Water and Wastewater Residuals Management Optimization Study - FINAL

Transcription

1 Water City of Penticton Water and Wastewater Residuals Management Optimization Study - FINAL Prepared by: AECOM Lakeshore Road tel Kelowna, BC, Canada V1W 3S fax Project Number: Date: April 2013

2

3 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Statement of Qualifications and Limitations The attached Report (the Report ) has been prepared by AECOM Canada Ltd. ( Consultant ) for the benefit of the client ( Client ) in accordance with the agreement between Consultant and Client, including the scope of work detailed therein (the Agreement ). The information, data, recommendations and conclusions contained in the Report (collectively, the Information ): is subject to the scope, schedule, and other constraints and limitations in the Agreement and the qualifications contained in the Report (the Limitations ); represents Consultant s professional judgement in light of the Limitations and industry standards for the preparation of similar reports; may be based on information provided to Consultant which has not been independently verified; has not been updated since the date of issuance of the Report and its accuracy is limited to the time period and circumstances in which it was collected, processed, made or issued; must be read as a whole and sections thereof should not be read out of such context; was prepared for the specific purposes described in the Report and the Agreement; and in the case of subsurface, environmental or geotechnical conditions, may be based on limited testing and on the assumption that such conditions are uniform and not variable either geographically or over time. Consultant shall be entitled to rely upon the accuracy and completeness of information that was provided to it and has no obligation to update such information. Consultant accepts no responsibility for any events or circumstances that may have occurred since the date on which the Report was prepared and, in the case of subsurface, environmental or geotechnical conditions, is not responsible for any variability in such conditions, geographically or over time. Consultant agrees that the Report represents its professional judgement as described above and that the Information has been prepared for the specific purpose and use described in the Report and the Agreement, but Consultant makes no other representations, or any guarantees or warranties whatsoever, whether express or implied, with respect to the Report, the Information or any part thereof. Without in any way limiting the generality of the foregoing, any estimates or opinions regarding probable construction costs or construction schedule provided by Consultant represent Consultant s professional judgement in light of its experience and the knowledge and information available to it at the time of preparation. Since Consultant has no control over market or economic conditions, prices for construction labour, equipment or materials or bidding procedures, Consultant, its directors, officers and employees are not able to, nor do they, make any representations, warranties or guarantees whatsoever, whether express or implied, with respect to such estimates or opinions, or their variance from actual construction costs or schedules, and accept no responsibility for any loss or damage arising therefrom or in any way related thereto. Persons relying on such estimates or opinions do so at their own risk. Except (1) as agreed to in writing by Consultant and Client; (2) as required by-law; or (3) to the extent used by governmental reviewing agencies for the purpose of obtaining permits or approvals, the Report and the Information may be used and relied upon only by Client. Consultant accepts no responsibility, and denies any liability whatsoever, to parties other than Client who may obtain access to the Report or the Information for any injury, loss or damage suffered by such parties arising from their use of, reliance upon, or decisions or actions based on the Report or any of the Information ( improper use of the Report ), except to the extent those parties have obtained the prior written consent of Consultant to use and rely upon the Report and the Information. Any injury, loss or damages arising from improper use of the Report shall be borne by the party making such use. This Statement of Qualifications and Limitations is attached to and forms part of the Report and any use of the Report is subject to the terms hereof. AECOM: AECOM Canada Ltd. All Rights Reserved. Rpt WWW Optimization Study FINAL.Docx

4

5

6

7

8

9 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Table of Contents Statement of Qualifications and Limitations Letter of Transmittal Distribution List page 1. Introduction Background Report Objectives Report Organization Water Treatment Plant Sludge Production Current Solids Loading Future Solids Loading Projections BioWin Modelling Review of Previous Work & Assumptions New Modelling Parameters Summary of Modelling Results Impacts to Wastewater Treatment Plant Introduction Individual Unit Treatment Process Impacts Primary Clarifiers Primary Sludge Fermenters Bioreactors Dissolved Air Floatation Centrifuges Digesters Volatile Solids Content - Biological Processes Summary of Impacts and Projected Long Term Impacts Okanagan Falls WWTP Residuals Residuals Management Estimated Capital and Operational Costs Annual Sludge Operating Cost Summary Net Present Value Comparison Summary of Net Present Cost Comparison Conclusions and Recommendations List of Figures Figure 1-1 WTP Residual Process Flow Schematic... 1 Figure 2-1 Typical Scenario - Daily Solids Loading by Source Constituent... 5 Figure 2-2 Worst Case and Typical Operation - Daily Solids Loading... 6 Figure 2-3 Projected WTP Peak Daily Solids Loading... 7 Figure 2-4 Projected WTP Annual Solids Loading... 7 Rpt WWW Optimization Study FINAL.Docx

10 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Figure 3-1 BioWin Process Model Configuration (2008)... 8 Figure 3-2 BioWin Process Simulation Results (2008 Study)... 9 Figure 3-3 BioWin Process Simulation Results (Summer) Figure 3-4 BioWin Process Simulation Results (Winter) Figure 4-1 WTP Residuals Load vs. AWWTP Flow List of Tables Table 2-1 WTP Daily Raw Water Flows... 4 Table 3-1 Phosphorous Removal as a Function of PACl Sludge Addition (2008 Study)... 9 Table 3-2 Penticton AWWTP Influent Data Comparison (24-hour composite) Table 3-3 Key BioWin Model Influent Data Table 3-4 BioWin Modelling Results (Winter) Table 3-5 BioWin Modelling Results (Summer) Table 4-1 Raw Sewage Suspended Solids Loading Table 4-2 Primary Sludge Production Table 4-3 Fermented Primary Sludge Production Table 4-4 Suspended Solids in the Bioreactor Table 4-5 Solids Loading in the DAF Table 4-6 Solids Loading in the Centrifuge Table 4-7 Digested and Fermented Primary Sludge Production Table 4-8 Summary of Impacts on AWWTP Processes Table 5-1 Annual AWWTP and WTP Operating Costs to Manage WTP Sludge Table 5-2 Net Present Value Comparison of WTP Sludge Management Scenarios Appendices Appendix A. Technical Memorandum - Water Treatment Plant Sludge Assessment May 2008 Appendix B. RDOS WWTP Sludge Memorandum Appendix C. Base Year Water Quality and Flow Data - Typical Operation and Worst Case Operation Appendix D. Net Present Value Detailed Cost Breakdown for each Scenario Rpt WWW Optimization Study FINAL.Docx

11 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 1. Introduction 1.1 Background In 2009, the City of Penticton completed several upgrades to the existing water treatment plant (WTP). As part of the WTP upgrades the existing residual handling process was upgraded to provide improved operational flexibility. In the past, the residuals management process limited the City to periodically discharge the plant s sludge to the sanitary sewer in significant discrete events. With the new on-site residuals process the City now has the option of allowing a controlled flow of sludge to the sewer or dewatering sludge on-site and sending only the centrate to the sanitary sewer. The upgraded residuals management process train consists of the following: Filter backwash waste equalization and pumping; Gravity lamella clarification and sludge thickening of filter backwash waste; On-site storage and mixing of the thickened sludge and the dissolved air flotation sludge, Centrifuge dewatering with centrate disposal to the sanitary sewer; and, Dewatered cake holding bins for truck hauling. A schematic of the upgrades residuals management process is provided in Figure 1-1. Figure 1-1 WTP Residual Process Flow Schematic Rpt WWW Optimization Study FINAL.Docx 1

12 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study The WTP presently operate the residuals process to collect the sludge on-site and divert a steady flow of sludge to sanitary sewer. This is the lowest operational cost approach for the WTP and has historically been accepted by the Advanced Wastewater treatment facility due to the phosphorous reduction benefits attributable to the WTP sludge. Taking into consideration the hydraulic and solids loading impacts to the Advanced Wastewater Treatment Plant, the current method of operation may not be the lowest cost approach for the City to manage the WTP sludge. As part of the Functional Design Phase of the Penticton AWWTP, AECOM investigated the negative and positive impacts the water treatment plant residuals sludge waste has on the operation of the City s AWWTP 1. To do this, AECOM developed and calibrated a BioWin model to quantify the effects the WTP sludge on the main secondary process at the AWWTP. The study indicated that, while the aluminum content of the WTP sludge enhanced the phosphorous removal, the long term impact of the additional inert solids loading would eventual limit the capacity of some of the AWWTP biological processes, i.e., bioreactor, fermenter and digester. AECOM is currently completing a condition assessment of the AWWTP s digesters, and has recently completed a similar assessment of the fermenters. The latter assessment outlined a series of short and long term structural remediation options for the fermenters. With respect to this current WTP sludge management study, the longer term plans for the remediation of both the fermenters and the digesters will be influenced by the quantity of WTP sludge that continues to be sent to the AWWTP for processing. The availability of WTP sludge in particular will influence the need for additional or enhanced fermenter capacity at the AWWTP. This rationalization of solids management is critical for the future plans of these particular wastewater treatment unit processes. With the recent modifications to the WTP (completed in 2009) and the AWWTP (completed in 2011) facilities, the City wants to determine the lowest life cycle cost approach to managing the WTP sludge, with consideration of the key financial impacts at the WTP and AWWTP. 1.2 Report Objectives During the preliminary design of the WTP, residuals sludge characterization and projections was based on operational and process assumptions developed in the WTP Capacity Upgrade Preliminary Design Report 2 (WTP Upgrade Pre-Design). Since the completion of the residuals process upgrades two factors have resulted in higher sludge production than previously estimated. The most significant of which is the City s decision to operate the plant using a larger proportion (annually) of Penticton Creek water. This decision, based on the limiting the electrical and chemical costs associated with the Okanagan Lake and Penticton Creek sources, results in higher chemical use that create larger volumes of sludge. The second factor is that the previous estimate of chemical doses was based on achieving the minimum regulated water quality standards while the current polymer and coagulant dosing is aimed at exceeding these values. This results in a very high standard of water quality being provided by the City but also leads to slightly higher solids production at the WTP. Since the completion of the WTP, the City has over two years of operating data available that will be used to verify the original assumptions for the WTP residuals projections and characterization. The objective of this report is to reevaluate the impact of the WTP residual sludge on the AWWTP, using the current operating data, and provide the City with a long term operational strategy that minimizes the overall cost of managing the WTP residuals sludge. 1 City of Penticton, Technical Memorandum - Water Treatment Plant Sludge Assessment, AECOM formerly Earth Tech Canada Ltd., May 5, City of Penticton, Treated Water Capacity Upgrade Preliminary Design Report, AECOM formerly Earth Tech Canada Ltd.., February Rpt WWW Optimization Study FINAL.Docx 2

