12LowpressureROmembranedesalinationofagriculturald

ELSEVIERDesalination155(2003)109-120DESALINATION]ocate/desalLow-pressureROmembranedesalinationofagriculturaldrainagewaterRon-WaiLee,JuliusGlatera,YoramCohen*,ChrisMartinb,KurtKovacc,MartinN.Milobard,DanW.BarteldaDepartmentofChemicalEngineering,UniversityofCalifornia,LosAngeles,LosAngeles,CA90095-1592,USATel.+1(310)825-8766;Fax[phone];email:[e-mail]oration,5001E.CommercenterDrive,Suite100,POBox12030,Bakersfield,CA93309,USACDepartmentofWaterResources,SanJoaquinDistrict,Fresno,CA93726-6913,USAaBuenaVistaWaterStorageDistrict,525NorthMainStreet,Buttonwillow,CA93206,USAReceived7October2002;accepted18December2002AbstractAgriculturaldrainagewaterisacomplexmixtureofdissolvedandsuspendedchemicalspeciesandmaycontainawidevarietyofmicroorganisms.Theapplicationofmembranesystemsfordesalinationofagriculturaldrainage(AD)waterrequirescarefulconsiderationoffeedwaterquality,suitablemembraneselectionandoperatingconditions.Inordertoevaluatethepotentialapplicabilityoflow-pressurereverseosmosis(RO)tothetreatrnentofADwater,adiagnosticapproachtomembraneselectionandprocessevaluationwasundertakeninsupportofapilotfieldstudyintheCaliforniaSanJoaquinValley.Fivecandidatemembraneswereevaluatedinadiagnosticlaboratorymembranesystemwhichprovidedaninitialselectionbasedonsaltrejectionandproductwaterfluxperformanceformodelsaltsolutionsofunivalentanddivalentcations.Biofoulingpotentialoftheselectedmembraneswasalsoevaluatedusingtwostandardsstrainsofbacteria.Preliminarypilotplantperformance,basedontheselectedmembranes,wasencouragingandhasprovidedthebasisforlong-termpilotplanttestingathigherrecoveriestoassesstheimpactoffluctuatingADwaterfeedcomposition.Keywords:Agriculturaldrainagewater;Reverseosmosis;Membranediagnostics,Desalination;BiofoulingI.IntroductionTiledrainageofirrigatedlandsispracticedinmanysemi-aridagriculturalregions.Adversegeologicalconditionsinsuchareasofteninvolveimperviouslayersunderlyingfertileland[1-3].*Correspondingauthor.Artificialdrainageispracticedinsuchareasinordertopreventwater-loggingandsalinitybuild-upintherootzoneofcrops.HydrologicandenvironmentalimpactsofartificialdrainagehavebeenextensivelyreviewedbySkaggsetal.[4].Thefertilesemi-aridCaliforniaSanJoaquinValleywasoneofthefirstregionstoinstalltile0011-9164/03/$-Seefrontmatter©2003ElsevierScienceB.V.AllrightsreservedPII:S001I-9164(03)00288-1110R.-W.Leeetal./Desalination155(2003)109-120drainagesystemsforirrigationwaterwhichhasprovedtobethemosteffectiveapproachofcon-trollingrootzonesalinity.Sincetheearly1970s,seriousconsiderationhasbeengiventosystemsforreclamationandreuseofagriculturaldrainagewater.Motivationforapplicationofthistech-nologyarosefromtwomajorissues.First,asuccessfulreclamationfacilitywouldhelptoaugmentdiminishingsuppliesofimportedirrigationwater.Second,volumereductionofenvironmentallyhazardousdrainagewatercouldalsobeachieved.Thefeasibilityofreverseosmosis(RO)fordrainagewaterreclamationwasfirstdemonstratedin1971atthehistoricpilotfacilityatFirebaugh,California[5,6].AlargerandconsiderablymoresophisticatedtreatmentplantwascompletedinthenearbytownofLosBafios[7-9]inthemid1980stostudyavarietyofoperatingparametersandtoassesstheeco-nomicfeasibilityofdrainagewaterreclamationwithROtechnologyasanimportantcomponent.Thisplantwasunfortunatelyshutdownin1987duetoconcernwithhighconcentrationsofselen-iumintheformofSeO2-ionfoundatKestersonthesiteofalow-lyingbasinforalltiledrainageinthatregion.TiledrainageintheWestCentralSanJoaquinvalleyhassincebeenterminated,resultinginaseverehardshipforthefarmingcommunity.Ifnotresumed,agradualsalinitybuild-upwillnecessitatetheretirementoflargeareasoffertileagriculturalland.Asearchforsolutionstothedrainageproblemispresentlyunderway,andagain,membranedesalinationhasbeengivenseriousconsiderationowing,inpart,toanewgenerationofhigh-performancelow-pressureROandnanofiltration(NF)membranesdevelopedduringthelastdecade[10,11].Low-pressureROmembranescanoperateatremarkablylowpressureswithexcellentproductwaterfluxandreasonablyhighlevelsofsaltrejection.However,selectionoftheappropriatemembraneforADwaterdesalinationmustinvolvecarefulconsiderationoffeedwaterquality.ConsiderationofwaterqualityinrelationtooptimizationofthedesalinationprocessisespeciallycriticalwithADwater,whichisacomplexmixtureofdissolvedandsuspendedorganicandinorganiccomponentsaswellasawidevarietyofmicroorganisms.TheacceptableTDSforirrigationwaterisabout750mg/L.However,TDSofADwaterfromtheSanJoaquinValleyvariesbetween3,000and15,000mg/Lmandmostsamplesareclosetosaturationwithrespecttogypsum(CaSOa2H20).WaterreusenecessitatesdesalinationofthiswatertoachievethedesiredTDSlevel.More-over,thecontrolofgypsumscaleformationiscriticaltoestablishingpracticalfieldinstallationsofmembranedesalinationofADwater.Anti-sealants,consistingprimarilyofpolyelectrolytes,havemetwithsomesuccessininhibitingmembranesurfacescalingbygypsum.Otherimportantaspectsaffectingmembraneperfor-mancearecolloidalparticlesandpotentialmicrobiologicalgrowth.Optimizationofmembranedesalinationsys