st. george water pollution control plant optimization study

ST. GEORGE WATER POLLUTION CONTROL PLANTOPTIMIZATION STUDY

TECHNICAL MEMORANDUM

SCREENING-LEVEL ASSESSMENT OFSLUDGE MANAGEMENT ALTERNATIVES

January 2012Our File: 110-003

GAMSBY AND MANNEROW LIMITEDCONSULTING PROFESSIONAL ENGINEERS

GUELPH – OWEN SOUND – KITCHENER – LISTOWEL – EXETER

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ST. GEORGE WPCP OPTIMIZATION STUDYTECHNICAL MEMORANDUM – SCREENING LEVEL ASSESSMENT OFSLUDGE MANAGEMENT ALTERNATIVES

TABLE OF CONTENTS

1.0 INTRODUCTION .......................................................................................................................... 1

2.0 BACKGROUND ............................................................................................................................ 1

3.0 DESCRIPTION OF EXISTING SLUDGE MANAGEMENT SYSTEM...................................... 2

3.1 DESCRIPTION OF SLUDGE MANAGEMENT SYSTEM – ST. GEORGE WPCP ............................ 23.2 DESCRIPTION OF SLUDGE MANAGEMENT SYSTEM – PARIS WPCP ...................................... 3

4.0 HISTORICAL SLUDGE DATA.................................................................................................... 5

5.0 SOLIDS MASS BALANCE........................................................................................................... 7

6.0 SCREENING-LEVEL ASSESSMENT.......................................................................................... 9

6.1 EVALUATION FRAMEWORK.................................................................................................. 96.2 DESCRIPTION OF PROCESS ALTERNATIVES......................................................................... 10

6.2.1 THICKENING .......................................................................................................... 106.2.2 STABILIZATION ...................................................................................................... 116.2.3 DEWATERING......................................................................................................... 136.2.4 THERMAL DRYING ................................................................................................. 156.2.5 INCINERATION........................................................................................................ 156.2.6 STORAGE ............................................................................................................... 166.2.7 ULTIMATE DISPOSAL ............................................................................................. 16

6.3 EVALUATION OF PROCESS ALTERNATIVES......................................................................... 16

7.0 RECOMMENDATIONS.............................................................................................................. 20

REFERENCES ......................................................................................................................................... 21

LIST OF TABLES

Table 3.1 Summary of Sludge Management Facilities at St. George WPCP

Table 3.2 Summary of Sludge Management Facilities at Paris WPCP

Table 4.1 Summary of Historical Plant Data (Annual Averages)

Table 4.2 Monthly Sludge Haulage Volumes

Table 4.3 Metals Concentrations in Aerobic Sludge (mg/kg on a dry solids basis)

Table 6.1 Typical Sludge Yield for Selected Treatment Processes

Table 6.2 Screening-Level Evaluation of Sludge Management Alternatives

LIST OF FIGURES

Figure 1 Process Flow Diagram – Existing Sludge Management System

Figure 2 Solids Mass Balance Diagram (April 2010 Average Values)

Figure 3 Process Flow Diagram – New Plant

Gamsb y and Manne row L im i t e d . Gue l p h , K i t c h e ne r , L i s t owe l , Owen Sound255 Woodlawn Rd W. Suite 210, Guelph, ON N1H 8J1 519-824-8150 fax 519-824-8089 www.gamsby.com

ST. GEORGE WATER POLLUTION CONTROL PLANTOPTIMIZATION STUDY

TECHNICAL MEMORANDUMSCREENING-LEVEL ASSESSMENT OF

SLUDGE MANAGEMENT ALTERNATIVES

1.0 INTRODUCTION

Gamsby and Mannerow Ltd. (G&M) together with process specialists from Conestoga-Roversand Associates (CRA), University of Western Ontario (UWO), and Huber EnvironmentalConsulting (HEC) were retained by the St. George Landowners’ Group to complete anOptimization Study of the St. George Water Pollution Control Plant (WPCP).

This Technical Memorandum identifies and assesses proven technologies applicable to sludgeand biosolids management at small municipal wastewater treatment plants. This Memo isintended to serve as a desk-top screening-level evaluation only and will form part of the finalOptimization Study document. Other Technical Memoranda were prepared by the project teamto cover other aspects of the overall Optimization Study.

2.0 BACKGROUND

The St. George WPCP is located at 43 Victor Boulevard in the Village of St. George and servesthe community of St. George by means of a gravity collection system. The plant serves anestimated population of 2,300 people. The community is primarily residential with somecommercial and institutional land uses. Consequently, the waste stream from the community isconsidered to be typical municipal domestic wastewater. The plant is owned by The County ofBrant and operated under contract by the Ontario Clean Water Agency (OCWA).

The St. George WPCP is an extended aeration activated sludge plant with a rated hydrauliccapacity of 1,300 m3/d and a design peak flow rate of 3,412 m3/d. The plant operates underMinistry of Environment Certificate of Approval No. 9415-6CQKH5 dated June 24, 2005.

The original plant was constructed in 1981 as a package extended aeration plant with a ratedhydraulic capacity of 1,063 m3/d. Main plant processes include grit removal, comminution,aeration, coagulant feed system for phosphorous removal, secondary clarification, disinfection bychlorine, tertiary media filtration, and aerobic sludge digestion. The plant also includes a back-updiesel generator. The effluent receiving stream is an unnamed tributary of Fairchild Creek.

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ST. GEORGE WPCP OPTIMIZATION STUDYTECHNICAL MEMORANDUM – SCREENING-LEVEL ASSESSMENT OFSLUDGE MANAGEMENT ALTERNATIVES

The plant was rerated in 2005 to a capacity of 1,300 m3/d as a result of upgrades that includednew fine bubble diffusers, a third air blower, inlet channel grinder, conversion from gaschlorination to liquid sodium hypochlorite, dechlorination facilities, and a larger aerobicdigestion facility. The new aerobic digester is a stand alone rectangular tank with approximately280 m3 of capacity and a dedicated positive displacement blower with a back up supplyconnection from the main plant aeration system. The digester has a grid of coarse bubblediffusers that operate continuously. The original aerobic digester was converted to a sludgeholding tank.

