Executive Summary. ES.1 Introduction

Transcription

1 Executive Summary ES.1 Introduction The East Central Regional Water Reclamation Facility (ECRWRF) is a 70-mgd conventional activated sludge secondary treatment plant. Portions of the main plant s secondary effluent are discharged to a 10-mgd advanced wastewater treatment (AWT) facility for supplemental potable water supply; and to a 22-mgd high-level disinfection facility to meet industrial cooling water demands at the Florida Power and Light West County Energy Center; the balance of secondary effluent is discharged to deep injection wells. An aerial site plan of the overall ECRWRF is shown on Figure ES-1. Currently, the ECRWRF biosolids are partially stabilized on-site by aerobic digestion, dewatered using belt filter presses, and then further stabilized at an off-site regional composting facility under a service contract with the Solid Waste Authority of Palm Beach County (SWAPBC). The existing composting facility service contract with the SWAPBC expires on September 30, 2014 and the ECRWRF biosolids will need to be handled in a different manner. Prior to commencement of this engineering report, the ECRWRF Operations Board had been negotiating with the SWAPBC to permanently route the biosolids to the SWAPBC Pelletization Facility. The SWAPBC receives a portion of ECRWRF biosolids at the pelletizer facility on an interim basis. The biosolids processing capacity at the SWAPBC Pelletizer Facility, based on the latest proposal from SWAPBC, ranges from approximately 59,200 to 59,930 wet tons per year depending on whether the daily maximum feed rate or annual contracted mass governs. As illustrated in Figure ES-2, average dewatered cake production rates have recently exceeded the SWAPBC capacity allotment. Page ES-1

2 Figure ES-1 SITE PLAN - EXISTING FACILITIES East Central Regional Water Reclamation Facility Biosolids Engineering Report

3 90,000 Figure ES-2 ECRWRF Projected 80,000 Dewatered Sludge (wet tons/year) 70,000 60,000 50,000 40,000 30,000 20,000 10,000 SWAPBC limit Historical dewatered sludge Projected dewatered sludge The purpose and scope of this engineering report are as follows: 1. Develop and calibrate BioWinTM process model of ECRWRF to accurately project solids production and predict performance of liquids and solids treatment processes. 2. Evaluate solids treatment process to increase solids destruction, including temperature-phased anaerobic digestion and emerging WAS pretreatment technologies. 3. Evaluate liquid processes to enhance biosolids treatment, including primary treatment; and treat recycle flows from proposed solids processing facilities to assure compliance with effluent nutrient limits for AWT and HLD plant effluents. 4. Evaluate economic feasibility of energy and heat recovery from digester gas. 5. Evaluate terms of proposed SWAPBC pelletizer agreement; analyze disposal options including SWAPBC pelletizer, onsite drying and third-party vendor treatment and/or disposal. Page ES-2

4 6. Calculate present value life-cycle costs of combined liquids treatment / solids treatment / disposal options and select recommended overall project approach. ES.2 Preliminary BioWinTM Process Modeling Detailed historical data collection and analyses were used to develop and calibrate a preliminary BioWin TM model of the ECRWRF plant. Flow enters the ECRWRF via three forcemains from the five contributing municipalities. A septage receiving station typically discharges to the headworks structure upstream of the screens from the West Palm Beach / Palm Beach, Palm Beach County / Lake Worth, and Riviera Beach influent streams. Preliminary treatment consists of screening and grit removal. The screened and degritted wastewater then flows through a 96 diameter underground pipe to the influent structure at the head of Aeration Basin No. 5. The ECRWRF operates with a Ludzack-Ettinger activated sludge process. Secondary treatment includes one anaerobic/aerobic Aeration Basin No. 5 (AB-5). Following AB-5, flow is typically split evenly between Aeration Basin Nos. 2 and 6 (AB-2 and AB-6). Mixed-liquor exiting AB-2 and AB-6 are distributed to Clarifier Nos. 1 through 8 via aerated channels. Return Activated Sludge (RAS) is returned to the influent structure at the head of AB-5 where it is mixed with secondary influent. Waste Activated Sludge (WAS) is withdrawn only from Clarifier No. 4 and Clarifier No. 8, where it is typically routed to decant tanks for thickening, or can alternately bypass the thickening process and be routed to the aerobic digester. Decant tank supernatant is returned to the Recirculation Pump Station No. 1 where it mixes with RAS before being returned to the head of AB-5. WAS from Clarifier No. 4 or Clarifier No. 8 is continually pumped to the decant tanks or can be bypassed directly to the aerobic digesters. The WAS is thickened at the decant tanks. The supernatant from the decant tanks gravity flows through the supernatant pump station (currently out of service) to Recirculation Pump Station No. 2. The thickened WAS (TWAS) from the decant tanks is pumped by the Decant Tank Sludge Transfer Pump Station to the Aerobic Digester. WAS is aerated and mixed in the aerobic digester via mechanical surface and floating surface mixers. Following aerobic digestion, partially digested WAS is transferred to the belt filter presses by the AB-1 Sludge Transfer Pumps. Figures ES-3 and ES-4 show process flow diagrams for liquids and solids processing trains, respectively. Historical influent flows and loads from Years 2008 through 2010 are graphed below in Figures ES-5, ES-6 and ES-7. Page ES-3

