超滤技术用于饮用水工业用水及废水处理

ArticleID:1007-8924(2003)04-0246-09Ultrafiltrationtechnologyforpotable,processandwastewatertreatmentHarryFutselaar,HenkSchonewille,HarryvanDalfsen,SHENLei(NORITMembraneTechnologyB.V.,P.O.Box731,7500ASEnschede,TheNetherlands)Abstract:Membranesareservingtheworldmoreandmoretosupporttheneedforhigherqualitywater.Sincethehistoricoutbreakofresistant,butlethalbacteriaindrinkingwater,membraneshavefoundtheirwaytobecomeasafetybarrierforthesebacteriaandvirusesinthedrinkingwa2terproductionanddistribution.Inthewastewatertreatmentmembranesareusefultoseparatesubstancesorparticlesfromthewastewaterforreuse.Anoverviewofthestate-of-the-artap2plicationsofultrafiltration(UF)fortheproductionofpotableandprocesswaterandthetreatmentofwastewaterwasintroduced.Keywords:ultrafiltration;capillarymembranes;potablewater;processwater;wastewaterCLCnumber:TQ028.8Documentcode:A1IntroductionThepollutionoffreshsurfacewaterandthein2creasingdemandswithregardtohealthandthequali2tyofourwatermagnifytheavailabilityproblem.Wa2terpurification,therefore,willplayakeyroleinthecomingdecadesintheworld-widegrowthinhealthandprosperity.Thereisaneedforrobust,selectiveandeconomicalpurificationtechniques.Inaddition,recyclingofwastewaterisgoingtodeterminealargepartofthesuccessofthesenewtechnologies.Mem2branefiltrationisoneofthemostpromisingtechnolo2giesthathasemergedinthepastdecadecoveringalltheserequirements.Thedevelopmentstartedinthesixtieswiththeintroductionofthefirstreverseosmosis(RO)mem2branesfordesalinationpurposes.Sincethen,mem2branetechnologyhasseenatremendousgrowthinde2velopmenteffort,creatingawholenewandextensivemarketofmembranefiltrationapplications.Besidesdesalinationtechnologies,awholerangeoffurtherdevelopedmembranefilterswascreatedrangingfromnanofiltrationNF(softeninganddecolouring)throughultrafiltrationUF(virusremoval)tomicro2filtrationMF(suspendedsolidsremoval).MostoftheearlyUFandMFprocessesusedthecross-flowprinciplewherethesuspensiontobefil2teredispumpedalongthemembranesurfaceinordertoavoidfoulingandonlyasmallportionisactuallyfilteredthroughthemembrane.Ofcourse,thispar2ticularmethodofoperationfeaturesafairlyhighener2gyconsumption,whichimmediatelystressesoneofthemajordrawbacksofmembranesystemsofthattime.CurrentlymanyUFandMFsuppliersstillfol2lowthisprinciple.Thisarticle,however,introducestheprinciplesandlargescaleexperienceofalowener2gyUFsystemmakingsustainablewatertreatment,recoveryandreuseareality.2Semidead-endultrafiltrationLookingatwatertreatmentschemes,andthehugeamountsofwatertobetreated,itbecameap2parentintheeightiesthatenergyconsumptionwastheimportanttopic.IfmembranefiltrationwastoReceiveddate:2003-06-24Correspondingauthor:HarryFutselaar,Tel.[phone],e-mail:[e-mail].234Vo1.23No.420038MEMBRANESCIENCEANDTECHNOLOGYAug.2003©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.becomeoneoftheleadingwatertreatmenttechnolo2giesforlargeapplications,energyconsumptionhadtobecut.Therefore,membranemanufacturersbegandevelopingenergyefficientmembranesystems,alsoknownasdead-endorsemidead-endsystems.Ba2sically,thesystemworkslikeacoffeefilter,elimi2natingallsolidsinsuspensionandretainingthemonthemembranesurface.Suchafiltrationprocesscan2notbemaintainedindefinitely,duetothefactthatthedrivingforceacrossthemembranehastobein2creasedcontinuallytokeeptheflowthroughthemembraneconstant.Thereforthesystemisback2washedbyreversingtheflowdirectionthroughthefilteratregularintervals,hencethenamesemidead-endfiltration.Thesolidsarewashedawaytodrainandthewholeprocessrepeatsitself.Whilebackwashingcanremovemostofthesolidsfromthesystem,inmostcasesrigorousmethodshavetobeappliedtocompletelycleanthemembrane.Duetothefactthatsomesubstancesclingtothemembranesur2face,theycannotberemovedbymechanicalforcealone.Thesesubstances,oftenoforganicandmicro2bialorigins,tendtoslowlybutsurelyblockorfoulthemembrane.Theyareeitherinsolution(smallor2ganiccompounds)andwilladheretothesurfaceormicrostructureofthemembrane,ortheyconstitutemicro-organismsthatareremovedbythemem2brane,butstartproducingextracellularsubstancesoncetheyhavesettledontothemembranesurface.Mostofthesefoulingsubstancescanberemovedbychemicals(reversiblefouling).3TechnologyDead-endmembranefiltrationwithhollowfi2breorcapillarymembranescanbedividedinthreeseparatesubprocesses:filtration,backwashingandchemicalcleaning.Filtrationisperformedinsideout;i.e.thefeedwaterisfedintothelumenofthefibresandexitsthemembraneattheshellside.Thefiltrateiscollectedandexitsthemembraneelementthroughacentralfiltratepipe(Fig.1).ThemajorbreakthroughofthistechnologycameFig.1Pressurevesselwithmembraneelementmounted(a)andMembranemodule(b)withthesemidead-endXIGATM-concept,basedontheX-Floweight-inchdead-endultra-filtra2tionmembraneelement.TheXIGATM-conceptuseseight-inchpressurevessels,ascommonlyadoptedintheROindustry.Insidethevessel,anumberofmembraneelementsarelined-out.Theelements,eachwithalengthofsixtyinch(1.5metre),arefilledwithcapillarymembranes.Themembranesaretypically0.8or1.5mmindiameter,providingamembraneareaof35or22m2inoneelement.Fig.2pr