3.0 DESCRIPTION OF EXISTING SLUDGE MANAGEMENT SYSTEM

3.1 DESCRIPTION OF SLUDGE MANAGEMENT SYSTEM – ST. GEORGE WPCP

The sludge management system at the St. George WPCP is a manual operation with control ofindividual process steps based primarily on periodic grab sample measurements of mixed liquorconcentration in the aeration tank and operating experience. Sludge is intermittently wasted tothe sludge holding tank based on maintaining a target solids concentration in the aeration tank(typically no greater than 4,000 mg/L). The sludge holding tank is operated manually withsupernatant decanted into the aeration tank most weekday mornings for 2 to 3 hours each time.Thickened waste activated sludge is transferred from the sludge holding tank to the new aerobicdigester approximately once every two to three weeks. The sludge transfer operation generallyinvolves five steps; wasting from the clarifier to the sludge holding tank, settling in the sludgeholding tank, decanting of supernatant to the aeration tank, brief mixing of settled sludge in thesludge holding tank, and sludge transfer from the sludge holding tank to the digester. Theaeration grid in the sludge holding tank is only used briefly between the decanting and sludgetransfer steps to mix the contents of the settled sludge prior to pumping to the digester.

Table 3.1 summarizes equipment associated with sludge management at the St. George WPCP.

Table 3.1 Summary of Sludge Management Facilities at St. George WPCP

Process Unit Description Capacity / Dimensions EquipmentSludge Holding Tank Annular segment of

package plant4.3m SWD84 m3

Coarse bubblediffuser header, airlift pump

Sludge Transfer Submersible sludge pump 35 L/s at 9.6m TDH FlygtDigester Blower Positive displacement

blower in self-containedoutdoor package

11 kW blower1000 m3/hr at 98 kPa

Aerzen ModelGM-15-L

Aerobic Digester Rectangular concrete tankwith full-floor coarsebubble diffuser grid

10.5m x 6.0m x 4.3mSWDvolume of 280 m3

Stamford ScientificInternationalAeration system

Sludge Loading Submersible sludge pump 12.6 L/s

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3.2 DESCRIPTION OF SLUDGE MANAGEMENT SYSTEM – PARIS WPCP

The overall sludge management system at the Paris WPCP is controlled manually although thepolymer blending and feed system is automated. Internal processes for the dewatering centrifugeare also automated. Specific steps in the sludge management system are under capacity at theplant and this constrains operation of upstream processes. Partially digested sludge from theSt. George plant is periodically hauled away to the Paris WPCP for further processing.Combined sludge from the two plants is digested aerobically, dewatered by chemicalconditioning, and followed by centrifuge dewatering. The dried sludge cake is hauled to abiosolids holding facility, then ultimately disposed on agricultural lands as a soil amendment.

Current operating practice results in waste activated sludge from St. George being subject toaerobic digestion at both plants. Plant operators reported that typical solids content of digestedsludge at the Paris plant is in the range of 1.5%. Digested sludge is chemically conditioned priorto delivery to the centrifuge with a coagulant (BASF Chemicals - Zetag 8868FS). The polymer isdiluted on site and injected into the sludge feed line ahead of the centrifuge. Polymer is mixedwith plant effluent water (ratio not known) and fed into the centrifuge at a typical rate ofapproximately 17 L/min. Digested sludge is fed to the centrifuge at a typical rate ofapproximately 6 L/s or 360 L/min. It is noted that there is very little contact time betweenpolymer injection and the centrifuge inlet.

The plant typically uses approximately 1 m3 of raw polymer every 10 days, which equates to acumulative total of 60-hours run time due to the centrifuge being able to operate for only6 hours/day because of limited on-site storage capacity for dewatered biosolids. The centrifugebuilding has space for only one collection bin for collection of dewatered biosolids.

The centrifuge bowl rotates at 3250 rpm and has an inside diameter of at 450 mm whichcorresponds with a centrifugal force of approximately 1,468 g’s. Plant operators report that thetypical solids concentration from centrifuge is in the range of 18-22%. The percent solidsincreases to approximately 25% at the off-site biosolids drying facility through passive dryingand gravity draining. Typical operation involves two to three bins of dried cake being hauledaway (by Westlake) each week to the County biosolids drying/storage facility. Bin volume is15 m3. The biosolids drying building has inside dimensions of approximately 20m x 30m. It isdifficult to pile biosolids too high due to the low angle of repose from polymer addition.

Critical steps in the overall biosolids management system that are currently under capacityinclude on-site storage or containment of dewatering biosolids and off-site storage of dewateredbiosolids. This impacts process operations of the St. George plant.

Dried biosolids are ultimately disposed on agriculture land through long-term arrangements withlocal farms. No land spreading occurs during winter. Acceptable timing for land spreading isfrom spring to fall only but is also dependent on weather, crop rotation, planting times, andharvest times. Sludge wasting is reduced in winter at St. George due to limited downstreamprocessing and storage capacity as described above.

Table 3.2 summarizes equipment associated with sludge management at the Paris plant.

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Table 3.2 Summary of Sludge Management Facilities at Paris WPCP

Process Unit Description Capacity / Dimensions EquipmentAerobic Digester 3-stage digester 1st stage – 790 m3

2nd stage – 790 m3

3rd stage – 800 m3

Coarse bubblediffuser grid

Digester Blowers Three positivedisplacement blowers, twoduty, one standby

each blower rated at 30 kWdelivering1500 m3/hr at 64 kPa

Aerzen

Sludge Transfer Transfer digested sludgeto dewatering centrifuge

Two pumps each rated at 25m3/hr at 14 TDH

Polymer System System rated at 5.6 kg/hr drypolymer feedPolymer dosing pump rated at18.75 L/hrHigh energy activation chamberPolymer batching tank – 2 m3

US FilterPolyBlend system

Conditioned Sludge Feed Positive displacement(progressive cavity) pump

Centrifuge feed pump rated at1,125 L/hr at 60m TDH1.1 kW 1,750 rpm

Seepex

In-line Grinder Centrifuge inlet VogelsangDewatering Centrifuge Solid bowl centrifuge Rated at 375 kg/hr dry solids

Size : 450mm dia., 3250 rpmbowlMotors : 70 kW bowl, 15 HPscrew

Alfa LavalModel : Aldec506

Dewatered SludgeConveyor

Shaftless screw conveyor Spirac

Sludge Cake HoldingParis WPCP

Enclosed building at ParisWPCP

One - 15m3 haul-away bin none

Biosolids StorageParis Landfill Site

Enclosed building Building approx. 20m by 30mStorage capacity of 1,200 cu.m.

none

Figure 1 presents a process flow diagram of the current sludge management system consisting ofprocess steps at both plants.

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4.0 HISTORICAL SLUDGE DATA

Historical plant data for calendar years 2004 through 2009 were obtained from OCWA and aresummarized in Table 4.1. Relevant data from the April 2010 sampling program is also presented.