13 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 1.3 Report Organization This report documents the WTP residuals projections, their impact to the AWWTP, and provides recommendations for a holistic approach to managing the City s WTP residuals sludge. The remainder of this report is sub-divided into several sections, as follows: Section 2 Water Treatment Plant Sludge Production describes the current and future solids loading anticipated from the WTP based on the current plant operating data; Section 3 BioWin Modelling presents the results of the updated BioWin modeling and compares these to the model results collected prior to the WTP and AWWTP upgrades; Section 4 Impacts to Wastewater Treatment Plant discusses the impacts the WTP residuals sludge will have on the individual processes at the AWWTP; Section 5 Residuals Management Capital and Operational Cost Estimate evaluates the operational and capital cost implications to manage the WTP residuals both at the WTP and the AWWTP; Section 6 Conclusions and Recommendations documents the conclusions from the assessment and provides recommendations on the lowest cost operating strategy for the current and the future operation of the City s WTP and AWWTP facilities. 2. Water Treatment Plant Sludge Production The amount of residual sludge produced at the WTP is a function of the treated water flow rate, raw water quality, and the individual process performance. We have generated estimates of the current and future total solids generation at the WTP using the recent plant operating data and assumptions of the individual process performances. The following discusses the parameters and assumptions used to develop the daily solids production for the Penticton WTP. To account for variability in potable water demands and the raw water quality conditions, we developed two scenarios to provide a range of anticipated solids loading values. Typical Operation utilizes plant operating data from 2011 (chemical dosing and raw water quality) and 2007 (daily flow), as describe below, and includes a 10% safety factor applied to the daily solids load. Daily flow rates and non-typical water quality data were modified to smooth out peaks and valleys in the raw data. Worst Case Condition is similar to the Typical Operation in that it is based on the plant operating data from 2011 and 2007; however, the water quality data was modified to simulate the most challenging water quality conditions for the Lake and Creek (i.e. high colour and turbidity) coinciding with the high demand period during the spring freshet. In addition, a 5% safety factor was applied to the total raw water flow and a 10% safety factor applied to the daily solids load. The 2007 daily raw water flow data was used to estimate the daily and annual solids generated at the WTP. The water demand in 2007 represents a typical year with an average flow of 21.7 ML/d and a peak day flow of 43.7 ML/d. These values are lower than those used in the Preliminary Design Report projections, which were 28.4 ML/d and 61.1 ML/d for average day and peak day flows respectively. Since 2004 the peak daily flow rate has continued to decline, in large part, due to the water conservation measures implemented by the City, e.g. system wide metering, seasonal water restrictions, and customer education. The magnitude of this trend was not clear at the time of the preliminary design report, especially in light of the 2004 and 2005 demand data that showed only a nominal impact from water conservation strategies and the rapid development growth. The average and Rpt WWW Optimization Study FINAL.Docx 3

14 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study peak daily flows since 2007 indicate that the water demands in the City have been fairly stable over the past 5 years. Provided in Table 2-1 is a summary of the average and maximum daily flows between 2005 and Table 2-1 WTP Daily Raw Water Flows Year Average Maximum Day The solids projections developed during the WTP Capacity Upgrade Preliminary Design Report were based on implementing an operating strategy that maximized the quality of the raw water entering the WTP. This approach used a two tiered approach, where at flows less than 60 ML/d the plant would rely predominantly on the Okanagan Lake water, with no more than 30% of the total flow being drawn from the Creek and 100% of the Lake source during summer (May to September). When the flows exceed 60 ML/d, 60 ML/d of Lake source would be used, and the remainder would be drawn from the Creek. As noted in the previous section, the City has simplified the operating strategy at the WTP to optimize the use of gravity supplied water; balancing the energy costs with chemical consumptions costs. The AWWTP identified a preference for the higher alkalinity sludge generated by the Okanagan Lake water. Sludge from the 70 / 30 Lake to Creek blend has sufficient alkalinity to support nitrification (<8.0); however as the flows increase beyond 85 ML/d and the 70 / 30 blend ratio is no longer achievable, ph adjustment may be required to maintain sufficient ph and alkalinity (ph >6.5) in the sludge to support nitrification in the bio reactor. The Westbench water system is expected to be connected to the City water system this year. The average daily flow to the Westbench community is projected to be 1.2 ML/d. The chemical usage data is based on 2011 plant operating data represents the most complete dataset since the commissioning of the WTP upgrades in The daily chemical use was determined by applying the actual chemical dose to the daily flow rates. Notable differences in the actual chemical use data and the values assumed during the WTP Preliminary Design include: The average annual coagulant use is higher than the levels estimated in the Preliminary Design Report. This is due to the extended period of 70 / 30 blend currently implemented by the City as well as a higher water quality being achieved; The actual flocculant aid polymer dose, of active polymer, is 0.8 mg/l as oppose to the estimated 0.5 mg/l; The conversion factors used to determine the solids captured in the clarification, filtration and thickening processes are as follows: 1 NTU of turbidity generates 1.5 mg/l TSS (2.0 mg/l TSS during Worst Case condition); Rpt WWW Optimization Study FINAL.Docx 4

15 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 1 TCU of true colour generates mg/l TSS; 1 mg/l polyaluminium chloride generates mg/l TSS; 1 mg/l of polymer (any type) generates 1 mg/l TSS; Based upon these assumptions, the current and future solids projections are presented in the following sub-sections. 2.1 Current Solids Loading The current WTP daily solids production, separated by solid source, is presented in Figure 2-1. It is clear in Figure 2-1 that the coagulant is the most significant contributor to the total solids loading, making-up roughly 70% of the total solids content. The second largest contributor, based on annual average, is the polymer content (flocculant aid and filter aid). The turbidity has the second largest single daily amount of solids content; however this occurs only for a short period during the spring freshet. The coagulant and filter aid doses are adjusted proportional to changes in the blended raw water quality. Figure 2-2 depicts the daily solid loading estimates for the Typical, Worst-Case, and WTP Preliminary Design residuals production. The peak daily solids production for each scenario coincides with the peak raw water flow rate, which occurs in early July. The key observation in comparing the three solids loading scenarios is the difference in the solids produced between July and October. Both the typical and worst case scenarios show solids projections 70%, or greater, than the WTP Preliminary Design Estimates. The other notable trend is the spike in solids production that occurs at the end of May and beginning of June. This spike is due to the changes in the Lake water quality as the facility operates with 100% Lake water during this period. The detailed daily flow, chemical dose, and raw water quality data is provided in Appendix C. Figure 2-1 Typical Scenario - Daily Solids Loading by Source Constituent Solids Loading (kg/d) % Lake Flow May 1st to June 30th Peak Turbidity Period Typical Peak Daily Solids Load of 550 Kg Colour Turbidity Polymers Coagulant Jan 31-Jan 02-Mar 01-Apr 01-May 31-May 30-Jun 30-Jul 29-Aug 28-Sep 28-Oct 27-Nov 27-Dec Rpt WWW Optimization Study FINAL.Docx 5

16 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Figure 2-2 Worst Case and Typical Operation - Daily Solids Loading Solids Loading (kg/d) % Lake Flow May 1st to June 30th Worst Case Peak Daily Solids Load of 632 Kg/d Solids Loading Typical Solids Loading Worst Case Jan 31-Jan 02-Mar 01-Apr 01-May 31-May 30-Jun 30-Jul 29-Aug 28-Sep 28-Oct 27-Nov 27-Dec 2.2 Future Solids Loading Projections The annual and peak daily solids projections for each scenario are been presented graphically in Figure 2-3 and Figure 2-4. The solids projections assume that the overall City water demand grows a rate of 2% per year and that the WTP staff continue operating the facility with a 70 / 30 raw water blend, except during the spring freshet (May 1 st to June 30 th ) when the plant switches to 100% Lake. Inspection of Figure 2-3 reveals that the annual solids loading projections for each scenario essentially parallel one another; where the Typical Operation, Worst Case, and Preliminary Design scenarios show an annual increase in solids loading of between 57 to 60% over the 50 year period. Similarly, the increase in the peak daily solid loadings parallels one another until approximately After which, the Worst Case solids loading projections begin to increase more rapidly than the Typical Operation scenario. The change in peak daily solids production after 2030 for the Worst Case scenario, particularly evident in Figure 2-4, results from the coinciding poor water quality with the peak day flow during the spring freshet. The rapid change in the Typical Operation Scenario is not evident until approximately Rpt WWW Optimization Study FINAL.Docx 6

