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ProcessingofWaterSupply

ProfessionalEnglishforEnvironmentalEngineering

Theobjectiveofmunicipalwatertreatmentistoprovideapotablesupply.Fordomesticuses,treatedwatermustbeaestheticallyacceptable—freefromapparentturbidity,color,odor,andobjectionabletaste.Qualityrequirementsforindustrialusesarefrequentlymorestringentthanfordomesticsupplies.Thus,additionaltreatmentmayberequiredbytheindustry.ProcessingofWaterSupply

Municipalwatertreatment

Commonwatersourcesformunicipalsuppliesaregroundwater,rivers,naturallakes,and

reservoirs.Waterqualitydependsonagriculturalpracticesinthewatershed,locationofmunicipalandindustrialoutfallsewers,riverdevelopmentsuchasdams,seasonoftheyear,andclimaticconditions.Periodsofhighrainfallflushsiltandorganicmatterfromcultivatedfieldsandforestland,whiledroughtflowsmayresultinhigherconcentrationsofwastewaterpollutantsfromsewerdischarges.Rivertemperaturemayvarysignificantlybetweensummerandwinter.ProcessingofWaterSupply

Municipalwatertreatment

Municipalwaterqualitycontrolactuallystartswithmanagementoftheriverbasintoprotectthesourceofwatersupply.Thequalityofwaterinalakeorreservoirdependsconsiderablyonseasonoftheyear.Pollutionandeutrophicationaremajorconcernsinsurface-watersupplies.Althoughsomecommunitiesareabletolocategroundwatersupplies,oralternatelesspollutedsurfacesourceswithinfeasiblepumpingdistance,themajorityofthenation'ssurfacesuppliesarefacingthethreadofcontamination.ProcessingofWaterSupply

Municipalwatertreatment

Municipalwaterqualitycontrolactuallystartswithmanagementoftheriverbasintoprotectthesourceofwatersupply.Theprimaryprocessinsurface-watertreatmentischemicalclarificationbycoagulation,sedimentation,andfiltration.Lakeandreservoirwaterhaveamoreuniformyear-roundqualityandrequirealesserdegreeoftreatmentthanriverwater.Naturalpurificationresultsinreductionofturbidity,coliformbacteria,color,andeliminationofday-to-dayvariations.Ontheotherhand,growthsofalgaecauseincreasedturbidityandmayproducedifficult-to-removetastesandodorsduringthesummerandfall.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsThespecificchemicalsappliedincoagulationforturbidityremovaldependonthecharacterofthewaterandeconomicconsiderations.Themostpopularcoagulantisalumaluminumsulfate).Asaflocculationaid,thecommonauxiliarychemicalisasyntheticpolymer.Activatedcarbonisappliedtoremovetasteandodorproducingcompounds.Chlorineandfluorideareposttreatmentchemicals.Prechlorinationmaybeusedfordisinfectionoftherawwateronlyifitdoesnotresultinformationoftrihalomethanes(THMs).ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsProcessingmayberequiredtoremovedissolvedgasesandundesirableminerals.Deep-wellsuppliesmaybechlorinatedtoprovideresidualprotectionagainstpotentialcontaminationinthewaterdistributionsystem.Incaseofshallowwellsrechargedbysurfacewaters,chlorinationcanbothdisinfectthegroundwaterandprovideresidualprotection.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsFluorideisaddedtoreducetheincidenceofdentalcaries.Dissolvedironandmanganeseinwellwateroxidizewhencontactedwithair,formingtinyrustparticlesthatdiscolorthewater.Removalisperformedbyoxidizingtheironandmanganesewithchlorineorpotassiumpermanganate,andremovingtheprecipitatesbyfiltration.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsExcessivehardnessiscommonlyremovedbyprecipitationsoftening.Limeand,ifnecessary,sodaasharemixedwithwellwater,andsettleableprecipitateisremoved.Carbondioxideisappliedtostabilizethewaterpriortofinalfiltration.Aerationisacommonfirststepintreatmentofmostgroundwatertostripoutdissolvedgasesandaddoxygen.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsClarificationbycoagulation,sedimentation,andfiltrationremovessuspendedimpuritiesandturbidityfromdrinkingwater.Thefinalstepisdisinfectionwhichproducespotablewater,freeofharmfulmicroorganism.Butothertreatmentprocessesmayberequired,particularlytoremovesomeofthedissolvedsubstances.Theseprocessesmaybeusedinadditiontoclarificationorappliedseparately,dependingonthesourceandqualityoftherawwaterProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsOpenchannelultravioletdisinfectionsystemGroundwater,forexample,doesnotordinarilyrequireclarificationbecausethewaterisfilterednaturallyinthelayersofsoilfromwhichitiswithdrawn.Disinfectionofgroundwatersupplies,requiredbylawforpublicwatersupplysystems,isbasicallyaprecautionarystep;groundwaterisusuallyfreeofbacteriaorothermicroorganisms.Ontheotherhand,becauseofitscontactwithsoilandrock,groundwatermaycontainhighlevelsofdissolvedmineralsthatmustberemoved.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsThetwoprimarysourcesofwastefromwatertreatmentprocessesaresludgefromthesettlingtank,resultingfromchemicalcoagulationorsofteningreactions,andwashwaterfrombackwashingfilters.Thesedischargesarehighlyvariableincomposition,containingconcentratedmaterialsremovedfromtherawwaterandchemicalsaddedinthetreatmentprocess.Thewastesareproducedcontinuously,butaredischargedintermittently.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsHistorically,themethodofwastedisposalwastodischargetoawatercourseorlakewithouttreatment.Thispracticewasjustifiedfromtheviewpointthatfilterbackwashwatersandsettledsolidsreturnedtothewatercourseaddednonewimpuritiesbutmerelyreturnedmaterialthathadoriginallybeenpresentinthewater.Thisargumentisnolongerconsideredvalid,sincewaterqualityisdegradedtotheextentthataportionofthewateriswithdrawn,andchemicalsusedinprocessingintroducenewpollutants.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystemsThesituationofeachwaterworksisuniqueandcontrolstosomeextentthemethodofultimatedisposalofplantwastes.Forexample,theymaybepipedtoamunicipalsewerforprocessingormaybedischargedtolagoons,providedthatsufficientlandareaisavailable.Ultimatedisposalbylandfill,orbargingtosea,requiresthickeningforeconomicalhandlingandhauling.Avarietyofalternativeprocessingmethodsareavailable;however,becauseofuniquecharacteristicsofeachplant'swaste,nospecificprocesscanbeuniversallyapplied.ProcessingofWaterSupply

