Performanceandmicrobialsurveyinginsubmergedmembran

Availableonlineat(2008)43–49PerformanceandmicrobialsurveyinginsubmergedmembranebioreactorforseafoodprocessingwastewatertreatmentPorntipChoksuchartSridanga,b,∗,AnthonyPottierc,ChristelleWisniewskic,AlainGrasmickcaDepartmentofCivilEngineering,FacultyofEngineering,PrinceofSongklaUniversity,Songkla90112,ThailandbMembraneScienceandTechnologyResearchCenter(MSTRC),PrinceofSongklaUniversity,Songkla90112,ThailandcLaboratoiredeG´eniedesProc´ed´esEauetBioproduits,Universit´eMontpellierII,PlaceEug`eneBataillon,34095MontpellierCedex05,FranceReceived10January2007;receivedinrevisedform29October2007;accepted5November2007Availableonline17November2007AbstractThemainobjectiveofthisstudyistoevaluatetheperformanceandthestructureofthemicrobialcommunityofasubmergedmembranebioreactor(MBR)forseafoodprocessingwastewatertreatmentandreuse.Thissystemwasoperatedcontinuouslyunderfavourablebiologicalconditions,withcompletebiomassretention.Intermsoforganicremovalandmembraneperformance,theMBRhadagoodefficiencytotreathighstrengthwithorganicloadingvariationcharacteristicofrealseafoodprocessingwastewater.TheoverallresultsshowedtheimportanceofecologicalmicrobialcompositionsineachstageofdevelopmentthatweredifferentinMBRincomparisonwithconventionalactivatedsludge.TheMBRsludgecouldtoleraterealstressessuchassalinityandvariationofCODandSSinletinawiderange,withalwaysgoodremovalefficienciesintermsofBODandCOD.Atthebeginningperiod,bulkingsludgewaspresent.After700hofoperation,thesludgecharacteristicsnotonlyshowedhealthyflocformationsandgoodsettling,butalsoconfirmedthestablestateofthesystemwithoutovergrowthfilamentousbacteria.Inevaluatingthefoulingpotentialofmembranebycakefiltrationtheory,itwasfoundthatsolublesubstances,solublemicrobialproductsand/orresidualorganicsplayakeyroleininducingmembranefouling.TheαWvaluesofthesolublefractionwerethreetimeshigherthanthoseoftheparticulatesofbacterialfloc.©2007ElsevierB.V.Allrightsreserved.Keywords:Membranebioreactor;Seafoodwastewater;Microbial;Foulingpotential;Performance1.IntroductionInThailand,seafoodindustryrepresentsoneofthesignifi-cantpartsofeconomicresourcesforexports,currentlyrankedinthetop10exportvalue,withanaverageannualincomeof320milliondollarstogetherwithapproximately10%growthrateeachyear.Interestingly,mostexpansionisfoundinthecoastalarea,especiallyinsouthernpartsofThailand.Never-theless,givensuchcontinuedgrowthinindustrialactivities,waterconsumptiondemandsunavoidablybecomeakeyfac-tor,estimatedat10–40m3t−1ofrawmaterials[1].Because∗Correspondingauthorat:DepartmentofCivilEngineering,FacultyofEngi-neering,PrinceofSongklaUniversity,90112Thailand.Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail](P.C.Sridang),[e-mail](C.Wisniewski),[e-mail](A.Grasmick).oflimitationsinnaturalresourcedegradation,wastewatertreat-mentplantisenvisagedtofavouron-sitewaterreuseandtopassstringentdischargestandards.Withtheserequirements,membranebioreactor(MBR)technologyisanattractiveoptionforthetreatmentofsuchindustrialwastewater.Thiskindofwastewatercontainsalargepartoffoodwasteeasilybio-degradableaswellashighcontentoforganicnitrogen,andaverysmallquantityofhighpollutantloading;hencethebiologicalwayoftreatmentandseparationprocessbymem-braneintermsofsubmergedmembranebioreactormaybeenvisaged.Thesystemsworkinginoutside–insidefiltrationmodehavebeenusedinseveralapplicationsofwaterandwastewaterover30yearsandstrategyhavebeendevelopedtopreventandreducemembranefoulingtoachieveprocessoptimizationinindustrialscale[2–4].Sub-criticalfluxconcepthasbeenintroducedandapproachedtoeachMBRconditionforlongrunoperation[5–7].Hydrodynamictechniquesareusedtocontrolandminimize0376-7388/$–seefrontmatter©2007ElsevierB.V.Allrightsreserved.doi:10.1016/j.memsci.2007.11.01144P.C.Sridangetal./JournalofMembraneScience317(2008)43–49reversiblefoulingthatiscausedbytheconcentrationpolariza-tionandparticledeposition.Theadsorptionandporeblockingphenomenafrommacromoleculessuchasproteins,polysac-charidesandorganiccolloidfractions,createdfrommicrobialmetabolismanditsactivities,arestillthemajorcauseofmem-branepermeabilitydecrease[7–10].Biologicalprocesscontrolnotonlyplaysakeyroletoprovidetheimprovementoftreat-mentefficiencybutalsoenhancethefiltrationperformance.Inaddition,conditioningofbiologicalsuspensionbycoagulantandadsorbentsuchaspowder-activatedcarbonisalsorecom-mendedandapprovedtominimizeloadsofirreversiblefouling[11–13].BasedonthepotentialitiesoftheMBRprocess,theobjec-tiveofthisworkistoevaluatetheperformanceofasubmergedmembranebioreactorandthestructureofmicrobialcommu-nitypresentinthereactorfortheseafoodprocessingwastewatertreatmentandreuse.2.Materialsandmethods2.1.Experimentalset-upandwastewaterDuetothehightreatmentperformanceofmembranebiore-actor[4–6],itwasselectedtotreatwastewaterfromaseafoodprocessingindustrysuchassurimiproducts.Theexperimentswerecarriedoutonalab-scaleMBR(Fig.1)whereaflatsheetmembranewasdirectlyimmersedinthereactorof35l.Themembraneusedwasapolyethersulfonemembranewithapor