污水处理技术外文翻译.docx
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污水处理技术外文翻译
本科毕业设计
外文文献及译文
文献、资料题目:
StudyonDisinfectionand
Anti–microbialTechnologiesforDrinkingWater
文献、资料来源:
期刊
文献、资料发表(出版)日期:
2001.1.9
院(部):
专业:
给水排水工程
班级:
姓名:
学号:
指导教师:
翻译日期:
2010.3.30
外文文献:
StudyonDisinfectionandAnti–microbialTechnologiesforDrinkingWater
ZHUKun,FUXiaoYong
(Dept.ofEnvironmentalEngineering,LANZhouRailwayUniversity,LANZhou730070,China)
Abstract:
Disinfectionby-productsproducedbythereactionbetweenchlorineanddissolvedorganiccompoundsandotherchemicalsareconsideredasaworryingprobleminthedrinkingwatertreatmentprocesssinceaseriesofmutageniccarcinogensubstancesareformedincludingtrihalomethanes(THMs).Amongthetesteddisinfectants(chlorine,ozone,chlorinedioxide,potassiumpermanganate,chloraminesandhydrogenperoxideetc.),chlorinedioxidehasprovedtobethemostfeasibleandeffectiveoxidantfordrinkingwatertreatmentandremovalofpathogensduetoitsoxidationefficiency,lowcostandsimplewayofutilization.Aseriesofexperimentsindicatethatchlorinedioxidecansignificantlyrestrainproductionoftrihalomethanes(THMs)andcontrolbacteriagrowthparticularlyforCryptosporidiumoocysts.Theexperimentsverifiedthatbothozoneandchlorinedioxideareabsolutelyvitaltoensurethatanymicroorganismsarisingfromfecalcontaminationofwaterstoragearedestroyed.Thepaperdiscussesoxidationcapacityofchlorinedioxide,especiallyforremovingpetroleumcompounds,whichisaffectedbyreactiontime,gasinjectionway,andpHoftreatedwater.
Keywords:
disinfection;oxidants;watertreatment;pathogens;chlorinedioxide
CLCnumber:
X523Documentcode:
A
1 Introduction
ChemicalandfiltrationprocessesaretwomainmethodsusedinChinafortreatingdrinkingwatermeanwhileUVradiationhasbeenusedsuccessfullyforwatertreatmentwithrelativelylowflowrate.Ontheindividualfamilylevel,usuallychemicaltreatmentisafeasiblealternative.Thefollowingguidelinesexistfortheselectionofsuitabledisinfectants:
thereactionmustbestrongenoughtoextinctbacteriaandcontrolgrowthofmicro-organisms,removalofcontaminantsshouldbedonebydecomposition,evaporationorprecipitationetc,toeliminateordecreasethetoxicity,oxidantsorreactionby-productsshouldnotbeharmfultohumanhealth,andthepurificationprocessesshouldbepracticalandeconomical.Theobjectiveofthispaperistoevaluateanddiscussavailabledisinfectantsfordrinkingwatertreatment.Thedifferentdisinfectantsarecomparedregardingpurificationefficienciesandapplicationapproaches.
2 ComparisonofDisinfectants
Disinfectants,suchaschlorine,chloramines,sodiumhypochlorous,chlorinedioxideandozoneetc.,wereprimarilyconsideredindrinkingwatertreatment.Theoxidationcapacitiesoftheseagentsmayberankedasfollowsinorderofdecreasedefficiency[1]:
O3>ClO2>HOCl>OCl->NHCl2>NH2Cl
ReferringtoFiessinger′s[2]suggestion,thepropertiesofthesedisinfectantsarecomparedinTab.1.Chlorineisshowntobeanexcellentdisinfectanttopreventwaterbornediseasessuchastyphoidfeveroverlongperiods.Chlorinereactsnotonlywithinoxidation,butalsobyelectrophilicsubstitutiontoproduceavarietyofchlorinatedorganicby-products,particularlytrihalomethanes(THMs)andothermutagens.HereTHMsmainlyrefertochloroform,bromoform,dibromochloromathaneandbromodichloromathaneetc.Sincethe1970`s,theusageofCl2indrinkingwaterdisinfectionhasbeenquestionedwithozonebeingsubstitutedasthepreferreddisinfectantinthewatersupplyplants.But,ozonecouldnotbeintroducedtotheruralfarmercommunityduetoitshighcostsandshorthalf-life(15~20min.).Aswithotherdisinfectants,ozonationalsoleadstoformationoforganicby-productssuchasaldehyde,ketones,andcarboxylicacids,andalsomutagenicitymaybeinducedifbromicanionexists.
