Electricfieldstreatmentforthereductionofmembranefo

PresentedattheconferenceonWastewaterReclamationandReuseforSustainability(WWRS2005),November8–11,2005,Jeju,Korea.OrganizedbytheInternationalWaterAssociation(IWA)andtheGwangjuInstituteofScienceandTechnology(GIST).Electricfieldstreatmentforthereductionofmembranefouling,theinactivationofbacteriaandtheenhancementofparticlecoagulationJong-OhKima*,Jong-TaeJunga,Ick-TaeYeomb,Gyung-HaeAohcaDepartmentofCivilEngineering,KangnungNationalUniversity,GangneungDaehangno120,Gangneung,Gangwon-do210-702,SouthKoreaTel.+8233640-2420;Fax[phone];email:[e-mail]nvironmentalEngineering,SungkyunkwanUniversity,Chunchun-dong300,Suwon,Kyonggi-do440-746,SouthKoreacR&DCenter,SamsungEngineeringCo.,Ltd,SEITower467-14,Dogok-dong,Gangnam-gu,Seoul,SouthKoreaReceived31July2005;accepted23December2005AbstractTheobjectiveofthisstudyistoevaluatetheeffectofelectricfieldsapplicationforthereductionofmembranefouling,theinactivationofmicroorganismsandtheenhancementofparticlecoagulation.Itwasfoundthatelectricfieldstreatmentpriortomicrofiltrationshowedinlargequantityofcumulativepermeatesthanthoseinnon-electricfields.Thisisattributedtothepromotionofparticlecoagulationandinteractionbetweenparticleandmembranesurface.Thenumberofactivebacteriawasreducedbyelectricfieldstreatment.Thismaybeapositiveresultforthepreventionofmembranebiofoulingaswellasmicrobialinactivation.Coagulantdosagecouldalsobesavedabout75%comparedwithnon-electricfieldsintermsofthe95%turbidityremovalat10(kV/cm).Therefore,itisexpectedtoimprovetheefficiencyandtheeconomicsoftheprocessbyprovidingelectricfieldsforwastewatertreatment.Keywords:Electricfields;Microfiltration;Membranefouling;Microbialinactivation;Coagulation1.IntroductionInordertoincreasetheefficiencyofmicro-filtration,electro-microfiltrationhasbeenusedforthetreatmentofwastewater.Thecontrolofmembranefoulingbytheapplicationofexter-naldc(directcurrent)electricfieldshasbeenstudiedinseveralapplications,andinsomecasesaclearenhancementhasbeenachieved.Thistreat-menttechnologyhasbeenfoundtobecapableof*Correspondingauthor.Desalination202(2007)31–37doi:10.1016/j.desal.2005.12.0350011-9164/06/$–Seefrontmatter©2006PublishedbyElsevierB.V.32reducingtheformationoffiltercakeandincreasingthefluxoffiltrate[1–3].Electricfieldsenhancedmicrofiltrationprovidesaveryefficienttechniquefortheremovalfromwaterofhydrophobicallymodifiedwastersolublepolymer[2].Anelectri-callyenhancedcrossflowmicrofiltration(EECMF)wasusedforthetreatmentofoxide-CMP(chemi-calmechanicalpolishing)wastewater[1].How-ever,therearefewcasestudiesofapplicationsaspre-treatmentstepinwastewatertreatment.Itisalsoreportedthatelectricfieldstreatmentasnon-thermalprocessarebeingdevelopedtoinacti-vatepathogenicmicroorganismsinfoodindustry[4,5].Inaddition,itwaseffectivetoremovenitrateionbyforminginsolublecomplexsaltunderelec-tricfields[6].Thisstudyfocusedonthefollowing:(1)membranefoulingreductionandoperationalfactorsforcumulativepermeates,(2)theinacti-vationofmicroorganism,and(3)theenhance-mentofcoagulationbyelectricfieldstreatment.2.Materialsandmethods2.1.SystemdescriptionFig.1showstheelectricfieldssystememployedinthisstudy.Model(Innoclean-L4V)with40cminheight,25cmindiameterand180mLinthevolumeofreactorwasused.Freshsewageofmunicipalwastewatertreatmentplantwasusedasfeed.Feedwasflowedatlowerpartofreactorandthendischargedatupperpartbyperistalticpump.Permeatewasobtainedfromametalmembranebysuctionofpump.Electricfieldsintensitywascontrolledintherangefrom0to40kV/cmbydirectcurrentpowersupply.Theinorganicmembraneformicrofiltrationwassup-pliedfromFibertechCo.,Ltd,Koreaandwasatubulartypecapableofsubmergedfiltration.Itismadeofstainlesssteel(SUS316L)materialandhasanominalporesizeof1mm.PACl(polyalu-minumchloride)asinorganiccoagulantwasusedfortheinvestigationofcoagulationenhancement.2.2.AnalysisExperimentalanalysisitemsarepH,suspendedsolids(SS),turbidity,totalorganiccarbon(TOC),generalbacteria,zetapotentialofparticlesandparticlesizedistribution.UsingpHmeter(modelOrion250A)andturbiditymeter(modelturb550IR),theyweremeasuredasafunctionoftime.TOCwasanalyzedbyTOC5000,Shimadzu,Japan.ZetapotentialofparticlesandparticlesizedistributionweremeasuredusingELS8000,OtsukaCo.,Ltd,Japan,andLS230Parti-clesizeanalyzer,BeckmanCoulterCo.USA,respectively.MeasurementsofotheritemssuchasthenumberofbacteriaandSSwereallquantifiedbystandardmethods[7].3.Resultsanddiscussion3.1.Microfiltrationperformance;effectofelectricfieldsintensityTherelationshipoftheelectricfieldsintensityandcumulativepermeateisshowninFig.2underdifferentappliedelectricintensity.Intherangefrom0to40kV/cm,cumulativepermeateincreasedattheearlystageofthefiltrationwhenFig.1.Schematicdiagramofelectricfieldssystem.ChargingelectrodeCounterelectrodeElectricunitControllerElectricfieldPermeatePumpPumpReservoirFeedtankMetalmembraneManometerJ.-O.Kimetal./Desalination202(2007)31–3733electricfieldsintensityincreased.Thismaybeascribedtothepromotionofparticlecoagulationandinteractionbetweenparticlesandmembranesurface.However,fortheelapseoffiltrationtimeab