5 8 MG EQ Basin 5 MG EQ Basin Grit Removal Drainage Septage HLD Facility Filter Backwash Supernatant P.S. Discharge Raw Wastewater From WPB / PB Septage P.S. Five (5) Screens Two (2) Vortex Grit Removal Gravity Belt Thickener Filtration Raw Wastewater From PBC / LW Raw Wastewater From RB Anoxic Aerobic Aeration Basin No. 5 Aeration Basin No. 2 Plant Lift Station AWT Facility Backwash/Sludge RAS RAS Aeration Basin No. 6 Clarifier No. 1 Clarifier No. 2 (Emergency Use) Chlorine Control Chamber No. 1 RAS RAS P.S. (Emergency Use) Chlorine Control Chamber No. 2 Sec Eff. to HLD Facility Sec Eff. to Deep Well Injection Clarifier No. 3 Clarifier No. 4 HLD Facility Reject Water Sec Eff. to AWT Facility WAS RAS Decant Tank and BFP Filtrate RAS P.S. WAS P.S. Clarifier No. 5 Clarifier No. 6 Legend: TM1.ai Clarifier No. 7 Clarifier No. 8 WAS to Decant Tanks (See Solid Stream Process Flow Diagram) = = System Input Dashed Line Indicates Out of Service or Future WAS RAS WAS P.S. WAS to Aerobic Digester Figure ES-3 ECRWRF Liquid Stream Main Process Flow Diagram ECRWRF Biosolids Engineering Report Executive Summary Preliminary BioWin Process Modeling

6 Gravity Belt Thickener (Out of Service) WAS (from Clarifier Nos. 4 and 8) Decant Tank No. 1 GBT Filtrate Aeration Basin No. 2, Aeration Basin No. 6, or 8 MG Eq Basin Decant Tank No. 2 To Off-site Composting Decant Tank No. 3 Decant Tank Sludge Transfer P.S. TWAS Aerobic Digester BFP Feed P.S. Four (4) Winklepresses Aeration Basins No. 2 and 6 Decant Water One (1) Klampress Supernatant P.S. (Out of Service) Belt Filter Press Filtrate BFP Filtrate P.S. Legend: WAS = System Input Gravity Flow to RAS P.S. for Clarifiers No. 3 and 4 = Dashed Line Indicates Out of Service TM1.ai Figure ES-4 ECRWRF Solid Stream Process Flow Diagram ECRWRF Biosolids Engineering Report Executive Summary Preliminary BioWin Process Modeling

7 Figure ES-5 Historical Influent CBOD5 Concentration and Load day average CBOD5 conc Average daily CBOD5 conc 30-day average CBOD5 load Average daily CBOD5 load 200, , , , , ,000 80,000 60,000 40, , Jan-08 Mar-08 May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10 Sep-10 CBOD 5 (mg/l) Nov-10 Jan-11 CBOD 5 (lb/day) Figure ES-6 Historical Influent TSS Concentration and Load , day average TSS conc Average daily TSS conc 30-day average TSS load Average daily TSS load 180, , ,000 TSS (mg/l) , ,000 80,000 TSS (lb/day) Jan-08 Mar-08 May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10 Sep-10 Nov-10 Jan-11 60,000 40,000 20,000 0 Page ES-4

8 Figure ES-7 Influent VSS Concentration and Load VSS (mg/l) day average VSS conc Average daily VSS conc 30-day average VSS load Average daily VSS load 200, , , , , ,000 80,000 60,000 40,000 20,000 VSS (lb/day) 0 0 Jan-08 Mar-08 May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10 Sep-10 Nov-10 Jan-11 The influent flowrate and CBOD 5 influent loading have remained relatively constant over the 2008 to 2010 period. TSS and VSS loading; however, increased by 28% and 26%, respectively, over the same three-year period. The BioWin TM model was calibrated using historical influent, effluent and operational data for the period of January 2008 through December The BioWin TM model configuration that was calibrated is illustrated in Figure ES-8. Page ES-5