17 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Figure 2-4 Projected WTP Annual Solids Loading Annual Solids (1000 Kg TSS/yr) Westbench Added to System 70/30 Pre-Design Estimate 70/30 Typical Operation 70/30 Worst Case Condition Year Figure 2-3 Projected WTP Peak Daily Solids Loading Creek flow required during Freshet (2029 Typical Operation and 2027 Worst Case) Maximum Day Solids (Kg TSS/d) Dewatering Capacity (10 hour operation) 70/30 Typical Operation 70/30 Worst Case Condition Year Rpt WWW Optimization Study FINAL.Docx 7

18 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study The existing sludge handling and dewatering equipment is rated for 6 8 m 3 per hour or approximately 160 Kg DS per hour 3. Assuming a typical operating period of 10 hours 4, the existing dewatering equipment can process up to 1600 Kg per day of dry solids. Comparing the on-site treatment capacity to the peak daily solids projections in Figure 2-4, the existing residuals management system has sufficient capacity to meet the projected solids loading, at a minimum, over the next 25 years. After 25 years the Worst Case sludge projection will equal or exceed the WTP s installed dewatering capacity during the peak day event. It should be noted that this exceedance is expected to be an isolated event and the City could manage these peak daily sludge events using the on-site storage tank or by directing the excess sludge to the sanitary sewer. As the frequency of the dewatering equipment operation increases, the City could consider purchasing a second, standby, centrifuge to provide mechanical redundancy. This would allow for un-planned repairs or maintenance of the duty centrifuge without interruption to the residuals management process. Alternatively, the City could divert the sludge to the sanitary sewer when completing maintenance on the single duty centrifuge, provided the AWWTP has sufficient hydraulic and solids loading capacity to manage the WTP sludge. In summary, the existing sludge handling and dewatering infrastructure is adequately sized to process the Typical Operation and Worst Case sludge conditions for the expected 25 year service life of the equipment. 3. BioWin Modelling 3.1 Review of Previous Work & Assumptions The original BioWin modelling work done in 2008 in support of the Penticton AWWTP upgrade was done largely to look at the impacts of return streams on the main biological process, determine projected sludge quantities to be used for design of solids handling processes, and to examine the impact of WTP sludge on the biological process. This model was calibrated using 2008 plant influent and effluent data, and on the whole, proved to be a good representation of the overall plant process. Figure 3-1 illustrates the model configuration used for this work. Figure 3-1 BioWin Process Model Configuration (2008) Filter Return BFP Filtrate Fermenter Return WTP Sludge Digester Supernatant PI Composite PE Composite Raw WW Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6 Cell 7a Cell 7b Tertiary Filter Influent SE Composite Cell 9 Cell 8 Sludge Blanket Primary Sludge to Fermenter WAS 3 The solids loading capacity of the dewatering equipment is based on an average sludge concentration of 2%. 4 Typical WTP staff operating shift is 10 hours. Rpt WWW Optimization Study FINAL.Docx 8

19 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study After the model was calibrated to reflect the 2008 process conditions at the AWWTP, the metal addition (aluminum) influent parameter was varied to better understand the impact WTP residuals would have on the removal of phosphorus at the AWWTP. The variation of the addition of aluminum in the model reflected a number of the different conditions that occurred at the WTP throughout the year, and was based on operating data provided by the WTP Operations Staff. Table 3-1 presents the results from the 2008 BioWin simulations, which are also shown graphically in Figure 3-2. It should be noted that the main period of focus for this study was from January to March. It was during this time that the WTP did not discharge residuals into the sanitary sewer. This was done in an effort to better understand the true phosphorus loads entering the AWWTP, without the influence of aluminum in the sewer. The complete report for this 2008 study is included with this report as Appendix A. Table 3-1 Phosphorous Removal as a Function of PACl Sludge Addition (2008 Study) Mass of Aluminum (kg/d) TP Secondary Effluent (mg/l) TP Final Effluent (mg/l) Ortho P Final Effluent (mg/l) WTP Operating Conditions Coagulant Addition no WTP sludge minimum daily average minimum monthly average monthly average (Jan to Mar) annual average maximum monthly average maximum daily average Figure 3-2 BioWin Process Simulation Results (2008 Study) TP (pre-filtration) Ortho P TP (final effluent) [P] (mg/l) Average Annual Effluent Total P Limit (ORIGINAL Operational Certificate PE 12212) WTP Sludge Discharged to Sewer (kg Al/d) Rpt WWW Optimization Study FINAL.Docx 9

20 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study This exercise provided a clear indication that the presence of excess aluminum in the sewer significantly reduced the concentration of ortho-phosphate prior to reaching the secondary process, and thus provided for a low total phosphorus concentration in the final plant effluent. Based on the modeling results, it appeared that an average day aluminum addition in excess of 20 kg/d in the sanitary system ensured that the effluent total phosphorus remained under the City s previous Operational Certificate level of 0.25 mg/l T-P (monthly average). 3.2 New Modelling Parameters With the change of the WTP s residuals management concept, along with the modifications to the AWWTP s treatment processes, a review of the 2008 BioWin model was undertaken. The model itself remains largely unchanged from the one used prior to the plant upgrade, due mainly to the fact that the biological process remains as it was prior to the recent upgrade. The main changes to model are with the return streams. The filter return flow is much lower than before based on the lower volume of backwash required for the cloth media filters, relative to the old sand filters. The belt filter press (BFP) has been replaced by a centrifuge, and now both the volume and organic loading (BOD, ammonia and phosphorus) of the centrate returning to the plant are higher. Finally, the digester supernatant is no longer a return stream to the process, as thickening in the digester by decanting supernatant is no longer practiced. Once these aspects of the model were confirmed, updated plant influent data was obtained, along with the new WTP residual data outlined in Section plant influent data was used for the modelling exercise as it represents the most recent full year of available data. It was also noted in the review of the 2011 data that the organic load appears to be higher in 2011 than it was in both 2007 and This comparison is outlined in Table 3-2. Based on the increase in influent constituent concentrations, a proportional increase was applied to some of the BioWin model s influent parameters (Table 3-3). Table 3-2 Penticton AWWTP Influent Data Comparison (24-hour composite) Constituent TSS (mg/l) COD (mg/l) Ammonia (mg/l) 21 N/A 27 Ortho-P (mg/l) Table 3-3 Key BioWin Model Influent Data Constituent COD (mg/l) TKN (mg/l) Total-P (mg/l) From this data review, a similar modelling exercise to that done in 2008 was undertaken, with a few variations. In 2008, the modelling exercise only examined the winter period (January to March), where for this modelling exercise, both winter (January to March) and summer (July to September) scenarios were examined to review the impacts of the seasonal nature of the WTP residuals on the AWWTP. The following sub-section outlines the modelling results. Rpt WWW Optimization Study FINAL.Docx 10

21 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 3.3 Summary of Modelling Results The results of the modelling exercise were as predicted, based on the experience gained from our previous study. The results show a sharp decline in total and ortho-phosphorus concentrations with increasing quantities of aluminum being made available in the sanitary system from the WTP residuals. The results from the BioWin simulations are presented in Tables 3-4 and Table 3-5 and shown graphically in Figures 3-3 and Figure 3-4. Table 3-4 BioWin Modelling Results (Winter) WTP Operating Conditions Coagulant Addition Mass of Aluminum (kg/d) Total P Secondary Effluent (mg/l) Total P Final Effluent 5 (mg/l) Ortho P Final Effluent (mg/l) None Minimum Day Minimum Month Average Maximum Month Maximum Day Table 3-5 BioWin Modelling Results (Summer) WTP Operating Conditions Coagulant Addition Mass of Aluminum (kg/d) Total P Secondary Effluent (mg/l) Total P Final Effluent 1 (mg/l) Ortho P Final Effluent (mg/l) None Minimum Day Minimum Month Average Maximum Month Maximum Day Total P Final Effluent based on solids removal efficiency of cloth media filters and BioWin predicted secondary effluent total phosphorus. Rpt WWW Optimization Study FINAL.Docx 11

22 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Figure 3-4 BioWin Process Simulation Results (Winter) TP (pre-filtration) Ortho P TP (final effluent) [P] (mg/l) Average Annual Effluent Total P Limit (Ammended Operational Certificate PE 12212) WTP Sludge Discharged to Sewer (kg Al/d) Figure 3-3 BioWin Process Simulation Results (Summer) TP (pre-filtration) Ortho P TP (final effluent) [P] (mg/l) Average Annual Effluent Total P Limit (Ammended Operational Certificate PE 12212) WTP Sludge Discharged to Sewer (kg Al/d) Rpt WWW Optimization Study FINAL.Docx 12

