2 19.1.6 Main Electrical Building Switchboard ......................................................................... 19-2 19.1.7 Main Electrical Building Miscellaneous Electrical ....................................................... 19-2 19.1.8 North Electrical Building ............................................................................................. 19-2 19.1.9 North Electrical Building Miscellaneous Electrical ..................................................... 19-2 19.2 Additional Design Criteria ........................................................................................................... 19-3 19.3 Decisions Required...................................................................................................................... 19-3 20. PLANT SCADA, CONTROLS, AND INSTRUMENTATION .......................................................... 20-1 20.1 Description and Functions .......................................................................................................... 20-1 20.2 Additional Design Criteria ........................................................................................................... 20-1 20.3 Decisions Required...................................................................................................................... 20-1 21. DISCHARGE ......................................................................................................................... 21-1 21.1 Description and Functions .......................................................................................................... 21-1 21.1.1 River/Canal ................................................................................................................. 21-1 21.1.2 Reclaimed Water – Rapid Infiltration Basins .............................................................. 21-1 21.2 Design Criteria and Applicable Codes ......................................................................................... 21-1 21.3 Decisions Required...................................................................................................................... 21-2 21.4 Permitting ................................................................................................................................... 21-2 22. PERMITTING AND APPROVALS ............................................................................................ 22-1 LIST OF FIGURES 8-1 Plant One-Line Diagram ................................................................................................................ 8-5 LIST OF TABLES 3-1 Reclaimed Water Permit Limits .................................................................................................... 3-1 3-2 Additional Water Quality Limits for Power Canal and Nisqually River Discharge ........................ 3-2 3-3 Design and Procurement Effluent Limits ...................................................................................... 3-2 4-1 Population and Flow Projections .................................................................................................. 4-2 4-2 Design Concentration for STEP and Gravity Sewer Systems in mg/L ........................................... 4-3 4-3 Phase 1 Influent Design Criteria .................................................................................................... 4-3 4-4 Phase 2 Influent Design Criteria .................................................................................................... 4-4 6-1 Structural Design Criteria for the Mechanical Building ................................................................ 6-1 6-2 Structural Material Design Criteria ............................................................................................... 6-2 10-1 Hypochlorite System Design Criteria .......................................................................................... 10-2 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm TABLE OF CONTENTS (CONTINUED) June 2020 │ 216-1781-042 v APPENDICES A Site Plan B Kubota Design Information Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 vii KEY TERMS ACI American Concrete Institute ANSI American National Standards Institute ASCE American Society of Civil Engineers AWC American Wood Council AWWARF American Water Works Association Research Foundation BOD biological oxygen demand CDPH California Department of Public Health CPVC chlorinated polyvinyl chloride DO dissolved oxygen EPDM ethylene propylene diene monomer gpm gallons per minute HMI human machine interface HVAC heating, ventilating, and air conditioning I/I inflow and infiltration IO input output IP internet protocol lbs pounds MBR membrane bioreactor MCC motor control center mg/L milligrams per liter mgd million gallons per day mL milliliters ML mixed liquor MLSS mixed liquor suspended solids MPN probable number NDS National Design Specification NEC National Electric Code NEPA National Environmental Policy Act NPDES National Pollutant Discharge Elimination System NWRI National Water Research Institute Orange Book Ecology Publication 93-37 WQ Criteria for Sewage Works Design ORP Oxidation Reduction Potential Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm KEY TERMS (CONTINUED) viii June 2020 │ 216-1781-042 OSHA Occupational Safety and Health Administration PLCs programmable logic controllers PRVs pressure-reducing valves PSE Puget Sound Energy PSQC permanent stormwater quality control PVC polyvinyl chloride RCW Revised Code of Washington RW reuse water SBRs sequencing batch reactors scfm standard cubic feet per minute SEAW Structural Engineers Association of Washington SERP State Environmental Review Process SMUs submerged membrane units STEP septic tank effluent pump SWBD switchboard SWGR switchgear TCP transmission control protocol TKN total Kjeldahl nitrogen TN total nitrogen TSS total suspended solids UPS uninterruptable power supply UV ultraviolet VFDs variable frequency drives WAC Washington Administrative Code WAS waste activated sludge WQ water quality WRF Wastewater Reclamation Facility Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 1-1 1. INTRODUCTION The scope of this project is to upgrade the City of Yelm Wastewater Reclamation Facility (WRF) to allow it to consistently meet Class A Reclaimed water standards. A new treatment system composed of a new membrane bioreactor (MBR) and all ancillary equipment needed to support the MBR treatment system is included in this project. This report focuses primarily on the MBR treatment system along with other improvements to be included Kubota has been designated by the City to be the basis of design for the MBR treatment system. A major objective of this Basis of Design Report will be to further define the scope of supply and services to be provided by Kubota, define WRF layouts, and define equipment sizing. Another objective of this report is to establish the fundamental design criteria and approach used for the rest of the design. Key criteria and assumptions are identified for each engineering discipline. This report should be read in conjunction with the Sewer Facilities Plan, Parametrix, June 2016 and the Wastewater Reclamation Facility Alternatives Analysis, Parametrix February 2020. A building layout with site plan can be found in Appendix A. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 2-1 2. PROJECT OVERVIEW The City of Yelm’s existing WRF was designed in 1995 to treat maximum monthly flows of up to 1.06 million gallons per day (mgd) to Class A reclaimed water standards using several treatment steps, including sequencing batch reactors (SBRs), equalization, continuous backwash granular media (Dynasand) filters, and chlorine disinfection. If the quality of the treated water meets permit limits for reclaimed water and there is a demand for reuse water, the reclaimed water is pumped to the beneficial use sites. Prior capacity estimates and modeling assumed the wastewater influent would have similar characteristics to typical domestic wastewater, but with higher total Kjeldahl nitrogen (TKN) and lower biological oxygen demand (BOD). However, the septic tank effluent pump (STEP) tank effluent has proven more difficult to treat than anticipated, resulting in a treatment biomass that is prone to bulking and poor gravity settling characteristics. Gravity-based settling challenges are not easily reflected in biological computer models. The WRF’s existing SBR process relies on gravity-based settling to achieve solids separation and maintain sufficient biomass to achieve the necessary treatment levels, so these settleability difficulties have created significant process problems. As a result, the plant has been unable to achieve reliable permit compliance even after switching to three-basin mode. The WRF has tried to increase the biomass in the system, but that resulted in high solids loading to the filters, which in turn led to frequent turbidity permit violations, a significant increase in cleaning labor and costs for the SBR decant equalization ponds, and significant operational problems with the filters. Plant staff have since run at lower biomass levels, which has led to difficulty maintaining an adequate population of nitrifying bacteria, particularly in winter, leading to ammonia and total nitrogen permit violations. In addition, major mechanical equipment (pumps, blowers, and valves) and electrical equipment (generators) across all elements of the treatment process are now at or approaching the end of their useful service life. Substantial maintenance expenditures should be assumed likely in the near to short term. This project will convert the existing two of the SBR basins to plug flow regime with anoxic and aerated zones. The third basin will not be used for this phase. A new MBR basin (1.29 mgd) will be constructed to allow the SBR plant to remain in operation during construction of said basin. The other items will include the following: • A new fine screen system to prevent fouling of the membranes. • A manually cleaned grit channel (modified in future when gravity system is connected). • Adding baffle walls to separate anoxic, aerated, and swing zones. • Separating the diffuser grid into sections, with each having an individual drop leg and valve for aeration control. • Mixers will be added to the anoxic and swing zones, in place of or alongside the existing mixers for the SBR system. • Construction of a crane system at the membrane tankage to facilitate module and equipment removal for maintenance. • Construction of a Mechanical Building and new recycle pumps and permeate pumps and piping for continuous operation Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 3-1 3. EFFLUENT CRITERIA The City of Yelm’s existing WRF has several permitted discharge outfalls with different water quality limits. Those limits applicable for design of this project are summarized here. The complete set of water quality limits can be found in the Yelm WRF National Pollutant Discharge Elimination System (NPDES) permit, incorporated in this document by reference. 3.1 Outfall Descriptions Reclaimed water, used both by off-site consumers and for groundwater recharge through surface percolation, is the primary wastewater disposal method at the Yelm STP. Discharge to the Centralia Power Canal is a secondary disposal method, and discharge to the Nisqually River is an emergency backup. 