9 Figure ES-8 BioWinTM Model Configuration AB2 Side Zone AB2 1 Side Zone 2 Influent Side Zone 1 Side Zone 2 AB2 Aer1 AB2 Aer2 Grit AB5 AX1 AB5 AX2 AB5 AX3 AB5 Aer1 AB5 Aer2 AB6 Aer1 AB6 Aer2 Eff Septage BOD OFF AB6 Side Zone AB6 1 Side Zone 2 Grit Septage COD ON AB1 Aer Dig-1 Sludge The main goal of the model is to predict solids production of the existing plant and potential liquids process improvement options. As shown in Table ES.1, the data calibrates well to the model for total solids removed. Year Table ES.1 Preliminary BioWin TM Model Hauled Sludge Calibration Hauled Sludge (dt/yr) Digested WAS (lb/d) Historical Calibrated Calculated Historical Calibrated Values Model Values Values 1 Values Model Values ,331 8,282 50,868 42,432 50, ,991 8,068 54,868 55,521 50, ,239 8,903 56,012 57,528 54,203 1 Assumption based on 90% mean range of solids capture for BFP s per WEF MOP 8 ES.3 Liquid Process Improvement Options This chapter presents the evaluation of liquids stream process improvement options for the improvement of biosolids operation and performance for the ECRWRF Biosolids Engineering Report project. Liquids processing improvement options that were evaluated are as follows: Option L1 Status quo; no liquids processing improvements Option L2S Addition of primary treatment; standard-rate clarification Option L2HR Addition of primary treatment; high-rate clarification Page ES-6

10 Potential benefits of primary treatment include higher volatile fraction to increase volatile solids reduction and increased gas production in proposed anaerobic digestion process for potential energy and heat recovery. Primary clarifiers would also remove significant BOD and TKN from the raw influent wastewater, resulting in reduced influent loading to the activated sludge process and therefore reduced aeration demand and energy savings. Required infrastructure under each primary treatment option is summarized in Table ES.2. Table ES.2 Primary Treatment Infrastructure Requirements, 70-MGD Units Option L2S Option L2HR Primary Clarifiers Number # 4 3 Diameter feet Sidewater depth feet Surface Overflow Rate gpm/ft2 1,000 2,000 Primary Effluent Pump Station Type of Pumps n/a Submersible Submersible Number of Pumps # 9 9 Total Horsepower, firm capacity hp 900 1,200 Primary Sludge Thickener Number # 2 2 Diameter feet Sidewater depth feet Odor Control System Number # 2 2 Type n/a Wet Scrubber Wet Scrubber Total Capacity scfm 40,000 28,000 As flows increase above 57.5 MGD, additional aeration treatment capacity will be required to maintain biological phosphorous removal and nitrification/denitrification, and the conversion of AB-1 to an aeration basin and the addition of two additional secondary clarifiers should be considered. Modification of the AB-5 influent and effluent structures would be required to split the flow to AB-5 and a newly modified AB-1. The preliminary BioWinTM model was used to estimate both TWAS and primary sludge production projections for Option L1, Option L2S, and Option L2HR. For each of the Page ES-7

11 above options, sludge production rates were estimated for the Annual Average Flow (AA), Maximum Month Flow (30-day), and Maximum Week Flow (7-Day) at current plant flowrate of 43.1 MGD, the 20-year design horizon plant flowrate of 57.5 MGD, and the design flowrate of 70.0 MGD. ES.4 Solids Process Improvement Options Chapter 3 evaluated multiple liquids processing options (no primary treatment, conventional primary treatment and high-rate primary treatment) and established projected sludge production rates for each liquid option over the 20-year planning period. These projected sludge production rates are used to evaluate the following solids process improvement options: L1/S1 Solids processing status-quo (continued use of decant tanks, aerobic digestion, belt filter press dewatering); based on sludge production projections from Liquids Processing Option L1 (status quo). L1/S2 Solids processing status quo, except replace belt filter press dewatering facility with new centrifuge dewatering facility; based on sludge production projections from Liquids Processing Option L1 (status quo). L1/S3 Upgraded WAS storage and thickening; new temperature-phased anaerobic digestion facility and centrifuge dewatering facility; based on sludge production projections from Liquids Processing Option L1 (status quo). L2STD/S3 Upgraded WAS storage and thickening; new temperature-phased anaerobic digestion facility and centrifuge dewatering facility; based on sludge production projections from Liquids Processing Option L2STD (standard-rate primary treatment). L2HR/S3 Upgraded WAS storage and thickening; new temperature-phased anaerobic digestion facility and centrifuge dewatering facility; based on sludge production projections from Liquids Processing Option L2HR (high-rate rate primary treatment). L1/S4 Upgraded WAS storage and thickening; new temperature-phased anaerobic digestion, with WAS pretreatment (cell lysis processes); and centrifuge dewatering facility; based on sludge production projections from Liquids Processing Option L1 (status quo). Process flow diagrams of Options S2, S3 and S4 are shown in Figures ES-9, ES-10 and ES-11. Required solids treatment infrastructure for each option is listed in Table ES.3. Page ES-8