23 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study It should be noted in Figures 3-3 and Figure 3-4 that the City s amended Operational Certificate shows a new annual average target for total phosphorus. This new value is 0.2 mg/l vs. the previous value of 0.25 mg/l, which was used in the 2008 modelling exercise. Based on the updated organic loadings to the AWWTP, the new modeling results indicate that an average day aluminum addition in excess of 22 kg/d in the sanitary system ensures that the effluent total phosphorus will remain under the City s Operational Certificate level of 0.2 mg/l T-P (monthly average). This value is below the minimum day load coming from the WTP for both winter and summer conditions. It is therefore reasonable to state that there is an excess of aluminum based WTP residuals in the sanitary system that are not providing any additional benefit with respect to the performance of the AWWTP. The impacts of this excess quantity on the AWWTP will be discussed in the following section. 4. Impacts to Wastewater Treatment Plant 4.1 Introduction The presence of water treatment plant residuals in the sanitary system has both benefits and drawbacks with respect to the performance of the City s wastewater treatment plant. The benefit, as noted in the previous section, is a reduced ortho-phosphorus loading to the biological process that results in lower total phosphorus in the final effluent. The impacts can be seen in two ways: increase in the overall solids loading to the plant; and a decrease in the volatile solids content of the resulting sludge. The higher solids loading and decrease in the volatile solids content can reduce the treatment capacity of such unit processes as: primary clarifier; fermenter; bioreactor; DAF; centrifuge; and digester. Table 4-1 highlights the overall impact the water treatment plant residuals have on the incoming plant solids load. Table 4-1 Raw Sewage Suspended Solids Loading Scenario Flow m 3 /d Raw Wastewater TSS Load kg/d Water Treatment Plant Residuals TSS kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 3, Summer (July to September) 14,000 3, Rpt WWW Optimization Study FINAL.Docx 13

24 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study The impact of this solids load can be quantified based on a single major assumption; that being how much of the WTP solids are captured in the wastewater treatment plant s primary clarifiers? Once this is determined, the impacts on the downstream processes will follow. Similar studies undertaken for other facilities have shown the removal rate in the primary clarifiers of WTP sludge to be as low as 20%. This is based upon the fact that WTP residuals are comprised of mostly colloidal material that does not readily settle by gravity. However, this should be coupled with the fact that the length:width ratio of the Penticton AWWTP primary clarifiers is greater than that normally encountered in wastewater treatment plants. Based upon this fact, and in the absence of a volatile solids balance around the primary clarifier, we will assume that the WTP solids settle at a rate of 30%, where the raw wastewater solids settling efficiency will be as noted in the Penticton AWWTP Functional Design Report 63%. 4.2 Individual Unit Treatment Process Impacts Primary Clarifiers The production of primary sludge is noted in Table 4-2. This table takes into account the low settling efficiency of the WTP sludge noted above. Table 4-2 Primary Sludge Production Scenario Flow m 3 /d Raw Primary Sludge TSS Load kg/d Water Treatment Plant Residuals TSS kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 2, Summer (July to September) 14,000 2, Primary Sludge Fermenters The primary sludge loading to the fermenters would show a similar impact to that encountered with the primary clarifiers (Table 4-3). The exception would be the WTP residuals. As the WTP residuals are already bound to the primary sludge feeding the fermenter, the reduction of WTP residual solids would be the same as for the raw fermented primary sludge. In this case, it is 77%, which is the % removal used in the 2008 Functional Design Report. Table 4-3 Fermented Primary Sludge Production Scenario Flow m 3 /d Raw Fermented Primary Sludge TSS Load kg/d Water Treatment Plant Residuals TSS kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 1, Summer (July to September) 14,000 1, Bioreactors The total influent suspended solids depicted in Table 4-1 above estimates a 5% - 11% increase on total daily WWTP solids loading. However, when inert sludge is discharged to a biological treatment system, the long solid retention times required to maintain a nitrifying population of bacteria results in a significant accumulation of inert solids, thereby increasing the mixed liquor suspended solids (MLSS) concentration and total mass although not increasing the volatile suspended solids (VSS) mass. Table 4-4 illustrates this dramatic impact. Rpt WWW Optimization Study FINAL.Docx 14

25 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Table 4-4 Suspended Solids in the Bioreactor Scenario Flow m 3 /d Raw Wastewater TSS Load kg/d Water Treatment Plant Residuals TSS kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 1, Summer (July to September) 14,000 1, The presence of inert suspended solids in the bioreactor will have little impact on air demands, mixing requirements and result in no inhibition of the nutrient removal processes. The waste activated sludge is removed using Dissolved Air Flotation (DAF) thickeners and thus the anticipated increase in load to the DAF would be similar to the increased concentration of MLSS in the bioreactor Dissolved Air Floatation As mentioned in the previous section, the anticipated increase in load to the DAF would be similar to the increased concentration of MLSS in the bioreactor. Therefore, the impact on the suspended solids concentration in the DAF thickener is as follows: Table 4-5 Solids Loading in the DAF Scenario Flow m 3 /d Raw Wastewater Loading Rate kg/d Water Treatment Plant Residuals Loading Rate kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 1, Summer (July to September) 14,000 2, Centrifuges The centrifuge dewaters a combination of primary fermenter/digester sludge and dissolved air flotation sludge. The fermented sludge produced is equivalent to the primary sludge loading minus the solubilized amount due to fermentation and digestion. Table 4-6 summarizes the solids loading due to domestic sewage load and the additional load from the WTP. Table 4-6 Solids Loading in the Centrifuge Scenario Flow m 3 /d Raw Wastewater Loading Rate kg/d Water Treatment Plant Residuals Loading Rate kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 2, Summer (July to September) 14,000 4, Compounding the effects the WTP sludge has on the system capacity, the addition of PACI sludge will reduce the anticipated solids capture and solids cake concentration from the centrifuge. However, this will not be viewed as a Rpt WWW Optimization Study FINAL.Docx 15

26 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study substantial impact as the dewatering already targets a lower solids cake concentration to accommodate the downstream composting operation. Therefore, operations staff will instead concentrate on maintaining a high solids capture with as low of a polymer dosage as possible Digesters The digesters are fed with sludge from the primary sludge fermenters, and as such the anticipated increase in load to the digesters would be similar to that of the fermenters. Therefore, the impact on the suspended solids concentration in the digesters is as follows: Table 4-7 Digested and Fermented Primary Sludge Production Scenario Flow m 3 /d Raw Digested & Fermented Primary Sludge TSS Load kg/d Water Treatment Plant Residuals TSS kg/d Increase due to WTP Residuals % Winter (January to March) 12,500 1, Summer (July to September) 14,000 1, Volatile Solids Content - Biological Processes There are two biological processes at the AWWTP that could be impacted by the discharge of WTP residuals to the sewer system: Primary Sludge Fermentation; and Biological Nutrient Removal. The fermentation of primary sludge should not be significantly impacted by the addition of 2% - 5% increase in solids loading. Additionally, a 2% - 5% reduction in VSS concentration should not significantly impact the fermentation of primary sludge. The Biological Nutrient Removal process is estimated to receive an additional 9% - 20% increase in solids loading and this will produce a similar decrease in VSS concentrations. Four issues result from these changes: WTP sludge will precipitate dissolved ortho-phosphorus in the sewer system and reduce the phosphorus loading on the biological process. As the amounts of WTP sludge are now being discharged on a consistent, daily basis, this will assist the process. However, if there are significant fluctuations due to system demand and more importantly raw water quality, this will create problems at the AWWTP as there will not be sufficient polyphosphate-accumulating organism (PAO) in the plant to use the influent dissolved ortho-phosphorous, thereby resulting in higher effluent discharges. Excessive WTP sludge discharges may reduce the incoming dissolved ortho-phosphorus to concentrations below that required for normal bacterial cell growth. This concentration is estimated to be between 1.0 to 1.5 mg/l ortho-phosphorus. A higher percentage of creek water being used as the source requires higher flocculant dosing requirements at the WTP, which will result in excessive WTP sludge loads to the system. The resultant lack of ortho-phosphorus will stimulate the growth of un-wanted filamentous bacteria in the bioreactor and poor sludge settling in the secondary clarifier will occur. Rpt WWW Optimization Study FINAL.Docx 16

27 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study Increases in Mixed Liquor Suspended Solids in the bioreactor of between 9% - 20% will significantly impact the operation of the secondary clarifiers. Deeper sludge blankets will result and excessive solids retention time in the clarifiers will result in phosphorus re-release. Rapidly changing solids loadings from the WTP will make optimization of the long sludge age biological nutrient removal process more difficult. The growth of phosphorus accumulating organisms in the biological phosphorus removal process requires a relatively consistent load of ortho-phosphorus to the system. This may not be a significant issue when WTP quantities are increasing and influent ortho-phosphorus concentrations are decreasing. However, when WTP quantities are decreasing the biological nutrient removal process will have to quickly adjust. To compensate for this, it is anticipated that the alum addition system at the AWWTP will require higher additional amounts to assist the biological removal process. 4.3 Summary of Impacts and Projected Long Term Impacts The impacts noted in the previous section have been summarized in Table 4-10 below. From a solids loading and volatile solids perspective, the impacts on the various processes range from minor to significant. These impacts mainly relate to reduced capacity of the unit processes, as opposed to any inhibitory or detrimental process operations impact. Table 4-8 Summary of Impacts on AWWTP Processes Unit Process Winter Summer Significance Primary Clarifier Sludge Production 2% increase 5% increase Minor impact Primary Sludge Fermenter Solids Loading 2% increase 5% increase Minor impact Primary Sludge Fermenter VSS Minor impact Bioreactor MLSS 9% increase 20% increase Significant impact Bioreactor VSS Moderate impact DAF Solids Loading 9% increase 20% increase Significant impact Centrifuge Solids Loading 5% increase 15% increase Moderate impact The challenge is being able to forecast what the long term impacts will be with the continued discharge of WTP residuals into the City s sanitary sewer system. The projected 15 year average 6 WTP residuals production is relatively linear and mirrors the projected flow to the AWWTP (Figure 4-1). If this linear trend continues, and the solids addition remains at a constant daily rate, the AWWTP should be able to accommodate this average inert solids load until 2027 when the plant s hydraulic and loading capacity is met. The key term is average with respect to the solids loading. As noted in Section 3 of this report, aluminum/solids concentrations much beyond minimum day to average day loadings provide no additional benefit to the AWWTP with regards to phosphorus reduction. Beyond these levels, the impacts will be reduced process unit capacities as noted in the preceding subsections. In the intervening years, an additional one or two secondary clarifiers and a DAF will need to be added to accommodate the increasing hydraulic and solids load on the plant. A new fermenter may also be required in the intervening years. As noted in the 2008 WTP Sludge Study (Appendix A) and in the BioWin modelling done in conjunction with this study (Figures 3-3. and Figure 3-4), there may be insufficient volatile fatty acid production to 6 15 years was selected as the AWWTP preliminary design report only forecasted flows to Rpt WWW Optimization Study FINAL.Docx 17