3.2 Reclaimed Water The water quality permit limits for reclaimed water are shown in Table 3-1. The total nitrogen (TN) limit is the most significant for design of the biological treatment system, and the total coliform limit is most significant for design of the ultraviolet (UV) system. Table 3-1. Reclaimed Water Permit Limits Parameter Average Monthly Average Weekly Daily/Sample Maximum BOD5 30 mg/L – – TSS 30 mg/L – – Total Nitrogen 10 mg/L – 15 mg/L Total Coliforms – 2.2/100 mL 23/100 mL pH – – 6.0 to 9.0 Turbidity 2 NTU – 5 NTU DO Measurably present at all times. Notes: BOD5 = biological oxygen demand; TSS = total suspended solids; mg/L = milligrams per liter; mL = milliliter; NTU = nephelometric turbidity unit; DO = dissolved oxygen 3.3 Surface Percolation Reclaimed water disposed of by groundwater recharge via surface percolation has additional permit requirements; however, these requirements do not generally affect this treatment design. The metals requirements are addressed through source water protection, nitrate (10 milligrams per liter [mg/L]) and nitrite (1 mg/L) limits will be met through the total nitrogen limit for reclaimed water, and disinfection and disinfection byproducts will be met by the total coliform and BOD requirements for reclaimed water. Thus, groundwater water quality criteria have not been incorporated in the Basis of Design. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 3-2 June 2020 │ 216-1781-042 3.4 Power Canal and Nisqually River The Power Canal and Nisqually River have nearly identical water quality permit limits (see Table 3-2), with residual chlorine and lead being the only differences. Of the additional water quality limits imposed compared with those for reclaimed water, the daily load limits on BOD and total suspended solids (TSS) are the most significant. At the maximum monthly design flow for Phase 2, the load limits result in an effective concentration limit of only 15.4 mg/L monthly average, or just over half the allowed concentration in reclaimed water. These concentrations are easily achieved by a membrane system, however. The additional ammonia limit of 3 mg/L will need to be met to achieve a total nitrogen limit of 10 mg/L for the reclaimed water and does not impose any additional design constraint. Table 3-2. Additional Water Quality Limits for Power Canal and Nisqually River Discharge Parameter Average Monthly Average Weekly BOD5 30 mg/L 250 lbs/d (15.4 mg/L at 1.94 mgd) 45 mg/L 375 lbs/d (23.1 mg/L at 1.94 mgd) TSS 30 mg/L 250 lbs/d (15.4 mg/L at 1.94 mgd) 45 mg/L 375 lbs/d (23.1 mg/L at 1.94 mgd) Fecal Coliform 100/100 mL 200/100 mL Total Ammonia 3 mg/L 4.5 mg/L Total Residual Chlorine (Power Canal) 0.5 mg/L 0.75 mg/L Total Residual Chlorine (Nisqually River) 0.047 mg/L 0.124 mg/L (Daily Maximum) Total Lead (Nisqually River) 10 µg/L 15 µg/L (Daily Maximum) Notes: BOD5 = biological oxygen demand; mg/L = milligrams per liter; lbs/d = pounds per day; mgd = million gallons per day; TSS = total suspended solids; mL = milliliter; µg/L = micrograms per liter 3.5 Effluent Water Quality Design Criteria The following design criteria shown in Table 3-3 will be used for design and procurement of MBR systems and UV equipment. BOD and TSS limits are lower than the permitted concentrations to make the best use of the MBR system, allow for future flows with the loading limits, and reduce chlorine demand. Turbidity is reduced from the current permitted value both to maximize effectiveness of UV disinfection and because we anticipate a reduced turbidity limit due to conversion to a membrane system. Table 3-3. Design and Procurement Effluent Limits Parameter Average Monthly Design Effluent Limit BOD5 < 10 mg/L TSS < 10 mg/L Total Nitrogen < 10 mg/L Total Coliforms < 2.2 / 100 mL Turbidity < 0.2 NTU Notes: BOD5 = biological oxygen demand; mg/L = milligrams per liter; TSS = total suspended solids; mL = milliliter; NTU = nephelometric turbidity unit Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 4-1 4. TREATMENT PROCESS 4.1 General Information The City of Yelm’s existing WRF was designed in 1995 to treat maximum monthly flows of up to 1.06 mgd to Class A reclaimed water standards using several treatment steps, including SBRs, equalization, continuous backwash granular media (Dynasand) filters, and chlorine disinfection. If the quality of the treated water meets permit limits for reclaimed water and there is a demand for reuse water, the reclaimed water is pumped to the beneficial use sites. The WRF has had difficulty consistently meeting permit limits, and an alternative analysis was completed earlier this year that determined that modifying the SBR process to an MBR process would allow the plant to better meet permit requirements. The approach will utilize existing SBR tanks for new process tanks, and a new MBR basin will be built adjacent to the existing tanks. Because an MBR process employs direct filtration of biomass and does not rely on gravity-based settling, it will be much more robust in the face of difficult influent characteristics. Additionally, MBR processes carry higher biomass levels relative to the treatment capacity, which will promote reliable nitrogen removal. 4.2 Design Criteria Design criteria are based on updates to the 2012 General Sewer Plan and the 2016 Facility Plan. Specific revisions include: • Updating the population forecast based on the Thurston Regional Planning Council Small Area Population Estimates and Population and Employment Forecast (2018 update). • Assuming future Master Planned Community development after 2025 will be gravity sewer rather than STEP sewer and adjusting flow and loading accordingly (see discussion below). • Updating loading projections based on more recent influent sampling. 4.2.1 Phased Design The design will be phased to tie capital expenditures more closely to actual growth. Phase 1 will be sufficient for annual average flow up to 1.25 mgd, sufficient for projections through 2030 (or later if actual growth is lower than projected growth). Phase 2 will be sufficient for annual average flow up to 1.80 mgd, sufficient for the 20-year design scope through 2040. For certain systems, phasing is not economically feasible because reduced equipment costs are offset by increased complexity. As a result, the following systems will be designed for Phase 1, with provision for future expansion in Phase 2: • Anoxic and Pre-Aeration Tanks • Membrane filtration • Membrane Tanks • Membrane air scour blowers • Permeate pumps • Aeration blowers Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 4-2 June 2020 │ 216-1781-042 • WAS Pumps • UV disinfection The reclaimed water pumping capacity was recently renovated and is already adequate for Phase 1, with provision for expansion. The following systems will be designed for the full Phase 2 capacity: • Piping and conveyance channels • Fine screens • Grit removal system • Influent chemical feed system • Feed forward pumps • Sludge wasting equipment • Electrical power capacity • Sludge pump station • Plant drain pump station 4.2.2 Flow, BOD, TSS, and TKN Loading Estimates Annual average flow from residential STEP systems was estimated at 43 gallons per day per person in the 2016 Facility Plan. This estimate was carried forward for this analysis. For gravity flow residential connections, an additional 25 gallons per day per person was assumed to account for extra inflow and infiltration (I/I), for a total of 68 gallons per day per person. Commercial and industrial dischargers are assumed to be STEP connections, and the flow rate was projected based on the 2016 Sewer Facilities Plan. See Table 4-1 for the projected flows. Table 4-1. Population and Flow Projections Phase 1 (2030 Projected Year) Phase 2 (2040 Projected Year) Population Flow (mgd) Population Flow (mgd) Residential STEP 15,970 0.69 17,310 0.74 Gravity 2,800 0.19 8,020 0.55 Commercial/Industrial STEP – 0.37 – 0.51 Total (AADF) 18,770 1.25 25,330 1.80 Notes: mgd = million gallons per day; STEP = septic tank effluent pump; AADF = average annual daily flow Based on historical data, the maximum monthly average flow rate is estimated at 1.1 times the annual average flow rate, and the peak hour flow for STEP systems was estimated at 2 times the annual average flow rate. For gravity systems, the peak hour flow was estimated based on the population and Figure C1-1 of the Ecology Publication 93-37 WQ Criteria for Sewage Works Design (Orange Book). Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 4-3 4.2.3 Design Concentrations BOD, TSS, and TKN concentrations for the STEP systems were estimated from historical influent data (see Table 4-2). BOD and TSS concentration were estimated based on the 90th percentile daily load in the maximum monthly flow over the period of 2018-2019. There is insufficient influent TKN concentration data since 2014 to statistically estimate the design concentration. Data from 2014 and prior showed a 90th percentile concentration of 72.9 mg/L. Notably, there was very little data at high flow rates, so load estimates based on this data are questionable. Additionally, a rising trend was evident so the 2016 Facility Plan used a design TKN concentration of 80 mg/L. Limited sampling since that time show the trend has leveled off rather than continuing , so a value of 72 mg/L was chosen for design. For the gravity system, loading was calculated from the STEP system design concentrations. It was assumed that the STEP tanks are removing 35 percent of the BOD, 70 percent of the TSS, and none of the TKN through settling. Dilution from I/I (based on the flow rates per person discussed previously) was also factored in, resulting in the design concentrations shown in Table 4-2. Table 4-2. Design Concentration for STEP and Gravity Sewer Systems in mg/L STEP Gravity BOD 239.0 232.5 TSS 66.0 139.1 TKN 72.0 40.0 Notes: STEP = septic tank effluent pump; mg/L = milligrams per liter; BOD = biological oxygen demand; TSS = total suspended solids; TKN = total Kjeldahl nitrogen 4.2.4 Design Influent Criteria From the flows and concentrations discussed above, the combined design flow, loading, and concentration were calculated for each phase as shown in Table 4-3 and Table 4-4. Table 4-3. Phase 1 Influent Design Criteria Annual Average (AADF/AADL) Parameter Residential STEP Gravity Commercial/ Industrial STEP Total Maximum Month (MMDF/ MMDL) Peak Hour (PHF) Flow mgd 0.69 0.19 0.37 1.25 1.37 2.77 % of AADF 55% 15% 30% 100% 110% 222% BOD mg/L 239.0 232.5 72.0 238.0 238.0 lbs/d 1,369 369 738 2,476 2,723 % of AADL 55% 15% 30% 100% 110% TSS mg/L 66.0 139.1 66.0 77.2 77.2 lbs/d 378 221 222 803 883 % of AADL 47% 28% 28% 100% 110% (Table Continues) Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 4-4 June 2020 │ 216-1781-042 Table 4-3. Phase 1 Influent Design Criteria (Continued) Annual Average (AADF/AADL) Parameter Residential STEP Gravity Commercial/ Industrial STEP Total Maximum Month (MMDF/ MMDL) Peak Hour (PHF) TKN mg/L 72.0 40.0 72.0 67.1 67.1 lbs/d 412 64 204 698 768 % of AADL 59% 9% 29% 100% 110% Notes: AADF = average annual daily flow; AADL = average annual daily load; STEP = septic tank effluent pump; MMDF = maximum month daily flow; MMDL = maximum month daily load; PHF = peak hour flow; mgd = million gallons per day; BOD = biological oxygen demand; mg/L = milligrams per liter; lbs/d = pounds per day Table 4-4. Phase 2 Influent Design Criteria Annual Average (AADF/AADL) Maximum Month (MMDF/ MMDL) Peak Hour (PHF) Parameter Residential STEP Gravity Commercial/ Industrial STEP Total Flow mgd 0.74 0.55 0.51 1.80 1.98 4.17 % of AADF 41% 30% 28% 100% 110% 232% BOD mg/L 239.0 232.5 239.0 237.0 237.0 lbs/d 1,484 1,058 1,017 3,558 3,914 % of AADL 42% 30% 29% 100% 110% TSS mg/L 66.0 139.1 66.0 88.2 88.2 lbs/d 447 633 281 1,323 1,456 % of AADL 34% 48% 21% 100% 110% TKN mg/L 72.0 40.0 72.0 62.3 62.3 lbs/d 447 182 306 935 1,029 % of AADL 48% 19% 33% 100% 110% Notes: AADF = average annual daily flow; AADL = average annual daily load; STEP = septic tank effluent pump; MMDF = maximum month daily flow; MMDL = maximum month daily load; PHF = peak hour flow; mgd = million gallons per day; BOD = biological oxygen demand; mg/L = milligrams per liter; lbs/d = pounds per day; TKN = total Kjeldahl nitrogen 4.2.5 A Note on the Effect of Gravity Sewer Connections Should the flow projected from gravity sewers instead be connected as STEP connections, the flow, BOD, and TSS loading would be lower than projected above due to removal in the STEP tanks. This would lower the aeration demand on the system, so the current projection is a current estimate. The reduced BOD would create a need for increased supplemental carbon for nitrogen removal. The influent carbon feed system will be designed to accommodate this. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 4-5 4.3 MBR System-Specific Design Criteria 4.3.1 Membrane Sizing The City has selected the Kubota flat plate membrane as the basis of design for the WRF. Kubota MBR membrane sizing is based on using the RW 400 membrane units. Each unit has a surface area of 6,243 ft2. Kubota has indicated 18 RW 400 units are required for the design flow of 1.37 mgd. To meet the redundancy requirements of the Department of Ecology, there should be at least one additional unit (N+1) to allow to meet hydraulic requirements with any unit out of service. 4.3.2 Process Air Blower Sizing MBR air scour and Aeration Tank process aeration systems will be provided by Kubota. Aeration tank process aeration system and blowers sizing is based on: • The aeration system shall be designed to provide a minimum of 1.25 pounds (lbs) O2/lb BOD5 and 4.6 lbs O2/lb. TKN applied at the maximum monthly Phase 1 loadings. Total AOR of 6,300 lbs O2/day. • Aeration calculations for coarse bubble diffusers shall be based on an alpha value of 0.8 or less. Aeration system calculations for fine bubble diffusers and jet aerators shall be performed using an α value of 0.52 and a β of 0.95. The oxygen transfer efficiency assumed for the fine bubble diffusers shall not exceed 1.6 percent/foot at the midpoint below the high and low water levels for the basin. • Oxygen transfer efficiency credits assumed to allow for the presence of additional mixing or other factors shall be clearly stated. • No oxygen demand credit for complete or partial denitrification were assumed in the calculations. The air diffuser system, including piping, shall be capable of delivering 125 percent of the design air requirements. Kubota has provided written confirmation and modeling calculations to confirm that its MBR process air system can achieve dissolved oxygen (DO) conditions above MBR peak design flows and loads. The Kubota documentation is contained in Appendix B. Kubota MBR blower sizing is based on providing the required air scour (approximately 138 standard cubic feet per minute (scfm) per submerged membrane unit) to properly maintain the operation of its submerged membrane units (total of eighteen units plus one/two standby being supplied for this project). 4.3.3 Effluent TN Requirement Another MBR system specific design effort centers on meeting the 10 mg/L TN reclaimed water permit limit. Parametrix will provide the following instrumentation and control components to better enhance the WRF Biological Nitrification/Denitrification process to consistently achieve TN permit limit of 10 mg/L TN: • Dissolved oxygen probes in anoxic tanks and aeration tanks. • Oxidation reduction potential (ORP) probe in the anoxic tanks. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 4-6 June 2020 │ 216-1781-042 • Online nitrate probe in permeate effluent line. • Control strategy for adjusting internal recycle flow rate. • MBR system process design scope. 4.4 Treatment System Components Design Criteria It is beneficial to tribe that Kubota’s scope includes applicable equipment necessary to maintain proper function of its membrane equipment. Key equipment and instrumentation to be provided by Kubota for contractor installation includes: • Two air blowers and one standby dedicated to supply process air to pre-aeration Tanks 1 and 2. • Two air blowers and one standby dedicated to supply scour air to the new MBR tank. • Three permeate pumps for MBR Tanks 1 and 2. Kubota will design pumps to operate only in gravity assist mode. Pumps will also be sized so as to deliver flows directly to the effluent pump gallery. • 18 RW 400 submerged membrane units (SMUs) plus 1 (each tank) unit required for redundancy. • Internal piping, SMU air diffusers, and supports for MBR Tanks 1 and 2. • Fine bubble air diffusers for pre-aeration Tanks 1 and 2. • Mixer for anoxic Tanks 1 and 2; one per tank. • DO, pH, and ORP probes anoxic Tanks 1 and 2; one DO, Ph, and ORP probe per tank. • DO probes for aeration Tanks 1 and 2; one DO probe per tank. • Two feed forward pumps that will have the ability to provide 5Q. • One nitrate analyzer for permeate flow. • Aeration Tank 1 and MBR 1 tank air piping pressure transmitters; one transmitter per tank. • Aeration Tank 2 and MBR 2 tank air piping pressure transmitters; one transmitter per tank. • MBR Tank 1 and 2 air flow meters; one flow meter per tank. • Permeate pressure transmitter; one each for MBR Tanks 1 and 2, one transmitter per tank. • Mass air flow meters for pre-aeration and scour air. This will result in the best coordination between instrumentation, controls, and automation programming, as well as reduce costs for control equipment. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 5-1 5. CIVIL DESIGN 5.1 General Information Civil design will cover site improvements underground piping, stormwater, and any potential grading 5.2 Design Criteria Civil design elements, including materials and construction methods, will be in compliance with the following reference documents: • Washington State Department of Transportation Standard Specifications for Road, Bridge, and Municipal Construction. • Washington State Department of Ecology Criteria for Sewage Works Design. • Washington State Department of Ecology Stormwater Manual. • City of Yelm Engineering Specifications and Standard Details Stormwater – Prepare Large parcel erosion and sediment control plan. Permanent stormwater quality control (PSQC) plan. 5.3 Applicable Codes Stormwater – Yelm Municipal Code 13.16. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 6-1 6. STRUCTURAL DESIGN 6.1 General Information The major structural elements for this project are: • New MBR basin. • New baffles/walls in the existing SBR basins. • Headworks facility (Open Air Facility). • Mechanical Room/Building. 6.2 Design Criteria 6.2.1 Structural Loads Table 6-1 outlines the primary structural loads for the Mechanical Building. Table 6-1. Structural Design Criteria for the Mechanical Building Load Load Value or Criteria Load Source Design Risk Category IIIa Roof Live Load Is = 1.10, Iw = 1.00, Ie =1.25 25 psf 2018 IBC Table 1604.5 Roof Snow Load 25 psf Ceiling Collateral Load 10 psf Floor Live Load 100 psf Office, lab, platforms 250 psf Process areas AASHTO H-20 Traffic areas As calculated Equipment loads Wind Load 120 mph Basic Wind Speed, Exposure C (Strength Level Design Loads per ASCE 7-16) Seismic Criteriab Site Soil Class D Ss = 1.25 Assumed values, subject to Geotech recommendations Fa = 1.00 Sds =0.833 S1 = 0.50 Fv = 1.50 Sd1 = 0.50 Crane/Hoist Loads Designed for specified load rating plus crane weight plus impact forces per ASCE 7-16 Foundationsb Soil bearing assumed to be 2,000 psf minimum 2018 IBC Table 1806.2 a Occupancy Category III, for importance factors on loadings per ASCE 7-16. b May be revised by geotechnical survey. Notes: AASHTO = American Association of State Highway Transportation Officials; psf = pounds per square foot; IBC = International Building Code; ASCE = American Society of Civil Engineers Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 6-2 June 2020 │ 216-1781-042 6.2.2 Materials Table 6-2 outlines the appropriate structural design parameters for the construction materials. Table 6-2. Structural Material Design Criteria Material Design Criteria Steel ASTM A992, A36, A53, A500 Concrete f′c = 5,000 psi at 28 days for all water containing structures f′c = 4,000 psi at 28 days for other cast-in-place concrete CMU f′m = 1,500 psi Heavy Timber Allowable stresses as governed by AWC National Design Standards 2018 Grating Fiberglass for corrosion resistance on platforms Serrated galvanized steel bar grate stair treads Notes: psi = pounds per square inch; CMU = concrete masonry unit; AWC = American Wood Council 6.3 Applicable Codes Applicable structural codes include: • 2018 International Building Code with Washington State and Thurston County Amendments. • American Society of Civil Engineers (ASCE) 7-16 Minimum Design Loads for Buildings and Other Structures. • Structural Engineers Association of Washington (SEAW) Snow Load Analysis for Washington. • American Concrete Institute (ACI) 318-14 Building Code Requirements for Structural Concrete. • ACI 350-06 Code Requirements for Environmental Engineering Structures. • ACI 530-05/ASCE 5-05/TMS 402-05 Building Code Requirements for Masonry Structures. • American National Standards Institute (ANSI)/ASCE 360-05 Specification for Structural Steel Buildings. • ANSI/American Wood Council (AWC) National Design Specification (NDS)-2018 National Design Standard for Wood Construction. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 7-1 7. MECHANICAL DESIGN 7.1 General Information The major non-MBR manufacturer supplied mechanical components for this project are: • Headworks fine screens. • Grit channel removal structure with future provision for mixer drive, grit pump, and grit classifier/washing equipment. • Equipment in the Anoxic and Aeration tanks. • Heating, ventilating, and air conditioning (HVAC) equipment for MBR Equipment Building and Control Building expansion. • UV equipment and piping. • Reclaimed water pump upgrades. • Crane system for lifting the MBR process membranes and monorail for blower equipment. • New plant drain pump station. • Modifications to the sludge pump station. • Investigate and rehabilitate all pressure-reducing valves (PRVs) along the route from the WRF to the discharge into the Nisqually River. 7.2 Design Criteria Project specifications will provide specific design information for each equipment component. Refer to Section 4 for design criteria details. 7.3 Applicable Codes The mechanical equipment will be designed according to the following codes (note that all codes will include any Washington State and Thurston County amendments): • International Building Code. • International Fire Code. • International Plumbing Code. • International Mechanical Code. • Washington State Energy Code. • National Fire Protection Association (NFPA) 70: National Electric Code (NEC) – 2019 Edition. • NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities – 2018 Edition. • Sheet Metal and Air Conditioning Contractors National Association, HVAC Duct Construction Standards. • Washington State Department of Ecology, Criteria for Sewage Works Design. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 7-2 June 2020 │ 216-1781-042 7.4 Pumps Installation of the pumps will include the following: • Two sewage pumps for the Little John Digester system. • Three feed forward pumps with variable speed motors to lift flow from anoxic Tanks 1 and 2 to aeration Tanks 1 and 2. • Three gravity assist permeate pumps with variable speed motors to pump treated flow from MBR tanks when gravity flow is not possible. • Four reuse water (RW) pumps with variable speed motors to pump water to reuse site, • Upgrade on-site reclaimed water pump station supplying bibs, site irrigation and other in-plant reuse water applications. • Two waste activated sludge (WAS) pumps for truck loading. See Section 18 for plant drain pump station and sludge pump station. 