12 Rehabilitated Gravity Belt Thickener Facility (3 existing, 1 new) WAS Decant Tank No. 1 GBT Filtrate Aeration Basin No. 2, Aeration Basin No. 6, or 8 MG Eq Basin Decant Tank No. 2 To Off-site Treatment/Disposal Decant Tank No. 3 TWAS Aerobic Digester BFP Feed P.S. Aeration Basins No. 2 and 6 Decant Water Supernatant P.S. Belt Filter Press Filtrate BFP Filtrate P.S. Legend: WAS = System Input Gravity Flow to RAS P.S. for Clarifiers No. 3 and 4 Centrifuge Dewatering Facility = Dashed Line Indicates Out of Service TM1.ai Figure ES-9 ECRWRF Solid Stream Process Flow Diagram Option S2 ECRWRF Biosolids Engineering Report Executive Summary Solids Process Improvement Options

13 FOG WAS Aerated WAS Storage Tank No. 1 Rehabilitated Gravity Belt Thickener Facility (3 existing, 1 new) Inter-Digester Transfer Pump (6) Aerated WAS Storage Tank No. 2 GBT Feed Pumps (4) TWAS P.S. (4) Mesophilic Digesters GBT Filtrate Aeration Basin No. 2, Aeration Basin No. 6, or 8 MG Eq Basin Existing Filtrate P.S. TPS TPS P.S. Thermophilic Digesters CFB Feed P.S. (4) To Off-site Composting/Pelletizer DS Transfer P.S. (4) TM1.ai Aeration Basins No. 2 and 6 Existing Supernatant P.S. Decant Water Centrifuge Centrate CFB P.S. Digested Sludge Holding Centrifuge Dewatering Facility Legend: WAS = System Input = New Facilities = Future Facilities Gravity Flow to RAS P.S. for Clarifiers No. 3 and 4 Figure ES-10 ECRWRF Solid Stream Process Flow Diagram Option S3 ECRWRF Biosolids Engineering Report Executive Summary Solids Process Improvement Options

14 Aerated WAS Storage Tank No. 1 WAS Cambi Process Aerated WAS Storage Tank No. 2 BFP Cake Pumps (8) Pre-Dewatering Belt Filter Press Facility (8, Future 9) Sludge Hopper Pulper Feed Pumps (3) Pulpers (2) Reactor Feed Pumps (4) Reactor (6, Future 8) Flash Tank (2) BFP Feed Pumps (8) Digester Feed Pumps (4) CDF Feed P.S. (4) To Off-site Composting/Pelletizer Belt Press Filtrate DS Transfer P.S. (4) Aeration Basins No. 2 and 6 Decant Water BPF P.S. Mesophilic Digesters Digested Sludge Holding Legend: WAS = System Input TM1.ai Existing Supernatant P.S. Gravity Flow to RAS P.S. for Clarifiers No. 3 and 4 Centrifuge Centrate Centrate P.S. Centrifuge Dewatering Facility = New Facilities = Future Facilities Figure ES-11 ECRWRF Solid Stream Process Flow Diagram Option S4 ECRWRF Biosolids Engineering Report Executive Summary Solids Process Improvement Options

15 Table ES.3 Infrastructure Requirements for Solids Processing Options, 70-MGD Units Option L1/S3 Option L2S/S3 Option L2HR/S3 WAS Storage Volume (existing) MG 2.0 Type of Aeration n/a Coarse bubble Total Blower Horsepower, firm hp 300 GBT Upgrades Refurbished Units # 3 New Units # 1 Total Units # 4 Thickened Sludge Conc. % 4.5 Anaerobic Digestion Thermophilic # Mesophilic # Diameter, each feet 90 Option L1/S4 Volume, each MG Centrifuge Dewatering Centrifuge Scroll Diameter Mm 700 Dewatered Cake Conc. % 20 Units (Off-site drying) # Units (Onsite drying) # WAS Pretreatment Pre-dewatering belt presses # n/a n/a n/a 9 Feed Sludge Conc. % n/a n/a n/a Number of reactors # n/a n/a n/a 8 Number of Boilers # n/a n/a n/a 2 Number of Pulper Tanks # n/a n/a n/a 2 Pretreated WAS Conc. % n/a n/a n/a 8-10 ES.5 Energy / Heat Recovery Options The upgrade of the ECRWRF provides an opportunity for the recovery of anaerobic digester gas to be utilized as fuel for the onsite production of electrical power. The generated power can be used to reduce purchased electrical power and as a source of thermal energy for digester heating. Page ES-9