Table 4.1. Summary of Historical Plant Data (Annual Averages)

YearEffluent Flow (m3/day) WAS Flow (m3/day) WAS Conc. (mg/L)

Average StandardDeviation Average Standard

Deviation Average StandardDeviation

2004 813 107 23 212005 822 87 23 192006 843 98 19 162007 812 82 22 152008 864 116 27 132009 860 101 26 15

April 2010 827 91 9,692 3,642

The historical annual average (2005 to 2009) of hauled sludge cake to the Brant CountyBiosolids Storage Facility ranged from 825 to 950 tonnes. This represents total combineddewatered sludge from both the St. George and Paris treatment plants. Approximately 1,274tonnes of sludge cake were hauled to the Facility in 2010 but the County indicated that this wasan abnormal year due to periods of high strength sewage at the Paris plant that contributed tohigher biosolids production. The facility typically receives 2 to 3 bins per week and the bin ratedvolume of 15 cu.m. (20 cu. yards).

Table 4.2 summarizes monthly volumes of aerobically digested sludge that is hauled from the St.George plant to the Paris plant.

Table 4.2. Monthly Sludge Haulage Volumes

MonthVolume (m3)

2006 2007 2008 2009 2010

January 258 258 301 258 129February 0 0 129 310 129

March 228 258 258 215 76April 129 258 129 301 205May 301 129 129 86 129June 0 129 215 430 86July 258 129 258 86 129

August 476 215 430 129September 200 129 190 86

October 0 215 215 129November 0 0 172 235December 258 129 0 258

Annual Totals 2108 1849 2426 2523 883*

Weekly Averages 41 36 47 49 --Daily Averages 6 5 7 7 --

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Notes* Based on seven months of operation.

Although the above data set is limited, it indicates an apparent increasing trend in sludge haulagevolumes, which is likely a result of overall development of the Village and correspondingincrease in sewage flows over the same period. The average annual flow profile indicated in theprevious table, including the lower value in 2007, is reflected in the average annual sludgehaulage data presented in the table directly above.

Table 4.3 summarizes digested sludge quality in terms of metals content from the St. GeorgeWPCP.

Table 4.3. Metals Concentrations in Aerobic Sludge (mg/kg on a dry solids basis)

Parameter Sym.O. Reg.267/03

Typ.Values1

Typ.Values2 2006 2007 2008

Arsenic As 170 10 4.3 0.30 0.30 0.50Cadmium Cd 34 10 3.4 0.052 0.24 0.42

Cobalt Co 340 30 6.5 0.12 0.10 0.91Chromium Cr 2,800 500 80 2.03 1.90 18.8

Copper Cu 1,700 800 550 8.09 7.8 58.7Mercury Hg 11 6 1.4 0.018 0.005 0.01

Molybdenum Mo 94 4 6.5 0.42 0.10 0.85Nickel Ni 420 80 12 0.60 0.47 3.95Lead Pb 1,100 500 48 0.95 0.30 2.45

Selenium Se 34 5 2.7 0.30 0.30 0.30Zinc Zn 4,200 1,700 506 8.35 8.6 74.10

Notes1 U.S EPA2 OMAFRA and MOE – Survey of Municipal Sewage Biosolids Quality 2002Metals concentrations for 2006 through 2008 are annual averages from OCWA Annual Reports. Data for the 2009operating year was not available.Average Zinc concentration in 2008 based on two data points: 8.20 mg/L in June and 140 mg/L in July.

Review of sludge metals content in the above table confirms that the quality of biosolids fromthe St. George WPCP is consistently low in metals and toxicity, reflecting the predominantlyresidential nature of the raw sewage to the plant. All values are below typical values reported inliterature for domestic wastewater and well below the limits stipulated in Regulation 267/03.

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5.0 SOLIDS MASS BALANCE

The following section presents a simplified solids mass balance based on results of the detailedsampling program conducted at the St. George WPCP during April 2010. See Figure 2 for aconceptual diagram of the solids mass balance. The basic concept is illustrated as follows:

The following are calculations using values from the sampling program.

Solids Mass Balance CalculationsBased on Average values for April 2010 Sampling Period

Influent Mass QuantitiesAverage Flow (m3/d) = 827Average Influent BOD-5 (mg/L) = 129Average Influent TSS (mg/L) = 169 (measured after grit channels)Average BOD Loading (kg/d) = 107Average TSS Loading (kg/d) = 139

Effluent Mass QuantitiesAverage Effluent BOD-5 (mg/L) = 3.0Average Effluent TSS (mg/L) = 2.3Average BOD Loading (kg/d) = 2.5Average TSS Loading (kg/d) = 1.9

Secondary ProcessAverage AT MLSS (mg/L) = 3,670Average AT MLVSS (mg/L) = 2,727AT Volatile Fraction of Solids = 0.74Biomass Yield Y (g VSS/g COD) = 0.4 (g biomass produced/g substrate consumed,

assumed value for domestic sewage in EAAS)Mass VSS produced in AT (kg/d) = 43 based on BOD-5

Solids entering systemfrom all streams

Solids produced withinall processes

Solids dischargedfrom all streams

Solids destroyed withinall processes

solids accumulated

(assumed equal to zero forsteady state conditions)

+

+

+

equals

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(86 based on volatile fraction of COD)TSS that must be wasted (kg/d) = 58 based on BOD-5

(86 based on volatile fraction of COD)Waste flow to holding tank (kg/d) = 56Waste flow to holding tank (m3/d) = 15

Sludge Holding TankDecant to Aeration Tank (m3) = 17 weekdays onlyAverage decant flow (m3/d) = 12Decant TSS concentration (mg/L) = 4,350Decant VSS concentration (mg/L) = 3,050Tank Volatile Fraction Solids = 0.70Estimated Fraction VSS Destroyed = 0.04Average decant mass flow (kg/d) = 53Estimated VSS Destroyed (kg/d) = 2Transfer to Digester (m3) = 67 once every 3 weeks on averageAverage flow to Digester (m3/d) = 3Sludge TSS concentration (mg/L) = 22,000Average mass to Digester (kg/d) = 70

Aerobic DigesterDigester Average TSS (mg/L) = 23,652Digester Average VSS (mg/L) = 16,190Digester Volatile Fraction Solids = 0.68Estimated Fraction VSS Destroyed = 0.06Estimated VSS Destroyed (kg/d) = 4Digester Supernatant Flow (mg/L) = n/a (Plant operators do not practice digester decant

back to aeration tank as this requires shutting off theaeration grid for settling, which results in cloggedaeration diffusers).