7.5 Lifting and Hoisting Equipment A bridge crane will be provided for removal of submerged equipment in the MBR process tanks. Portable hoisting equipment will be provided for submersible pump and mixer removal. An overhead lifting rail in the MBR Equipment Building for blowers will also be provided. 7.6 Piping The WRF piping systems will use the piping guidelines provided as recommended by Parametrix and as shown in the project specifications. Generally, exterior permeate piping (outside of the MBR tank) will be ductile iron where exposed and polyvinyl chloride (PVC) where not exposed to sunlight. Potable water piping will be polyethylene, copper, or PVC. Odor control buried or nonexposed piping will be PVC. Sodium hypochlorite piping will be chlorinated polyvinyl chloride (CPVC) or polyethylene hose. Process air and MBR tank interior piping will be stainless steel. Sludge (drain and process) or force main piping will be ductile iron or PVC. Valves for the WRF piping systems will be as recommended by Parametrix and as shown in the project specifications. 7.7 Plumbing The following plumbing will be required for this project: • Heavy-duty floor drains in wet areas. • Hose bib water stations at key locations for wash down, housekeeping, and site area irrigation. • Ductile iron and PVC drain pipes. • Water heater for shower and sinks. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 7-3 7.8 HVAC The MBR Equipment Building HVAC design criteria include the following: • Outdoor Design Temperatures: ➢ Summer: 83 degrees Fahrenheit. ➢ Winter: 24 degrees Fahrenheit. • MBR Equipment Building Mechanical and Electrical Rooms: ➢ Ventilate at four air exchanges per hour to reduce corrosion potential and to provide fresh air. ➢ Maintain temperature above 48 degrees Fahrenheit using an electric unit heater. ➢ Ventilation will keep space below 93 degrees Fahrenheit (83 degrees Fahrenheit plus 10 degree Fahrenheit differential) at all times. ➢ Include waste heat from lights, motors, variable frequency drives (VFDs), etc., in cooling design. ➢ Electrical Room cooling capacity based on “spring storm” defined as 60 degree Fahrenheit outside air temperature with associated heat loads from electrical gear running at full capacity. • Exposed Mechanical Yard Piping Freeze Protection: ➢ Heat tape pipe tracing (receptacle plug-in type) and insulation of exposed yard piping, water piping with diameters less than 3 inches. Pipes above 4 inches in diameter will not be heat traced or insulated. 7.9 Corrosion Protection Corrosion protection is required for this project and includes: • Coatings for corrosion protection to various project surfaces such as concrete and steel; see project specifications. • Stainless steel fasteners on all pipe connections. • Equipment pads to protect anchor bolts and for housekeeping. • Air exchange in Blower and Electrical Rooms. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 8-1 8. ELECTRICAL DESIGN 8.1 General Information The electrical design will include electrical improvements to the power distribution equipment and motor controls as follows: • Control Building: The existing service entrance motor control center (MCC), standby power MCC, panelboards, and distribution transformers will be replaced. • Blower Building: The existing service entrance switchgear, MCCs, panelboards, and distribution transformers will be replaced. The existing VFDs, which control the existing blowers in the Blower Building, will be replaced. The standby generator located outside the Blower Building will be replaced. The existing failed active harmonic filters will be demolished. • Solids Building: The existing switchboard, VFDs, panelboard, and transformer will be replaced. • Maintenance Building: The existing panelboard, damaged safety disconnect switch, and standby generator will be replaced. • Main Electrical Building: See Chapter 19. • North Electrical Building: See Chapter 19. • Electrical Duct Banks: The power distribution, motor control, plant controls, and communications will be placed into concrete or CDF encased underground duct banks. • Electrical Support of Process Improvement: The electrical design will support the following process improvements: ➢ MBR system. ➢ Influent chemical feed. ➢ Control Building expansion. ➢ Headworks screening and grit removal. ➢ Process equipment and modifications. ➢ Process air upgrades. ➢ Conversion of the SBR process to the MBR process. ➢ Disinfection system. ➢ Reject water pump station. ➢ Plant drain and sludge pump station. ➢ Plant Supervisory Control and Data Acquisition System (SCADA), controls, and instrumentation. The power distribution grounding/bonding system design will comply with the NEC for buildings and structures supplies by a feeder or branch circuit. The electrical design will include equipment and construction specifications along with engineering drawings to identify equipment locations, details, schedules, and calculations. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 8-2 June 2020 │ 216-1781-042 8.1.1 Plant Electrical Distribution The existing plant electrical power distribution system will be upgraded from the two utility service entrances (Control Building and Blower Building) to one utility service entrance at the new Main Electrical Building. See Chapter 19 for the electrical service entrance. The new Main Electrical Building power distribution system will provide redundant power through the use of main-tie-main switchgear, switchboards, and MCCs. This type of distribution system will have two sources of power (System A and System B) feeding each piece of power distribution equipment to provide resiliency in the event of a power outage; see Figure 8-1. The upgraded MCC and Switchboard tie circuit breaker will be normally OPEN for isolation. The tie circuit breaker can be CLOSED when either System A or System B is powered OFF, allowing the entire MCC or switchboard (SWBD) to remain energized, see Figure 8-1. The design will include mechanical interlocks to prevent the tie circuit breaker from being CLOSED when both main circuit breakers are CLOSED. See Chapter 19 for details on the service entrance from the electrical utility provider, Puget Sound Energy (PSE). 8.1.2 Site Electrical New underground conduit duct banks will be installed for power distribution and plant controls and communications. Underground conduit duct banks will connect to each existing and new buildings, as well as process area where connections and reconnections are required. Underground conduit duct banks for wired plant communications would replace the existing ethernet radio antennas, and the ethernet radio antennas will be returned to the City of Yelm. 8.2 Design Criteria The design of the power distribution equipment will be configured with redundancy guidelines as specified in the following industry design criteria: • Department of Ecology Publication 93-37 Water Quality (WQ) Criteria for Sewage Works Design (Orange Book). • EPA-430-99-74-001: Design Criteria for Mechanical, Electrical, and Component Reliability. • The plant power will be designed based upon a main-tie-main power distribution system to provide redundancy. Each switchgear, switchboard, and MCC will be configured with the main- tie-main distribution. The electrical design criteria will specify ultralow harmonic VFDs for motors requiring variable speed control. The electrical design will identify classified areas and specify electrical construction and equipment to comply with classified spaces. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 8-3 8.3 Applicable Codes The following electrical codes, most recent publication, will be followed: • NFPA 70: NEC. • NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities. • Revised Code of Washington (RCW)/Washington Administrative Code (WAC) Rules for Electrical Installations (including RCW 296-46B). ATS-1 G xxKW M GEN-X OUTDOOR STBY POWER SWGR-SE1 SWGR-SE2 M UTILITY TRANSFORMER KKK M1 TIE M2SWGR-100 SWGR-200 SPARE SPARE M-T-M MCC-300 MCC-400 M-T-M SWBD-500 SWBD-600 M-T-M MCC-700 MCC-800 NORTH ELECTRICAL BUILDING MAIN ELECTRICAL BUILDING (FUTURE) TBD UTILITY TRANSFORMER (FUTURE) NORTH ELECTRICAL BUILDING BLOWER BUILDING SYSTEM A SYSTEM B Figure 8-1 PLANT ONE-LINE DIAGRAM YELM WRF PHASE 2 UPGRADE DATE: June 4, 2020 FILE: PS1781042-F-E1 Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 9-1 9. INSTRUMENTATION AND CONTROL DESIGN 9.1 General Information In order to provide a highly integrated system and minimize the design timeline, the instrumentation and control system will be divided into two sections. Kubota will provide all the required controls for all equipment supplied as a part of the MBR facility by Kubota. Expanded capabilities for control and monitoring of additional equipment supplied by the installation general contractor will be provided by additional programmable logic controllers (PLCs) or modify existing PLCs and interfaced with the plants existing SCADA designed by Parametrix. This will include headworks screening, chemical addition, UV disinfection, and the monitoring of plant ancillary equipment (generator, utility water, etc.). Communications between the PLCs will be by ethernet transmission control protocol (TCP)/internet protocol (IP) through a fiber optic network and managed switches located in the Parametrix-designed network communication panels. Common data required by each system will be made available over the communication network. Coordination with Kubota regarding their scope of supply will be required to ensure that the control systems are compatible. Additional coordination with other equipment suppliers will also be required depending on the type of control provided. Suppliers not providing control panels with integrated PLC control will supply a list of required input output (IO) control points for proper equipment operation. These control points will be wired to an existing plant PLC for automated control and SCADA integration by Parametrix. 9.2 Design Criteria Parametrix will produce a written set of process operation strategies for all equipment and processes not provided by Kubota. This description will include automatic operation, alarms, operator input, and a description of the human machine interface (HMI) for each system. 9.3 Applicable Codes • UL508A Industrial Control Panels. • UL698A Industrial Control Panels Relating to Hazardous Locations. 9.4 Remote Monitoring and Communications The existing computer-based SCADA system that currently reside at the WRF will be modified to incorporate the new MBR system and supporting equipment. The SCADA software platform to be utilized will is Avaya Wonderware. The software will be modified to graphically display process information from the WRF and remote water facilities. The software will also be designed to collect historical information and trend process variables. The existing software auto dialer system is composed of two separate systems in a primary-backup configuration. The primary system is located at city hall in a secure location, and the backup system resides at the WRF facility. The auto dialer system will be also be modified to include all new equipment and account for additional process monitoring. The software auto dialer system works in tandem with the SCADA system. The software auto dialer will provide detailed alarm information to the operations personnel remotely via the phone and text messages. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 9-2 June 2020 │ 216-1781-042 9.5 Security Alarm Plant security and safety are important considerations in remote environments. Monitoring for equipment status, tampering (via equipment alarms), and intrusion (via motion detectors or door switches) will be performed by the plants 24/7 monitored security system. Additional areas will be added to the system as need for complete coverage and operational safety. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 10-1 10. CHEMICAL FEED BUILDING 10.1 Description and Functions Chemical generation, storage, and feed equipment will be housed in a new Chemical Feed Building located on the west side of the existing SBR basins and/or the existing Chemical Storage Building located adjacent to the chlorine contact tanks. The chemicals fed to the influent will be as follows: • Magnesium hydroxide slurry to maintain adequate alkalinity for nitrification. • MicroC 2000 or similar to provide carbon for denitrification. • Sodium hypochlorite to reduce influent hydrogen sulfide toxicity, provide a chlorine residual for the reclaimed water, and remove organic fouling during the membrane clean-in-place procedure. 10.2 Design Criteria 10.2.1 Magnesium Hydroxide To provide sufficient alkalinity to maintain the pH and provide for nitrification, magnesium hydroxide will be supplied as a slurry or in powdered form for mixing on-site. A duplex chemical feed pump skid will have a maximum flow rate sufficient to meet the alkalinity demand at the Phase 2 peak hour flow rate at the design TKN concentration. Assumptions for design include: • Design influent TKN concentration. • All TKN is nitrified, and eight parts of alkalinity as CaCO3 are consumed per part of TKN-nitrogen. • There is 10 mg/L effluent nitrate, and denitrification returns 3.5 parts of alkalinity per part of nitrogen. • A minimum of 80 mg/L of alkalinity will be maintained after nitrification and denitrification to maintain the pH within acceptable limits. The storage and mixing tank will have a volume sufficient for a week’s worth of chemical at the Phase 2 maximum month average flow and loading rates. 10.2.2 Supplemental Carbon Supplemental carbon will be supplied as a non-toxic, non-flammable liquid such as MicroC 2000. The carbon source will be acceptable to the membrane manufacturer. It will be supplied in bulk or in standard totes. Online storage will be large enough for 3 days’ worth of supplemental carbon at the Phase 2 maximum month flow and loading rates. If bulk storage, the tank will be large enough for 1.5 times a typical full truckload. If totes are used, there will be sufficient area on-site to store 2 weeks’ worth of totes. A duplex chemical feed pump skid will be provided with a maximum flow rate sufficient to meet the carbon demand for denitrification for the Phase 2 peak hour flow rate at the design BOD and TKN concentrations. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 10-2 June 2020 │ 216-1781-042 10.2.3 Hypochlorite Hypochlorite will be used at the facility to maintain a disinfection residual in the reclaimed water, for membrane clean-in-place operation, and as an oxidant in the influent to reduce hydrogen sulfide toxicity. The design criteria are in Table 10-1. The system will be composed of the following: • Salt storage. • Brine storage and mixing tank. • Hypochlorite generator and control panel. • Hypochlorite storage tank. • Chemical feed pump skid. Table 10-1. Hypochlorite System Design Criteria System Criteria Description Brine Storage Tank Volume Large enough for 1 week at peak day flow Hypochlorite Generator Generation Rate Provide 5 mg/L at the peak day flow Hypochlorite Storage Tank Volume Provide 1 day of storage at 5 mg/L dose at the peak day flow Other Double-walled tank to provide secondary containment Chemical Feed Pump Skid Flow Rate Sufficient to provide 5 mg/L reclaimed water dose at the peak hour flow rate Arrangement Triplex skid: 1 for reclaimed water dosing, 1 for influent dosing and to transfer hypo for membrane CIP, and 1 standby Notes: mg/L = milligrams per liter; CIP = Clean in place 10.2.4 Other The above chemical feed equipment will be housed in new or existing buildings. The estimated area required for each system is 200 square feet, for a total of 600 square feet. Long-term chemical storage of salt, magnesium hydroxide powder, or supplemental carbon totes will be elsewhere on-site or outdoors. The Chemical Feed Building will contain electrical power distribution equipment (i.e., panelboard) to support the chemical feed equipment. The building HVAC will be designed to prevent freezing, condensation, or overheating but will not be designed for human comfort. 10.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 11-1 11. CONTROL BUILDING EXPANSION 11.1 Description and Functions The existing Control Building would be modified to convert the old Chlorine Disinfection Rooms and Gas Dechlorination Rooms into storage areas. In addition, the Control Building would be expanded to allow for a dedicated conference/meeting room separate from kitchen facilities and individual operator office rooms. A 1,000-square-foot expansion of the Control Building would occur as part of this work item. 11.2 Additional Design Criteria See Structural Design, Chapter 6. 11.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 12-1 12. HEADWORKS 12.1 Description and Functions A new headworks facility will be required in conjunction with the new MBR. Fine screens and grit removal will be installed to ensure that debris and grit is removed to protect the integrity of the membranes. Grit removal is mainly being included to provide for the gravity system connection in the future. 12.2 Design Criteria The connection for gravity force main would be installed just upstream of the screens so that this flow did not have to pass through the existing influent structure with the STEP wastewater flow. The headworks will also serve as the transition point of the pressurized force mains to gravity flow. The headworks interior concrete surfaces will be provided with a protective coating that is resistant to hydrogen sulfide corrosion. Influent Fine Screens – Huber drum screens are preferred by the City staff. Two screens (one duty, one standby), with 2 millimeter (mm) round aperture opening), rotating drum, in-channel screens will protect membranes per MBR warranty requirements. Washing and compacting of screenings will be provided to minimize screenings odors and hauling costs. An integrated washer-compactor will be included with each fine screen. Each screen will be sized to accommodate the buildout peak hour flow of 4.2 mgd. Screens will have an open air installation but with channels covered to minimize odor propagation. The City staff have stated a preference for a manual removal type grit channel system. A vortex grit tank would be typical for this type of installation, and only the tank will be included in the design but with a bypass connection to the manual type system desired by the City. Grit removal system will include a channel to slow wastewater velocity so grit can settle by gravity and then be manually removed with a shovel. Next to the manual system would be a cast-in-place concrete vortex grit chamber that in the future will include a motorized mixing impeller and an above-grade, self- priming grit pump. A grit classifier would also not be installed now but could be added when the grit chamber was put in use. This vortex grit system will be capable of removing 95 percent of grit greater than 50 mesh in size, 85 percent of grit greater than 70 mesh in size, and 75 percent of grit greater than 100 mesh in size. 12.3 Additional Information The following facilities are existing: • Influent Structure: This structure provides a constant static head on the STEP system force main, which is important for STEP system operation. The structures surfaces are selected for their resistance to hydrogen sulfide corrosion. • Influent Sampler: The influent sampler will be located in an enclosed shelter beside the headworks. The refrigerated sampler will be flow paced using signals from the force main flow meters. The influent sampler will draw sample flow from the headworks channel downstream of screens and grit removal. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 13-1 13. EXISTING SBR TANKS – GENERAL REHABILITATION 13.1 Description and Functions There are three existing SBR tanks. Tanks and surrounding areas need rehabilitation to provide for a smooth transition to an MBR system and comply with safe guidelines set by Occupational Safety and Health Administration (OSHA)/WAC for workers’ safety. Conversion of the existing tanks to continuous flow process trains for the MBR are discussed in subsequent chapters. 13.2 Additional Design Criteria The existing SBR tanks need general improvements for safety and to improve maintenance, reliability, and worker safety. The following would be completed as part of this work element: • Handrails: Handrails, or midrails if necessary, will be added to improve all around access into the SBR tanks and will comply with WAC 296-800-25015 and WAC 296-24-75011 to account for stair width (minimum of 22 inches for fixed stairs) and ability to support 200 lb/ft on the top rail. Existing handrails need rehabilitation to the previously mentioned code. Rails must remain in good repair and free of sharp edges. • Fall Protection: Existing tank access ladders in excess of 20 feet high will need protective cages or safety devices. Additional items that may be included are safety chains or gates at handrailing openings and fall protection anchor points. • Existing Electrical Components: Rehabilitation and recoating of existing electrical conduits and junction boxes to ensure proper temperature, ventilation specification, and protection against corrosion. Electrical equipment will also have appropriate labels/placards as necessary. The replacement and new electrical equipment and components installation method will comply with the electrical classification space specified in NFPA 820. • General Tank Repairs: Tank walkways, walls, and floor concrete will be patched and cracks repaired to prevent and seal any leaks that have developed, repair corrosion damage, prevent corrosion of metal reinforcement, and eliminate trip hazards. Tank bottoms will also be grouted with a slope to facilitate effective drainage during maintenance and cleaning. 13.3 Decisions Required Width of stairs? Or is it only ladders? How high and where will rails attach? Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 14-1 14. PROCESS EQUIPMENT AND MODIFICATIONS 14.1 Description and Functions An aeration and mixing system is a highly critical system in maintaining the biology of the WRF secondary treatment process. Included in this work element is the conversion of the existing SBRs to a continuous flow biological nutrient removal process. Specific work will consist of converting two of the existing three SBR tanks into continuous flow process trains. Each train would process 50 percent of the Sewer Facilities Plan design flows and loads. The third process tank would not be used, but could be used in the future for equalization or additional process or MBR basins. Key items for this work element include: • Newer direct-driver, energy-efficient hybrid positive displacement blowers. • Add baffle walls to separate aerated and anoxic zones. • New mixers needed for anoxic zones. • New piping for mixed liquor recycle. • New WAS and mixed liquor recycle pumps. • Temporary piping for construction sequencing. • Air Piping: Control valves, actuators, and air scour piping. • Special operations and maintenance enable plant operation during construction (e.g., Temporary pumping to install fine screen system). • Electrical power distribution and motor controls are described in Chapter 8 and Chapter 19. 