ColdWeatherNitrificationofLagoonEffluentUsin

COLDWEATHERNITRIFICATIONOFLAGOONEFFLUENTUSINGAMOVINGBEDBIOFILMREACTOR(MBBR)TREATMENTPROCESSMr.FlemmingG.Wessman1andMr.ChandlerH.Johnson1AnoxKaldnes,Inc.,58WeybossetStreet,4thFloor,Providence,RIABSTRACTSince2000,thepopulationatJohnstown,Coloradohasincreasedover22%,andshowsnosignsofslowingdown.Facedwithmoreresidentsandimpendingyearroundammonialimits,theTownofJohnstownwasforcedtoupgradetheirwastewatertreatmentfacility.TheexistingtreatmentfacilityinJohnstownconsistedofthreelagoons,whosemainpurposewastoachievesettlingoftotalsuspendedsolidsandorganicmatter(BOD)removal.Tomeetthenewincreaseinflowsandnutrientlimits,theTownofJohnstownhadtwochoices:eliminateallexistinglagoonsandbuildanewconventionalactivatedsludgefacility,orcontinuetoutilizetheexistinglagoonsfororganicmatterreductionandaddadownstreampost-nitrificationfixedfilmtreatmentsystem.Bychoosingthelatteroption,theTownofJohnstownmanagedtosaveabout50%ofthecostofbuildingawholenewplant.Thepost-nitrificationMBBRwasinstalledduringthewinterof2003/2004andbroughtonlineinJune2004.December2004tomid-January2005,theaverageinfluentwatertemperaturewas4.2°C,theMBBRtreatmentsystemremovedanaverageofover40%ofinfluentNH3-N.Infact,theeffluentNH3-Ndecreasedby35%,42%,and58%inDecember,January,andFebruary,whencomparedwiththesamemonthsinthewinterpriortotheinstallationoftheMBBRtreatmentsystem.Throughoutthewarmermonths,theMBBRtreatmentremovedanaverageof85%ofinfluentNH3-NwhiletheeffluentBODhasbeen,onaverage,lessthan1mg/L,makingitveryeasyfortheplanttomeetitspermitrequirementsmonthaftermonth.KEYWORDSWastewater,treatment,MovingBed™biofilmprocess,MBBR,experiences,nitrification,Lagoon.INTRODUCTIONSince2000,thepopulationatJohnstown,Coloradohasincreasedover22%,andshowsnosignsofslowingdown.Facedwithmoreresidentsandimpendingyearroundammonialimits,theTownofJohnstownwasforcedtoupgradetheirwastewatertreatmentfacility.Johnstownislocatedabout50milesnorthofDenver,andduringwintertimetheirlagoonwastewatertemperaturesfrequentlydipbelow40°F(4.5°C).TheexistingtreatmentfacilityinJohnstownconsistedofthreelagoons,whosemainpurposewastoachievesettlingoftotalsuspendedsolidsandorganicmatter(BOD)removal.Tomeetthenewincreaseinflowsandnutrientlimits,theTownofJohnstownhadtwochoices:eliminateallexistinglagoonsandbuildanewconventionalactivatedsludgefacility,orcontinuetoutilizetheexistinglagoonsfororganicmatterreductionandaddadownstreampost-nitrificationfixedfilmtreatmentsystem.Bychoosingthelatteroption,theTownofJohnstownmanagedtosaveabout50%ofthecostofbuildingawholenewplant.4738WEFTEC®.06Copyright2006WaterEnvironmentFoundation.AllRightsReserved©Fixedfilmtechnologiesarewellknownforbiologicaltreatmentofammoniaincoldtemperaturesasthebacteria/biofilmgrowsonasubstrate/mediaandarekeptwithinthesystemratherthenbeingwashedoutduringcoldertemperaturesasaconventionalactivatedsludgesystemwouldtypicallyseehappen.TheTownofJohnstowninvestigatedtheMovingBedBiofilmReactor(MBBR)treatmenttechnologyformeetingitsneweffluentammoniaandincreasedflowrequirements.Overalltreatmentrequirementsforthesystemaresummarizedinthetablebelow.MonthEffluentlimit(mgNH4-N/L)January16February12Mars5.1April2.9May1.5June1.3July1.2August1.2September1.1October1.1November2.2December13Table1.OveralltreatmentrequirementsTheabilityoftheMBBRtobedesignedforafutureflowcapacitybysizingthetankagefortheultimatebuildoutflowandloadswasattractiveastheinitialinvestmentonlyrequiredmediatomeetthecurrentflowsandloads.Oncethesystemsflowsandloadsincreasedthetownonlyhastoaddadditionalmediatoprovidetheadditionalsurfaceareaneededforbiofilmgrowth.DESCRIPTIONOFTHEMOVINGBED™BIOFILMREACTORTheideabehindthedevelopmentoftheKaldnesMovingBed™biofilmprocess(MBBR™biofilmprocess)wastoadoptthebestfeaturesoftheactivatedsludgeprocessaswellasthoseofthebiofilterprocesswithoutincludingtheworst.Contrarytomostbiofilmreactors,theMovingBed™biofilmreactorsutilisesthewholetankvolumeforbiomassgrowth,asdoestheactivatedsludgereactor.Contrarytotheactivatedsludgereactor,however,theMBBRdoesnotneedanysludgerecycle,asisalsothecaseinotherbiofilmsystems.Thisisachievedbyhavingthebiomassgrowoncarriersthatmovefreelyinthewatervolumeofthereactor,keptwithinthereactorvolumebyasievearrangementatthereactoroutlet.Sincenosludgerecirculationtakesplace,onlythesurplusbiomasshastobeseparated-aconsiderableadvantageovertheactivatedsludgeprocess.Thereactormaybeusedforbothaerobic,anoxicoranaerobicprocesses,seeFigure1.4739WEFTEC®.06Copyright2006WaterEnvironmentFoundation.AllRightsReserved©a.Aerobicreactorb.Anoxicandanaerobicreactorc.Thebiofilmcarrier(K1)Figure1-PrincipleoftheMBBR™biofilmtechnologyandshapeoftheoriginalbiofilmcarrier(K1)Inaerobicprocesses,thebiofilmcarriermovementiscausedbytheagitationsetupbytheair,whileinanoxicandanaerobicprocessesamixerkeepsthecarriersmoving.Intheaerobicreactorsaspecialmediumbubbleaerationsystemhasbeendeveloped.Thistypeofaerationsystemisveryrobustandwillnotrequireanymaintenanceorreplacement.Theoxygentransferrate(OTR)ishighduetothepresenceofthebiofilmcarriers.TestshaveshownthattheOTRisequaltowhatyouachievewith