OptimizingIFASandMBBRDesignsUsingFullScale

OptimizingIFASandMBBRDesignsUsingFull-ScaleDataHeatherM.Phillips1*,MarkMaxwell1,TerryJohnson1,JamesBarnard1,KenRutt2,JimSeda2,BlairCorning3,JMGrebenc3,NatalieLove3,StephenEllis31Black&VeatchCorporation2CityandCountyofBroomfield,Colorado3SouthAdamsCounty(Colorado)WaterandSanitationDistrict*Towhomcorrespondenceshouldbeaddressed.Email:[e-mail]dawealthoffull-scaledataareavailablefordesigningintegratedfixedfilmactivatedsludge(IFAS)andmovingbedbiofilmreactor(MBBR)facilitiestodaythatwerenotavailabletenyearsago.Thequestionnowisnot“howmuchmediaisneeded?”but“howcanweminimizecostsandmaximizeplantcapacitybyplacingtherightamountofmediaintherightplace?”TheIFASfacilityinBroomfield,Colorado,andtheMBBRfacilityattheWilliamsMonacoWastewaterTreatmentPlant(WWTP)inSouthAdamsCounty,Colorado,havebeeninserviceforoverfouryears.Operatorshavedocumentedbiomassquantitiesandnutrientprofileswithinindividualzonesovertheyears,andthisfull-scaledata,coupledwithpilot-scaleandbench-scaletestresults,hasbeenkeytooptimizingtheplantexpansions.TheBroomfieldPhase2expansioniscurrentlyunderconstruction,andtheWilliamsMonacoexpansionisinthestudyphase.KEYWORDS:Integratedfixedfilmactivatedsludge(IFAS),movingbedbiofilmreactor(MBBR),modeling,calibration,biologicalnutrientremoval(BNR),full-scale.INTRODUCTIONBiofilmprocesseshaveundergonesignificantadvancesinrecentyears.Thefirstbiofilmprocess,thetricklingfilter,datesbacktothe1800s.Othertechnologies,suchastherotatingbiologicalcontactor(RBC)andbiologicalfilters,havealsobeenaroundformanyyears.Processesusingfixedmediawithinaerationbasinshaveevolvedfromusingsheetsofasbestosinthe1930sand1940s,tostaticplasticmediainthe1960s,andropemediastartinginthe1970s(WEF,draftunderpublication).Free-floatingplasticmediaweredevelopedinNorwayinthemid-1980sattheNorwegianUniversityofScienceandTechnology(NTNU).Theprocesswaspatentedandcommercializedin1989astheKMTMovingBedBiofilmReactor(MBBR)throughanagreementwithKaldnes(Tønsberg,Norway),creatingthesubsidiaryKaldnesMiljøteknolgiAS(Ødegaardetal.,1994).Theprocesshasbeenappliedsuccessfullythroughouttheworld,startingwithfacilitiesinNorwayinthe1990s.Free-floatingplasticmediaisnowavailablefromseveralmanufacturers.Itisimportanttodifferentiatebetweenthetwotypesofprocessconfigurationsinwhichmediacanbeimplemented:MBBR,andintegratedfixedfilmactivatedsludge(IFAS).Bothprocessesusethesamemedia,butIFAShasareturnactivatedsludge(RAS)component,makingitahybridprocesswithbothsuspendedandbiofilmgrowth,whereasanMBBRdoesnotincludeaRASWEFTEC®.08Copyright©2008WaterEnvironmentFederation.AllRightsReserved.5002streamsoitonlyhasbiofilmgrowth.Forbothsystems,screens(commonlytermed“sieves”)areinstalledwithinthebasinstoretainthefree-floatingmediaandkeepitfromwashingintotheclarifier.SchematicsoftheIFASandMBBRprocessesareshownonFigure1.WasteActivatedSludgeMBBRWasteActivatedSludgeIFASReturnActivatedSludgeSuspended+BiofilmGrowthBiofilmGrowthHigherclarifiersolidsloadingrateLowerclarifiersolidsloadingrateFigure1:SchematicsofIFASandMBBRProcessesHighlightingtheirDifferencesThetwofacilitiesdiscussedinthispaperrepresentthe“firstgeneration”ofdomesticplantsinNorthAmericatoutilizefree-floatingplasticmedia,andbothhavebeeninservicesince2003.TheCityandCountyofBroomfield,ColoradoownandoperateanIFASfacilitywithAnoxKaldnes(K1)mediaattheBroomfieldWastewaterReclamationFacility(WWRF).TheSouthAdamsCountyWaterandSanitationDistrictownsandoperatesanMBBRfacilitywithAnoxKaldnes(K1)mediaattheWilliamsMonacoWWTP,inHenderson,Colorado.Thispaperdiscussesthedesignandperformanceoftheexistingfacilities,aswellascurrenteffortsforthe“secondgeneration”expansions.ThePhase2improvementsareunderconstructionattheBroomfieldWWTF,andtheexpansionoftheWilliamsMonacoWWTPisinthepreliminarystudyphase.TheBroomfieldWWTP(IFAS)AttheBroomfieldWWTF,rawwastewaterispumped,screened,de-gritted,andsentthroughprimaryclarificationbeforeenteringthesecondaryprocess.Secondarytreatmentconsistsoftwotrainsofpre-anoxic,anaerobicandanoxicbasins,followedbyoxicbasinswithIFAS(AnoxKaldnesK1)mediaata30percentfillfraction,andsecondaryclarifiers(Figure2).PrimaryeffluentandRASenterthe“pre-anoxic”zone,sincetherawinfluentcontainednitrateswhentheplantwasoriginallydesigned.Positivedisplacementblowersandcoarse-bubblediffuserssupplyairtotheprocesswithastrongrollingactiontoprovidemediaturnover.Thefacilityhaslocallyimposednutrientlimitsof0.10mg/Ltotalphosphorus(TP)and10to15mg/Lnitrate(NO3N)tosupportitsreclaimedwatersupplyprogram.ThefacilityhasUVdisinfection.Aflowequalizationpondprovidespartialequalization,andbiosolidsareprocessedonsitethroughdissolvedairfloatationthickening,anaerobicdigestion,andcentrifugedewatering.Dewateredcakeisland-appliedattheCity’sfarm.AsummaryofthemajordesignparametersislistedinTable1.WEFTEC®.08Copyright©2008WaterEnvironmentFederation.AllRightsReserved.5003MixedLiquorRecycleMixedLiquorRecycleRASfromClarifiersToSecondaryClarifiersPrimaryEffluentFEQReturnFlowJunction/SplitterBoxAnaerobicandAnoxicBasins(mixedliquoronly)IFASAerationBasins(mediaandmixedliquo