Effectofprefermentationondenitrifyingphosphorusrem

EffectofprefermentationondenitrifyingphosphorusremovalinslaughterhousewastewaterM.Merzoukia,b,N.Berneta,*,J.P.Delgene`sa,M.BenlemlihbaInstitutNationaldelaRechercheAgronomique,LaboratoiredeBiotechnologiedel
Environnement,AvenuedesEtangs,11100Narbonne,FrancebLaboratoiredeMicrobiologiedel
Environnement,Faculte´desSciencesDharMehraz,B.P.1796,Fe´s,MoroccoReceivedinrevisedform3November2004;accepted23November2004Availableonline20January2005AbstractAnanaerobic–anoxicsequencingbatchreactor(A2SBR)coupledwithafixed-bednitrificationreactorforsimultaneouscarbon,nitrogenandphosphorusremovalwasevaluatedusingslaughterhousewastewater.Whereasthetreatmentcouldnotbesuccessfullycarriedoutontherawwastewater,theprocessshowedverygoodnutrientremovalperformancesafterprefermentation.Therem-ovalsofCOD,N-NH4andP-PO4achievedwere99%,85%and99%,respectively.Theincreaseinvolatilefattyacid(VFA)andphosphateconcentrationsintheeffluentafterprefermentationmayexplainthehighlevelsofbiologicalcarbon,nitrogenandphos-phorusremovalobserved.Asimpleprefermentationis,therefore,necessarybutsufficienttoensuregoodperformancesoftheden-itrifyingenhancedbiologicalphosphorusremoval(EBPR)process.
2004ElsevierLtd.Allrightsreserved.Keywords:Anoxicphosphorusremoval;Enhancedbiologicalphosphorusremoval(EBPR);Sequencingbatchreactor(SBR);Fixed-bednitrification;Prefermentation;Slaughterhousewastewater;Volatilefattyacids(VFA)1.IntroductionEnhancedbiologicalphosphorusremoval(EBPR)isbasedontheselectiveenrichmentofbacteriaaccumulat-ingpolyphosphate,obtainedinaprocesswithacycleofalternatinganaerobicandaerobicphases.Asanalterna-tivetothisprocessforbiologicalphosphorusremoval,theanaerobic–anoxicsequencingbatchreactor(A2SBR)processhasbeenrecentlyproposedbydifferentresearchers(Vlekkeetal.,1988;Wanneretal.,1992;Kubaetal.,1993;Bortoneetal.,1994;Sormetal.,1996).TheA2SBRisanattractiveprocessbecauseofthesavingoforganicmatterandenergyascribedtoaerationandlowsludgeproductionforcompletephosphorusandnitrogenremoval(Kubaetal.,1993,1994,1996).Dur-ingtheanaerobicperiod,thepolyphosphate-accumulat-ingorganisms(PAO)takeupcarbonsources,preferablyvolatilefattyacids(VFA),andstorethemaspolyhy-droxyalkanoates(PHA).Thedegradationofpolyphos-phatecausesareleaseofphosphateintothebulkliquid,andaproductionofenergynecessaryforanaer-obicuptakeofcarbonsourcesandtheirconversionintoPHA.Duringthesubsequentaerobicoranoxicphase,PAOtakeupphosphatefromthebulkliquidandstoreitintheformofpolyphosphate,whilePHAisusedasacarbonandenergysource(JenkinsandTandoi,1991).Thephosphorusuptakeunderanoxicconditionsisattributedtotheactivityofdenitrifyingphosphorusaccumulatingorganisms(DNPAO)capableofaccumu-latinghighamountsofpolyphosphate(Minoetal.,1995).Thephosphorusandnitrogenare,therefore,re-movedsimultaneouslybytheseorganisms.ThisisoneofthemainadvantagesofapplyingtheA2SBRprocessforbiologicalnutrientremoval.0960-8524/$-seefrontmatter
2004ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2004.11.017*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](N.Bernet).BioresourceTechnology96(2005)1317–1322Theconceptofbiologicalphosphorusremovalunderalternatinganaerobicandanoxicconditionscombinedwithafixed-bednitrificationreactorwasproposedforthefirsttimebyWanneretal.(1992)andJeniceketal.(1993).Thisinnovativeprocess,calledDEPHA-NOXbyBortoneetal.(1996),showedverygoodperfor-mancesforphosphorusandnitrogenremovalfrommunicipalwastewater.Manyindustries,suchasfoodindustriesincludingslaughterhouses,producelargequantitiesofwastewatercontaininghighconcentrationsoforganicmatter(COD),suspendedsolids,nitrogenandphosphoruscompounds.Inthepresentwork,anintegralprocessforsimultaneouscarbon,nitrogenandphosphorusremovalwasproposed,tobeappliedtoindustrialwaste-water.ThisprocessisanA2SBRcoupledwithafixed-bednitrificationreactor.Thefeasibilityandstabilityofthiscombinedsystemwereinvestigatedwhiletreatingaslaughterhousewastewater.2.Methods2.1.Experimentalset-upThetreatmentprocessusedinthepresentworkisschematisedinFig.1.ASBRwasoperatedforsimulta-neousdenitrificationandenhancedbiologicalphospho-rusremoval(anaerobic–anoxicSBR,A2SBR).TheSBRwascombinedwithafixed-bedreactorwhichwasoper-atedunderaerobicconditionsfornitrification.2.2.Anaerobic–anoxicSBR(A2SBR)PhosphorusremovalwascarriedoutintheA2SBRinoculatedwithsludgefromanactivatedsludgetreat-mentplant(Roanne,France).TheworkingvolumeoftheSBRwas1.5l.pHvalueintheSBRwasstrictlycon-trolledto7±0.1bytheadditionof0.5NH2SO4orNaOH.Theoverallhydraulicretentiontimewas12h.TheA2SBRwasoperatedinacycleof6hwhichcon-sistedoffourphases:(1)1.5hanaerobicphase.Atthebeginningofthisphase,0.75lwastewaterwassuppliedtothereactor,whichcontained0.75lmixedliquorinitially,over7min.(2)0.5hfirstsettlingandfeedingperiod.After22minofsettlement,1lanaerobicsupernatant(NHþ4andPO3
4rich)wasdirectlyfedintothefixed-bedreactor.(3)3.5hanoxicphase.Onelitrenitrateandphosphatericheffluentfromthefixed-bedreactor(storedinanexchangetank,seeSection2.3)wassenttotheA2SBRover3hataflow-rateof5.6mlmin
1(fed-batchmode).Attheendoftheanoxicphase,theex