DesignandOperatingConsiderationsforaPostDen

DesignandOperatingConsiderationsforaPostDenitrificationMBBRtoAchieveLimitofTechnologyEffluentNOx1mg/landeffluentTP0.18mg/lB.Stinson1,M.Peric1,D.Neupane1,M.Laquidara1,E.Locke1,S.Murthy2,W.Bailey2,S.Kharkar2,N.Passarelli2,R.Derminassian2,J.Carr2,M.Sultan2,G.Shih2J.Barnard3,G.Daigger3,D.Parker3,C.Randall3,T.Wilson31Metcalf&Eddy,14504GreenviewDrive,Suite400,Laurel,MD,207082DCWASA,5000OverlookAvenueSW,WashingtonDC,200323ExpertTechnicalAdvisoryPanel(InAlphabeticalOrder)Black&Veatch,CH2MHill,Brown&Caldwell,VirginiaTech.,AECOMWaterAcknowledgmentto:BjornRustenandCharlesBott.AlsoIDItechnical&pilotsupportstaff.ABSTRACTDenitrifyingMovingBedBiofilmReactor(MBBR)technologyhasbeenattractingincreasinginterestoverthepastdecadebecauseofitsmechanicalsimplicity,easeofmaintenanceandreportedlyreliablenutrientremovalperformanceevenundercoldwetweatheroperatingconditions.Thistechnologyhasnothoweverbeendemonstratedtobecapableofconsistentlyachievinglimitoftechnology(LOT)totalnitrogen(TN)andtotalphosphorus(TP)effluentgoalssuchasthoserequiredbysomedischargersintheChesapeakeBay,i.e.TN3mg/landTP0.18mg/l.InanefforttodetermineifapostdenitrificationMBBRpolishingprocessmaybeacosteffectiveandreliableadd-ontreatmenttechnologytoachieveits’futureEnhancedNutrientRemoval(ENR)effluentgoals(effluentNOxofbetween0.5and1mg/l,andTP0.18mg/l),theDistrictofColumbiaWaterandSewerAuthority(DCWASA)operatedapilotscaledenitrifyingMBBRprocessfora6monthperiodtoexamineitsperformanceoverarangeofdesign&operatingconditions.ThispaperwillreviewtheresultsofthatstudyandreportonthedesignandoperatingconsiderationsdevelopedforthesuccessfulimplementationofaLOTpostdenitrificationMBBRProcess.KEYWORDS:PostDenitrificationMovingBedBiofilmReactor(MBBR),LimitofTechnology(LOT),EnhancedNutrientRemoval(ENR),Designcriteria,NitrateandCarbonHalfSaturationCoefficients,PhosphorusLimitations,BiomassDensityMeasurements.INTRODUCTIONTheDCWaterandSewerAuthority’s(DCWASA)BluePlainsAdvancedWastewaterTreatmentFacility(AWTF)isa370MGD(AverageDryWeatherFlow)plantthatservesapopulationofmorethan2,000,000peopleinthemetropolitanDCarea.TheexistingwastewatertreatmentprocessesattheBluePlainsAWTareshownbelowinFigure1andconsistofpreliminaryandprimarytreatment,secondarytreatment,nitrification/denitrification,effluentfiltration,chlorination/dechlorinationandpostaeration.AnaerialphotographofthesiteisprovidedinFigure2todemonstratetheconfinednatureofthesite;boundedbyahighwayononeside,thePotomacRiverontheotherandexistinginfrastructuretotheNorth.ThephotoalsoindicatesthatthereisonlyaverylimitedamountoflandavailableintheSouthWestcornerofthesite,fortheconstructionofadditionalENRfacilitiesinthefuture.1225NutrientRemoval2009Copyright©2009WaterEnvironmentFederation.AllRightsReserved.PrimaryPrimaryClarifiersClarifiersHighHigh--rateASrateASreactorsreactorsSecondarySecondaryClarifiersClarifiersNitrificationNitrificationDenitrificationDenitrificationASreactorsASreactorsNitrificationNitrificationDenitrificationDenitrificationClarifiersClarifiersFinalDualFinalDual--mediaFiltersmediaFiltersDischargetoDischargetoPotomacPotomacRiverRiverSitepreservedforfutureBiosolidFacilitiesAvailableAvailablerealestaterealestateAvailableAvailablerealestaterealestateBarScreensBarScreensandGritandGritChambersChambersFigure1:BluePlainsAWTFExistingLiquidTrainProcessNitrification/DenitrificationReactorsNitrification/DenitrificationSedimentationTanksFigure2:AerialViewofBluePlainsAWTF1226NutrientRemoval2009Copyright©2009WaterEnvironmentFederation.AllRightsReserved.DCWASAcurrentlyoperatestheBluePlainsAWTFtomeetaneffluentTNlimitof7.5mg/LandaTPlimitof0.18mg/l.AnewpermitisanticipatedthatwillrequireadditionalTNreductionstoachieveaneffluentTNoflessthan3mg/lasestablishedbytheChesapeakeBayENRgoals.TheplantinvestigatedvariousalternativestomeettheanticipatedfutureLOTTNandTPgoalsconcurrently.OneoftheprocessapproachesconsideredinvolvedincorporationoftheinnovativeMovingBedBiofilmReactor(MBBR)technologyasadenitrificationpolishingstepdownstreamoftheexistingnitrification/denitrification(N/DN)activatedsludgesystem.ItwasperceivedthattheMBBRtechnologymayofferthepotentialtobeasmallfootprintprocessalternativewiththepotentialtofitwithinthelimitedspaceavailable.TounderstandtheviabilityoftheMBBRtechnologyasapostdenitrificationpolishingprocessanditsabilitytoreliablyandcost-effectivelyassistinmeetingthefuturestringenteffluentENRrequirements,apilottestprogramwasundertakenbetweenDecember2007andearlyJuly2008.GOALSANDOBJECTIVESTheoverallgoalofthepilottestprogramcanbedescribedasbeingtwo-fold;ƒTNgoal-todeterminethedesignandoperatingconditionsunderwhichthepostdenitrificationMBBRprocesscanreliablyandcost-effectivelyachieveeffluentNOxconcentrationsofo0.5mg/Lduringaveragetowarmweatherconditions(wastewatertemperatures≥17°C),whichaccountsforthetypicaloperatingconditionsforeightmonthsoftheyearintheUSAMidAtlanticregion,ando1mg/Lduringwinterconditions(wastewatertemperaturesbetween12and17°C,withasustainedaveragemonthlytemperatureaslowas12°C),whichaccountsforthetypicaloperatingconditionsfor