The-effect-of-different-carbon-sources-on-respiratory-denitrification-in-biological

JOURNALOFFERMENTATIONANDBIOENGINEERINGVol.82,No.3,277-285.1996TheEffectofDifferentCarbonSourcesonRespiratoryDenitrificationinBiologicalWastewaterTreatmentNATUSCKAM.LEE’*ANDTHOMASWELANDER’,*DepartmentofBiotechnology,CenterforChemistryandChemicalEngineering,LundUniversity,P.O.Box124,S-22100Lund,landAnoxAB,IdeonResearchPark,S-22370Lund,2SwedenReceived12December1995/Accepted30June1996Therespiratorydenitrificationactivityofactivatedsludgebacteriawithdiierentcarbonsources(aceticacid,crudesyrup,hydrolyzedstarch,methanol-withandwithoutasmallamountofyeastextract)wasstudiedinlong-termcontinuouscultivationsandbatchtests.Massbalancecalculationsshowedthatthemainproductinlong-termcultivationswithallcarbonsourceswasmolecularnitrogen.However,thetypeofcarbonsourcehadasignificantinfluenceonthedenitrificationrate,denitrificationyield,sludgeyieldandthecompositionofthemicroflora.Withacetateandmethanolhigherdenitrificationyields,lowersludgeyieldsandmoretrue(endproductN&denitrifyingbacteriawereobtainedthanwithcrudesyrupandhydrolyzedstarch.Furthermore,withacetateahighergrowthrateandahigherdenitrificationratewasobtainedthanwithmethanol.[Keywords:biologicalwastewatertreatment,nitrogenremoval,respiratorydenitrification,aceticacid,hydrolyzedstarch,methanol]Respiratorydenitrificationisoneofthemainmicro-biologicalprocessesfornutrientremovalinbiologicalwastewatertreatment.Precededbyammonificationandnitrification,whichreduceorganicnitrogenintooxidizedinorganicnitrogencompoundssuchasnitrate,denitrifi-cationisthelaststepinthenitrogencyclewherethenitrateistransformedthroughseveralintermediaryproducts(NO*-,NO,N20)tomolecularnitrogen.Itisananaerobicprocesswheretheoxidizednitrogencom-poundservesasanelectronacceptor,whiletheelectrondonormaybeofeitherinorganicororganicnature(1).Inmunicipalwastewatertreatment,therespiratorydenitrificationreliesuponacarbonsourceasanelectrondonor.However,theconcentrationofavailablecarbonsourceinthewastewatermaynotalwaysbesufficient,sothatanexternalcarbonsourcemaybeneeded(2).