ApplicationofMicroFiltrationOsmosisTechniques

ApplicationofMicroFiltration/ReverseOsmosisTechniquesinRegenerationofPetro-chemicalWastewaterCheChunboDepartmentofEnvironmentalEngineeringHarbinUniversityofCommerceHarbin,Chinae-mail:[e-mail]—Micro-flocculationandcontinuousmicrofiltration(CMF)processeswereusedforpretreatmentofreverseosmosis(RO),UsingCMFandROtechniques,petro-chemicalwastewateraftersecondarytreatmentwasregenerated.Theconductivityofthetreatedwastewaterisbelow100ȝs/cm,oilisbelow1mg/L,turbidityisbelow0.5NTU,SDIisbelow3,andthewastewatersallmeettherequirementofROinletwater.Theconductivityofthetreatedwastewaterisbelow100ȝs/cm,thedesalinizationrateofROsystemisabove98%.Completelyreachthewaterstandardofthemakeupwaterintheboiler.Keywords-microfiltration;reverseosmosis;petro-chemicalwastewater;regenerationtreatmentI.INTRODUCTIONPetrochemicalwastewaterduetoahighconcentrationoforganicpollutants,poorbiodegradability,pHlargechanges,easytoformashockloadcharacteristics,itisdifficulttousethetraditionaltreatmentprocesstoachievethewaterrecyclingrequirements[1].Membranefiltrationtechniqueisaliquidseparationtechnology,withhighefficiency,lowenergyconsumptionandeasyoperation.Comparedtotraditionalmethodsofwastewatertreatment,membranetechnologyhasmanyadvantages,suchasthecirculatoryuseofwastewaterandrecoveryofusefulsubstances[2].TheROasagoodprospectinwastewaterreuse.ButbecauseROhasstrictrequirementsoftheincomingwaterwhichlimitsitsapplications.TheCMFhasastrongadaptabilitytotherawwaterquality,ithasastableproducingwateranditishighautomat,whichmakeitanidealpretreatmenttoensureROrunsafely[3-4].Continuousmicrofiltration/reverseosmosistechniqueswereusedtododeeptreatmenttothetwo-stagetreatedwastewaterinpetro-chemicalplantstoproducewaterreusedasthemakeupwaterinboiler.II.EXPERIMENTPARTSEA.RawwaterqualityandtherequirementsofproducingwaterTaketheproducingwaterofsecondsedimentationpondfrompollutionwastewatertreatmentplantasrawwater,itsrawwaterquality:turbidityisbelow5NTU,oilisbelow10mg/L,theconductivityisbelow2000ȝS/cm,CODCrisbelow150mg/L.Therequirementsofproducingwater:theconductivityisbelow100ȝS/cm,turbidityisbelow1NTU.Oilshallnotbedetected.B.TechnicalprocessRawwaterrunsintocolumnafterusingthesynthesizedtreatmentofmicro-flocculationPolyaluminiumChlorideandupflowmovingbedfiltertoremovethesuspendedmatterandmacromolecularcolloid.AndproducingwatercomesintoROsystemtodofurthertreatmentsaftergoingthroughthecarbonfiltertoremovetheorganiccompounds,somepigmentandtheresidualchlorinethatisharmfultoreverseosmosismembrane.ThehollowfibermembraneisAmericanTao4040membranemodule,madeofPVDFthereareinterlockingporesfrom1to10ȝminthepipewall,singlemembranefluxis0.5t/h,areais7m2,withsodiumhypochloritesterilizationaddingmedicinesystemandchemicalcleaningsystem.Thesystemusesanewkindofexternalpressurehollowfibermembranecleaningtechniqueonthemicrofiltrationmembranetorealizeonlinecleaningandrealizecontinuousproducing.ReverseosmosismembraneusesAmericanTaoBW30-365FRmembranemodule,singlemembranefluxis0.27t/h,areais12m2,singlemembranerecoveryrateis15%,desalinizationrateisabove98%.Equippedwithchemicalcleaningsystemtopreventmembranescalingandoxidationaddingscaleinhibitorandreducingagent.ConcretetechnicalprocessisshowninFigure1.C.AnalysisprojectsandmethodsCODCr:CTL-12fastcryoscopy,conductivity:DS-11conductivitymeter,Oilcontent:infraredspectrophotometry,turbidity:WGZ-100Electro-opticalturbiditymeter.Figure1.TechnicalProcessProducingwaterROsystemSecurityfilterActivatedcharcoalfiltrationMicro-filtrationpoolCMFsystemChemicalcleaningsystemMicro-flocculationpoolWastewaterUpflowmovingbedfilterTraditionaltreatmenttechnics2010InternationalConferenceonChallengesinEnvironmentalScienceandComputerEngineering978-0-7695-3972-0/10$26.00©2010IEEEDOI10.1109/CESCE.2010.845282010InternationalConferenceonChallengesinEnvironmentalScienceandComputerEngineering978-0-7695-3972-0/10$26.00©2010IEEEDOI10.1109/CESCE.2010.84527III.RESULTSANDDISCUSSIONSA.TheeliminationofturbidityFigure2showsthatCMFhasgoodeliminationeffectonsuspensionsandcolloidandtheturbidityofproducingwaterisbetween0and1.0NTU(averageis0.5NTU),eliminationrateisabove99%.Thisisbecauseinthesituationthatrawwaterturbidityishigh,inordertoenhanceCMFsystemsturbidityeliminationeffect,addingflocculantintotherawwatertodomicroflocculation,andthismakesmicrofiltrationmembraneinterceptnearlyallthecolloidandsuspendedparticulate,providinggoodpretreatmenttoreverseosmosis[5].Duetotheturbiditymetermainlyusedinthedetectionofphotosensitivesuspendedsolidsinthewater,non-photosensitivecolloidandparticlescannotbedetected,soSDIvalueisusedforfurtherjudgefromCMFsystem.Fromfigure3,SDIfromCMFwaterisbelow3,andmeetsthedemandsoffillingtheROsystemwithwater.B.TheeliminationoforganiccompoundsAsshowninfigure4,theremovalrateoforganicmatterinwatertoreach27.5%and72.2%forCMFsystem.TheeliminationeffectonorganiccompoundsofCMFisrelatedalotwiththeturbidityoftheemissionswater,suspensionandthecontentofcolloidinemissionswaterisbiggerwhentheturbidityisbigger,andthesuspensionandcolloidcanabsorbalotoforganiccompo