14.2 Additional Design Criteria Please refer to mechanical requirements in Chapter 7. 14.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 15-1 15. PROCESS AIR DIFFUSER REPLACEMENT 15.1 Description and Functions The existing diffuser distribution piping in the SBR tanks is approaching their end of life and requires replacement. Additional modification is necessary for the conversion to an MBR process, including removing diffusers from the anoxic zone, separating the diffuser grid into sections to meet reliability requirements, and providing diffusers with low maintenance requirements that are suitable for the high mixed liquor concentrations associated with MBRs. This work involves completely replacing the existing PVC fine bubble diffuser membrane holder system, fine bubble diffuser ethylene propylene diene monomer (EPDM)-based membranes, and associated supports in two of the existing SBR tanks (new process tanks) with new diffusers. Key items for the work element include: • Air Headers: The existing air headers will be reused. They will be inspected and repaired as needed. • Drop Legs: Additional drop legs will be added, each with an isolation valve accessible from the walkway to allow sections of the diffuser grid to be isolated in the event of a failure. The drop legs and grid sections will be sized so that sufficient oxygen transfer can be achieved with the largest section out of service. This will provide the required redundancy and reliability to meet Orange Book requirements. • Diffusers: The new diffusers will be selected to provide efficient oxygen supply accounting for the reduced oxygen transfer rates associated with high mixed liquor concentrations in MBR systems. They will also be designed to reduce maintenance needs. • Diffuser Distribution Grids: The existing diffuser distribution grids are nearing their end of life and will be replaced. The grid will also be modified to account for multiple drop legs with isolated zones in each train. 15.2 Additional Design Criteria Additional design criteria for the process aeration system, including oxygen transfer requirements, can be found in Section 4.3.2, Process Air Blower Sizing. Membrane air scour diffusers are to be provided by the membrane manufacturer as part of the membrane system. 15.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 16-1 16. CONVERSION OF EXISTING SBR PROCESS TO MBR PROCESS 16.1 Description and Functions In this work item, a new MBR tank with sufficient membranes for the projected 2030 flow will be installed. To prevent membrane damage and fouling from debris, fine screens and a grit channel will be installed to process the WRF influent flow. Also, the MBR process would use continuous and recirculating flows rather than flow batching to accomplish treatment, requiring new pumping systems. This work element includes the following: • The City has designated Kubota membrane as the basis of design to allow design to proceed with a known membrane manufacturer. Other membranes may be considered during bidding to meet bidding requirements. • Construction of a new membrane tank. • A major modification of the influent hydraulic control structure and associated influent piping system to allow flow transition into the following fine screen system. • The addition of an open-air fine screening facility followed by a covered grit channel before it enters the biological process. • Construction of a new MBR Process Building to house internal recycle and permeate pump systems. • New permeate pumps if required by the membranes. • New energy-efficient blowers for membrane air scour. • New membrane clean-in-place equipment, including chemical storage tanks and feed equipment. • Installation of a crane system to provide a membrane module and equipment removal system to allow ease of maintenance. • Install a floating scum/grease removal unit in the anoxic basin and a scum pipe prior to the weir box in the MBR basin. • City is contemplating changes to the solids handling equipment; currently that work is not part of this scope. 16.2 Additional Design Criteria The conversion process will require a number of key steps, including the following: • Construct headworks facility. • Construction new MBR tank. • Test and commission headworks and MBR for start-up. • Install temporary pumps to allow recycle between two SBRs and MBR; location of the pumps will be determined in cooperation with Kubota (in SBR or MBR tank). Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 16-2 June 2020 │ 216-1781-042 • SBR Transition Step 1: ➢ Run one SBR as normal. ➢ Run the other two SBRs without a settling cycle and mixing during decant; allow mixed liquor suspended solids (MLSS) to increase so that the MBR may run at full capacity. • SBR Transition Step 2: ➢ When MBR is able to run at capacity, transfer mixed liquor (ML) from the SBR tank in normal mode to the other two SBR tanks running in modified mode. ➢ Operate in two-SBR mode with no settling and mixing during decant. ➢ Start modification of the first SBR tank to a continuous flow tank. • SBR Transition Step 3: ➢ Test and commission new process tank (feed forward pumps, etc.). ➢ Transfer ML from one of the SBR tanks to new process tank. ➢ Activate new process tank. ➢ Once new system is up and operating, transfer remaining mixed liquor from SBR tank and begin final modification. ➢ Drain and clean remaining tank. ➢ Test and commission second process tank and bring online (if necessary). Additional design criteria will be developed jointly with Kubota. 16.3 Decisions Required Where will the temporary pumps be located (SBR or MBR), or could feed forward pumps be installed prior to the transition? Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 17-1 17. DISINFECTION SYSTEM 17.1 General The City has chosen to use a closed-vessel UV disinfection system to reduce maintenance requirement and minimize power usage. Through use of the enclosed reactor system, algae growth and bacteria reactivation are minimized. The system will utilize high-efficiency, high-output, low-pressure amalgam lamps to provide the adequate dosage for the minimum of power usage. MBR permeate flow will travel by gravity or be pumped (depending on head conditions) to the UV units for disinfection prior to discharge. The system will consist of two enclosed reactors, with each reactor sized to treat the Phase 1 maximum month flow or half of peak-hour flow 1.41 mgd. The UV system would need to operate away from chlorine, corrosive chemicals, and chlorine gas vapors, so these locations for the UV system will be considered. In order to keep the existing chlorine contact channels in operation during construction, the new UV disinfection equipment could be installed above the existing standby chlorine contact tank. Because the reclaimed water system flows will still need to be provided with chlorine residual, a smaller liquid hypochlorite chlorine-based system will be installed to feed liquid hypochlorite into the WRF reclaimed water pump station discharge piping downstream of UV disinfection. The following key items that will be included in this work element are: • A multi-unit UV system, designed with redundancy to meet National Water Research Institute (NWRI) guidelines for ultraviolet disinfection for water reuse. • Liquid hypochlorite on-site generation equipment (if implemented over bulk delivery), hypochlorite bulk storage, and feed system. • Hypochlorite mixing system incorporated into pressurized reclaimed water discharge piping. • Structural modifications to fit the UV system in an existing building. 17.2 Additional Design Criteria The disinfection system will be designed to meet California Title 22 water reuse requirements for dosage (80 milliliters [mL]/cm2), transmittance (70 percent), and total coliform treatment limits (<2.2 most probable number [MPN] total coliform per 100 mL). The UV disinfection will also have to meet State Reclaimed Water Facility Manual and NWRI certification requirements as required by Washington State. For reuse applications in California, the California Department of Public Health (CDPH) has approved the Trojan UV Fit 32AL50 model for Title 22 reuse applications. Validation testing was done in accordance with the NWRI/American Water Works Association Research Foundation (AWWARF) UV guidelines. The enclosed UV units can be powered by a 480 volt power supply. 17.3 Other These energy-efficient lamps draw only 250 watts per lamp. Access to internal components (lamps, sleeves, cleaning system) can be done through an entrance at one end of the unit. A safety switch automatically deactivates the reactor power if the service cap is removed. This feature is to protect the operators. To keep the lamps clean and provide maximum Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 17-2 June 2020 │ 216-1781-042 dosing, the reactors have an automatic wiping system to maintain sleeve cleanliness. A UV intensity sensor will also continuously monitors UV output to ensure dose delivery To confirm disinfection requirements, a refrigerated effluent sampler will draw permeate from a pressurized location downstream of UV light disinfection units. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 18-1 18. PUMP STATIONS 18.1 Description and Functions WRF critical in-plant pumping stations – including the plant drain, sludge, intermediate, reject water, and the WAS – are in need of major upgrades, refurbishments, or demolition. Work in this area will include the following: • Constructing a new plant drain pump station. • Refurbishing the sludge pump station, formerly called the plant drain and sludge pump station. • Demolishing the intermediate pump station since it is not required for the operation of an MBR- based system. • Demolishing the reject water pump station since it is not required for the operation of an MBR- based system. 18.1.1 Plant Drain Pump Station Under this work element, the following work would be accomplished: • Plant drain pump station would have a minimum design flow capacity of 350 gallons per minute (gpm). Pumps would be provided with VFDs to allow changes in dewatering solids dewatering/thickening rates. • New Plant Drain Piping: Existing drains would be disconnected from the existing plant drain and sludge pump station and connected to the new pump station. The gravity belt thickener reject water would be connected to the new pump station and disconnected from the reject water pump station. Additional drains would be added for the new membrane tank(s) and new buildings and valve vaults. 18.1.2 Sludge Pump Station (Existing Plant Drain and Sludge Pump Station) Under this work element, the following work would be accomplished: • Pump replacement. • Replacement or expansion of existing valve vaults to improve valve access, removal, and repair. • Replacement of valves and gates. • Replacement of flow meters. • Electrical improvements. 18.1.3 Intermediate Pump Station Under this work element, the intermediate pump station would be demolished and abandoned. It is not required for the operation of an MBR-based system. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 18-2 June 2020 │ 216-1781-042 18.1.4 Reject Water Pump Station Under this work element, the reject water pump station would be demolished and abandoned. It is not required for the operation of an MBR-based system. 18.1.5 Waste Activated Sludge (WAS) Pump Station Under this work element, the following work would be accomplished: • Pump replacement. • Potential replacement or expansion of existing piping and valves. 