Digester Supernatant TSS (mg/L) = n/a

Sludge Hauling2009 Annual Report (m3) = 2523Solids Hauled in April 2010 (m3) = 205Avg. TSS concentration (mg/L) = 23,652 (April 2010)Average Daily Mass (kg/d) = 162 (April 2010)

Overall Plant Summary :Total Solids in Influent = 139 kg/daySolids Generated = 56 kg/daySolids added (ferric chloride coag.) = 18 kg/dayTotal Solids into System = 213 kg/day

Total Solids in Effluent = 1.9 kg/daySolids destroyed in Holding Tank = 2 kg/daySolids destroyed in Digester = 4 kg/daySolids Hauled Away = 162 kg/dayTotal Solids Leaving System = 170 kg/day

% Difference between Mass in and Mass out = -20% unaccounted (loss)

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6.0 SCREENING-LEVEL ASSESSMENT

6.1 EVALUATION FRAMEWORK

One of the approaches to optimize any sludge management strategy at a municipal wastewatertreatment plant is to select core treatment processes that minimize sludge yield at the source.Treatment processes that produce a healthy biomass with good settling, thickening, anddewatering characteristics are also preferred.

The following table summarizes reported sludge yield values for common treatment processesused at municipal wastewater treatment plants.

Table 6.1. Typical Sludge Yield for Selected Treatment Processes

Core Treatment Process Sludge Yieldkg TSS/kg BOD-5 removed

Conventional Activated Sludge (CAS) 0.85Extended Aeration Activated Sludge (EAAS) 0.80

Biological Nutrient Removal (BNR) 0.65Sequencing Batch Reactor (SBR) 0.80

Membrane Bioreactor (MBR) 0.70Integrated Fixed-Film Activated Sludge (IFAS) 0.65

Sources:1. Ministry of the Environment, Design Guidelines for Sewage Works, 20082. Wastewater Engineering: Treatment and Reuse, Metcalf and Eddy, 20033. Wastewater Treatment Plants, Qasim, 19994. Design of Municipal Wastewater Treatment Plants, WEF and ASCE, 1992

Inorganic solids removed from the treatment plant such as screenings and grit that are interceptedand removed at the headworks are not included in this report. This document presents ascreening-level assessment of appropriate treatment technologies for processing and ultimatedisposal of organic solids, specifically waste activated sludge (WAS) and scum that are removedor separated from the wastewater treatment system at the secondary clarifier.

There are a wide variety of solids processing steps and technologies available for municipalwastewater treatment plants. Principal operations involved in sludge treatment along withvarious technologies and methods established that were selected for evaluation for the St. GeorgeWPCP are as follows:

1. Thickening• gravity thickening• flotation thickening• rotary drum thickening• gravity belt thickening

2. Stabilization• aerobic digestion• anaerobic digestion• alkaline stabilization

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• composting3. Dewatering

• chemical conditioning• centrifugation• filter press• sludge drying beds

4. Drying• thermal drying

5. Incineration6. Storage7. Ultimate Disposal

• land application• landfilling• sold as a marketable product

A general description of each process is presented below. Processes that were selected forevaluation were considered most appropriate for the quantity and nature of biosolids produced atthe St. George plant. Consideration was also given to accommodating ultimate planned growthof the community.

6.2 DESCRIPTION OF PROCESS ALTERNATIVES

6.2.1 Thickening

Thickening is a process of increasing the solids fraction of sludge by separating and removing aportion of the free (i.e. not bound within solid floc) liquid. Physical unit processes are typicallyused to thicken undigested sludge. Reduction of the liquid portion reduces the volume of sludgeto be processed in all subsequent sludge treatment steps. In general, performance of mostthickening methods, including the ones discussed below, are sensitive to the quality of the feedsludge.

Gravity ThickeningThe existing sludge holding tank essentially functions as a gravity thickener. The tank isoperated as a sludge settling tank with manual intermittent decant of supernatant and occasionaltransfer of thickened sludge to the aerobic digester. Although the existing tank is equipped with acoarse bubble diffuser grid, it is only used briefly following decanting in order to completely mixthe settled sludge prior to transfer to the digester. Sampling conducted for the OptimizationStudy indicates that the sludge holding tank achieves an increase in total solids content fromapproximately 1% to approximately 2%.

Gravity thickening tends to be used for primary sludges or mixtures of primary and wasteactivated sludges. Gravity thickening vessels should be equipped with a collector mechanismsimilar to a clarifier to collect and remove settled sludge and floating scum. The existing sludgeholding tank is not equipped with such a mechanism as it was designed originally to function asa holding tank only.

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Flotation ThickeningDissolved air flotation (DAF) thickening involves introduction of a clear liquid stream that issaturated with compressed air into the waste activated sludge stream. Waste activated sludge(WAS) is generally less dense than primary sludge and therefore can readily be thickened byfloatation as opposed to settling. The clear liquid stream is typically plant effluent water andcompressed air is injected into a pressurized feed line to the DAF tank. Waste activated sludgemixed with dissolved air in solution enters the base of an open DAF tank and rapidlydepressurizes to atmospheric pressure and the air is released into the tank contents as a stream offine bubbles. The rising bubbles intercept sludge particles, carrying them to the surface where thefloated sludge is skimmed off by a scraper mechanism into an effluent channel for furthertreatment such as stabilization. DAF systems can achieve thickened solids concentrations of 3%to 5% without polymer addition, and 4% to 6% with polymer addition. DAF performancedepends primarily on sludge characteristics (especially SVI, lower is better), air-to-solids ratio(typically 2% to 4%), solids loading rate, and polymer application. For the St. George WPCP,this process is expected to produce thickening in the range of 3% to 4.5% of WAS. Clarifiedsubnatant from the DAF is returned to the start of the biological treatment process.

Rotary Drum ThickeningRotary drum thickeners typically consist of a steel drum with a series of slowly rotatingcylindrical mesh screens. Polymer addition is often part of rotary drum thickening to conditionthe sludge to create flocs and improve dewatering characteristics. Feed sludge is thickenedthrough physical straining with thickened sludge retained on the surface of the screens whilewater drains through the screens to a sump. Drained water is typically returned to the start of thebiological process while thickened sludge is transferred to the next sludge treatment such asstabilization. Rotary drum thickeners should be equipped with a spray backwashing system,variable frequency drive to optimize rotational speed, and interchangeable screens. Literaturereports that rotary drum thickeners can increase solids content of waste activated sludge from atypical value of 1% solids to a range of 2.5% to 3.5% with solids recovery greater than 90% withchemical conditioning.