16 Options considered for using the digester gas are as follows: Option DG2 Digester heating only using hot water boiler at digestion facility Option DG3 Energy / Heat recovery with new reciprocating engine generator(s) Option DG4 Energy / Heat recovery with retrofitted emergency turbine generator(s) Required infrastructure to implement Options DG3 and DG4 are summarized below: Table ES.4 Infrastructure Requirements for Energy / Heat Recovery Options, 70-MGD Units Option DG3 Option DG4 Electrical Capacity, total kw 1,600 1,750 Capital Costs $ 8,000,000 4,900,000 Payback Period, without grants Option L1/S3 years 47.5 None Option L2HR/S3 years 10.7 None Option L2S/S3 years 10.5 None Payback Period with grants Option L1/S3 years 17.3 None Option L2HR/S3 years Option L2S/S3 years Note that the payback analyses in the chapter are limited to the combined heat and power facilities and do not take into account the additional net present worth costs of primary treatment facilities. Primary treatment costs, as well as these combined heat and power facility costs, are factored into net present worth costs of combined treatment options in Chapter 6. ES.6 Screenings-Level Analysis of Combined Options Chapter 6 develops life-cycle cost analyses for each of the ten (10) combined treatment options and three (3) biosolids disposal options listed below. Combined Treatment Option 1 (L1/S1) Liquids and solids status quo. Combined Treatment Option 2 (L1/S2) Liquids status quo and centrifuge dewatering. Page ES-10

17 Combined Treatment Option 3 (L1/S3/DG2) Liquids status quo, temperaturephased anaerobic digestion, heat recovery for digester heating only and centrifuge dewatering. Combined Treatment Option 4 (L1/S3/DG3) Liquids status quo, temperaturephased anaerobic digestion, energy/heat recovery with new reciprocating engine generator(s), and centrifuge dewatering. Combined Treatment Option 5 (L1/S3/DG4) Liquids status quo, temperaturephased anaerobic digestion, energy/heat recovery with upgraded emergency turbine generator(s), and centrifuge dewatering. Combined Treatment Option 6 (L2S/S3/DG3) Addition of primary treatment (standard loading rates), temperature-phased anaerobic digestion, energy/heat recovery with new reciprocating engine generator(s), and centrifuge dewatering. Combined Treatment Option 7 (L2S/S3/DG3) Addition of primary treatment (standard loading rates), temperature-phased anaerobic digestion, energy/heat recovery with upgraded emergency turbine generator(s), and centrifuge dewatering. Combined Treatment Option 8 (L2HR/S3/DG4) Addition of primary treatment (high-rate clarifiers), temperature-phased anaerobic digestion, energy/heat recovery with new reciprocating engine generator(s), and centrifuge dewatering. Combined Treatment Option 9 (L2HR/S3/DG4) Addition of primary treatment (high-rate clarifiers), temperature-phased anaerobic digestion, energy/heat recovery with upgraded emergency turbine generator(s), and centrifuge dewatering. Combined Treatment Option 10 (L1/S4) Liquids status quo; temperaturephased anaerobic digestion with WAS pretreatment (for enhanced volatile solids reduction to meet SWAPBC capacity constraints. Biosolids Disposal Option 1 Maximum dewatered cake to the SWAPBC pelletizer facility; balance to landfill or third party vendor. Biosolids Disposal Option 2 All dewatered cake to onsite thermal dryer; hauled and marketed by third party vendor. Biosolids Disposal Option 3 All dewatered cake to third party vendor for onsite or offsite treatment, disposal and marketing. Page ES-11

18 Table ES.5 Summary - Net Present Worth Total Costs (Treatment plus Disposal) Option BD-1 Option BD-2 SWAPBC Pelletizer Onsite Dryer Combined Treatment Option Option BD-3 3 rd Party Vendors CTO-1 (L1/S1) $191,775,000 $195,373,000 $191,963,000 CTO-2 (L1/S2) $175,052,000 $174,060,000 $168,410,000 CTO-3 (L1/S3) $166,761,000 $165,731,000 $159,869,000 CTO-4 (L1/S3/DG3) $172,881,000 $168,589,000 $165,989,000 CTO-5 (L1/S3/DG4) $185,736,000 $182,281,000 $178,844,000 CTO-6 (L2STD/S3/DG3) $200,766,000 $196,657,000 $193,034,000 CTO-7 (L2STD/S3/DG4) $208,656,000 $205,383,000 $200,924,000 CTO-8 (L2HR/S3/DG3) $195,019,000 $190,947,000 $187,267,000 CTO-9 (L2HR/S3/DG4) $205,030,000 $201,796,000 $197,278,000 CTO-10 (L1/S4) $176,531,000 $179,210,000 $167,459,000 $250,000,000 Figure ES-12 Summary - Net Present Worth Total Costs $225,000,000 $200,000,000 $175,000,000 $150,000,000 $125,000,000 $100,000,000 $75,000,000 $50,000,000 $25,000,000 $0 1st bar = SWA and landfill 2nd bar = Onsite dryer 3rd bar = Contract provider CTO 1 CTO 2 CTO 3 CTO 4 CTO 5 CTO 6 CTO 7 CTO 8 CTO 9 CTO 10 Status Quo Anaerobic Digestion Primary Clarifiers Thermal Page ES-12

