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JournalofEnvironmentalSciences26(2014)1014–1022∗,ShengyongJia,HaifengZhuang,QianZhao,PengXuStateKeyLaboratoryofUrbanWaterResourceandEnvironment,HarbinInstituteofTechnology,Harbin150090,China,E-mail:hbl527@163.comarticleinfoArticlehistory:Received22June2013revised31October2013accepted07November2013Keywords:alkalinitynitritationcoalchemicalindustrywastewatermovingbedbiofilmreactorDOI:10.1016/S1001-0742(13)60517-3abstractNitrogenremovalvianitrite(thenitritepathway)ismoresuitableforcarbon-limitedindustrialwastewater.Partialnitrificationtonitriteistheprimarysteptoachievenitrogenremovalvianitrite.Theeffectofalkalinityonnitriteaccumulationinacontinuousprocesswasinvestigatedbyprogressivelyincreasingthealkalinitydosageratio(amountofalkalinitytoammoniaratio,mol/mol).Thereisacloserelationshipamongalkalinity,pHandthestateofmatterpresentinaqueoussolution.Whenalkalinitywasinsufficient(comparedtothetheoreticalalkalinityamount),ammoniaremovalefficiencyincreasedfirstandthendecreasedateachalkalinitydosageratio,withanabruptremovalefficiencypeak.Generally,ammoniaremovalefficiencyrosewithincreasingalkalinitydosageratio.Ammoniaremovalefficiencyreachedto88%from23%whenalkalinityadditionwassufficient.Nitriteaccumulationcouldbeachievedbyinhibitingnitriteoxidizingbacteria(NOB)byfreeammonia(FA)intheearlyperiodandfreenitrousacidinthelaterperiodofnitrificationwhenalkalinitywasnotadequate.OnlyFAworkedtoinhibittheactivityofNOBwhenalkalinityadditionwassufficient.IntroductionWithhumanprogressandtheimprovementoflivingstan-dards,anincreasingamountofcontaminantscontainingnitrogenhavebeendischargedintotheenvironment.Thelargeamountofnitrogendischargedintowaterbodieshasunderminedthenitrogencycleinnature,causingworld-wideeutrophicationthatoccursrepeatedly.Nitro-genremovalhasbeenahotanddifficultresearchissueintheenvironmentalprotectionarea.Numerousnewthe-oriesandtechnologyhavebeendevelopedonthebasisoftraditionaltreatmenttheoriesandprocesses.Severaltypicalnewtheoriesandprocesseshaveemergedsuchas:nitrogenremovalvianitritepathway(Hellingaetal.,1998;VanHulleetal.,2007),anaerobicammoniumoxidation(Mulderetal.,1995;Strousetal.,1998),thecombinationofpartialnitrificationtonitriteandanaerobicammoniumoxidation(CANON)(Strousetal.,1999;Thirdetal.,2001)∗Correspondingauthor.E-mail:han13946003379@163.comandtheenhancedbiologicalnitrificationbacteriaprocess(Salemetal.,2002),drawingaconsiderableamountofattentionofscholars.Newnitrogenremovaltheoriesandprocesseshaveshowngreatadvantagescomparedtotradi-tionaltheoriesandtechnology,especiallynitrogenremovalviathenitritepathwayandCANON,whicharebothbasedonpartialnitrificationtonitrite.Thenitritepathwayisamorepracticalprocessamongthesenewprocesses.Theoretically,nitrogenremovalvianitriteyieldsa25%reductioninoxygendemandand40%reductionincarbonsourcerequirementfordenitrification.Coalchemicalindustrywastewaterisdischargedintheprocessesofcoalgasificationandcoalchemicalproduction(Yangetal.,2006;Wangetal.,2010),thecomposi-tionofwhichisverycomplex,containingvarioustoxiccompoundsandalargenumberofrefractoryorganicandinorganiccontaminants,withpoorbiodegradability(Mara¯n´onetal.,2008).Thewastewatercharacteristicsvarysignificantlyaccordingtothecoalqualityusedintheproduction.Morethan244kindsoforganiccom-JournalofEnvironmentalSciences26(2014)1014–10221015poundshavebeendetectedinthewastewater.Phenoliccompoundsarethemainpollutants.Thewastewateralsocontainspolycyclicaromatichydrocarbons,heterocycliccompounds,long-chainhydrocarbons,ammonia,cyanideandthiocyanate(Nakhlaetal.,1990;Gaietal.,2008;Felf¨oldietal.,2010;Yuetal.,2010).Althoughthewastew-aterispretreatedviaammonia-stripping,italsocontainsahighconcentrationofammonia.Nitrogenremovalwasunsatisfactoryinthesuspendedactivatedsludgeprocessduetothepresenceoftoxicandinhibitorymatterandlim-itedavailablecarbonsources(Kumaretal.,2000).Underhighconcentrationsofphenoliccompoundsandinhibitors,nitrifyingbacteriawereout-competedinthesuspendedactivatedsludgesystembythefastgrowthofheterotrophicmicroorganisms(Kimetal.,2007).However,themovingbedbiofilmreactorhasprovedtobeaneffectivepro-cesstoremovebothorganiccontaminantsandammoniainthetreatmentofcoalchemicalindustrywastewater(Lietal.,2011).Consideringthelimitedcarbonsourcecharacteristicandcomplexcompositionofcoalchemicalindustrywastewater,nitrogenremovalviaanitritepathwaythatrequireslesscarbonsourceisadesirablemethodforthetreatmentofcoalchemicalindustrywastewater.Alkalinityplaysavitalroleinnitrification,especiallycarbonatealkalinity.Alkalinityisnotonlytheinorganiccarbonsourceofheterotrophicnitrifyingbacteria,butalsobalancestheacid-baselevelofthemixture,affectingthestateofmatterpresentinaqueoussolution.Inthiscontext,amovingbedbiofilmreactor(MBBR)wasadoptedtotreatcoalchemicalindustrywastewatertoinvestigatetheeffectsofvariationsofnitrogenandalkalinityonthetreatmentprocess.Thestudyinvolvedfi