Gravity Belt ThickeningGravity belt thickeners typically consist of a slow moving porous belt over which sludge isdistributed from an inlet distribution box to separate sludge solids from free water. There are aseries of wiper blades that concentrate the sludge, increase the retention time, and direct ittowards the outlet. As with other mechanical dewatering processes, polymer feed of the influentsludge improves dewatering performance and is recommended. The belt is driven by sprocketsand the belt is washed on the return pass while drainage and wash water are collected in anunderdrain for return to the head of the biological process. Literature reports that gravity beltthickeners can dewater activate sludge to 3% to 6% solids concentrations (higher with polymeraddition) with solids recovery rates greater than 90%.

6.2.2 Stabilization

Stabilization refers to the process of reducing pathogenic and odour causing organisms andsubstances in sludge, as well as reducing the potential for stabilized sludge to subsequentlydecompose and putrefy. These nuisance processes are related to the organic (i.e. volatile) fractionof solids and consequently the primary objective of sludge stabilization is to eliminate as muchvolatile organics in the sludge as practical and maintain environmental conditions that prevent

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these organisms from surviving and proliferating. Stabilization also reduces the volume of sludgeto be handled, improves dewatering characteristics, and in some cases can produce methane gasfor use as an energy source.

Aerobic DigestionThe St. George WPCP and Paris WPCP currently practice aerobic stabilization of wasteactivated sludge from their secondary clarifiers. Aerobic digestion is a common methodology forstabilization and mass reduction of waste activated sludge at small extended aeration plants(capacity up to 17,000 m3/day). Aerobic digestion by definition requires an adequate air supplyand this is often provided with an aeration system similar to an aeration tank, with aerationproviding oxygen for biomass energy and synthesis as well as to mix the contents of the reactor.A typical aerobic digestion process operates at a very low food-to-micro-organisms ratio suchthat micro-organisms are in the endogenous phase where they consume their own cell tissue toobtain energy. This is the mechanism which results in reduction of the organic (i.e. volatile)fraction of solids.

Aerobic digesters should be designed to provide 45 days solids retention time (SRT) includingSRT within the upstream biological treatment process. Aerobic digestion capacity shouldtypically be in the range of 0.25 to 0.40 m3 per m3 of influent wastewater. Volatile suspendedsolids (VSS) reduction of 20% to 25% can be realized at SRTs in the range of 40 to 50 days. Ifthickening is performed prior to digestion, the volume of digester tankage can be reduced inapproximate proportion to the increase in solids concentration from the WAS level.

Anaerobic DigestionAnaerobic digestion is one of the most well-established methods of sludge stabilization and massreduction used in the municipal wastewater treatment industry, particularly at larger plants(capacity greater than 17,000 m3/day). Single stage anaerobic digestion typically consists ofmixed reactors with no air or oxygen supply. Two-stage mesophilic (temperature range of 30 ºCto 38 ºC) anaerobic or “high-rate” digestion has a primary digester that is heated and mixedfollowed by a secondary digester that is unheated and unmixed.

Anaerobic digesters typically are covered tanks which facilitate capture and beneficial reuse ofmethane gas that the process generates. Well operated anaerobic digesters achieve destruction oforganic matter as well as sulphates. The primary processes in an anaerobic reactor are hydrolysis(decomposition in the liquid phase), fermentation or acidogenesis [formation of soluble organicacids and short chain volatile fatty acids (SCVFA)], and methanogenesis (microbial conversionof SCVFA’s to methane and carbon dioxide).

Alkaline StabilizationAlkaline stabilization is a chemical-based method of sludge stabilization where the pH of thesludge is raised to at least 12 for a minimum contact time in order to create an environment thatinactivates micro-organisms and pathogens so that bacteria and viruses cannot survive orreplicate. Mixing is required to bring the solids into contact with the chemical and create ahomogenous mixture. Occasionally, addition of supplemental heat is incorporated into thisprocess. Due to the nature of this stabilization method, there is no associated reduction in thequantity of organic matter (i.e. no volatile solids destruction) but rather an increase in the totalmass of solids due to chemical addition. Therefore, downstream sludge processing steps mustaccount for this inherent increase in sludge quantity as well as change in chemical nature.

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Hydroxide chemicals such as lime (calcium or potassium hydroxide) are commonly used. Inorder to achieve stabilization of municipal WAS, the mixture of solids and chemical should bemaintained at a pH of at least 12 for a period of at least 72 hours.

CompostingComposting is a relatively simple low-tech method of aerobic sludge stabilization that usesnatural decomposition processes. Composting is suited to dewatered sludges that are placed inpiles or windrows that are periodically turned over or gently mixed to achieve a combination ofaerobic and anaerobic natural decomposition. Natural aerobic decomposition can achievetemperatures within the pile or windrow in the pasteurization range of 50 ºC to 70 ºC. Amoderate level (20% to 30%) of volatile solids reduction can be achieved if these temperaturescan be maintained for at least 72 hours as pathogenic substances are converted to carbon dioxideand water. Feed sludge may require an amendment or bulking agent to facilitate thedecomposition processes. The final product should be biologically stable with minimal odourand suitable as a soil amendment. A well-operated composting facility can achieve up to 50%mass reduction, although the final product volume will be similar to the feed volume due toreduction in density and addtion of bulking agents.

The end use of composted material or humus is regulated in Ontario by the Canadian FoodInspection Agency (CFIA) under the Fertilizers Act 1985. MOE prepared a reference documentfor establishing and operating composting facilities; Interim Guidelines for the Production andUse of Aerobic Compost in Ontario. Design and operation of composting facilities must includebuffer zones, storage requirements, leachate collection and treatment, and odour and vectorcontrol measures.

6.2.3 Dewatering

Sludge dewatering is used to reduce the moisture content of sludge, consequently reducing thevolume of material to be handled in subsequent treatment steps, including transport and ultimatedisposal. Dewatering goes beyond thickening described above to reduce the proportion of floc-bound and capillary water in sludges. Sludge dewatering is primarily a physical unit processalthough chemical conditioning of stabilized sludge is often used to enhanced sludge dewateringcharacteristics. It is noted that phosphorus removal chemicals such as ferric chloride, which isused at the St. George plant, will reduce allowable sludge loading rates and result in a dewateredsludge cake with lower solids content due to the presence of a coagulant chemical in the sludge.Dewatering typically follows the stabilization process.

The capacity of mechanical dewatering facilities should be sufficient to avoid accumulation inupstream thickening and stabilization processes. Otherwise, alternative/supplemental wet sludgestorage capacity must be provided. Ventilation, flushing water, overhead hoists, and adequatesurrounding space for maintenance should be provided for mechanical dewatering equipment.