19 The following conclusions can be drawn from the screenings-level net present worth (NPW) cost analysis: 1. Combined Treatment Option CTO-3 has the lowest NPW cost. 2. Status quo options (CTO-1 and CTO-2) have higher O&M costs that result in higher NPW costs. 3. Primary treatment scenarios in Combined Treatment Options CTO-6 through CTO-9 have higher NPW costs, mostly due to capital costs and cost of primary effluent pumping. 4. Energy / heat recovery options CTO-4 and CTO-5 are not cost-effective due to cost of primary treatment. 5. WAS pretreatment (CTO-10) is more expensive than CTO-3. ES.7 Whole-Plant Calibrated BioWin TM Modeling Although the plant s historical data provides adequate information on basic influent wastewater characteristics and loadings, supplemental sampling was conducted to better define the wastewater characterization and to provide detailed fractionation data of the influent for accurate process modeling. Prior to running the process simulation model to evaluate performance and alternatives for sludge production, model calibration is required to increase confidence in the process simulation modeling. For this project, model calibration consisted of wastewater fractionation, solids calibration, and aeration basin profile calibration/verification. The first step in model calibration is to accurately define the wastewater fractions for input into the simulation model. This was followed by steady state simulations of yearly and monthly performance to confirm the fractionation based on solids calibration and effluent predictions. Yearly and monthly calibration results are summarized in Tables ES.6 and ES.7. Page ES-13

20 Table ES.6 Yearly Calibration Summary 4 yr Avg. ( ) Parameter Data Model Results WAS Rate (MGD) MLSS (mg/l) 4,050 4,060 WAS (mg/l) 10,456 10,524 TWAS (lb/d) 70,377 71,159 Digested Sludge (lb/d) 54,444 56,032 Hauled Sludge (lb/d) 48,439 49,817 Table ES.7 Monthly Calibration Summary Solids Production TWAS (lb/d) Digested Solids (lb/d) Hauled Sludge (lb/day) Month Historical Model Historical Model Historical Model May ,404 90,907 69,556 69,184 58,227 57,907 Mar ,361 86,656 66,857 67,056 57,477 57,668 Jan ,415 82,428 60,943 64,753 56,288 59,832 Mar ,178 82,694 66,273 65,754 62,602 62,137 Jan Mar ,673 73,273 54,435 50,897 50,017 50,505 Sep - Nov ,323 69,744 49,473 55,034 46,100 51,182 May Jun ,585 62,282 49,560 48,840 44,204 44,456 ES.8 Final Recommendations ES.8.1 Recommended Solids Treatment and Disposal Facilities Sludge production projections from the calibrated BioWin TM model were compared to previous estimates from the screenings-level analyses to determine the projected change in solids mass loading rates to thickening, digestion, dewatering and disposal processes. Sludge production projections at annual average loading rates increased by approximately 7% (70.0 MGD) to 12% (43.1 MGD) over the loadings used prior to model calibration. However, the maximum month loadings were essentially equal to the previous maximum month loadings due to a decrease in the maximum month peaking factor. Since proposed design criteria are based largely on maximum month loading Page E-16

21 rates, final sizing of proposed solids treatment facilities remains unchanged from the screenings-level analyses developed in Chapter 6. Although selection of a combined treatment strategy was fairly straightforward based on lowest preset worth cost, additional evaluation was required to develop a recommendation on the most effective biosolids disposal approach. For the reader s convenience, biosolids disposal options are summarized below: Biosolids Disposal Option No. 1 (BD1) This option would route dewatered biosolids cake to the SWAPBC biosolids processing facility for thermal drying. Excess dewatered biosolids cake, if any, beyond the contracted processing capacity would be routed to a landfill, or other off-site residuals handling facility, for ultimate treatment. Biosolids Disposal Option No. 2 (BD2) This option would include the installation of an on-site thermal drying facility at the ECRWRF plant site. The thermal drying facility, during the first phase development to a capacity of 57.5 MGD (CY- 2035), would be sized with evaporative capacity sufficient to process all of the anticipated residuals from the facility. Final product from the on-site thermal drying facility would be hauled and marketed by a contact vendor. Biosolids Disposal Option No. 3 (Option BD3) This option would route the dewatered biosolids cake to a contract vendor for processing and ultimate management. During initial evaluations, it was assumed that contract management could be either on-site or off-site and could include additional treatment or landfilling. However, the ECR Board s Interlocal Agreement only allows operation and maintenance of the ECRWRF by City of West Palm Beach utilities staff. A summary of revised total present worth costs for Biosolids Disposal Options is presented in Figure ES-13. Page ES-17