28 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study allow for full biological phosphorus removal in the possible absence of WTP residuals-based aluminum in the sewer. This risk should be considered by the City, as it appears to be fairly clear that the WTP residuals are assisting with the removal of phosphorus from the effluent. Were this stream to be discontinued, the City may struggle to meet its total phosphorus limit without having to add greater quantities of supplemental aluminum downstream of the biological process in the form of alum. However, it assumed that this scenario is highly unlikely to occur. The onset of the construction of a new fermenter would be more likely to be brought on by the current deteriorating condition of the existing fermenters. Figure 4-1 WTP Residuals Load vs. AWWTP Flow 35, , Flow (m3/d) 25,000 20,000 15,000 10,000 WTP Flow AWWTP Flow WTP Solids Solids Loading to Sewer (kg/d) 5, Year Okanagan Falls WWTP Residuals Since the 2008 WTP sludge study was completed, an additional aspect to the operation of the AWWTP has been developed. The management of waste solids at the new Okanagan Falls WWTP has been designed based upon trucking fermented primary sludge (FPS) and thickened waste activated sludge (TWAS) as separate loads to the Penticton AWWTP. The intent is to introduce the FPS into the septage receiving process and the TWAS directly into the AWWTP s TWAS vault. An analysis of this approach was undertaken and summarized in a technical memorandum addressed to the Regional District of Okanagan-Similkameen (RDOS) (Appendix B). This concept of operation is scheduled to commence in early 2013 when the OK Falls WWTP is commissioned and in operation. The addition of these two waste streams increases the solids load to the plant by roughly 5%; which is viewed as being relatively negligible with regards to the overall plant operation. These solids will also not contain the same quantity of inert material as the WTP sludge, so will more readily assimilate into the AWWTP s biological processes. In addition to these facts, unlike the WTP sludge stream the costs associated with handling this additional load will be captured in surcharges that will be passed onto the RDOS by the City. Rpt WWW Optimization Study FINAL.Docx 18

29 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 5. Residuals Management Estimated Capital and Operational Costs Selecting the optimum operational strategy to manage for the City s WTP sludge needs to consider the net present value or costs to handle the sludge at both the WTP and AWWTP. The existing infrastructure at the WTP and AWWTP infrastructure can facilitate multiple operational strategies ranging from treating 100% of the sludge at the WTP to diverting 100% to the AWWTP. For the purposes of this we have selected three City wide operational strategies to assist the City with determining the most cost effective approach. This section presents the 20 year net present value costs for the WTP and AWWTP costs of the following three operational strategies to manage the WTP sludge: Scenario 1: No WTP Sludge to the AWWTP includes onsite dewatering of all sludge produced at the WTP. The dewatered sludge is collected in bins and hauled to the City s landfill. Without the aluminum content from the WTP sludge, the AWWTP will require a new fermenter at year one to meet the effluent phosphorous discharge permit requirements. In addition, new secondary clarifiers and a return activated sludge (RAS) pump station will be required at the AWWTP by DAF and Bioreactor upgrades will be triggered by population growth by Scenario 2: Partial WTP Sludge to the AWWTP allows up to 22 kg/d or 142 kg DS/day of WTP sludge to be processed at the AWWTP. The WTP sludge in excess of these values is dewatered at the WTP and hauled to the City s landfill. This scenario is based on maximizing the phosphorus reduction benefits from the WTP sludge aluminum content, while limiting the impacts to the AWWTP unit processes. With the WTP sludge, the AWWTP Fermenter will only require structural upgrades, providing sufficient fermentation capacity through the 20 year assessment period. An initial structural upgrade of the Fermenter is included at year 2013, followed by a more involved upgrade/replacement in The inert solids loading associated with the WTP sludge will precipitate the need to upgrade the secondary clarifiers and RAS pump station by In addition, the capacity of the DAF and the Bioreactors will need to be increased in 2027 to account for the increased suspended solids loading form the WTP sludge. Scenario 3: Full WTP Sludge to the AWWTP is the current operating strategy implemented by the City and assumes 100% of the sludge generated at the WTP is diverted directly to the sanitary sewer and treated at the AWWTP. Similar to Scenario 2, this operating strategy realizes the phosphorous removal benefits of the aluminum content in WTP and will only require the structural upgrades to the fermenter at 2013 and The increase inert solids loading from the WTP sludge will accelerate the timing of the secondary clarifiers and RAS pump station to Similarly, the new DAF and bioreactor will need to be replaced by 2025 to accommodate the increased suspended solids concentration from the WTP sludge. A summary of the annual operating costs and net present value comparisons are discussed in the following subsections. Rpt WWW Optimization Study FINAL.Docx 19

30 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 5.1 Annual Sludge Operating Cost Summary A summary of the annual operating costs for each option is presented in Table 5-1. The table is intended to assist the City assess and allocate the annual operation budgets for the AWWTP and WTP for each operational scenario. Table 5-1 Annual AWWTP and WTP Operating Costs to Manage WTP Sludge Items Annual Operational Costs to Manage WTP Sludge Scenario 1: No WTP Sludge to the AWWTP Scenario 2: Partial WTP Sludge to the AWWTP Scenario 3: Full WTP Sludge to the AWWTP 1.0 AWWTP Dewatering Equipment Costs 1. Labour $ - $9,282 $10, Power and Chemical $ - $12,922 $14, Cake Hauling and Tipping Fees $ - $506 $944 NPV Sub-Total $ - $22,710 $26, WTP Dewatering Equipment Costs 1. Labour $10,830 $5,020 $ - 2. Power and Chemical $14,768 $1,846 $ - 3. Cake Hauling and Tipping Fees $7,644 $3,544 $ - NPV Sub-Total $33,242 $10,410 $ - Total City Operations Cost $33,242 $33,120 $26,320 The following assumptions were used to generate the net present value estimates presented in Table 5-2: Scenario 1 assumes that the fermenter upgrades are complete and therefore the operation impact to the AWWTP is limited; Scenario 2 and 3 include 3.5 and 4 additional dewatering hours per week, respectively, to process the WTP solids loading at the AWWTP; WTP sludge loads are based on the 2012 average values presented in Table 2-2 of the report for Typical Operation conditions; WTP dewatering labour based on batch operation in 10 hour operating intervals. Assumed a total of 4 labour hours required per 10 hour dewatering cycle. Labour rate of $30/hr plus 70% to account for fringe benefits was used for a total labour cost of $51/hr; Unit cost of electricity is $0.08 per kw-hr; Dewatered sludge cake is hauled to the RDOS landfill at an overall cost of $90 per metric tonne 7 ; The centrifuge polymer and electrical costs are assumed to be equal whether the sludge is process at the WTP or the AWWTP. To estimate of annual operating costs the total electrical and chemical cost to operate the centrifuge (either at the AWWTP or the WTP) is estimated to be $71/hr. The annual operating costs presented in Table 5-1 are based on 2012 sludge projections. For budgeting purposes these values will need to be updated based on the allocation year. 7 This cost could be zero as the sludge is acceptable as landfill cover; however thiswould need to be negotiated with the RDOS. Rpt WWW Optimization Study FINAL.Docx 20

