污水处理工业废水回用中英文对照外文翻译文献.docx
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污水处理工业废水回用中英文对照外文翻译文献
(文档含英文原文和中文翻译)
中英文资料对照外文翻译
Catalyticstrategiesforindustrialwaterre-use
Abstract
Theuseofcatalyticprocessesinpollutionabatementandresourcerecoveryiswidespreadandofsignificanteconomicimportance[R.J.Farrauto,C.H.Bartholomew,FundamentalsofIndustrialCatalyticProcesses,BlackieAcademicandProfessional,1997.].Forwaterrecoveryandre-usechemo-catalysisisonlyjuststartingtomakeanimpactalthoughbio-catalysisiswellestablished[J.N.Horan,BiologicalWastewaterTreatmentSystems;TheoryandOperation,Chichester,Wiley,1990.].Thispaperwilldiscusssomeoftheprinciplesbehinddevelopingchemo-catalyticprocessesforwaterre-use.Withinthiscontextoxidativecatalyticchemistryhasmanyopportunitiestounderpinthedevelopmentofsuccessfulprocessesandmanyemergingtechnologiesbasedonthischemistrycanbeconsidered.
Keywords:
CODremoval;Catalyticoxidation;Industrialwatertreatment
1.Introduction
Industrialwaterre-useinEuropehasnotyetstartedonthelargescale.However,withpotentiallongtermchangesinEuropeanweatherandtheneedformorewaterabstractionfromboreholesandrivers,theavailabilityofwateratlowpriceswillbecomeincreasinglyrare.Aswaterpricesrisetherewillcomeapointwhentechnologiesthatexistnow(orarebeingdeveloped)willmakewaterrecycleandre-useaviablecommercialoperation.Asthatfutureapproaches,itisworthstatingthemostimportantfactaboutwastewaterimprovement–avoiditcompletelyifatallpossible!
Itisbesttoconsiderwaternotasanaturallyavailablecheapsolventbutrather,difficulttopurify,easilycontaminatedmaterialthatifallowedintotheenvironmentwillpermeateallpartsofthebiosphere.Apollutantisjustamaterialinthewrongplaceandthereforedesignyourprocesstokeepthematerialwhereitshouldbe–containedandsafe.Avoidanceandthenminimisationarethetwofirststepsinlookingatanypollutantremovalproblem.Ofcourseavoidancemaynotbeanoptiononanexistingplantwhereanychangesmayhavelargeconsequencesforplantitemsifmajorflowsheetrevisionwererequired.Alsoavoidancemaymeansimplytransferringtheissuefromtheaqueousphasetothegasphase.Thereareadvantagesanddisadvantagestobothwaterandgaspollutantabatement.However,itmustberememberedthatgasphaseorganicpollutantremoval(VOCcombustionetc.,)ismuchmoreadvancedthantheequivalentwaterCODremovalandthereforeworthconsideration[1].Becausetheseaspectscannotbeover-emphasised,athirdstepwouldbetovisitthefirsttwostepsagain.Clean-upisexpensive,recycleandre-useevenifyouhaveacosteffectiveprocessisstillmorecapitalequipmentthatwillloweryourreturnonassetsandmaketheprocesslessfinanciallyattractive.Atpresentthebesttechnologyforwaterrecycleismembranebased.Thisistheonlytechnologythatwillproduceasufficientlycleanpermeateforchemicalprocessuse.However,thetechnologycannotbeusedinisolationandinmany(all)caseswillrequirefiltrationupstreamandatechniqueforhandlingthedownstreamretentatecontainingthepollutants.Thus,hybridtechnologiesarerequiredthattogethercanhandletheallaspectsofthewaterimprovementprocess[6,7,8].
Hencethegeneralrulesforwastewaterimprovementare:
1.Avoidifpossible,considerallpossiblewaystominimise.
2.Keepcontaminatedstreamsseparate.
3.Treateachstreamatsourceformaximumconcentrationandminimumflow.
4.Measureandidentifycontaminantsovercompleteprocesscycle.Lookforpeaks,whichwillprovecostlytomanageandattempttoruntheprocessasclosetotypicalvaluesaspossible.Thispaperwillconsidertheindustriesthatareaffectedbywastewaterissuesandthetechnologiesthatareavailabletodisposeoftheretentatewhichwillcontainthepollutantsfromthewastewatereffluent.Thepaperwilldescribesomeoftheproblemstobeovercomeandhowthetechnologiessolvetheseproblemstovaryingdegrees.Itwillalsodiscusshowthecostdrivershouldinfluencedevelopersoffuturetechnologies.
2.Theindustries
TheprocessindustriesthathaveasignificantwastewatereffluentareshowninFig.1.Theseprocessindustriescanbeinvolvedinwastewatertreatmentinmanyareasandsomeillustrationsofthisareoutlinedbelow.
Fig.1.Processindustrieswithwastewaterissues.
2.1.Refineries
Theprocessofbringingoiltotherefinerywilloftenproducecontaminatedwater.Oilpipelinesfromoffshorerigsarecleanedwithwater;oilshipsballastwithwaterandtheresultcanbesignificantwaterimprovementissues.
2.2.Chemicals
Thesynthesisofintermediateandspecialitychemicalsofteninvolvetheuseofawaterwashsteptoremoveimpuritiesorwashoutresidualflammablesolventsbeforedrying.