22 Figure ES-13 Summary of Revised Total Present Worth Costs for Biosolids Disposal Options $200,000,000 $195,000,000 $190,000,000 $185,000,000 $180,000,000 $175,000,000 $170,000,000 $165,000,000 $160,000,000 $155,000,000 $150,000,000 $145,000,000 $140,000,000 $135,000,000 $130,000,000 $125,000,000 BD1 - SWA and Landfill BD2 - Onsite Dryer BD3 - Contract Provider - #3 CTO 3 It should be noted that while net present worth costs for Options BD1 (SWAPBC) and BD2 (Onsite Drying) were developed based on detailed facility sizing, capital costs and O&M costs, limited information is available for the wide-ranging, non-binding proposals received to date from third-party contract vendors under Option BD3. Option BD3 proposals received to date include (a) hauling to off-site co-composting facilities; (b) design-build or design build-operate of an onsite thermal drying facility, and (c) hauling to a off-site drying facility. Should the ECR Board select Option BD3, the Board would need to conduct a separate open procurement process to select the third-party vendor. Given the diversity of options to date and the likelihood that additional vendors would propose other technical solutions, development of detailed scope requirements and technical specifications for an apples-to-apples review of proposals would be challenging. As illustrated above, net present worth costs for BD3 options are competitive, but do not result in a significant cost advantage over Options BD1 and BD2. Given the procurement challenges discussed above, Option BD3 should be deferred. Should the Page ES-18

23 Board decide to implement Combined Treatment Option CTO-3, implement a short-term biosolids disposal option and defer a decision on long-term bisolids disposal options altogether, Option BD3 could be reconsidered when long-term disposal decisions are reevaluated. Therefore, further evaluation will focus on Biosolids Disposal Options BD1 (SWAPBC) and BD2 (Onsite Dryer). A comparison of capital costs, net present operating costs and total present worth costs for Options BD1 and BD2 are summarized in Table ES.8. Table ES.8 Net Present Worth Cost Summary Biosolids Disposal Options BD1 and BD2 Option BD1 (Contract with SWAPBC) Option BD2 (Onsite Drying Facility) Capital Cost $13,532,000 $24,140,000 Net Present Operating Costs $56,360,000 $41,380,000 Total Present Worth Costs $69,892,000 $65,520,000 Option BD2 (Onsite Drying Facility) requires a higher capital cost but its lower annual O&M costs result in lower total present worth cost when compared to Option BD1 (SWAPBC). Lower annual O&M costs associated with Option BD2 (Onsite Dryer) can be attributed to the following factors: Lower pass-through costs (industrial water, wastewater treatment, odor control chemicals Lower unit cost for natural gas No dewatered cake transport charges Lower administrative costs Biosolids Option BD-2 (Onsite Thermal Drying) has a lower total present worth (treatment and disposal) cost than Biosolids Option BD1 (SWAPBC). If the Board selects Biosolids Option BD1, the ECRWRF allotment constraint at SWAPBC would require supplemental disposal through landfilling by SWAPBC or through a third party vendor. Therefore, Option BD2 (Onsite Thermal Drying Facility) is recommended. Page ES-19

24 ES.8.2 Sidestream Management The potential impact of solids treatment sidestream flows on the liquids treatment facilities must be considered. The calibrated BioWin TM model indicates that if anaerobic digestion is added to the ECRWRF, equalization is required to meet the nutrient reduction goals (ammonia, nitrates and phosphorous) of the main plant. Therefore, as part of the proposed anaerobic digestion improvements, the following is a summary of sidestream management recommendations: 1. Implement centrate equalization and pumping by converting existing Decant Tank No. 3 to a Centrate Equalization Tank with a new Equalized Centrate Pump Station. 2. Note that centrate equalization may not be required if an on-site drying facility is constructed under Biosolids Disposal Options BD2. It is assumed that an onsite drying facility would be operated continuously; therefore, the centrifuge dewatering facility feeding the onsite drying facility would also be operated continuously and discharge a constant the centrate sidestream load the main plant s secondary treatment process. The need for centrate equalization should be determined during detailed design. 3. The dynamic BioWinTM modeling indicates that if equalization is implemented, sidestream treatment specifically for nutrient removal will not be required for the current main plant, AWT and HLD treatment goals. 4. However, the calibrated model indicates that there is a strong potential for struvite formation and precipitation. For this reason it is recommended that sidestream treatment for struvite precipitation prevention be considered. In this analysis a struvite precipitation process (Ostara) and ferric salt addition (to digesters) were considered and were determined to be viable options for control of struvite precipitation and the ECRWRF. It is recommended that these two options be considered further during final design for the prevention of struvite problems in the proposed anaerobic digestion and solids handling system. ES.8.3 Site Plan A site plan for proposed solids treatment and disposal facilities (Options CTO-3 and BD2) is presented on Drawing SIT-1. ES.8.4 Capital Costs Table ES.9 presents a summary of capital costs for proposed solids treatment and disposal facilities: Page ES-20