Chemical ConditioningAlthough chemical conditioning is not specifically a dewatering method, it is included here as itis a common pre-treatment step ahead of dewatering to enhance the performance of manydewatering technologies in the municipal wastewater treatment industry. Metal salts, lime, andpolymers are common chemical conditioners. Chemical conditioning is employed to coagulatesolid particles and release absorbed water. The type of sludge to be dewatered is the most

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important factor in selecting the type and dosage of chemical conditioner. Polymers are the mostcommon chemical conditioners used for centrifuge and belt filter press dewatering. Pilot testingis recommended in order to select the most appropriate chemical in conjunction with theproposed dewatering technology and ultimate disposal method.

In all applications, thorough mixing of the conditioning chemical with the sludge is critical.Aerobically digested sludge from the St. George and Paris plants undergoes chemical pre-treatment ahead of a dewatering centrifuge at the Paris plant. The chemical conditioner used is acationic (positively charged) polymer, Zetag 8868FS, which is a coagulant that forms floc inmunicipal sludges. Sewage sludges tend to exhibit a net negative charge which makes theparticles stable and repel each other, thus resisting flocculation into larger solids that facilitateseparation.

CentrifugationCentrifuges are widely used in the municipal wastewater treatment plants for sludge dewateringand a solid bowl decanting centrifuge is used at the Paris plant to dewater digested sludge fromthe St. George and Paris plants. Dewatering centrifuges such as the one at the Paris plant use theprinciple of centrifugal force in a horizontally-mounted rotating cylindrical bowl to separatesolid particles and floc from water under the influence of centrifugal forces generated byrotation. Inside the rotating bowl is a helical screw to direct and compress solids to one of thevessel while liquid (centrate) is drained to the opposite end, and directed back to the start of thetreatment process. Bowl length-to-diameter ratio, rotational speed, and bowl flow pattern are keyvariables in equipment selection. Solids content of 20% to 25% and solids capture of 90% to95% can be achieved using centrifuges on stabilized waste activated sludge with chemicalconditioning. Centrifuge performance is very much dependent on sludge characteristics,particularly sludge volume index (SVI). Centrifuges are being increasingly used for sludgethickening as well.

Centrifuge capacity is affected by sludge temperature, which is relevant to the St. George andParis plants since these plants are relatively small and both employ aerobic digestion in opentanks. As temperature decreases, sludge viscosity increases, thereby reducing effective centrifugecapacity. Centrifuge equipment should be selected for the lowest expected operating temperature.

Filter PressThere are two common types of filter presses widely used at municipal wastewater treatmentplants; belt-filter presses and plate-filter presses. The principal difference between the twotechnologies is that plate filter presses operate at much higher pressures and consequently canachieve much high solids content in the filter cake although plate filter presses are more energyintensive. It is standard practice to apply chemical conditioning to sludge prior to being fed to afilter press to enhance performance.

Belt-filter presses for dewatering are similar to that described above for thickening. Theygenerally consist of a gravity drainage section followed by a low pressure or compression sectionfor further dewatering, and a shear section where the belts pass around rollers in a serpentinepath. Porous filter clothes circulate on a conveyor with the pressure section including rollers thatsqueeze the sludge for additional dewatering. Sludge cake solids concentrations in the range of12% to 20% can be achieved. Filtrate is returned to the influent while dried filter cake iscollected in a hopper for further processing and/or final disposal.

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Plate-filter presses use a series of parallel plates mounted on a common frame to mechanicallydewater conditioned sludge under high pressure. Conditioned sludge is fed into the spacesbetween each plate, and a hydraulic piston applies pressure of 700 kN/m2 to 1550 kN/m2 (100 psito 225 psi) to the plate. Filtrate is captured and returned to the plant influent, while dried filtercake is captured in a container for further processing and/or final disposal. Plate filter presses canachieve high solids content in the range of 45% to 70%.

Sludge Drying BedsSludge drying beds are often used at small plants where there is available space and favourableclimate. Beds are typically shallow outdoor cells where thin layers of digested sludge are spreadfor gravity draining, evaporation and solar drying of the sludge in exposed shallow cells. Bedsmay be lined with granular material such as sand or an impervious bottom (e.g. paved) with anunderdrain system. Chemical conditioning can significantly reduce drying time in sludge dryingbeds.

Although sludge drying beds are better suited to warm dry climates, they can be a suitable back-up dewatering option for plants in Southern Ontario in emergency situations or on a temporarybasis if mechanical dewatering systems are out of service.

6.2.4 Thermal Drying

Sludge drying refers to methods used for volume and weight reduction of sludge with solidscontent of end product often exceeding 90% and is typically in granular or dry pellet form asopposed to dewatered sludge which tends to be the consistency of wet soil. There are variousmethods of heat transfer that have been used, including hot air convection, indirect orconduction, and infra-red radiation drying.

6.2.5 Incineration

Incineration refers to high temperature thermal oxidation of dewatered sludge resulting in asignificant reduction in mass and volume. The heat value of organic matter present in sludge isreleased through the combustion process. A supplemental fuel source such as natural gas(methane) or fuel oil is required for this process. The required fuel depends largely upon the typeof sludge and the degree of conditioning and dewatering used prior to incineration. Typically, aminimum solids concentration of 30% is required for sludge to sustain burning on its own. Endproducts are carbon dioxide, water and a relatively small quantity of dry ash.

Incineration can result in the greatest reduction of sludge volume and total destruction of organicand toxic compounds, but involves high capital and operating costs, complex operation, and theneed to address potentially hazardous air emissions from the combustion process. The nature ofincineration makes this a relatively expensive and complex system to construct and maintain.There are very few incinerators in operation in Ontario for sludge reduction and they are locatedat large urban centres where economies of scale exist.

Brant County currently does not practice this step in their existing sludge and biosolidsmanagement system for the St. George or Paris plants. This step is not considered to beapplicable to these plants and consequently will not be evaluated further.

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6.2.6 Storage

Stabilized and dewatering sludge from municipal wastewater treatment plants should not exhibitproblems with odours, attraction of vectors or further putrefaction. Sludge management systemsrequire a storage component for stabilized dewatered sludge prior to ultimate disposal, especiallyfor use as a soil amendment on agricultural lands. Options for sludge storage include coveredstorage buildings, sludge storage lagoons, and tanks or basins. If ultimate disposal of stabilizeddewatered sludge is landfilling, the capacity of the storage step can be minimized. Currently,Brant County stores biosolids (stabilized dewatered sludge) at an enclosed storage facility priorto ultimate land disposal as a soil amendment.