31 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 5.2 Net Present Value Comparison A summary of the net present values for each option is presented in Table 5-2. The detailed breakdowns of the net present value costs for each scenario are included in Appendix D. Table 5-2 Net Present Value Comparison of WTP Sludge Management Scenarios Items Net Present Value over 20 Years (2012) 3.0 Advanced Wastewater Treatment Plant.1 New Secondary Clarifiers & RAS Pump Station Scenario 1: No WTP Sludge to the AWWTP Scenario 2: Partial WTP Sludge to the AWWTP Scenario 3: Full WTP Sludge to the AWWTP $2,432,000 $2,630,000 $2,845,000.2 New Fermenter $1,635, Fermenter Rehabilitation - $476,000 $476,000.4 New DAF $308,000 $333,000 $360,000.5 New Bioreactor $2,002,000 $2,166,000 $2,342,000.6 Extra Dewatering Hours - $168,000 $192, Water Treatment Plant 1. Dewatering Equipment Operation - Labour $256,000 $151,000 - Total 20 Year NPV $6,633,000 $5,924,000 $6,215,000 The following assumptions were used to generate the net present value estimates presented in Table 5-2: The secondary clarifier, RAS pump station, and DAF capital costs were taken from 2008 Functional Design Report; The Fermenter costs were taken from an estimate provided to the City as part of their 2012 capital budget; The capital cost for the new bioreactor is based on scaling the Westside RWWTP pre-tender cost estimate. The costs of the bioreactor include concrete, blowers, diffusers and piping. Net present values based on a 20 year period ( ) with a 4% discount rate. Scenario 2 and 3 include 3.5 and 4 additional dewatering hours per week, respectively, to process the WTP solids loading at the AWWTP. The AWWTP dewatering costs include labour with fringe benefits, polymer and power costs; WTP sludge loads are based on the average values presented in Table 2-2 of report for Typical Operation conditions; WTP dewatering labour based on batch operation in 10 hour operating intervals. Assumed a total of 4 labour hours required per 10 hour dewatering cycle. Labour rate of $30/hr plus 70% to account for fringe benefits was used for a total labour cost of $51/hr with 3% price escalation annually; Unit cost of electricity is $0.08 per kw-hr with 3% price escalation annually Centrifuge polymer and electrical costs are equal whether the sludge is process at the WTP or the AWWTP and have therefore been excluded from this analysis. Rpt WWW Optimization Study FINAL.Docx 21

32 AECOM City of Penticton Water and Wastewater Residuals Management Optimization Study 5.3 Summary of Net Present Cost Comparison Scenario 1 results in the highest initial cost and long term capital cost. This option defers the AWWTP DAF and bioreactor capital upgrades to be triggered solely by growth. This financial benefit is offset be the need to complete a major fermenter upgrade in 2013 due to the absence of the WTP sludge in the sanitary sewer. This operational scenario results in the net present cost of the three scenarios over the 20 year period. Scenario 3, the City s current operating strategy, results in the lowest overall operational cost of the three scenarios. With AWWTP currently centrifuging as part of the regular operation and the additional cost to treat the WTP sludge is less than if the sludge was centrifuged at the WTP. This benefit is offset by the WTP solids loading expediting need for the hydraulic and solids loading capacity upgrades of the clarifier, DAF and bioreactor. Scenario 2 offers the lowest net present value by maximizing the benefit of the WTP sludge s aluminum content while limiting the inert solids loading from the WTP sludge to 142 Kg DS/day. The overall operational cost is higher than the other two scenarios due to the duplication of labour resources to dewater at both the WTP and AWWTP. The reduced solids loading allows the deferral of the clarifier, DAF and bioreactor upgrades two additional years than would be required under the current method of operation, or Scenario Conclusions and Recommendations Since the commissioning of the WTP upgrades in 2009, the City has chosen to divert the WTP sludge to the sanitary sewer where it eventually reaches the AWWTP. In the past, this operational strategy has been implemented as the preferred approach because of the lower WTP operational costs as well as the improved phosphorous removal observed at the AWWTP. Results of the net present value assessment confirmed that this operational strategy offers the lowest operational cost between the WTP and AWWTP. However, as a long term operational strategy, diverting all the WTP sludge to the sanitary sewer will accelerate the need to upgrade the hydraulic and solids loading capacity of the AWWTP. This results in a 5% higher total net present cost, including operational and capital discount, then if the AWWTP were to only receive the portion of the WTP sludge necessary to achieve their phosphorous effluent limit of 0.2 mg/l T-P. Based on our assessment of the capital and operational costs the City can continue to divert the WTP sludge to the sanitary sewer until the capacity of the secondary clarifiers is reached, which we expect will happen in the next 3 to 5 years. At such time, we recommend that the City begin treating the WTP sludge at the WTP and divert to sewer only the amount need to satisfy the City s phosphorous effluent limit. This operational approach will offer the City the lowest overall cost solution to manage the WTP sludge. In interim, we recommend that the City continue to monitor the performance of the secondary clarifier; the limiting process infrastructure. When the capacity of the secondary clarifiers is reached the City operating budgets should include provision for the modified operational costs that will be required to dewater and haul the sludge at the WTP and the AWWTP. It should be noted that several variables including changes in raw water quality, equipment failure\downtime, or water and wastewater process upsets could trigger the need to begin processing sludge at the WTP earlier than the identified 3 to 5 year timeframe. We therefore recommend that the City have the infrastructure and operational plan in place to be prepared to process sludge at the WTP, when required. Rpt WWW Optimization Study FINAL.Docx 22

33 Appendix A Technical Memorandum - Water Treatment Plant Sludge Assessment May 2008

34

35 D R A F T T E C H N I C A L M E M O Date: May 5, 2008 Project #: (03) To: Berne Udala, City of Penticton cc: Will Wawrychuk, Earth Tech From: David Lycon, Earth Tech Subject: Water Treatment Plant Sludge Assessment 1.0 BACKGROUND At the City of Penticton s Advanced Wastewater Treatment Plant (AWWTP) one of the most significant impacts to the overall process is the presence of the water treatment plant s (WTP) residuals stream which is discharged to the sanitary sewer. The WTP residuals stream comes from one of two sources; a daily discharge from the bottom of the treatment plant s clarifier, and a larger periodic discharge from the treatment plant s residuals holding basin. The residual is a polyaluminum chloride (PAC) waste stream that varies on a monthly basis depending on which source the water treatment plant is using to produce its treated water. The water treatment plant can draw from either Lake Okanagan or Penticton Creek, and as the proportion of creek water increases, the quantity of PAC sludge being discharged to the sewer also increases. While the presence of the residual aluminum salt in the sewer is helpful in precipitating the ortho-phosphate, there are several operational issues associated with this inorganic stream. This added inert solids loading eventually concentrates as one goes further downstream in both the liquid and solid processing streams, reducing process volume available for biological processes (bioreactor, fermenter, and digester). This is especially noteworthy with respect to the operation of the fermenter, as this additional loading of inert solids reduces the production of volatile fatty acids within the given solids retention time. As part of its scope of service for the Functional Design Phase of the Penticton AWWTP Upgrade Project, Earth Tech has undertaken an analysis to determine what effects the WTP residuals are having on the biological process. It is our initial assertion that it is the presence of this stream that is allowing the City to achieve such low total phosphorous concentrations in their effluent. In an effort to quantify the effect of the WTP residuals on the process, we proposed that for a period of at least six weeks that the presence of the residuals in the sewer be eliminated. To accommodate this work, the WTP only processed lake water to reduce the PAC dosage, and they stored all residual solids on site during this trial. 2.0 BIOWIN MODELING Prior to reducing the flow of residuals to the sewer, a process modeling exercise was undertaken using BioWin 3.0 TM. The specific inputs used for this model are outlined in detail in Section 3 of the Function Design Report (pp. 26 to 28), and the model configuration used for this analysis is illustrated in Figure 1. The metal addition influent parameter was used in this model to simulate the addition of WTP residual sludge into the sewer. This influent parameter can be used to simulate the addition of aluminum in the form of either PAC, alum (both on a concentration and weight percent basis) or free aluminum (on a concentration basis). L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

36 Draft Technical Memo Page 2 Figure 1. BioWin Process Model Configuration Filter Return BFP Filtrate Fermenter Return WTP Sludge Digester Supernatant PI Composite PE Composite Raw WW Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6 Cell 7a Cell 7b Tertiary Filter Influent SE Composite Cell 9 Cell 8 Sludge Blanket Primary Sludge to Fermenter WAS Once the model had been calibrated to reflect the current process conditions at the AWWTP, the metal addition influent parameter was varied to better understand the impacts on phosphorous removal. The variation of the addition of aluminum reflects a number of different conditions that occur at the WTP throughout the year, and was based on operating data provided by the WTP Operations Staff. For example, during the period of interest (Jan to Mar), it was determined that the average mass loading of aluminum discharged to the sewer equated to 27 kg/d. It was also interesting to note that though a higher dosage of coagulant is used in the winter months due to the higher percentage of creek water treated, the overall mass loading is higher in the summer due to the significantly higher treated water flows. Table 1. presents the results from the BioWin simulations, and the results are also shown graphically in Figure 2. Table 1. Phosphorous Removal as a Function of PAC Sludge Addition Mass of Aluminum (kg/d) TP Secondary Effluent (mg/l) TP Final Effluent (mg/l) Ortho P Final Effluent (mg/l) WTP Operating Conditions Coagulant Addition no WTP sludge minimum daily average minimum monthly average monthly average (Jan to Mar) annual average maximum monthly average maximum daily average L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