18.2 Additional Design Criteria The mechanical equipment will be designed according to the following codes (note that all codes will include any Washington state and Thurston County amendments): • International Building Code. • International Fire Code. • International Plumbing Code. • International Mechanical Code. • Washington State Energy Code. • NFPA 70: NEC – 2008 Edition. • NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities – 2008 Edition. • Sheet Metal and Air Conditioning Contractors National Association, HVAC Duct Construction Standards. • Washington State Department of Ecology, Criteria for Sewage Works Design. 18.3 Decisions Required Project specifications will provide specific design information for each equipment component. Refer to Chapter 4 for design criteria details. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 19-1 19. ELECTRICAL BUILDINGS AND SERVICE ENTRANCE 19.1 Description and Functions 19.1.1 Main Electrical Building Service Entrance The new power distribution system will be designed and configured to accept two separate utility service entrances (System A and System B). The utility provider, PSE, presently has only one medium voltage power circuit to this industrial area, which includes the City of Yelm Water Reclamation Facility. The new plant power distribution system will be configured to accept a second independent PSE service entrance in the future when it becomes available. Initially, the new plant power distribution system will be connected to only one service entrance, which will provide power to both System A and System B. The service entrance will include provisions for PSE to install their metering and associated equipment. The service entrance disconnect, and metering will be located in the Main Electrical Building. 19.1.2 Standby Generator The standby power generator is the redundant backup power source in the event of a utility outage. The standby generator will be sized to support the electrical load of the treatment plan including office/lab areas. The standby power generator will be specified with diesel engine and a fuel tank sized to support 24 hours of generator operation. The electrical design will plan for one standby power generator, but if cost evaluations determine that two smaller generators cost less than one large generator, then we will specify two generators. The standby generator in a weatherproof/sound attenuating enclosure will be installed outdoors in the electrical yard. 19.1.3 Main Electrical Building Automatic Transfer Switch The design will include an ATS in the Main Electrical Building. In the event of a utility power outage, this ATS will signal the standby generator to run and will automatically transfer to the standby generator power source when it becomes available. When utility power returns, the ATS will transfer power back to the normal utility power source. The ATS will be configured as an isolation bypass ATS, which allows maintenance to be performed without disruption of the power sources to the plant power distribution. 19.1.4 Main Electrical Building 480V Switchgear The Main Electrical Building will include a 480V, 3 Phase 3 Wire metal enclosed switchgear (SWGR) with draw out low voltage power circuit breakers. The 480V SWGR will include arc flash quenching technology for personal and equipment protection. The 480V SWGR will be designed with a main-tie- main configuration to distribute power from multiple power sources (System A and System B) for a redundant power distribution system. The main-tie-main circuit breakers will have mechanical interlocks so the tie circuit breaker can be CLOSED only when one of the main circuit breakers is OPEN. The 480V SWGR will distribute electrical power to the MCCs and SWBDs in the Main Electrical Building as well as to the MCC located in the North Electrical Building. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 19-2 June 2020 │ 216-1781-042 19.1.5 Main Electrical Building Motor Control Center The Main Electrical Building will include a 480V, three-phase, three-wire MCC. This MCC will include across-the-line motor controllers, soft-start motor controllers, and feeder circuit breakers. The MCC will be designed with a main-tie-main configuration for redundancy. The main-tie-main circuit breakers will have mechanical interlocks so the tie circuit breaker can be CLOSED only when one of the main circuit breakers is OPEN. The motors which required variable speed control will be controlled by VFDs. The VFDs will be mounted separately, outside the MCC enclosure. 19.1.6 Main Electrical Building Switchboard The Main Electrical Building will include a 480V, three-phase, three-wire SWBD. This SWBD will include 480V circuit breakers for branch circuit and feeder power distribution. The SWBD will be designed with a main-tie-main configuration for redundancy. The main-tie-main circuit breakers will have mechanical interlocks so the tie circuit breaker can be CLOSED only when one of the main circuit breakers is OPEN. 19.1.7 Main Electrical Building Miscellaneous Electrical The Main Electrical Building will include miscellaneous electrical equipment, such as the following: • Low-voltage distribution transformers. • 208/120V panelboards. • Plant controls panels. • Uninterruptable power supply (UPS). • LED lighting. 19.1.8 North Electrical Building The North Electrical Building will include a 480V, three-phase, three-wire MCC. This MCC will include across-the-line motor controllers, soft-start motor controllers, and feeder circuit breakers. The MCC will be designed with a main-tie-main configuration for redundancy. The main-tie-main circuit breakers will have mechanical interlocks so that the tie circuit breaker can be CLOSED only when one of the main circuit breakers is OPEN. The motors that required variable speed control will be controlled by VFDs. The VFDs will be mounted separately, outside the MCC enclosure. 19.1.9 North Electrical Building Miscellaneous Electrical The North Electrical Building will include miscellaneous electrical equipment, such as the following: • Low-voltage distribution transformers. • 208/120V panelboards. • Plant controls panels. • LED lighting. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 19-3 19.2 Additional Design Criteria The design of the power distribution equipment will be configured with redundancy guidelines as specified in the following industry design criteria: • Depart of Ecology Publication 93-37 WQ Criteria for Sewage Works Design (Orange Book). • EPA-430-99-74-001: Design Criteria for Mechanical, Electrical, and Component Reliability. • The plant power will be designed based upon a main-tie-main power distribution system to provide redundancy. Each switchgear, switchboard, and MCC will be designed with the main- tie-main configuration. The electrical design criteria will specify ultralow harmonic VFDs for motors requiring variable speed control. The electrical design will identify classified areas and specify electrical construction and equipment to comply with classified spaces. The uninterruptable power supply will be specified as on-line type topology. 19.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 20-1 20. PLANT SCADA, CONTROLS, AND INSTRUMENTATION 20.1 Description and Functions The following efforts would be included under this work element: • Replace existing radio communication between buildings with fiberoptic network backbone. • Provide new flow monitoring instrumentation for the effluent flow discharged from the UV system and chlorine contact basin to river or canal discharge. • Upgrade SCADA system to current software version during early construction phase prior to MBR system startup. Upgrade SCADA hardware as required. • Programing and integration of equipment packages for a complete MBR system. • Work with equipment vendors to integrate supplied control systems into city SCADA system. PLC programming of the MBR is by the MBR supplier. 20.2 Additional Design Criteria City programming standards (tag naming convention) for vendor supplied equipment will be communicated to vendors. 20.3 Decisions Required None at this time. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 21-1 21. DISCHARGE 21.1 Description and Functions The WRF is permitted to discharge effluent to two surface water bodies (the Centralia Power Canal and the Nisqually River) as well as to distribute Class A reclaimed water for irrigation and/or surface percolation at rapid infiltration basins. A description of each of the outfalls and their corresponding permit requirements can be found in Chapter 3. 21.1.1 River/Canal Effluent from the WRF is discharged via a side channel outfall into the Centralia Power Canal (which drains into the Nisqually River). An emergency side channel outfall discharge is maintained directly to the Nisqually River but it is used only when the Centralia Power Canal is taken out of service for inspection and maintenance. The outfall to the canal side discharge consists of 12-inch-diameter PVC pipeline and is approximately 3,225 linear feet and contains three air-vacuum valves. The outfall to the river side discharge is accessed by closing a 12-inch gate valve just west of the canal at Station 30+87. The pipeline continues for an additional approximately 3,960 linear feet beyond the gate valve. There are two air-vacuum valves on this portion of the line. The air-vacuum valves installed along the outfall piping alignment have not been recently inspected or maintained since installation. 21.1.2 Reclaimed Water – Rapid Infiltration Basins The reclaimed water produced at the WRF is distributed to customers throughout the service area, including irrigation customers at schools, commercial landscaping, parks, and City streetscapes; commercial applications, such as a school bus washing facility; and groundwater recharge at the City’s Cochrane Park. No work is expected on the reclaimed water piping, delivery, or infiltration network; however, the volume discharged to this system for disposal in the rapid infiltration basins will be increased from approximately 50,000 gallons/day to 200,000 gallons/day. 21.2 Design Criteria and Applicable Codes Review/verification of hydraulic calculations previously prepared to confirm that sufficient capacity exists for the existing, intermediate, and future flow conditions. Modeling of the outfall pipe and inspection/repair of the five air-vacuum valves will be required as part of this project. The mechanical equipment will be designed according to the following codes (note that all codes will include any Washington state and Thurston County amendments): • International Plumbing Code. • International Mechanical Code. • Washington State Energy Code. • Washington State Department of Ecology, Criteria for Sewage Works Design. Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm 21-2 June 2020 │ 216-1781-042 21.3 Decisions Required It is assumed that the existing pipeline will have the necessary capacity to discharge the treated effluent. If capacity is deficient, it may be necessary to add mechanical assistance. 