Storage for land application is required due to strict conditions for land disposal including timeof year, climate and weather conditions, planting and harvest times, and availability of land.Under Regulation 267/03, MOE and OMAFRA require a minimum storage capacity forstabilized sludge (i.e. biosolids) of 240 days per year to accommodate seasonal disposalrequirements (i.e. no application during periods of frozen ground) and inclement weather. It isnoted that the angle of repose of stabilized and dewatered sludge can be affected by priorchemical conditioning which may reduce the stable vertical height and side slopes of a pile ofsludge, increasing the footprint of sludge storage facilities.

Design of biosolids storage facilities must consider upstream sludge treatment processes andinclude redundancy and firm capacity as well as contingency measures if facilities are out ofservice, such as an alternative storage location. The capacity of storage facilities should besufficient to avoid accumulation in upstream dewatering processes. Other design considerationsfor enclosed sludge storage facilities include ventilation, proximity to sensitive land uses,collection and treatment of leachate, prevention of run-on and runoff drainage, prevailing winddirection, odour and vector control, control and containment measures to prevent contaminationof local land and groundwater, and expected height that biosolids can safely be piled (slump).

6.2.7 Ultimate Disposal

Options that are considered applicable for ultimate disposal of stabilized dewatering sludge(biosolids) from the St. George WPCP is application to agricultural land as a soil amendment,land filling, or sale as a marketable product such as fertilizer. The County currently has approvedarrangements with local farms for land application of biosolids. Co-disposal of sludge withmunicipal solids waste may allow solids concentrations as low as 3%. Biosolids used as landfillcover materials require further processing such as stabilization and high solids content (typicallyat least 18%).

6.3 EVALUATION OF PROCESS ALTERNATIVES

Evaluation of process alternatives was based on the following criteria:

• System performance• Biological treatment process and corresponding sludge characteristics• Treatment of recycle/decant/filtrate/centrate streams• Capital cost

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• Operational cost• System energy requirements• End of use or ultimate disposal method• Operational complexity• Plant size and economies of scale• Adjacent land use• Environmental impacts• Nature of sludge (e.g. metals content)• Contingency planning

Alternatives that offer a high level of performance while minimizing capital and operating costs,and therefore life cycle costs, were favoured. System energy requirements are a contributingfactor to operating costs as well as environmental impact and ecological footprint of the plant.The current end use for biosolids from the St. George and Paris plants is agricultural landapplication, and this is a key consideration in the evaluation process. The County and OCWAhave expressed their preference for systems that are relatively simple and operationally robust.The St. George and Paris plants are relatively small so processes that do not require economiesof scale to be supported are considered more appropriate.

The St. George WPCP is located within 250 metres of residential land use while residentialdevelopment surrounds the Paris plant. Therefore, systems that minimize nuisance noise andodour emissions as well as truck traffic for sludge hauling will be favoured. Currently, thevillage of St. George is almost entirely residential with no large industrial discharges to the plant.Therefore, the sludge is expected to continue to have low metals content similar to historicalvalues. Paris does have a small portion of industrial flow including some food processingindustries. Although recycle and decant stream from sludge thickening, dewatering, andstabilization processes may be relatively small hydraulic load, they can represent a significanthigh strength load, especially in terms of nitrogen. The scheduling of the waste stream operationsmust be coordinated with the main liquid train treatment processes so that these high strengthloads can be assimilated without causing process upsets. Regardless of which processes areultimately selected for sludge management, a contingency plan for sludge management should bein place in case of system failure or process upset.

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ST. GEORGE WPCP OPTIMIZATION STUDYTECHNICAL MEMORANDUM – SCREENING-LEVEL ASSESSMENT OF SLUDGE MANAGEMENT ALTERNATIVES

Table 6.2. Screening-Level Evaluation of Sludge Management Alternatives

Process Description Typical Performance Advantages Disadvantages OperationalRequirements

PotentialEnvironmental

ImpactsCapital Cost Operating

Cost

Thickening

Gravity Thickening Relatively low solids concentration(~ 2%).

Commonly used at small plants.Simple operation, polymer additioncan be incorporated to improve solidsseparation.

Current tank has no scraper /skimmer mechanism, cannot beretrofitted due to tank shape.Possible odour problems in warmweather.

Low operationalrequirements.

Low energy use Low Low

Dissolved Air Flotation (DAF) Good results, solids concentrations of 3%to 4.5%, solids capture of 80% to 85%,higher with polymer addition.Polymer addition typically incorporated toimprove performance.

Widely used, well established method.Reliable, flexible operation.Can accommodate growth, plantexpansion.

Pilot testing recommended fordetailed design.Equipment must be installed in abuilding.

Moderate operator skilllevel required.Typical polymerrequirement: 2 kg to 5kg/dry tonne.

Moderate energy use Moderate Moderate

Rotary Drum Thickening (RDT) Good results, solids concentrations of3.0% to 4.0%, solids capture of 80% to85%, higher with polymer addition.Polymer addition typically incorporated toimprove performance.

Limited use.Reliable, flexible operation.Can accommodate growth, plantexpansion.




Gravity Belt Thickening Good results, solids concentrations of 3%to 6%, solids capture of 80 to 85%, higherwith polymer addition.Polymer addition typically incorporated toimprove performance.

Widely used, well established method.Reliable, flexible operation.Less energy intensive than DAF’s andRDT’s.Can accommodate growth, plantexpansion.




Stabilization

Aerobic Digestion Moderate VSS destruction.Moderate pathogen reduction.Moderate odour potential.Moderate potential to putrefy.

Common well-established method atsmall plants.Relatively simple operation.

High energy use for aeration andmixing.

Low High energyconsumption foraeration and mixing.

Moderate Moderate

Anaerobic Digestion Moderate VSS destruction.Moderate pathogen reduction.Moderate odour potential.Moderate potential to putrefy.

Well-established method but limiteduse at small plants.Beneficial use of captured methanegas.

More complex operation thanaerobic digestion.

Moderate Potential fuel sourcefrom methane gas.

High High

Alkaline Stabilization No VSS destruction.High pathogen reduction.Moderate odour potential.Moderate potential to putrefy.

Good pathogen destruction.Good odour control.Results in nutrient-rich product.

Results in an increase in totalsolids to be handled.No organic matterassimilation/reduction.

Moderate Chemical feed andhandling facilitiesrequired.Low energy use.

Moderate Moderate

Composting Moderate VSS destruction.Moderate pathogen reduction.High odour potential.High potential to putrefy.

Relatively simple naturally-basedprocess.Environmentally friendly process.Produces usable product for soilamendment.

Requires addition of a bulkingagent such as wood chips, leaves.Volume of compost producedtypically grater than volume ofsludge.High potential for nuisanceodours.

Low Relatively low energyrequirements.Potential odours.