37 Draft Technical Memo Page 3 Figure 2. BioWin Process Simulation Results [P] (mg/l) WTP Sludge Discharged to Sewer (kg Al/d) TP (pre-filtration) Ortho P TP (final effluent) Average Annual Effluent Total P Limit (Operational Certificate PE 12212) This exercise provided a clear indication that the presence of excess aluminum in the sewer is significantly reducing the concentration of ortho-phosphate prior to reaching the secondary process, and thus providing for a low ortho-phosphate concentration in the effluent. 3.0 REMOVAL OF WTP SLUDGE FROM SEWERS In consultation with both Water Treatment and Wastewater Treatment Plant staff, the practice of discharging the WTP s clarifier underflow and sludge holding basin contents to the sewer was discontinued from January 21, 2008 to March 10, During this time, an extensive sampling program was undertaken to determine how the various unit processes reacted to the removal of this stream. It was thought that the removal of the WTP sludge from the sewer system would have the positive effect of increasing the percentage of volatile suspended solids in the primary sludge entering the fermenters. This in turn could allow for the increased production of short chain volatile fatty acids (VFAs), which would then aid in the biological phosphorous removal process. Prior to the test, it was uncertain what this net result would be with respect to phosphorous removal. In an effort to quantify this, samples of the fermenter overflow were taken weekly and VFA fractionation was done for each sample. The results for acetic and propionic acid are illustrated in Figure 3. The graph shows that throughout the test period, VFA production did not appear to change, even over the transition through five sludge ages in the fermenter. L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

38 Draft Technical Memo Page 4 Figure 3. VFA Production 250 Average Production for Past Ten Years 200 [SCVFA] (mg/l) Jan Jan Jan Jan Feb Feb-08 1-Mar Mar-08 Acetic Acid Propionic Acid As a rule of thumb, the quantity of VFA required for efficient removal of phosphorous from the wastewater stream is between 3 and 6 kg VFA/kg ortho-p removed. Prior to the removal of the water treatment plant sludge, ortho-phosphate concentrations entering the plant averaged 2.5 mg/l (based on 2007 data for the January to March time frame). At an influent flow of 13 ML/d, this equates to approximately 33 kg/d of ortho-p in the influent. Assuming that the overflow from the fermenter is approximately 600 m 3 /d, the required VFA concentration would have to range between 165 and 330 mg/l to achieve an acceptable level of phosphorous removal. Assuming that only the acetic and propionic fractions of the VFA stream are of interest, the historical plant average is 165 and 95 mg/l, respectively for a sum total of 260 mg/l. This falls within the prescribed range noted above for acceptable phosphorous removal. As expected, the removal of the water treatment plant sludge from the sewer increased the concentration of the influent ortho-phosphate, from 2.5 mg/l to an average of 3.7 mg/l. This in turn equated to an influent ortho-p load of 48 kg/d (50% increase). Based on the same fermenter overflow of 600 m 3 /d, the VFA concentration requirement now ranged from 240 to 480 mg/l. As mentioned above, and illustrated in Figure 3, the VFA production did not change appreciably after the removal of the WTP sludge from the sewer system. Based on this fact the available VFA sum of 260 mg/l, though within the prescribed range, was now considered to be insufficient to fully remove the ortho-phosphate from the wastewater. This was confirmed upon reviewing effluent ortho-p and total P concentrations (Figures 4 and 5). L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

39 Draft Technical Memo Page 5 Figure 4. Ortho-phosphate Removal [Ortho-P] (mg/l) Jan Jan Jan-08 2-Feb Feb Feb-08 3-Mar Mar-08 Influent Effluent As the effluent ortho-phosphate is part of the plant s daily sampling and analysis routine, there is quite a bit of data to illustrate the effect of the WTP sludge removal. Figure 4 indicates that the ortho-p removal efficiency began to degrade approximately 18 days after the removal of the aluminum stream from the sewer. In terms of the fermenter and digester operation, this equates to 3 and 1.5 sludge ages, respectively. Based on the sampling data, it is noted that the ortho-p concentration in the digester sludge went up considerably somewhere between January 23 rd and January 30 th (from an average of 10 mg/l to an average of 30 mg/l). However, the ortho-p concentration in the fermenter overflow remained relatively constant throughout the test period. The sum total of the return streams account for some of the net increase in effluent ortho-p, and it is assumed that the lack of VFA to maintain acceptable bio-p removal is also an equal contributor to this phenomena. With respect to total phosphorous, the trend is not as apparent (Figure 5.) as that illustrated for ortho-p. This is due mainly to the smaller data set which makes it more difficult to see a readily visible trend. It does appear that total phosphorous concentration in the influent stream does increase almost immediately after the WTP sludge is removed from the system, and overall there is an increase in total phosphorous in the effluent in and around the same time that the ortho-p concentrations begin to increase. L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

40 Draft Technical Memo Page 6 Figure 5. Total Phosphorous Removal [Total P] (mg/l) Jan Jan Jan-08 2-Feb Feb Feb-08 3-Mar Mar-08 Influent Effluent 4.0 PHOSPHOROUS UPTAKE POTENTIAL TEST An additional test was conducted during the absence of water treatment plant sludge to determine what the uptake potential is of the phosphorous accumulating organisms (PAOs). Under normal operating conditions, the ortho-phosphate concentration in the effluent is nearly zero, suggesting that the PAOs could have additional assimilative capacity. As a means of determining this, the following test was conducted approximately every three days during the testing period: 1. a 500 or 1000 ml sample of MLSS leaving the final aerated zone of the bioreactor is collected; 2. ortho-phosphate in the form of potassium ammonium phosphate is added to the MLSS sample to raise the dissolved ortho-p concentration to 10 mg/l; 3. the sample is then aerated for 15 minutes; and 4. once complete, the residual ortho-p in the sample is measured. L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

41 Draft Technical Memo Page 7 The excess ortho-p removal capability, or phosphorus uptake potential is then defined as the difference between the initial ortho-p concentration of 10 mg/l and the residual ortho-p remaining after the 15 minutes of aeration. The results of this analysis are illustrated below in Figure 6. It appears that there is an immediate drop in phosphorous uptake potential when the WTP sludge was removed from the system. After February 12 th, the excess ortho-p removal capability began to decrease further, which was in and around the time that the ortho-p started to show up in the digester sludge and final effluent. Figure 6. Phosphorous Uptake Potential [Ortho-P] (mg/l) Jan Jan Jan-08 2-Feb Feb Feb-08 3-Mar CONCLUSIONS AND RECOMMENDATIONS Based on the results of the analyses conducted during the removal of the WTP sludge, and as confirmed by the BioWin model, there is a strong correlation between the presence of aluminum in the sewer and the removal efficiency of ortho-p at the AWWTP. Once the aluminum from the WTP sludge is removed from the sewer system, there is a marked reduction in phosphorous removal efficiency. Towards the end of the trail, the total phosphorous concentration in the final effluent began to approach 1.5 mg/l, which is close to the not to exceed level of 2.0 mg/l in the plant s Operational Certificate. L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

42 Draft Technical Memo Page 8 In order to move towards a solution that both provides reliable phosphorous removal and elimination of the incidences where the inert solids load to the plant is excessive, a two phased approach should be utilized. The first approach is a relatively inexpensive option that is tied into the proposed expansion of the water treatment plant. An automated diversion valve should be installed downstream of the centrifuge feed pump that will allow thickened water treatment plant residuals to be diverted to the sewer when called for by the AWWTP. This constant, gradual loading will ensure that the influent ortho-phosphorous remains low, if required, and will ensure that the biological processes are not suddenly overloaded with inert solids. The second approach should involve the enhancement of the fermentation process at the AWWTP. If VFA production could be increased by 50%, the requirement for water treatment plant sludge would be minimized/eliminated. This would also involve the use of a process that will produce a fermenter supernatant (overflow) that will be sufficiently high in VFAs and low enough in total suspended solids to allow for introduction directly into the bioreactors anaerobic zones. As suggested in the Functional Design Report, this would entail that the fermenters be run in a static thickening mode. This can be achieved by either retrofitting the existing fermenters with a new thickening mechanism, or by constructing a new, purpose built static thickening fermenter. L:\work\113000\113040\03-Report\WWW Optimization Study\WTP Sludge Tech Memo (Rev 0).doc

43 Appendix B RDOS WWTP Sludge Memorandum

44

45 AECOM 3292 Production Way, Floor tel Burnaby, BC, Canada V5A 4R fax Memorandum To Alfred Hartviksen, P.Eng. RDOS Page 1 CC Ian Chapman City of Penticton Will Wawrychuk, P.Eng. AECOM Subject From Reviewed By DRAFT Okanagan Falls WWTP Sludge Hauling Evaluation (Rev1) Susan Spruston, P.Eng. David Lycon, P.Eng. Date February 7, 2012 Project Number Introduction The existing Okanagan Falls wastewater treatment plant is due to be replaced by a new tertiary WWTP. Construction of the new plant has recently begun and is scheduled for completion in During the design of the new WWTP, an evaluation of the sludge management process showed that it would be more cost effective to haul the residual sludge to the Penticton AWWTP for further processing (dewatering and composting) until such time that the Okanagan Falls plant is expanded to meet Stage 2 design flows. At that time it is anticipated that on-site dewatering and grit removal will be added to the process. The Regional District of Okanagan-Similkameen (RDOS) made a formal request to haul sludge to the Penticton AWWTP in a letter to the City of Penticton dated October 27, The City of Penticton Council considered this request on December 6, 2010, and approved the idea in principal subject to a number of conditions and criteria to be evaluated by a qualified professional. As such, AECOM has been retained by the RDOS to review the technical and financial impacts associated with hauling the residual sludge from the Okanagan Falls WWTP to the Penticton AWWTP. This technical memorandum documents the findings of the evaluation. 2. Sludge Volumes and Solids Load It is proposed that two residual streams from the Okanagan Falls WWTP be trucked to the Penticton AWWTP; the fermented primary sludge (FPS) and the thickened waste activated sludge (TWAS). To minimize the potential for re-release of ortho-phosphate, it was further proposed that FPS and TWAS be transported to the AWWTP separately. In addition, both the TWAS and FPS storage tanks are equipped with coarse bubble aeration systems to mix and aerate the contents of the tanks just prior to pumping out for sludge transport. The predicted sludge volumes from the Okanagan Falls WWTP are summarized in Table 1. Based on a population growth rate of 2.5% (AECOM 2010) these sludge flow rates are expected to be reached in 2035 or sooner if significant developments are added to the system. Year 1 (2013) volumes are estimated to be 56% of the Stage 1 design flows. (Sludge hauling may begin in the fall of 2012, however the first full year of sludge transfer is expected to be 2013.) Draft Sludge Hauling Memo_ Rev 1