25 PROPOSED BIOSOLIDS IMPROVEMENTS SITE PLAN

26 Table ES.9 Capital Cost Summary Phase 1 (57.5 MGD) Phase 2 (70 MGD) Sitework $860,000 $20,000 WAS Storage $2,690,000 $0 Gravity Belt Thickening Upgrades $1,660,000 $0 Anaerobic Digestion Facilities $32,340,000 $9,830,000 Centrifuge Dewatering Facility $8,630,000 $0 Septage/FOG Receiving $1,020,000 $0 Odor Control Facilities $540,000 $0 Subtotal, Treatment Facilities $47,740,000 $9,850,000 Mobilization, Demobilization, Bonds & Insurance (5%) $2,390,000 $500,000 Contractor General Conditions, Overhead and Profit (20%) $10,030,000 $2,070,000 Estimating Contingency (15%) $9,030,000 $1,870,000 TOTAL, TREATMENT FACILITIES $69,190,000 $14,290,000 Subtotal, Onsite Thermal Drying Facility $21,800,000 $0 Mobilization, Demobilization, Bonds & Insurance (5%) $1,100,000 $0 Contractor General Conditions, Overhead and Profit (included in subtotal) in subtotal $0 Estimating Contingency (5%) $1,200,000 $0 TOTAL, ONSITE THERMAL DRYING FACILITY $24,100,000 $0 GRAND TOTAL, CONSTRUCTION $93,290,000 $14,290,000 Engineering and Administration (14%, excluding estimating contingencies) $11,630,000 $1,740,000 TOTAL PROJECT COSTS $104,920,000 $16,030,000 ES.8.5 Project Delivery Methods Section 8.5 of the report presents descriptions and comparisons of the following project delivery methods: Traditional or Design-Bid-Build (DBB) Design-Build (DB) Construction Manager at Risk (CMAR) Design-Build-Operate (DBO) Page ES-21

27 Parameters to be considered by the Board when selecting a project delivery method include change orders, risk of claims/litigation, schedule, cost and quality. This report does not advocate a recommended project delivery method; but rather presents information for the Board s use in making a policy decision. ES.8.6 Implementation Schedule Sludge thickening, dewatering and disposal infrastructure should be constructed under Phase 1 to meet the full rated capacity of the 70-mgd ECRWRF. Since FDEP does not require sludge stabilization, anaerobic digestion facilities can be constructed in two phases. Under Phase 1, six (6) digesters can be constructed to serve a plant capacity of 57.5 mgd, which represents a 20-year planning horizon. These Phase 1 thickening, digestion and dewatering facilities would represent a Current Common Core project with flexibility for future expansion. Phase 2 construction can be thought of as Future Flexible Facilities. While the baseline concept shown for Phase 2 includes construction of the last two digesters, the Board could monitor the continuing development of emerging WAS pretreatment (cell lysis) technologies; should cell lysis technologies become more cost-effective on a lifecycle basis, the Board would have the option to implement WAS pretreatment in lieu of constructing the last two digesters. In addition, implementing new anaerobic digestion facilities would allow the aerobic digester to be converted back to Aeration Basin 1 (under a subsequent, separate project). Based on calibrated BioWin TM modeling, use of Aeration Basin 1 in parallel to Aeration Basin 5 would improve biological nutrient reduction (BNR) performance in the main plant; and would allow for draining, cleaning and rehabilitating/upgrading structures and diffused aeration systems in Basins 2, 5 and 6 on a long-term rotating schedule to improve overall treatment plant performance, efficiency and reliability. These basin upgrades have the potential to result in significant life-cycle cost savings. Therefore, the Phase 1 construction schedule assumes all facilities would be constructed in a single project. Within this single project, we recommend that WAS thickening and centrifuge dewatering facilities be expedited under an interim milestone to increase dewatered cake solids and reduce hauling and disposal costs as soon as possible. A short-term Phase 1 construction schedule is shown in Figure ES-14. Page ES-22

28 Figure ES-14 Project Schedule Phase 1 ECRWRF Biosolids Improvements Construction will be completed in 2016, after the current composting agreement with SWAPBC expires. The Board should implement an interim three-year disposal agreement with SWAPBC or with 3 rd party vendors (e.g., Synagro or H&H) ton until permanent facilities come on-line. Preliminary investigations indicate that the cost of interim disposal through third party vendors would be approximately $50 per wet ton, which is comparable to the long-term disposal costs evaluated in this report. ES.8.7 Board Decisions at Report Review Workshop At a final draft review workshop conducted at the April 11, 2012 ECRWRF Board meeting, the Board reached consensus on the following project decisions: Combined Treatment Option CTO-3 (Liquids status quo, temperature-phased anaerobic digestion, heat recovery for digester heating only and centrifuge dewatering). Biosolids Disposal Option BD2 (Onsite Thermal Drying). Page ES-23

29 Traditional design-bid-build project delivery method. Implementation of project in Phases 1 and 2 as outlined in the project implementation schedule. Page ES-24