Low Low

Dewatering

Chemical Conditioning Recommended common pre-conditioningstep to each dewatering method.

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ST. GEORGE WPCP OPTIMIZATION STUDYTECHNICAL MEMORANDUM – SCREENING-LEVEL ASSESSMENT OF SLUDGE MANAGEMENT ALTERNATIVES

Process Description Typical Performance Advantages Disadvantages OperationalRequirements

PotentialEnvironmental

ImpactsCapital Cost Operating

Cost

Centrifugation Cake Solids: 20% – 25%.Solids Capture: 90% to 95%(with chemical conditioning).

Well established method.Suitable for small municipal plantswith domestic sewage.Higher solids concentration and solidscapture than gravity thickening.Can accommodate growth, plantexpansion.

Energy intensive.Requires bench or pilot testing toverify design.

Moderate Moderate energy use.Chemical feed andhandling facilitiesrequired.

Moderate Moderate

Filter Press (Belt) Cake Solids: 12% – 20%.Solids Capture: 85% to 95%(with chemical conditioning).

Well established method.Suitable for small municipal plantswith domestic sewage.Higher solids concentration and solidscapture than gravity thickening.Can accommodate growth, plantexpansion.

Energy intensive.Requires bench or pilot testing toverify design.

Moderate Moderate energy use.Chemical feed andhandling facilitiesrequired.

Moderate Moderate

Sludge Drying Beds Variable performance based on weatherconditions and chemical conditioning.

Simple low-tech operation.Potential use as a temporary oremergency back-up dewateringmethod.

Well suited to warm dry climate.Significant space requirements.

Low Low energy use.Chemical feed andhandling facilitiesrequired.

Low Low

Thermal Drying

Thermal Drying Cake Solids: up to 90%. Significantly reduced volume of solidsto handle.

Expensive and complexoperation.

High High energyconsumption.

High High

Incineration Near total destruction of volatile solidswith small quantity of ash remaining.Requires relatively high feed solids (min.30%).

Near total reduction of solid mass.Near total destruction of organic andvolatile matter.

Expensive and complex system tooperate and maintain.Poorly suited to small plants dueto lack of economies of scale.

Very High Emissions fromcombustion processmust be captured,scrubbed.Small quantity of inertash remaining forultimate disposal.

Very High Very High

StorageCovered building Passive drying and gravity draining can

increase solids content a few percentagepoints.

Simple low tech system. Does not easily accommodateincrease in product, buildingtypically requires expansion.Biosolids must be well stabilizedand dewatered to avoid nuisanceodours and putrefaction.

Low Low Moderate Low

Ultimate Disposal

Land Application Existing method. Have valid MOE Certificate ofApproval.Established method with approveddisposal sites.

Inherent limitation on applicationrates and times impact upstreamprocesses.

Low Energy use fortransport andapplication.

Moderate Moderate

Landfilling Possible contingency method if anapproved site is available.

Must identify an approved site. Low Energy use fortransport.

Low Low

Sold as a Marketable Product Potential revenue source that couldoff-set processing, packaging, andmarketing costs.

Requires a high quality endproduct and high degree of publicacceptance.

Requires other skillsbeyond typical biosolidsskill set.

Packaging andmarketing.

Moderate Potentialrevenuesource

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7.0 RECOMMENDATIONS

1. From the Technical Memorandum on Screening-Level Assessment of Biological TreatmentAlternatives: Convert the core biological treatment process at the St. George WPCP fromextended aeration activated sludge (EAAS) to biological nutrient removal (BNR) based onthe anoxic/oxic (AO) or Modified Ludzack Ettinger (MLE) process. A primary purpose ofthis conversion is to minimize the amount of sludge produced in the biological treatmentprocess (i.e. at the front-end of the system).

2. Retain the existing sludge holding tank, which functions as a gravity thickener. Also retainthe existing aerobic digester and digested sludge loading facilities for tanker trucks.

3. Provide a thickening step between the existing sludge holding tank and the existing aerobicdigester to increase the solids content of WAS from a range of 1% to 2%, to a range of 3%to 4.5%. This would result in a corresponding proportional decrease in the quantity of sludgeto be handled in each subsequent sludge management step. Based on review of appropriatethickening methodologies, the recommended thickening method is either a rotary drumthickener or a DAF system. Drainage water from the thickening step would be returned tothe start of the aeration tank.

4. Increase capacity in the overall sludge management system at off-site facilities toaccommodate expansion of the St. George WPCP. Specifically, additional storage capacityfor dewatered sludge must be provided at the Paris plant, and additional off-site storage ofdewatered biosolids must be provided at the Brant County sludge storage facility.

5. Continue with current practice of off-site processing for subsequent dewatering, storage, anddisposal steps of digested sludge produced at the St. George WPCP. This has the advantagesof using existing facilities at the Paris WPCP, Brant County storage site, and approved landdisposal sites. This concurs with the recommended strategy in the Biosolids ManagementStrategy Class EA completed by the County in 2002. It is not considered economically oroperationally viable to establish dedicated facilities for these sludge processing steps at theSt. George WPCP property.

Figure 3 presents a proposed process flow diagram for a new plant described above, includingsludge management upgrades.

All of which is respectfully submitted.

GAMSBY AND MANNEROW LIMITED

Per: Per:

Paul McLennan, P.Eng. Grant Parkinson, P.Eng.

CONESTOGA ROVERS AND ASSOCIATES

Per:

Andrew Lugowski, P.Eng.

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REFERENCES

Ministry of Environment (MOE), Amended Certificate of Approval Municipal and PrivateSewage Works, St. George WPCP, Number 9415-6CQKH, 2005

Ministry of Environment (MOE), Amended Certificate of Approval Municipal and PrivateSewage Works, Paris WPCP, Number 4668-5NCHWF, 2009

Ontario Clean Water Agency (OCWA) St. George WPCP Operations Manual, March 2005

Nutrient Management Act and Regulation 267/03 General – Application of Nutrients on Land

MOE and Ministry of Agriculture, Food and Rural Affairs (OMAFRA) Guidelines for theUtilization of Biosolids and Other Wastes on Agricultural Land, 1996

MOE Interim Guidelines for the Production and Use of Aerobic Compost in Ontario

Ministry of Environment (MOE) Design Guidelines for Sewage Works, 2008

Gamsby and Mannerow Limited, Process Capacity Assessment, April 2009

Metcalf and Eddy, Wastewater Engineering, 4th edition, 2003

KMK Consultants Limited, Class EA for Biosolids Management Strategy for the Paris andSt. George WPCP’s, May 2002

st. george water pollution control plant optimization study

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