外文翻译饮用水处理通过用金属膜制成的凝固微滤来去除天然有机物质.docx

外文翻译饮用水处理通过用金属膜制成的凝固微滤来去除天然有机物质.docx

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外文翻译饮用水处理通过用金属膜制成的凝固微滤来去除天然有机物质

中文4300字,2600单词，1.4万英文字符

出处：

LeiknesT,ØdegaardH,MyklebustH.Removalofnaturalorganicmatter（NOM）indrinkingwatertreatmentbycoagulation–microfiltrationusingmetalmembranes[J].JournalofMembraneScience,2004,242（1–2）:

47-55.

外文资料

Removalofnaturalorganicmatter（NOM）indrinkingwatertreatmentbycoagulation–microfiltrationusingmetalmembranes

ToroveLeiknes,HallvardØdegaard,HåvardMyklebust

Abstract

DrinkingwatersourcesinNorwayarecharacterizedbyhighconcentrationsofnaturalorganicmatter（NOM）,lowpH,lowalkalinityandlowturbidity.TheremovalofNOMisthereforeinmanycasesageneralrequirementinproducingpotablewater.DrinkingwatertreatmentplantsarecommonlydesignedwithcoagulationdirectfiltrationorwithNFspiralwoundmembraneprocesses.Thisstudyhasinvestigatedthefeasibilityandpotentialofusinginorganicmetalmicrofiltrationmembranesinasubmergedmembraneconfigurationwithcoagulationpre-treatmentfordrinkingwaterproduction.Variationsinoperatingmodesandconditionsweretested,fromdead-endoperationtosemisequencingbatchoperationusingairscouringandbackwashingcyclesformembranecleaningandfoulingcontrol.Fluxesaround180LMHattransmembranepressuresbelow0.3barwhereachievedoverproductioncyclesinexcessof50h.Treatmentefficienciesingeneralshowed>95%colourremoval,∼85%UVremoval,65–75%TOCremovaland<0.2NTUturbidityandnon-detectablesuspendedsolidsinthepermeate.TheinitialresultsshowthatMFmetalmembranesisaninterestingalternativetosandfiltrationincoagulation/directfiltrationfortreatingdrinkingwater.

Keywords:

Naturalorganicmatter、Coagulation–microfiltration、Metalmembranes

1.Introduction

About90%ofNorwegiandrinkingwatersuppliesarefromsurfacewatersources,generallyfromlakeswhichtypicallyhaveverylowturbidity,alkalinityandhardnessbuthighcolourresultingfromnaturalorganicmatter（NOM）.OneofthemajorproblemsofusingsurfacewatersourcesinnorthernclimatesishighcontentofNOMandtotalorganiccarbon（TOC）.RemovalofNOMisrequiredsincecolouredwaterisunattractivetoconsumers,resultsincolouringofclothesduringwashing,cancauseodorandtaste,increasescorrosionandbiofilmgrowthinthedistributionnetwork,andisaprecursortotheformationofdisinfectionby-products（DBP）whenwaterisdisinfected.HalogenatedcompoundsresultingfromchlorinationofdrinkingwatercontainingconcentrationsofNOMhasbeenamajorconcernsincetheirdiscoveryintheearly1970sassomeofthechlorinationby-productsarecarcinogenic.DrinkingwatersourcesinNorwayarecommonlydescribedashavinghighcolour,lowpHandlowalkalinitywheretypicalvaluesaregiveninTable1.TheremovalofNOMisthereforeamajortreatmentrequirementintheproductionofpotablewaterwhereconcentrationstypicallyinthe30–80mg/LPttruecolourrangearereducedtolessthan10mg/LPt.

ThemostcommondrinkingwatertreatmentplantdesignsinNorwayarebasedoncoagulationanddirectfiltrationornanofiltration（NF）membranefiltrationprocesses[13].Coagulationdirectfiltrationplants（enhancedcoagulation）arestillthedominanttreatmentplantdesignoption.

Inthelast10–15yearsmembraneprocessesbasedonnanofiltration（NF）usingspiralwouldmoduleconfigurationshavebeensuccess-fullyusedinNorwayforremovingNOM,andapproximately100membraneplantsareinoperationtoday.TheNFmembraneplantsarecommonlydesignedtooperatewithaconstantfluxof∼17Lm−2h−1（LMH）atatransmembranepressure（TMP）of3–6barwithawaterrecoveryof∼70%.SomeofthedisadvantagesoftheNFspiralwoundmembranesystemsusedarearelativelylowrecovery,highenergyconsumptionsduetotheoperatingpressures,andfoulingbytheNOMandsub-micronparticulatesresultingintheneedforadailycleaningprocedureinadditiontotheperiodicmaintenancecleaningprocedures[13,14].Inarecentsurveyaboutexperienceswithdifferenttreatmentplanttypes,boththeoperatorsandownersoftreatmentplantsusingmembranesweregenerallyverysatisfiedwithusingmembranetechnology.However,thesurveyalsoindicatedaninterestinalternativemembranetreatmentplantdesignsthatweremoreenergyefficientandwhichcouldreducethenecessarycleaningfrequencybyefficientfoulingcontrol.Twoapproachescanbefollowedtoachievethis;usingvariouspre-treatmentoptionsoftherawwaterpriortotheNFfiltrationunitsorbyusingdifferenttypesofmembranes,membranemodulesandoperatingoptions.Studiesusingmicrofiltration（MF）andultrafiltration（UF）membranesaswellasalternativemembranemoduledesigns（hollowfibercross-flowmodulesandsubmergedmodules）combinedwithpre-treatmentbycoagulationtoreduceandcontrolfoulinghavebeenreported[1,4–7,9–11].Theyalldemonstratetheadvantagesandben-efitsofcombiningcoagulationpre-treatmentwithmembranefiltrationwhenUFandMFmembranesareused.