2.3.Petrochemicals
Ethyleneplantsneedtoremoveacidgases(CO2,H2S)formedinthemanufactureprocess.Thissituationcanbeexacerbatedbytheneedtoaddsulphurcompoundsbeforethepyrolysisstagetoimprovetheprocessselectivity.Causticscrubbingistheusualmethodandthisproducesasignificantwatereffluentdisposalproblem.
2.4.Pharmaceuticalsandagrochemicals
Theseindustriescanhavewaterwashstepsinsynthesisbutinadditiontheyareoftenformulatedwithwater-basedsurfactantsorwettingagents.
2.5.Foodsandbeverages
ClearlyusewaterinprocessingandCODandBODissueswillbetheendresult.
2.6.Pulpandpaper
Thisindustryusesverylargequantitiesofwaterforprocessing–aqueousperoxideandenzymesforbleachinginadditiontothestandardKrafttypeprocessingofthepulp.Itisimportanttorealisehowmuchhumansocietycontributestocontaminatedwaterandaninvestigationoftheflowratesthroughmunicipaltreatmentplantssoonshowsthesignificanceofnon-processindustryderivedwastewater.
3.Thetechnologies
ThetechnologiesforrecalcitrantCODandtoxicpollutantsinaqueouseffluentareshowninFig.2.Theseexamplesoftechnologies[2,6,8]availableorindevelopmentcanbecategorisedaccordingtothegeneralprincipleunderlyingthemechanismofaction.Ifinadditiontheadsorption(absorption)processesareignoredforthiscatalysisdiscussionthenthecategoriesare:
1.Biocatalysis
2.Air/oxygenbasedcatalytic(ornon-catalytic).
3.Chemicaloxidation
1.Withoutcatalysisusingchemicaloxidants
2.Withcatalysisusingeitherthegenerationof_OHoractiveoxygentransfer.BiocatalysisisanexcellenttechnologyforMunicipalwastewatertreatmentprovidingaverycost-effectiveroutefortheremovaloforganicsfromwater.Itiscapableofmuchdevelopmentviatheuseofdifferenttypesofbacteriatoincreasetheoverallflexibilityofthetechnology.Oneissueremains–whattodowithalltheactivatedsludgeevenaftermassreductionbyde-watering.Thequantitiesinvolvedmeanthatthisisnotaneasyproblemtosolveandre-useasafertilizercanonlyusesomuch.Thesludgecanbetoxicviaabsorptionofheavymetals,recalcitranttoxicCOD.Inthiscaseincinerationandsafedisposaloftheashtoacceptablelandfillmayberequired.Airbasedoxidation[6,7]isveryattractivebecauseprovidingpurergradesofoxygenarenotrequirediftheoxidantisfree.Unfortunately,itisonlyslightlysolubleinwater,ratherunreactiveatlowtemperaturesand,therefore,needsheatandpressuretodeliverreasonableratesofreaction.Theseplantsbecomecapitalintensiveaspressures(from_10to100bar)areused.Therefore,althoughtherunningcostsmaybelowtheinitialcapitaloutlayontheplanthasaverysignificanteffectonthecostsoftheprocess.Catalysisimprovestheratesofreactionandhencelowersthetemperatureandpressurebutisnotabletoavoidthemandhencedoesnotofferacompletesolution.ThecatalystsusedaregenerallyGroupVIIImetalssuchascobaltorcopper.Theleachingofthesemetalsintotheaqueousphaseisadifficultythatinhibitsthegeneraluseofheterogeneouscatalysts[7].Chemicaloxidationwithcheapoxidantshasbeenwellpractisedonintegratedchemicalplants.Theusualexampleiswastesodiumhypochloritegeneratedinchlor-alkaliunitsthatcanbeutilisedtooxidiseCODstreamsfromotherplantswithinthecomplex.Hydrogenperoxide,chlorinedioxide,potassiumpermanganateareallpossibleoxidantsinthistypeofprocess.Thechoiceisprimarilydeterminedbywhichisthecheapestatthepointofuse.Asecondaryconsiderationishoweffectiveistheoxidant.Possiblythemostresearchedcatalyticareaisthegenerationanduseof_OHasaveryactiveoxidant(advancedoxidationprocesses)[8].Thereareavarietyofwaysofdoingthisbutthemostusualiswithphotonsandaphotocatalyst.ThephotocatalystisnormallyTiO2butothermaterialswithasuitablebandgapcanbeused[9,10].Theprocessescanbeveryactivehowevertheengineeringdifficultiesofgettinglight,acatalystandtheeffluentefficientlycontactedisnoteasy.Infactthepoorefficiencyoflightusagebythecatalyst(eitherthroughcontactingproblemsorinherenttothecatalyst)makethisprocessonlysuitableforlightfromsolarsources.PhotonsderivedfromelectricalpowerthatcomesfromfossilfuelsarenotacceptablebecausethecarbondioxideemissionthisimpliesfaroutweighsandCODabatement.Hydroelectricpower(andnuclearpower)arepossiblesourcesbutthebasicinefficiencyisnotbeingavoided.HydrogenperoxideandozonehavebeenusedwithphotocatalysisbuttheycanbeusedseparatelyortogetherwithcatalyststoeffectCODoxidation.Forozonethereistheproblemofthemanufacturingroute,coronadischarge,whichisacapitalintensiveprocessoftenlimitsitsappl