Tab.1Comparisonofvariousoxidants
ComparisonCl2ClO2O3KMnO4NH2ClH2O2
THMformation+++-----
Disinfectioneffects++++++++-+-+
Enhancedbiodegradability
++++++-+
Tasteremoval-++++-+
Ironandmanganese++++++++-+
Ammonia+++-----
Formationofmutagensortoxicsubstances
+++-+-+-+-+-
-noeffect; +littleeffect; ++effect; +++largesteffect
Manystudieshavepointedoutthatdisinfectionisabsolutelyvitaltoensurethatanymicroorganismsarisingfromfecalcontaminationofwaterstoragearedestroyed.Theselectionoftheavailabledisinfectantsmustconcerntoreduceriskfrommicrobialcontaminationofdrinkingwaterandthepotentialincreaseinriskfromchemicalcontaminationthatresultfromusinganyofthedisinfectants.Thebiocidalefficiencyofcommonlyuseddisinfectants-ozone,chlorinedioxide,chlorineandchloraminesarerankedalmostwiththesameorderastheoxidizingcapacity,butthestabilityofthosearefollowingtheorderas[3]:
Chloramines>Chlorinedioxide>Chlorine>Ozone
3 Purificationoforganicpollutantsbychlorinedioxide
AccordingtoWHOguidelinefordrinkingwaterquality,muchconsiderationshouldbepaidtobenzenehomologouscompounds;therefore,thestudyonpurificationeffectsofchlorinedioxideisfocusedonpetrochemicalpollutants.Aseriesofexperimentswerecarriedouttosimulatetheoxidationprocessesofcontaminatedwater.Thepollutedsolutionswerepreparedinadarkbarrel(10Lcapacity)ofsevenkindsofbenzenehomologouscompounds-Benzene,toluene,ethylbenzene,p-phenylmethane,o-phenylmethane,m-phenylmethaneandstyrene.Samplesweretakentodeterminetheinitialconcentrationofthecompoundspriortothetests.StandardchlorinedioxidesolutionwasproducedfromsodiumchloritereactedwithHClsolutionof10%[4].TheGR-16AGas-chromatographwithFIDdetectorShenyangLZ-2000wasusedformeasurementofCl2,ClO2,ClO-2andClO-3[5].OilconcentrationsweredeterminedwithanUV-120-20spectrophotometer(Shimadzu)followingtheproceduredescribedbyAPHA[4].OrganiccompoundsinthewatersamplesweremeasuredwithaGC-MS(QP-1000A).ClO2andO3werestandardizedbyiodimetrictitrationatpH7.
Forthepurposeofchemicaldisinfectionfordrinkingwater,chlorinewasinstantaneouslyignoredduetotheformationofTHMsandothermutagenicsubstances.Theresultsindicatedthatpotassiumpermanganateandhydrogenperoxidedidnothaveenoughoxidationcapabilitytodecomposepetroleumcontaminantsachievingonly46%,and5.7%decompositionofstyrene,respectively.Ozonecouldnotbeselectedduetoitshighcost,complexoperationandshorthalf-lifealthoughitisanexcellentoxidantforwatertreatment.Chlorinedioxidewasthenextmostsuccessfulalternativefordisinfection.Thebenefitsinclude-effectiveoxidationcapacity,algicidaleffectandnegligibleformationofhalogenatedby-products.Basedoneconomicandoperationalrequirement,themixinggasmethodiseasilyused.TheresultsobtainedsuggestthatdisinfectionofdrinkingwaterwithozoneandorchlorinedioxideseemstobeasuitablealternativestotheuseofNaClOforcontrollingtheformationofnon-volatilemutagens[6].
Inthelaboratoryexperiments,theoxidantsozone,chlorinedioxide,potassiumpermanganateandthemixinggas(mainlycontainedClO2andacertainamountofCl2,O3andH2O2)weretestedforremovalofthepetroleumcompounds,andresultsareshowninTab.2.
Tab.2Comparisonofoxidationcapacityforthevariousoxidants
OrganicCompoundsInitialconc.O3ClO2H2O2MixingGasKMnO4
/mg·L–1
Oil11.3467.245.8061.80
Benzene3.6178.371.4082.30
Toluene5.2391.883.0095.20
Ethylbenzene8.3795.191.1094.50
p–phenylmethane7.8695.890.50100
o-phenylmethane8.3695.990.301000
m–phenylmethane9.2995.487.301000
Styrene9.3696.284.75.710046.1
Astudywasconductedtoelucidatethedecaypathwayofmonochloramineinthepresenceandabsenceofnaturalorganicmatter(NOM)[7].Itwasfoundthatnaturalorganicmatteractedprimarilyasareductantratherthancatalyst.Thisconclusionwasverifiedusingaredoxbalance,andmuchofoxidizingcapacityofmonochloraminegoestowardsNOMoxidation.Cleaningagentsanddisinfectantsfromhousekeeping,hospitals,kitchensaresourcesofabsorbablehalogenatedorganiccompounds(AOX)inmunicipalwastewater.TheamountofAOXgeneratedstronglydependsonthenatureandconcentrationsofdissolvedandsolidorganiccompounds,theconcentrationofactivesubstances,temperature,pHandreactiontime[8]Whenthemixinggasesreactwithwatermoleculesandorganicmicro-pollutants,hypochlorousacidisformedbychlorine,chloriteandchlorateionsareproducedfromchlorinedioxideinaseriesofredoxreactions.Theprincipalreactionsaresummarizedasfollows:
ClO2+organic→ClO-²+oxidizedorganic
(1)
2ClO-²+Cl2=2ClO2+2Cl-
(2)
2ClO-²+HOCl=2ClO2+2Cl-+OH-(3)
2ClO2+HOCl+H2O=2ClO-³+HCl+2H+(4)
TherateofchlorateyieldcanbedescribedbyEquation(5):
d[ClO3]/dt=2k[ClO2][HOCl](5)
inwhichk=1.28M/minat25℃[9].
Thestoichiometryoftheundesirablereactionsthatformchlorateinlowconcentrationofchloriteorpresentsofexcesschlorineisgivenas:
ClO-²+Cl2+H2O=ClO-³+2Cl-+2H+(6)
ClO-²+HOCl=ClO-³+Cl-+H+(7)
Atalkalineconditions:
ClO-²+HOCl+OH-=ClO-³+Cl-+H2O(8)
Typically,chlorinedioxideisusedindrinkingwatertreatmentandtheconcentrationsarerangingfrom0.1to2.0mg/L[10].However,therelevantby-productsofchlorinedioxidetreatme