Membranesindrinkingwatertreatmentarecommonlybasedonspiralwoundsystemsorcross-flowhollowfiber/tubularsystems.Thesemembraneprocessesarepres-suredrivenmembranemodulesandmountedindifferentarraydesignstooptimizetheprocess.Energycostsrequiredtopressurizethemembranevesselsandmaintainhighenoughfluidcross-flowvelocitiesoftenisasubstantialcomponentofthesesystems.Submergedmembranedesignsofferanewapproachbothtothemembranemoduledesignandlowpressureoperatingconditionswhichcanbebeneficialfortheoverallenergyrequirementstooperateaprocess.Thesubmergedmembraneprocessdesigncombinedwithcoagulationpre-treatmentwaschosenforthisstudyasanalternativetreatmentprocesstocoagulationdirect-flirtationfortheremovalofNOM.Inorganicmetalmembraneswerealsochosenasthemembraneisbothchemicallyandphysicallyrobust,allowingforalternativecleaningstrategiesforfoulingcontrolcomparedtowhatisfeasiblewithpolymericmembranes.

TheobjectiveofthisstudyhasbeentoinvestigatethefeasibilityandpotentialofinorganicMFmetalmembranescombinedwithcoagulationforthetreatmentofdrinkingwaterfromhighlycolouredsurfacewater.Alowpressuresub-mergedmembranemoduleconfigurationwaschosencombinedwiththecoagulationpre-treatment.Themetalmem-braneshavebeensuppliedbyHitachiMetalsLtd.,Japan.

2.Experimental

2.1.Productionofrawwater

Alltheexperimentsinthisstudywereconductedwithfeedwaterhavingacolourof50mg/LPtatpH7whichistypicalandrepresentativeforNorwegianrawwatersources.ThefeedwatertothemembranereactorwaspreparedusingaNOMconcentratefromafull-scaleionexchangetreatmentplantbymixingtheconcentrateintotapwatertomakeupthedesiredcomposition.Analysisofthereconstructedwatershowedthatthefeedwaterisrepresentativeofthenaturalwatersource.Reconstructedfeedwaterwaschosenforthestudytomaintainthesameinitialconditionsforallexperimentsconductedsuchthattheperformanceoftheprocessundervaryingoperatingconditionscouldbeevaluatedandcompared.Hydrochloricacid（HCl）wasusedforpHadjustmentandcontroltoensureoptimalpHof6.3±0.2forthecoagulationstep.Thereconstructedrawwaterwithacolourof50mg/LPthadaDOCconcentrationof6.1±0.25mg/LCandaUV254-absorbanceof31.1±1.1m−1.

Thecoagulantusedwasapolyaluminiumchloride（PAX-16）,aqueoussolutionfromKemiraChemicalsAS.Preliminarycoagulationtestswerefirstconductedinjar-teststofindtheoptimumpHandcoagulantdosagenecessarytoremovetheNOM.Dosagesof2,3,4and5mg/LAlweretestedattheoptimalpHof6.3±0.1todeterminethecolourremoval.Resultsrevealedthataspecificaluminiumdosageof5mg/LAlremoved94%oftruecolour,87%ofUV-absorbingcompounds,and71%ofDOC[9].Theremovalofcolourdidnotincreasemuchfromadosageof4–5mg/LAl,however,theremovalofDOCdidin-creaseaswellastheZetapotentialoftheparticlesformed.Adosageof5mg/LAlwasthereforechosenasthepreferredcoagulantamount.TheZetapotentialoftheparticlesformedincreasedfromaround−22to+5mVwithincreasingdosage.ThisincreaseintheZetapotentialwasalsoconsideredbeneficialcomparedtothelowerdosageswhichgavenegativeZetapotentialvalues.However,theaverageZetapotentialoftheparticlesinthemembranereactorweremeasuredtobearound−7.75±4.19mV.Thelowervaluefoundmaybeduedifferentconditionsinthemembranereactorcomparedtothejar-testssuchaseffectsofsludgeconcentration,hydraulicandflocculationconditions,how-ever,thevaluemeasuredisclosetoaneutralchargewhichisbeneficialfortheaggregateformation.Allexperimentswerethereforeconductedwithacoagulantdoseof5mg/LAlproducingafeedwatertothemembranereactorwithapHofaround6.3±0.2.

Flocculationofthefeedwaterwasdoneusingapipeflocculatortomaintainarapiddevelopmentofthemicro-flocs.Thepipeflocculatorwasdesignedwithahydraulicretentiontime（HRT）of30sandahydraulicgradientGof400s−1.Thesuspendedsolidsconcentrationinthefeedwateraftercoagulation/flocculationwithacoagulantdoseof5mg/LAlwasaround25mg/LSS.

2.2.Membranemodulespecification

ThemetalmembranesprovidedbyHitachiMetalLtd.aremadeassheets.Eachsheetisconstructedbysinteringmetalpowderinasupportlayertoformthemembrane.Thenominalporesizeofthemembranehasbeencharacterizedusingboththebubblepointmethodandaparticlesizeexclusionanalysis.Thesemethodsdeterminedthemembranehavinganominalporesizeof0.95and0.2m,respectively.A