Responsesofbiofilmcharacteristicstovariations

ResponsesofbiofilmcharacteristicstovariationsintemperatureandNH4+-Nloadinginamoving-bedbiofilmreactortreatingmicro-pollutedrawwaterShuangfuZhang,YayiWang⇑,WeitaoHe,MinWu,MeiyanXing,JianYang,NaiyunGao,DaqiangYinStateKeyLaboratoryofPollutionControlandResourcesReuse,CollegeofEnvironmentalScienceandEngineering,TongjiUniversity,SipingRoad,Shanghai200092,PRChinahighlightsThepilot-scaleMBBRshowedgoodperformanceforNH4+-Nremovalfromrawwater.PS,PNandPLaregoodindicatorsofbiomassdevelopmentanddetachment.TemperatureandNH4+-NloadingaffecttheratiosofPS/VS,PN/VS,HS/VSandPL/VS.ThecompetitivenessofAOBandNOBwerepromotedbyincreasingNH4+-Nloading.ThebiofilmcharacteristicsprovidedetailedinsightsintoMBBRtreatingrawwater.articleinfoArticlehistory:Received19October2012Receivedinrevisedform25December2012Accepted26December2012Availableonline4January2013Keywords:Micro-pollutedrawwaterTemperatureNH4+-NloadingBiofilmcharacteristicsMoving-bedbiofilmreactorabstractApilot-scalemoving-bedbiofilmreactor(MBBR)forbiologicaltreatmentofmicro-pollutedrawwaterwasoperatedover400daystoinvestigatetheresponsesofbiofilmcharacteristicsandnitrificationper-formancetovariationsintemperatureandNH4+-Nloading.ThemeanremovalefficiencyofNH4+-NintheMBBRreached71.4±26.9%,andbatchexperimentswereperformedtostudynitrificationkineticsforbet-terprocessunderstanding.Sevenphysical–chemicalparameters,includingvolatilesolids(VS),polysac-charides(PS)andphospholipids(PL)increasedfirstly,andthenrapidlydecreasedwithincreasingtemperatureandNH4+-Nloading,andproperlycharacterizedtheattachedbiomassduringbiofilmdevel-opmentanddetachmentintheMBBR.Thebiofilmcompositionsweredescribedbysixratios,e.g.,PS/VSandPL/VSratiosshoweddifferentvariationtrends,indicatingdifferentresponsesofPSandPLtothechangesintemperatureandNH4+-Nloading.Furthermore,fluorescentinsituhybridization(FISH)anal-ysisrevealedthatincreasedNH4+-Nloadingscausedanenrichmentofthenitrifyingbiofilm.2013ElsevierLtd.Allrightsreserved.1.IntroductionEutrophicationofsurfacewatershasbecomeaseriousenviron-mentalprobleminChinaandcausesmanyproblemsindrinkingwatertreatment.LakeTaihu,thethirdlargestfreshwaterlakeinChina,isatypicalexample,withitseutrophicecosystemandan-nualcyanobacteriablooms.TherawwaterfromsucheutrophicsurfacewatersismainlypollutedbyNH4+-Nandorganicmatter.Inparticular,theNH4+-Nconcentrationreachesashighas3mg/Linsomesurfacewaters.Inconventionaltreatmentprocesses,NH4+-Nisremovedviapre-chlorination,whichincreasesthedoseofchlorineandharmfuldisinfectionby-productsareformedwhenchlorinereactswithorganicmatters(GallardandvonGunten,2002).Also,residualNH4+-Ncanbesubstratefortheregrowthofnitrifyingbacteriaindrinkingwaterdistributionsystems,destroy-ingthebio-stabilityofdrinkingwater(Reganetal.,2003).Indeed,NH4+-Ninmicro-pollutedrawwaterhasbecomeapotentialthreattothesupplyofsafedrinkingwaterinChina.Nevertheless,NH4+-Ncanbeeffectivelyremovedthroughnitri-ficationinbiofilmprocesses.Thebiofilmprocessisconsideredtobeanideal,economicalwaytoremoveNH4+-N,andithasbeenwidelyusedasabiologicalpretreatmentindrinkingwatertreat-mentplantswhentreatingmicro-pollutedrawwater,especiallyinChina.ThemainbiofilmprocessesappliedforNH4+-Nremovalinmicro-pollutedrawwaterarethebiologicalaeratedfilter(Yuetal.,2007),biologicalcontactoxidation(Chuetal.,2011),themoving-bedbiofilmreactor(MBBR)(Xieetal.,2005),andthemembranebioreactor(LiandChu,2003).Amongstthese,theMBBRhasaspecificfeaturethatreliesontheuseofsuspendedcarriers,0960-8524/$-seefrontmatter2013ElsevierLtd.Allrightsreserved.⇑Correspondingauthor.Tel./fax:[phone].E-mailaddress:[e-mail](Y.Wang).BioresourceTechnology131(2013)365–373ContentslistsavailableatSciVerseScienceDirectBioresourceTechnologyjournalhomepage:(Bassinetal.,2012b).Comparedwithfixed-bedbiofilmreactors,MBBRsystemsshowlowerheadlossesandnocloggingproblems.Moreover,existingbiologicaltanksforotherprocessescanbereadilymodifiedtotheMBBRcon-figuration,insteadofconstructingnewfacilities.Mostofall,thisprocesshasprovedtobeeffectiveforNH4+-Nremoval,evenatlowtemperature(Hemetal.,1994).Becauseofthesespecialfeatures,MBBRtechnologyhasbeenwidelyappliedtothetreatmentofvariouswastewatersinlabora-tory-andfull-scalesystems(Bassinetal.,2012b).However,NH4+-NremovalinMBBRsystemstreatingmicro-pollutedrawwaterhasrarelybeenstudied.Inparticular,therehavebeennoreportsonthedevelopmentofnitrifyingbiofilmsforthetreatmentofmi-cro-pollutedrawwatercontainingrelativelyhighNH4+-Nconcen-trations(e.g.1.0–6.0mg/L).Also,therehavebeennostudiesontheuseofbiofilmconstituentsintermsofpolysaccharides(PS),pro-teins(PN),humic-likesubstances(HS)andphospholipids(PL)todescribevariationsintheattachedbiomassandbiofilmcomposi-tionsinMBBRsystemstreatingmicro-pollutedrawwater.Further-more,littleinformationisavailableonthebiofilmcompositionsandnitrifyingcommunityinsuchMBBRsystems(LazarovaandManem,1995).Overall,characterizingnitrifyingbiofilmsintermsofth