21.4 Permitting The Washington State Environmental Review Process (SERP) will also be incorporated into the design effort to provide necessary federal elements to maximize funding sources. SERP embraces the spirit of National Environmental Policy Act (NEPA) “to prevent or eliminate damage to the environment.” The intent of SERP will be to follow the approach outlined in the Department of Ecology Water Quality Program’s “Revolving Fund State Environmental Review Process and Federal Cross Cutter Guidelines” and to proactively position the future projects for next steps (loans, grants, etc.). Water Reclamation Facility – Phase 2 Basis of Design Report City of Yelm June 2020 │ 216-1781-042 22-1 22. PERMITTING AND APPROVALS The Washington SERP will also be incorporated into the design effort to provide necessary federal elements to maximize funding sources. SERP embraces the spirit of NEPA “to prevent or eliminate damage to the environment.” The intent of SERP will be to follow the approach outlined in the Department of Ecology Water Quality Program’s “Revolving Fund State Environmental Review Process and Federal Cross Cutter Guidelines” and to proactively position the future projects for next steps (loans, grants, etc.). The WRF upgrade project will need to apply and receive the following permits and approvals: • City of Yelm Building Permit. • NPDES Construction Stormwater Permit. • Department of Ecology Approval of Construction Documents. Appendix A Site Plan LEGEND PROPERTY LINE I FENCE LINE OUTFALL PIPE ROUTE ELECTRICAL DUCT BANK ---------- PAVED ROAD 0 / 39 GRAVEL ROAD / NEW FACILITY OR EXPANSION UPGRADED FACILITY CONTROL BUILDING DEACTIVATED FACILITY ✓ CHEMICAL /SOLIDS / HANDLING BUILDING MAINTENANCE BUILDING 38— -- ---- ------ {,731 40 0 0 -- o F_ ^ c /i� �/ / \ \\ `33 O �/ \ ;43\ 3 / \ `28 / 1 I p _ % (44 27 31 / I I 49 23 22 60 / o 7 8 I�– 72 1 9 �I I 12 52 I 21 10 11 5 I / 48 / � I o II I © 46 1 / O 50 OVERFLOW AIR RELEASE ASSEMBLY 55 OUTFALL PIPE (TO CANAL OR RIVER) 72 MBR EQUIPMENT BUILDING 51 PLANT REUSE CHECK VALVE VAULT 57 RW STORAGE TANK DRAIN AIR GAP SLAB 73 ELECTRICAL BUILDING 52 SLUDGE PS CHECK VALVE VAULT UPGRADE Cvd PLANT DRAIN PUMP STATION 73P6 STANDBY GENERATOR 503 REJECT WATER CHECK VALVE VAULT 65 STAND BY CHLORINE CONTACT TANK 73b POWER TRANSFORMER 54 RECLAIMED WATER (RW) STORAGE TANK 71 MBR SCREENING FACILITY 74 NEW MEMBRANE TANK OUTFALL TO CANAL AND NISQUALLY RIVER 74 13 75 76 4 4 71 77 BLOWER BUILDING 5 FUTURE MEMBRANE TANK 76 INFLUENT EQUALIZATION TANK 77 EFFLUENT FLOW METER Parametria DATE: June 16,2020 FILE:PS1781042-F6-10 PRIMARY PROCESS AREAS N INFLUENT FACILITIES F] DISINFECTION & DECHLORINATION SUPPORT SYSTEMS 0 ���111 100 SECONDARY TREATMENT - MBR Q SLUDGE STORAGE, PUMPING & PROCESSING OUTFALL TERTIARY TREATMENT O RECLAIMED WATER PUMPING & STORAGE FLOW MEASUREMENT & SAMPLING SCALE IN FEET SCHEDULE OF SUB PROCESS AREAS 1 INFLUENT METERING VAULT Z� INFLUENT HYDRAULIC CONTROL STRUCTURE Z3 INFLUENT CHEMICAL STORAGE/FEED FACILITY <4 MBR TANKS (FORMER SEQUENCING BATCH REACTOR TANKS) 5 SBR DECANT FLOW METER MANHOLE UPGRADE © SBR DECANT EQUALIZATION STORAGE PONDS - DEACTIVATED O INTERMEDIATE PUMP STATION (IPS) - DEACTIVATED ® VALVE BOX - DEACTIVATED 9 IPS FLOWMETER VAULT - DEACTIVATED 10 STATIC MIXER 'A' - DEACTIVATED 11 STATIC MIXER 'B' - DEACTIVATED 12 EFFLUENT FILTERS - DEACTIVATED 13 UV DISINFECTION UPGRADE 14 RECLAIMED WATER PUMP STATION AND WETWELL C) MCC ROOM ik CONTROL ROOM (BLOWER BUILDING) C� RESTROOM 1 STORAGE ROOM <9 BLOWER ROOM - DEMOLISH BLOWERS AND INSTALL LIQUID HYPOCHLORITE SYSTEM 21 SLUDGE PUMP STATION UPGRADE 22 REJECT WATER PUMP STATION 23 SLUDGE STORAGE TANKS 25 SOLIDS HANDLING ROOM UPGRADE 26 CHEMICAL FEED AND STORAGE ROOM UPGRADE C 1 PROCESS MAKE-UP WATER SUPPLY ROOM UPGRADE 28 ELECTRICAL AND MCC ROOMS 31 RESTROOM 33 LABORATORY 34 BREAKROOM 35 OFFICE EXPANSION 36 PROCESS CONTROL ROOM 37 OUTFALL LINE PIG PORT 38 SEPTIC TANK /3\9 RV/SEPTAGE PUMP STATION UPGRADE 40 STANDBY GENERATOR -QTY 2 (TO BE REMOVED) 41 HVAC HEAT PUMP 42 POWER TRANSFORMER -QTY 2 (TO BE REMOVED) 43 MAINTENANCE GARAGE 44 STEP SYSTEM SUPPLY ROOM <6 WAS PUMP STATION UPGRADE ,48 WAS PINCH VALVE VAULT UPGRADE 49 CHECK VALVE VAULT - DEACTIVATED Figure 6-10 Liquid Stream Alternative 3 WRF Site Plan Sewer Facilities Plan Yelm, Washington Appendix B Kubota Design Information 1 City of Yelm Water Reclamation Facility – Phase 1 Upgrades Process Calculations A summary of the process design calculations is presented below. This analysis was performed using the flow conditions (Table 1) and influent data (Table 2) presented below. The Maximum Monthly Flow was used as the design basis for biological calculations. Design calculations below are based on a minimum temperature of 10°C. Table 1. Design Flow Conditions Condition Design Flow Unit Average Annual Flow 1.26 MGD Max Month Flow 1.39 MGD Peak Hour Flow 2.81 MGD Table 2. Influent and Effluent Characteristics Constituent Influent Loading Expected Effluent Concentration BOD 235.5 mg/L < 5 mg/L TSS 76.6 mg/L < 5 mg/L TKN 66.9 mg/L TN - < 10 mg/L Return Rate The rate of the return of the activated sludge is determined based on the mass balance for total nitrogen: 𝐿∙𝐿𝐿𝑖𝑛𝑑𝑙𝑡𝑑𝑛𝑡=𝐿𝑅∙𝐿𝐿𝑅+𝐿∙𝐿𝐿𝑑𝑑𝑑𝑙𝑡𝑑𝑛𝑡 Where, 𝐿𝑅=𝐿𝐿 Therefore: 𝐿× 67 =𝐿𝐿× 10 +𝐿× 10 𝐿=57 10 =5.7 Therefore, a return flow of 6Q is selected for this project. 2 Anoxic Reactor Design The anoxic reactor is sized based on the load of nitrogen that is required to be denitrified. The TN load for denitrification is calculated based on the TN load that is nitrified in the aerated zones and returned to the anoxic zone with a given return rate (6Q). On the other hand, the aerated zone is sized for full nitrification. Therefore, the TN load that is nitrified can be calculated by subtracting the total load of nitrogen entering the system minus the nitrogen which exits in the WAS. The total nitrogen load is first calculated based on the influent flow rate and concentration. 𝐿𝑙𝑙𝑎𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐿𝑙𝑎𝑎=𝐼𝑙𝑎𝑙𝑙𝑎𝑙𝑙 𝐴𝑙𝑙𝑙 𝑙 𝐼𝑙𝑎𝑙𝑙𝑎𝑙𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐴𝑙𝑙𝑎𝑎𝑙𝑙𝑙𝑎𝑙�ℎ𝑙𝑙 𝐿𝑙𝑙𝑎𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐿𝑙𝑎𝑎=1.39 𝐿𝐴𝐴 𝑙 66.9 𝑙𝑎 𝐿 𝐿 𝑙 8.34 (𝑎𝑎𝑙 𝐿𝑎𝑎𝑙𝑙 𝑙𝑎 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙)=776.0 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 The nitrogen load in waste sludge is calculated as follows. 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 �ℎ𝑙 𝑉𝑎𝑙𝑙𝑎 𝐿𝑙𝑙𝑎𝑎𝑎= 𝐴𝐿𝐴 𝐿𝑙𝑎𝑎 𝑙 𝐿𝑙𝑙𝑎𝑎𝑎 𝑌�ℎ𝑎𝑙𝑎 𝐿𝑎𝑙�ℎ𝑙 𝑙 𝐿𝑙𝑙𝑎𝑎𝑎 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐴𝑙𝑙𝑎𝑎𝑙𝑙𝑙𝑎𝑙�ℎ𝑙𝑙 This requires calculating the BOD load, which is calculated based on the influent flow rate and concentration. 𝐴𝐿𝐴 𝐿𝑙𝑎𝑎=1.39 𝐿𝐴𝐴 𝑙 235.5 𝑙𝑎 𝐴𝐿𝐴 𝐿 𝑙 8.34 =2731.8 𝑙𝑎𝑙 𝐴𝐿𝐴 𝑎𝑎𝑙 Assuming a sludge yield ratio of 0.60 lb SS/lb BOD and nitrogen content of 0.07 lb N/lb SS in the sludge, the rate of mass of nitrogen discharged in the waste sludge is then calculated using the formula detailed above. 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 �ℎ𝑙 𝑉𝑎𝑙𝑙𝑎 𝐿𝑙𝑙𝑎𝑎𝑎=2731.8 𝑙𝑎𝑙 𝐴𝐿𝐴 𝑎𝑎𝑙 𝑙 0.6 𝑙𝑎 𝐿𝐿 𝑙𝑎 𝐴𝐿𝐴 𝑙 0.07 𝑙𝑎 𝐿 𝑙𝑎 𝐿𝐿 =114.7 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 The TN load for nitrification can be calculated as: 𝐿𝑙𝑙𝑎𝑙 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐿�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙=𝐿𝑙𝑙𝑎𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐿𝑙𝑎𝑎−𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 �ℎ𝑙 𝑉𝑎𝑙𝑙𝑎 𝐿𝑙𝑙𝑎𝑎𝑎 𝐿𝑙𝑙𝑎𝑙 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐿�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙= 776.0 −114.7 =661.3 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 Total load for denitrification then can be determined: 𝐿𝑙𝑙𝑎𝑙 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐴𝑎𝑙�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙=𝐿𝑙𝑙𝑎𝑙 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐿�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙 × 𝐿 𝐿+1 𝐿𝑙𝑙𝑎𝑙 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐴𝑎𝑙�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙=661.3 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 × 6 7 =566.8 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 3 The anoxic tank is sized based on the total load for denitrification, the designed mixed liquor suspended solids concentration in the anoxic tank, the Kubota standard denitrification rate of 0.021 lb N/lb VSS-d at 10°C, and a MLSS to MLVSS ratio of 0.8. Considering a design MLSS concentration of 12,000 mg/L in the MBR zone, MLSS concentration in the anoxic zone would be 10,285 mg/L (0.086 lb SS/gal) with 6Q return flow. The size of the denitrification reactor is then calculated as: 𝐴𝑙𝑙𝑙�ℎ𝑎 𝐿𝑎𝑎𝑎𝑙𝑙𝑙 𝑉𝑙𝑙𝑙𝑙𝑎=𝐿𝐿 𝑙𝑙𝑎𝑎 𝑎𝑙𝑙 𝑎𝑎𝑙�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙 𝐴𝑎𝑙�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙 𝐿𝑎𝑎𝑎𝑙�ℎ𝑙𝑙 𝐿𝑎𝑙𝑎 × 𝐿𝑙𝑙𝑙𝑎𝑙𝑎𝑎𝑎 𝐿𝑙𝑙�ℎ𝑎𝑙 𝐴𝑙𝑙𝑎𝑎𝑙𝑙𝑙𝑎𝑙�ℎ𝑙𝑙 = 566.8 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 0.021 𝑙𝑎 𝐿 𝑙𝑎 𝑉𝐿𝐿∙𝑎𝑎𝑙 𝑙 0.086 𝑙𝑎 𝐿𝐿 𝑎𝑎𝑙 𝑙 0.8 𝑙𝑎 𝑉𝐿𝐿 𝑙𝑎 𝐿𝐿 =𝟎𝟖𝟎,𝟎𝟎𝟎 𝒆𝒂𝒍 Total nitrogen removed is calculated as: 𝐿𝑙𝑙𝑎𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐿𝑎𝑙𝑙𝑙𝑎𝑙=𝐿𝑎𝑙𝑙𝑙𝑎𝑙 𝑎𝑙 𝐴𝑎𝑙�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙+𝐴�ℎ𝑙𝑎�𝑎𝑙𝑎 �ℎ𝑙 𝑙�𝑎 𝑉𝑎𝑙𝑙𝑎 𝐿𝑙𝑙𝑎𝑎𝑎 𝐿𝑙𝑙𝑎𝑙 𝐿�ℎ𝑙𝑙𝑙𝑎𝑎𝑙 𝐿𝑎𝑙𝑙𝑙𝑎𝑙=566.8 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙+114.7 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙=681.6 𝑙𝑎𝑙 𝐿 𝑎𝑎𝑙 Which is equal to 87.8% removal. The Effluent TN concentration then can be determined as: 𝐴𝑎𝑎𝑙𝑙𝑎𝑙𝑙 𝐿𝐿=𝐼𝑙𝑎𝑙𝑙𝑎𝑙𝑙 𝐿𝐿− 𝐿𝑎𝑙𝑙𝑙𝑎𝑎 𝐿𝐿 𝐴𝑎𝑎𝑙𝑙𝑎𝑙𝑙 𝐿𝐿=66.9 𝑙𝑎 𝐿 𝑙 − 87.8% 𝑙 66.9 𝑙𝑎 𝐿 𝑙 𝑬𝒆𝒆𝒍𝒕𝒆𝒍𝒕 𝑻𝑵= 𝟖.𝟎𝟎 𝒍𝒆 𝑵 𝒍 4 Aeration Zone Design Kubota design for the biological reactor volumes is based on the max month flow and load. However, sizing the MBR zone is based on the required membrane surface area considering all the flows including the peak flows. In addition, the MBR zone is also part of the biological treatment process because of the constant aeration provided for membrane scouring. In designing the aerated zone, first the aerated volume provided in the MBR zone is determined. It will then be subtracted from the total required aerated volume required for full nitrification and BOD removal. The result is considered as the required Pre-Aeration (PA) reactor volume. Based on the influent flow rates listed in Table 1, Kubota proposes two (2) MBR tanks each containing ten (10) RW400 submerged membrane units. The minimum required MBR tank length and width to accommodate the membrane units are 34’ and 14’, respectively. Considering 18’ of side water depth for MBR tanks, each tank provides 64,569 gallons of aerated volume. Therefore, the MBR zone provides 129,138 gallons of total aerated volume. Pre-Aeration (PA) Tank Design Required PA Volume for BOD Removal The BOD load that enters the aerated zone (MBR + PA) is the BOD load in the influent after a fraction of it is consumed through denitrification in the anoxic tank. Assuming 2.80 lb BOD/lb TN for rate of BOD removal by denitrification, total BOD removal required in MBR and PA can be calculated: 𝐿𝑙𝑙𝑎𝑙 𝐴𝐿𝐴 𝐿𝑎𝑙𝑙𝑙𝑎𝑙 𝐿𝑎𝑙𝑙�ℎ𝑙𝑎𝑎 �ℎ𝑙 𝐿𝐴𝐿 𝑎𝑙𝑎 𝐿𝐴=2731.8 𝑙𝑎 𝑎𝑎𝑙−(2.80 lb 𝐴𝐿𝐴 𝑙𝑎 𝐿𝐿 × 566.84 lb 𝐿𝐿 𝑎𝑎𝑙) =1,144.7 𝑙𝑎 𝐴𝐿𝐴 𝑎𝑎𝑙 The BOD that can be removed in the MBR zone is determined by knowing the MBR zone volume (129,138 gal), Kubota standard BOD removal rate of 0.10 lb BOD/lb VSS-d at 10°C, MLSS concentration of 0.1 lb SS/gal (12,000 mg/L) in the MBR zone, and a MLSS to MLVSS ratio of 0.8: 𝐿𝑎𝑙�ℎ𝑙𝑙𝑙 𝐴𝐿𝐴 𝐿𝑎𝑙𝑙𝑙𝑎𝑎 �ℎ𝑙 𝐿𝐴𝐿 =𝐴𝐿𝐴 𝐿𝑎𝑙𝑙𝑙𝑎𝑙 𝐿𝑎𝑙𝑎 × 𝐴𝑎𝑙𝑎𝑙𝑎𝑎 𝑉𝑙𝑙𝑙𝑙𝑎 𝑙𝑎 𝐿𝐴𝐿 × 𝐿𝐿𝐿𝐿 𝐴𝑙𝑙𝑎𝑎𝑙𝑙𝑙𝑎𝑙�ℎ𝑙𝑙 �ℎ𝑙 𝐿𝐴𝐿= 0.1 𝑙𝑎 𝐴𝐿𝐴 𝑙𝑎 𝑉𝐿𝐿∙𝑎× 129,138 𝑎𝑎𝑙 × 0.1 𝑙𝑎 𝐿𝐿 𝑎𝑎𝑙× 0.8 𝑙𝑎 𝑉𝐿𝐿 𝑙𝑎 𝐿𝐿=1,034.6 𝑙𝑎 𝐴𝐿𝐴 𝑎𝑎𝑙 To achieve a full BOD removal, the PA tank should be sized to remove the remainder of the BOD that is not removed through denitrification and in the MBR tank. Therefore: 5 𝐿�ℎ𝑙�ℎ𝑙𝑙𝑙 𝐴𝐿𝐴 𝑙𝑙 𝑎𝑎 𝐿𝑎𝑙𝑙𝑙𝑎𝑎 �ℎ 𝐿𝐴=1,144.7 −1,034.6 =110.1 𝑙𝑎 𝐴𝐿𝐴 𝑎𝑎𝑙 𝐿𝐴 𝐿𝑎𝑎𝑎𝑙𝑙𝑙 𝑉𝑙𝑙𝑙𝑙𝑎=𝐴𝐿𝐴 𝐿𝑙𝑎𝑎 𝑎𝑙𝑙 𝐿𝑎𝑙𝑙𝑙𝑎𝑙 𝐴𝐿𝐴 𝐿𝑎𝑙𝑙𝑙𝑎𝑙 𝐿𝑎𝑎𝑎𝑙�ℎ𝑙𝑙 𝐿𝑎𝑙𝑎 × 𝐿𝑙𝑙𝑙𝑎𝑙𝑎𝑎𝑎 𝐿𝑙𝑙�ℎ𝑎𝑙 𝐴𝑙𝑙𝑎𝑎𝑙𝑙𝑙𝑎𝑙�ℎ𝑙𝑙 = 110.1 𝑙𝑎𝑙 𝐴𝐿𝐴 𝑎𝑎𝑙 0.1 𝑙𝑎 𝐴𝐿𝐴 𝑙𝑎 𝑉𝐿𝐿∙𝑎 𝑙 0.086 𝑙𝑎 𝐿𝐿 𝑎𝑎𝑙 𝑙 0.8 𝑙𝑎 𝑉𝐿𝐿 𝑙𝑎 𝐿𝐿 =𝟎𝟎,𝟎𝟎𝟖 𝒆𝒂𝒍 Required PA Volume for Nitrification By using a similar approach for nitrogen, considering Kubota standard nitrification rate of 0.013 lb TN/lb VSS-d at 10°C, minimum PA tank volume for nitrification can be determined: 𝐿�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙 �ℎ𝑙 𝐿𝐴𝐿=133.4 𝑙𝑎 𝑇𝑁 𝑑𝑎𝑦 𝐿�ℎ𝑙𝑙�ℎ𝑎�ℎ𝑎𝑎𝑙�ℎ𝑙𝑙 𝐿𝑎𝑙𝑙�ℎ𝑙𝑎𝑎 �ℎ𝑙 𝐿𝐴=527.9 𝑙𝑎 𝑇𝑁 𝑑𝑎𝑦 𝐿�ℎ𝑙�ℎ𝑙𝑙𝑙 𝐿𝑎𝑙𝑙�ℎ𝑙𝑎𝑎 𝑉𝑙𝑙𝑙𝑙𝑎 �ℎ𝑙 𝐿𝐴=𝟎𝟖𝟎,𝟎𝟎𝟎 𝒆𝒂𝒍 Therefore, the PA tank is designed to have 596,041 gallons capacity to achieve full BOD removal and full nitrification.