Impactsoftemperatureandnitrifyingcommunity

Impactsoftemperatureandnitrifyingcommunityonnitrificationkineticsinamoving-bedbiofilmreactortreatingpollutedrawwaterShuangfuZhanga,YayiWanga,⇑,WeitaoHea,MinWua,MeiyanXinga,JianYanga,NaiyunGaoa,MianliPanbaStateKeyLaboratoryofPollutionControlandResourcesReuse,CollegeofEnvironmentalScienceandEngineering,TongjiUniversity,SipingRoad,Shanghai200092,PRChinabCenterforPharmacologicalEvaluation,ShanghaiInstituteofPharmaceuticalIndustry,Shanghai200040,PRChinahighlightsNitrificationkineticswasstudiedinaMBBRtreatingpollutedrawwater.Temperatureandnitrifyingcommunityimpactsonnitrificationkineticswerefocused.Temperatureimpactwasaffectedbysevereinhibitionoftemperaturebelow5.0C.Variationinnitrifyingcommunityinfluencedtemperatureimpactsonnitrification.Temp.coeffi.were1.099and1.098,respectively,forNH3/NO2oxidationkinetics.graphicalabstractarticleinfoArticlehistory:Received12May2013Receivedinrevisedform1September2013Accepted20September2013Availableonline29September2013Keywords:PollutedrawwaterMoving-bedbiofilmreactorTemperatureNitrifyingcommunityTemperaturecoefficientNitrificationkineticsabstractAlthoughnitrificationkineticshavebeenwidelystudiedinwastewatertreatmentsystemstooptimizethedesignandoperationofthenitrificationprocess,moreinformationisstillneededtofullyunderstandthekineticsofmoving-bedbiofilmreactors(MBBRs)usedforbiologicalpretreatmentoflowammoniaconcentrationpollutedrawwater.Inthisstudy,nitrificationkineticsofapilot-scaleMBBRtreatingpol-lutedrawwaterwerestudiedwhilefocusingontheimpactsoftemperatureandthenitrifyingcommu-nity.Nitrificationbatchtestswereconductedwithaninitialammoniaconcentrationof2.0mgL1andvaryingrawwatertemperaturesof2.8–28.3C.Theoxidationratesofammoniaandnitriteincreasedwithtemperature,althoughthebiomassconcentrationsdecreasedfrom348.7to188.9mgVSL1astem-peratureincreasedfrom16.1to28.3C.Thespecificammoniaandnitriteoxidationrateswerealsohighlydependentontemperature.Becauseofsevereinhibitionattemperaturesbelow5.0C,thetemperatureimpactswerecalibratedbyeliminatingthekineticdatameasuredbelow5.0C.Moreover,thevariationsinfunctionalmicroorganismsforAOB(b-ProteobacterialAOB)andNOB(Nitrobacterspp.)werenormalizedforthemodifiednitrificationkinetics.Thus,thefinaltemperaturecoefficientswere1.099and1.098forammoniaandnitriteoxidationkinetics,respectively,demonstratingthetemperatureimpactsonnitrifi-cationkineticsinMBBRstreatingpollutedrawwater.2013ElsevierB.V.Allrightsreserved.1.IntroductionDischargesofindustrialanddomesticwastewateroftenleadtoseriousdeteriorationofsurfacewaterqualityinmanydevelopingcountries.InChina,theconcentrationsofammoniainsomepollutedsurfacewaterbodieshavereached2mgL1ormore[1],presentingdifficultchallengesforchlorinedisinfectionduringdrinkingwatertreatment.Pre-chlorinationiscommonlyusedtoremoveammoniafrompollutedrawwater.However,thisprocesshasseveraldisadvantages,includingincreasedprocesscostsasso-ciatedwithincreasedchlorinedosage,difficultprocesscontroldue1385-8947/$-seefrontmatter2013ElsevierB.V.Allrightsreserved.⇑Correspondingauthor.Tel./fax:[phone].E-mailaddress:[e-mail](Y.Wang).ChemicalEngineeringJournal236(2014)242–250ContentslistsavailableatScienceDirectChemicalEngineeringJournaljournalhomepage:[2,3]andre-growthofnitrifyingbacteriaindrinkingwaterdistributionsystemsowingtothedecayofchloramineformedduringpre-chlorination[4,5].Accordingly,removalofammoniafrompollutedrawwaterinanefficientwaywhileavoidinghealthrisksassoci-atedwiththeformationofharmfulby-productsposesgreatchal-lengestowaterpretreatments.RittmannandHuck[6]foundthatammoniainpollutedrawwatercouldbeefficientlyremovedbybiologicalpretreatments,thusminimizingtheformationofdisinfectionby-products,whichcanbeaccomplishedinbiofilmprocesses[3,7,8].Themoving-bedbiofilmreactor(MBBR)wasdevelopedforwastewatertreatmentabout30yearsago[9,10].Suchreactorsarefilledwithsuspendedcarriers,whichmoveandcirculatewhileprovidinganattachablesurfaceforslow-growingmicroorganismssuchasnitrifyingbacte-ria.Thesereactorsenableoperationincontinuousmodewithoutbackwashingorsludgereturn[9,10].Ammoniaremovalfrompol-lutedrawwaterwasrecentlysuccessfullyachievedinMBBRs[11,12].Nitrifyingbacteriaaresensitivetotemperature[13,14],whichmakestemperatureakeyinfluencingammoniaremovalratesinMBBRsystems[12,15].Thedependenceofnitrificationkineticsontemperaturehasbeenwidelyinvestigatedinthepastseveraldecadeswiththepurposeofoptimizingthedesignandoperationofnitrificationreactorsforammoniaremoval.Forsuspendedgrowthsystems,PainterandLoveless[16]reportedatemperaturecoefficienthof1.076,whichdescribedthedependenceofthebiologicalreactionrateontemperature.SimilarvalueswerealsoreportedbyBarnesandBliss[17]inthetemperaturerangeof5–30C.Thetemperatureimpactsonnitrificationratewerefoundtobelowerthanexpectedinfixed-filmbiofiltersdesignedforammoniaremovalinrecirculatingaquacultureproductionsys-tems.Whenoxygenislimited,thedecre