46 Page 2 Sludge Hauling Study Technical Memorandum Table 1. Okanagan Falls WWTP Sludge Volume Stage 1 Design (Year 2035) Fermented Primary Sludge Average 29 Fermented Primary Sludge Max. Month 34 Thickened Waste Activated Sludge Average 41 Thickened Waste Activated Sludge Max. Month 48 Volume, m 3 /wk The expected solids concentrations of the two streams are expected to be similar to that of Penticton s, therefore the volume can be used for comparing the quantities of sludge at the two plants. Figure 1 illustrates the estimated average sludge volumes for both the Okanagan Falls WWTP and the Penticton AWWTP in Year 2013 and Year Figure 1. FPS and TWAS Sludge Sludge Flowrate, m 3 /wk OK Falls FPS, Avg Penticton FPS, Avg OK Falls TWAS, Avg Penticton TWAS, Avg Note will be the first full year of sludge transfer, construction of the Okanagan Falls WWTP is scheduled form commissioning / completion in 2012 and sludge tranfer shall begin at that time. As illustrated, the sludge from the Okanagan Falls WWTP is between 5-8% by volume when compared to the sludge streams at the Penticton AWWTP. 3. Capacity of Penticton AWWTP Solids Handling Processes As previously noted, the two streams will be trucked separately to the Penticton AWWTP to minimize the impact on the treatment process. The FPS shall be discharged into the septage receiving station, and the TWAS will be discharged directly into the TWAS tank at the AWWTP. A schematic of the AWWTP process incorporating these two streams is provided in Figure 2. Draft Sludge Hauling Memo_ Rev 1

47 Page 3 Sludge Hauling Study Technical Memorandum Figure 2. Penticton AWWTP Process Flow Diagram Okanagan Falls Thickened Waste Activated Sludge Okanagan Falls Thickened Fermented Primary Sludge Draft Sludge Hauling Memo_ Rev 1

48

49 Page 4 Sludge Hauling Study Technical Memorandum 3.1 Septage Receiving The septage receiving station of the Penticton AWWTP was installed in 2008, replacing the RDOS receiving station at the Campbell Mountain Landfill. The new septage station includes a truck unloading bay and mechanical equipment for septage screenings. Septage haulers discharge waste through a 100mm (4inch) line, and the septage then flows through a rock trap to a septage screen. The rock trap is an IPEC separator designed to remove large rocks and debris protecting the downstream equipment. The septage screen is a Parkson Helisieve Plus with 6mm round openings designed to remove solids including rags, rocks and plastics prior to introducing the septage into the plant process. Incoming flows are managed through feedback of flow and level to the drivers so that they can optimize unloading speeds. The screenings then drop into a bin for disposal and the screened septage is discharged into the septage vault. The rated capacity of the screen is 38 L/s. AWWTP operations staff note that the system operates as intended. The contents of the septage vault are pumped directly to Digester 2 using a progressive cavity pump, installed in 2008 as part of the septage project. Pumping septage to the Digester is completed manually by the operators as required, approximately once a week. Overall, the capacity of the septage receiving station is sufficient to handle the volume of FPS from Okanagan Falls. However, with the increased use of this system it may be prudent to purchase a back-up septage sludge pump to provided redundancy for the existing sludge pump. It was noted, that alternative conveyance/storage options can be used if the septage pump is out of service. The total number of septage loads for the past 3 years is provided in Table 2. It is anticipated that hauling FPS from Okanagan Falls will add an additional 4 truck loads per week in Year 1 (2013). Operations staff noted that traffic associated with haulers has not been a problem, and the additional volume of trucks from the Okanagan Falls haulers are not anticipated to be an issue. Table 2. Penticton AWWTP Septage Year No. Hauled Waste Loads No. Of Okanagan Falls Sludge Loads Total No. Of Loads 2013 (Estimate) 448* 205** 653 * Based on average number of loads in three previous years, assumes no growth in hauled waste. ** Based on average sludge production values of 17m 3 /wk FPS and 23 m 3 /wk TWAS in Year Digestion Fermented primary sludge is digested in two completely mixed anaerobic digesters. The combined active volume of the two digesters is 2,880m 3, an equivalent 14 day HRT at current loading. The addition of Okanagan Falls FPS will add an incremental load to the system, also resulting in an incremental increase to biogas production. No modifications to the digestions system are required to accommodate the Okanagan Falls FPS. One potential difference in the quality of the sludge from the Okanagan Falls WWTP, is that there is no grit removal at the Okanagan Falls, therefore there may be some grit in the sludge. Grit can accumulate in digesters and cause premature wear to pumps. However, since the volume of Draft Sludge Hauling Memo_ Rev 1

50 Page 5 Sludge Hauling Study Technical Memorandum Okanagan Falls sludge is small relative to the total volume of sludge at the AWWTP the potential impact of the grit is deemed acceptable. 3.3 TWAS Holding Tank The TWAS holding tanks have an active volume of 250m 3. The contents of the TWAS tanks are aerated intermittently to maintain aerobic conditions in the tank. TWAS is pumped from the TWAS holding tanks to the dewatering centrifuges. The TWAS storage is sized to provide 3 days of storage under maximum month loading conditions in the summer. Discharging two trucks of Okanagan Falls TWAS loads (maximum number of trucks to arrive in a three day period), into the TWAS holding tanks will decrease the minimum storage time to 2.8 days at maximum month design flows. The only modification required to the system is the addition of a new tie-in point to allow the sludge haulers to discharge Okanagan Falls TWAS directly into the TWAS tank (see Figure 4, in Section 4.1). The proposed location is the west side of the dewatering building. 3.4 Sludge Dewatering Centrifuges are used to dewater blended TWAS and digested FPS. The centrifuge dewatering system is sized to process 12m 3 /hr, operating a maximum of 38hrs per week. The existing system will be able to handle the additional load from Okanagan Falls sludge without any modification. The only impact will be an incremental increase in operating run time and polymer use. The increase will be linear to the increased amount of sludge, for example a 8% increase in sludge will generally equate to a 8% increase in run time and polymer usage. As previously noted there will be no grit removal at the Okanagan Falls WWTP and therefore there is a increased risk of wear on the centrifuge equipment. However, as also noted, the volume of sludge from Okanagan Falls is low and therefore the relative quantity of grit is acceptable. 3.5 Impact on the Liquid Stream The impact on the Penticton AWWTP liquid stream is attributed to the additional load of the centrate return stream from the centrifuge dewatering process. However, this load is small relative to the influent loading to the plant. BOD and TSS recycle stream loads from Okanagan Falls sludge are estimated to be between % of plant influent. The ammonia load in the centrate will also increase, however the quantity is negligible. 3.6 Compost Facility The Penticton compost facility provides additional processing for the dewatered sludge from the AWWTP. The compost facility is located at the RDOS landfill site approximately 7km from the AWWTP. The process uses static pile aeration and screening, to produce a Class A biosolids. The biosolids are sold from the site to the public. The facility operates under the BC Organic Matter Recycling Regulation for operations under < 20,000 metric tonnes produced. Currently the facility is operating at approximately 30% capacity. Also, the recent implementation of centrifuge dewatering has reduced the volume of sludge Draft Sludge Hauling Memo_ Rev 1

51 Page 6 Sludge Hauling Study Technical Memorandum transferred from the AWWTP to the compost site. Therefore, the additional sludge from OK Falls will not require any modifications to the composting process. 4. Cost Implication 4.1 AWWTP Capital Improvements The following capital improvements are recommended to accommodate the discharge of Okanagan Falls waste sludge into the AWWTP process. A new tie-in point to receive TWAS and discharge the sludge directly into the TWAS storage tanks located under the dewatering building. The proposed tie-in point will be located on the West side of the dewatering building. A new curb and drain is recommended to direct any spillage during unloading back into the TWAS tank. The pipework shall go through the wall and a magmeter will be installed in the dewatered sludge pump room adjacent to the wall (Figure 3). The pipework will drop TWAS either directly down into TWAS Tank 1 located under the pump room, or into TWAS Tank 2 located North of Tank 1. Estimated cost of the Tie-in is $16,000 including construction drawings and administration Purchase of a shelf spare septage sludge pump. Equipment cost $18,000 Figure 3. TWAS Connection Sketch Flowmeter Isolation Valve To TWAS Tank 2 To TWAS Tank AWWTP Operating Costs The processing of sludge from the Okanagan Falls WWTP at the Penticton AWWTP will result in incremental operations cost increases. Therefore the service charge to Okanagan Falls should reflect these actual costs and can be calculated by assigning a percentage of each cost account to Draft Sludge Hauling Memo_ Rev 1