Controlofcarbonandammoniumratioforsimultane

InternationalBiodeterioration&Biodegradation59(2007)1–7ReviewControlofcarbonandammoniumratioforsimultaneousnitrificationanddenitrificationinasequencingbatchbioreactorYing-ChihChiua,,Li-LingLeeb,1,Cheng-NanChangb,AllenC.ChaocaDepartmentofEnvironmentalEngineering,NationalIlanUniversity,I-LanCity,Taiwan26041,ROCbGraduateInstituteofEnvironmentalScienceandEngineering,TunghaiUniversity,Box5-819,TaichungCity,Taiwan40704,ROCcDepartmentofCivilConstructionandEnvironmentalEngineering,NorthCarolinaStateUniversity,Raleigh,NC27695,USAReceived11April2006;receivedinrevisedform13July2006;accepted1August2006Availableonline2October2006AbstractThisstudyshowshowthecarbonandnitrogen(C/N)ratiocontrolsthesimultaneousoccurrenceofnitrificationanddenitrificationinasequencingbatchreactor(SBR).DatademonstratedthatalowC/Nratioresultedinarapidcarbondeficit,causinganunbalancedsimultaneousnitrification–denitrification(SND)processinSBR.WhentheinitialCOD/NH4+-Nratiowasadjustedto11.1,theSND-basedSBRachievedcompleteremovalofNH4-NandCODwithoutleavinganyNO2-Nintheeffluent.Thenitrogenremovalefficiencydecreasesgraduallywithincreasingammonium-loadingratetotheSND–SBRsystem.Altogether,datashowedthatappropriatecontrolsofcarbonandnitrogeninputarerequiredtoachieveanefficientSND–SBR.AnestablishedSNDtechnologycansaveoperationtimeandenergy,andmightreplacethetraditionaltwo-stagebiologicalnitrificationanddenitrificationprocess.r2006ElsevierLtd.Allrightsreserved.Keywords:Carbonsource;Heterotrophicnitrification;Oxidation–reductionpotential(ORP);Simultaneousnitrificationanddenitrification(SND)Contents1.Introduction.................................................................................12.Materialsandmethods..........................................................................22.1.Compositionofthesyntheticwastewater.........................................................22.2.OperationalconditionsoftheSND-basedSBRsystem...............................................22.3.Analyticalmethods........................................................................33.Resultsanddiscussion..........................................................................33.1.Effectofinsufficientcarbonsource.............................................................33.2.Influenceofammonium-loadingrate............................................................54.Conclusions.................................................................................6Acknowledgments.............................................................................7References..................................................................................71.IntroductionThetraditionalbiologicalprocessusedinwastewatertreatmenttoachievenitrogenremovalinvolvesseparateaerobicandanaerobicphasesthataregenerallycarriedoutinseparatebioreactorsorbydifferentaerationintervalsARTICLEINPRESS:10.1016/j.ibiod.2006.08.001Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](Y.-C.Chiu).1Presentaddress:EnergyStrategyResearchLab.,IndustrialTechnologyResearchInstitute,Chutung,Hsinchu,Taiwan310,ROC.(MetcalfandEddy,1991).However,Ferguson(1994)proposedthatheterotrophicmicroorganismsmaybeinvolvedinnitrificationandsimultaneousaerobicdeni-trification.Someheterotrophicnitrifiershavebeenre-portedtodenitrifynitrite(NO2)andnitrate(NO3)aerobically(Robertsonetal.,1988;ZartandEberhard,1998).Otherstudiesshowthatnitrificationanddenitrifica-tionoccurconcurrentlyinasinglereactorunderaerobicconditions(vonMu¨nchetal.,1996;Zengetal.,2003),whichisoftenreferredtoasthesimultaneousnitrificationanddenitrification(SND)process.TheSNDprocessrepresentsasignificantadvantageovertheconventionalseparatednitrificationanddenitrificationprocesses.SNDoccursnaturallyinsidemicrobialbiofilmsandflocksduetotheoxygengradientthatestablishesacrossthebiomass(vonMu¨nchetal.,1996).Nitrifiersareactiveinareasofhighdissolvedoxygen(DO)concentration,whereasdenitrifiersareactiveinareasofverylowDOconcentration.TheunevendistributionofDOinsidethebiomassallowssimultaneousproliferationofnitrifyinganddenitrifyingbacteria.Ontheotherhand,someheterotrophicbacteria,e.g.,Alcaligenesfaecalis(vanNieletal.,1992)andThiosphaerapantotropha(RobertsonandKuenen,1988),arecapableofperformingSNDbyusingorganicsubstratesaerobicallyassourcesofcarbonandenergytoconvertammonium(NH4+)aerobicallyintonitrogengas(Stouthameretal.,1997).PathwaysofheterotrophicSNDmetabolismaredifferentfromthoseofautotrophicnitrifiersandhetero-trophicdenitrifiers.Ammoniumishydroxylatedtohydro-xylamine(NH2OH)byammoniummonooxygenaseunderaerobicconditions.Subsequently,hydroxylamineisoxi-dizedtonitritebyhydroxylamineoxidase.Finally,nitriteisdirectlytransformedintoN2.TheSNDprocessisalsotermed‘‘aerobicdeammonification’’(Bocketal.,1995;vanLoosdrechtandJetten,1998).Hellingaetal.(1998)designedanSND-basedreactorinwhichaerobicheterotrophicbacteriaremovednitriteproducedfromammoniabyNitrosomonasinthesamereactor.RobertsonandKuenen