Municipalwatertreatment

Surface-watertreatmentsystems英語翻譯的詞義選擇(二)

詞義具體化引申(1)Byexperimentation,imagination,andreasoning,mathematicsarediscoveringnewfactsandideasthatscienceandengineeringareusingtochangeourcivilization.

譯文：數(shù)學家們通過實驗、想象和推理，正在不斷發(fā)現(xiàn)各種新事實和新觀念，以便科學家和工程師可以用來改造我們的文明世界。

“mathematics”一詞為“數(shù)學”，將其具體化引申為“數(shù)學家”；“scienceandengineering”具體化引申為“科學家和工程師”；“civilization”一詞為“文明”，將其具體化引申為“文明世界”。Translation

英語翻譯的詞義選擇(二)

詞義抽象化引申

(1)Thecontributorsincomponenttechnologyhavebeeninthesemi-conductorcomponent.

譯文：元件技術中起主要作用的因素是半導體元件。

“contributor”一詞為“捐款人，捐助者，投稿者”，而在此句中表示起作用的“因素”。

(5)Malaysia,whichposteditshighestgrowthrateinadecade,istheregion'snewstarperformer,withIndonesiacloseonitsheels.

譯文:10年中，馬來西亞的發(fā)展速度最快。它是該地區(qū)新出現(xiàn)的最出色的經(jīng)濟發(fā)展國，印度尼西亞緊隨其后。“star”用來指“因出演成功而名揚四方的演員或歌星”，“starperformer”當然也可指“扮演最重要角色的演員”或“領銜主角”。通過整個句子，我們知道，“starperformer”與東南亞各地區(qū)各國的經(jīng)濟發(fā)展有關，可將其引申為“最出色的經(jīng)濟發(fā)展國”，符合語境。Translation

Exercise

Softeningbyionexchangecanproducewaterwithalmostzerolevelsofhardness,butthisisnotreallydesirable.Verysoftwatermaybeaggressive,orcorrosive,causingdamagetometalpipesandplumbing.Hardnesslevelsofabout100mg/Lareconsideredoptimumfordrinkingwater.Thereisalsosomeevidencethatthepresence