ASLUDGECHARACTERIZATIONASSAYFORAEROBIC

Wat.Res.Vol.31,No.3,pp.471478,1997©1997ElsevierScienceLtdPergamonPrintedinGreatBritain.AllrightsreservedPll:S0043-1354(96)00281-30043-1354/97$17.00+0.00ASLUDGECHARACTERIZATIONASSAYFORAEROBICANDDENITRIFYINGPHOSPHORUSREMOVINGSLUDGEA.WACHTMEISTER,T.KUBA~,M.C.M.VANLOOSDRECHT@*andJ.J.HEIJNEN@DepartmentofBiochemicalEngineering,DelftUniversityofTechnology,Julianalaan67,2628BCDelft,TheNetherlandsAbstract--Itwasrecentlyrecognizedthatdenitrifyingbacteria,aswellasaerobicbacteria,contributetothebiologicalphosphorusremovalprocess.Forevaluationofthephosphorusremovalprocessitisnecessarytohavetestsenablingapropercharacterizationofthemicrobialpopulationintheactivatedsludge.Inthisstudyweevaluatedthepossibilityofanoxicphosphorusreleaseoraerobic/anoxicphosphorusuptaketestsforsludgecharacterization.Heretoweemployedsludgemixturesofenrichmentculturesfromlaboratorysequencingbatchreactor(SBR)systemsoperatedunderaanaerobic-aerobic(A/O)oranaerobic-anoxic(A2)conditions.Itisshownthatinterpretationofphosphorusreleasetests,withorwithoutnitratepresent,isdifficult.Ontheotherhandacomparisonofphosphorusuptakeunderaerobicandanoxicconditionsleadstoastraightforwardcharacterizationofthemicrobialpopulationinthephosphorusremovingorganisms,withrespecttotheirphosphorusremovalactivityunderaerobicandanoxicconditions.©1997ElsevierScienceLtd.AllrightsreservedKeywords--activatedsludge,biologicalphosphorusremoval,denitrification,denitrifyingphosphorusremovingbacteria,nitrate,sludgecharacterizationINTRODUCTIONAppeldoorn,1993;Kubaetal.,1994).Figure1showsanexampleofthephosphorusreleaseactivitywithRecentlyithasbeenshownthatbesidesoxygen,andwithoutnitrateinbatchtestsusingactivatednitratecanbeutilizedasanelectronacceptorforsludgeobtainedfroma(modifiedUCT-type)wastebiologicalphosphorusremovalfromwastewaterwatertreatmentplantintheNetherlands(Kubaet(Comeauetal.,1986,1987;Vlekkeetal.,1988;al.,1995).OneofthemainreasonsforthereductionPokethitiyooketal.,1990;ShinetaL,1992;Wannerofphosphorusreleasebynitratemightbetheetal.,1992;Kerrn-Jespersenetal.,1993,1994;Kubasimultaneousphosphorusuptakeduetodenitrifyingetal.,1993;Bortoneetal.,1994).Thetypeofdephosphatationbydenitrifyingphosphorusremov-organismscapableofdenitrifyingdephosphatationingbacteria(DPB).Ifthishypothesisiscorrect,acanbeeasilyaccumulated,byreplacingtheaerobicbatchtestofphosphorusreleaseinsimultaneousphaseinaconventionalanaerobic-aerobicphos-presenceofCODandnitratecouldbeusefulforthephorusremovalsystembyananoxicphase(Kubaetevaluationofarelativeproportionofadenitrifyingal.,1993).dephosphatationcapacityinphosphorusremovingNitrateisawell-knowninhibitingfactortotheorganisms.Fromthedifferenceofthephosphorusphosphorusreleaseprocessintheanaerobicphasereleaseactivitywithandwithoutnitrate,therelativewhereCODisavailable(Yeomanetal.,1986;Jenkinsproportionmaybecalculated.However,theexactandTandoi,1991;Rensink,1992;vanStarkenburgmetabolismofphosphorusreleaseforDPBaswellasetal.,1993).Inpractice,biologicalphosphorusaerobicphosphorusremovingbacteriainsimul-removalprocessesareoftencombinedwithtaneouspresenceofCODandnitrateisnotyet(de)nitrification(e.g.modifiedUCTprocesses)whichknown.caneasilyleadtointroductionofnitrateintotheAnalternativeassaycouldutilizethecharacteristicanaerobicphase.Inordertoelucidatethereasonforthatalldenitrifyingmicroorganismsknowncanusetheinhibitingeffectofnitrateonphosphorusrelease,oxygenasanelectronacceptor,whereasonlysomeseveralresearchershaveconductedbatchtestswithaerobicorganismscanutilizenitrateasanelectrontheactivatedsludgeinthesimultaneouspresenceofacceptor.DPB,therefore,areexpectedtofunctionCODandnitrate(IwemaandMeunier,1985;underaerobicoranoxicconditions,whereasaerobicHascoetandFlorentz,1985;Comeauetal.,1990;phosphorusremovingbacteriaareinactiveunderanoxicconditions.Thus,adirectcomparisonofphosphorusuptakeactivitiesunderaerobicand*Authortowhomallcorrespondenceshouldbeaddressed,anoxicconditionsmayleadtoastraightforward471472A.Wachtmeisteretal.characterizationofthemicrobialpopulationinthefirst10minoftheanaerobicphase.Intheanoxicphase,phosphorusremovingsludge.0.1Lnitratesolution(1.64gNL-])waspumpedintothereactorwithaconstantflowrateduringthefirstIl0rain.Inthisresearch,phosphorusreleasebatchtestsinTheoverallhydraulicretentiontime(HRT)was0.5dayssimultaneouspresenceofCODandnitratewereandthesludgeretentiontime(SRT)wasapproximately14conductedbyusingDPBsludgeenrichedunderdays.pHwasstrictlycontrolledat7.0___0.05byadditionofanaerobic-anoxicconditionsandaerobicphosphoruslNHCIorNaOH,toavoidchemicalphosphateremovingsludgeenrichedunderanaerobic-aerobicprecipitation.Anaerobic-aerobic(A/O)SBR.TheconventionalA/Oconditions.BesidestheanoxicphosphorusreleaseSBRwasoperatedunderalmostsimilarconditionstotheA2tests,phosphorusuptakebatchtestswereconductedSBR,exceptfortheSRT.TheSBRoperationandpropertiesunderaerobicandanoxicconditionswithactivatedoftheA/Osludgearedescribedelsewhere(Smoldersetal.,sludgefromafullscalewastewatertreatmentplant1994a,b).TheHRTwas0.5daysandtheSRTwasapproximatelyforphosphorusandnitrogenremoval.Th