水处理专业英语阅读1WaterPollutionandPollutants 6页

1WaterPollutionandPollutantsTherelationshipbetweenpollutedwateranddiseasewasfirmlyestablishedwiththecholeraepidemicof1854inLondon,England.Protectionofpublichealth,theoriginalpurposeofpollutioncontrol,continuestobetheprimaryobjectiveinmanyareas.However,preservationofwaterresources,protectionoffishingareas,andmaintenanceofrecreationalwatersareadditionalconcernstoday.WaterpollutionproblemsintensifiedfollowingWorldWarIIwhendramaticincreasesinurbandensityandindustrializationoccurred.Concernoverwaterpollutionreachedapeakinthemid-seventies.Waterpollutionisanimprecisetermthatrevealsnothingabouteitherthetypeofpollutingmaterialoritssource.Thewaywedealwiththewasteproblemdependsuponwhetherthecontaminantsareoxygendemanding,algaepromoting,infectious,toxic,orsimplyunsightly.Pollutionofourwaterresourcescanoccurdirectlyfromseweroutfallsorindustrialdischarges(pointsources)orindirectlyfromairpollutionoragriculturalorurbanrunoff(nonpointsources).ChemicallypurewaterisacollectionofH2Omolecules—nothingelse.Suchasubstanceisnotfoundinnature—notinwildstreamsorlakes,notincloudsorrain,notinfallingsnow,norinthepolaricecaps.Verypurewatercanbepreparedinthelaboratorybutonlywithconsiderabledifficulty.Wateracceptsandholdsforeignmatter.Municipalwastewater,alsocalledsewage,isacomplexmixturecontainingwater(usuallyover99percent)togetherwithorganicandinorganiccontaminants,bothsuspendedanddissolved.Theconcentrationofthesecontaminantsisnormallyverylowandisexpressedinmg/L,thatis,milligramsofcontaminantperliterofthemixture.Thisisaweight-to-volumeratiousedtoindicateconcentrationsofconstituentsinwater,wastewater,industrialwastes,andother\ndilutesolutions.Microorganisms.Whereverthereissuitablefood,sufficientmoisture,andanappropriatetemperature,microorganismswillthrive.Sewageprovidesanidealenvironmentforavastarrayofmicrobes,primarilybacteria,plussomevirusesandprotozoa.Mostofthesemicroorganismsinwastewaterareharmlessandcanbeemployedinbiologicalprocessestoconvertorganicmattertostableendproducts.However,sewagemayalsocontainpathogensfromtheexcretaofpeoplewithinfectiousdiseasesthatcanbetransmittedbycontaminatedwater.Waterbornebacterialdiseasessuchascholera,typhoid,andtuberculosis,viraldiseasessuchasinfectioushepatitis,andtheprotozoan-causeddysentery,whileseldomaproblemnowindevelopedcountries,arestillathreatwhereproperlytreatedwaterisnotavailableforpublicuse.Testsforthefewpathogensthatmightbepresentaredifficultandtimeconsuming,andstandardpracticeistotestforothermoreplentifulorganiamathatarealwayspresent(inthebillions)intheintestinesofwarm-bloodedanimals,includinghumans.Solids.Thetotalsolids(organicplusinorganic)inwastewaterare,bydefinition,theresiduesaftertheliquidportionhasbeenevaporatedandtheremainderdriedtoaconstantweightat103℃.Differentiationbetweendissolvedsolidsandundissolved,thatis,suspended,solidsareaccomplishedbyevaporatingfilteredandunfilteredwastewatersamples.Thedifferenceinweightbetweenthetwodriedsamplesindicatesthesuspendedsolidscontent.Tofurthercategorizetheresidues,theyareheldat550℃for15minutes.TheashremainingisconsideredtorepresentinorganicsolidsandthelossofvolatilemattertobeameasureoftheorganiccontentSuspendedsolids(SS)andvolatilesuspendedsolids(VSS)arethemostuseful.SSandBOD(biochemicaloxygendemand)areusedasmeasuresofwastewaterstrengthandprocessperformance.VSScanbeanindicatoroftheorganiccontentofrawwastesandcanalsoprovide\nameasureoftheactivemicrobialpopulationinbiologicalprocesses.Inorganicconstituents.Thecommoninorganicconstituentsofwastewaterinclude:1.Chloridesandsulphates.Normallypresentinwaterandinwastesfromhumans.2.Nitrogenandphosphorous.Intheirvariousforms(organicandinorganic)inwastesfromhumans,withadditionalphosphorousfromdetergents.3.Carbonatesandbicarbonates.Normallypresentinwaterandwastesascalciumandmagnesiumsalts.4.Toxicsubstances.Arsenic,cyanide,andheavymetalssuchasCd,Cr,Cu,Hg,Ph,andZnaretoxicinorganicswhichmaybefoundinindustrialwastes.Inadditiontothesechemicalconstituents,theconcentrationofdissolvedgases,especiallyoxygen,andthehydrogenionconcentrationexpressedaspHareotherparametersofinterestinwastewater.Organicmatter.Proteinsandcarbohydrateconstitute90percentoftheorganicmatterindomesticsewage.Thesourcesofthesebiodegradablecontaminantsincludeexcretaandurinefromhumans;foodwastesfromsinks;soilanddirtfrombathing;washing,andlaundering;plusvarioussoaps,detergents,andothercleaningproducts.Variousparametersareusedasameasureoftheorganicstrengthofwastewater.Onemethodisbasedontheamountoforganiccarbon(totalorganiccarbon,orTOC)presentinthewaste.TOCisdeterminedbymeasuringtheamountofCO2producedwhentheorganiccarboninthesampleisoxidizedbyastrongoxidizerandcomparingitwiththeamountinastandardofknownTOC.Mostoftheothercommonmethodsarebasedontheamountofoxygenrequiredtoconverttheoxidizablematerialtostableendproducts.Sincetheoxygenusedisproportionaltothe\noxidizablematerialpresent,itservesasarelativemeasureofwastewaterstrength.ThetwomethodsusedmostfrequentlytodeterminetheoxygenrequirementsofwastewateraretheCODandBODtests.TheCOD.orchemicaloxygendemand,ofthewastewateristhemeasuredamountofoxygenneededtochemicallyoxidizetheorganicspresent;theBOD.orbiochemicaloxygendemand,isthemeasuredamountofoxygenrequiredbyacclimatedmicroorganismstobiologicallydegradetheorganicmatterinthewastewater.BODisthemostimportantparameterinwaterpollutioncontrol.Itisusedasameasureoforganicpollution,asabasisforestimatingtheoxygenneededforbiologicalprocesses,andasanindicatorofprocessperformance.Theamountoforganicmatterinwaterorwastewatercanbemeasureddirectly(asTOC,forexample),hutthisdoesn’ttelluswhethertheorganicsarebiodegradableornot.Tomeasuretheamountofbiodegradableorganics,weuseanindirectmethodinwhichwemeasuretheamountofoxygenusedbyagrowingmicrobialpopulationtoconvert(oxidize)organicmattertoCO2andH2Oinaclosedsystem.Theoxygenconsumed.orbiochemicaloxygendemand(BOD).isproportionaltotheorganicmatterconverted,andthereforeBODisarelativemeasureofthebiologicallydegradableorganicmatterpresentinthesystem.Becausebiologicaloxidationcontinuesindefinitely,thetestforultimateBODhasbeenarbitrarilylimitedto20days,whenperhaps95percentormoreoftheoxygenrequirementhasbeenmet.Eventhisperiod,however,istoolongtomakemeasurementofBODuseful,soafive-daytest,BOD5,carriedoutat20℃,hasbecomestandard.TherateoftheBODreactiondependsonthetypeofwastepresentandthetemperatureandisassumedtovarydirectlywiththeamountoforganicmatter(organiccarbon)present.\n单词表choleran.霍乱evaporatev蒸发epidemicn.流行，传染differentiationn.区分recreationala娱乐性的filterv过滤imprecisea.不精确的evaporatev.挥发alga,algaen.海藻，藻类20℃20degreecentigradecontaminantn污染物categorizevt分类contaminatevt.污染residuen残渣infectiousa.传染性的volatilea挥发性的unsightlya.难看的contentn含量sewern.下水道chloriden.氯化物outfalln.排放口sulphaten.硫化物runoffn.排水，流放口nitrogenn氮laboratoryn实验室phosphorousn磷sewagen.污水，废水detergentn.清洁剂organica有机的carbonaten.碳酸盐inorganica无机的bicarbonaten.重碳酸盐suspendv.悬浮calciumn.钙盐concentrationn浓度magnesiumn.镁盐milligramn.毫克arsenicn.砷constituentn.组成物cyaniden.氰dilutea稀释的cadmiumn镉suitablea.适当的chromen铬moisturen.潮湿水分coppern铜microben.微生物mercuryn汞virusn.病毒leadn铅protozoan.原生动物zincn锌microorganismn微生物hydrogenionn氢离子pathogenn.病菌病原体parametern.参数excretan.排泄物粪便carbohydraten.碳水化合物\nwaterbornea.水传播的biodegradablea可生物降解的typhoidn.伤寒sinkn.下沉污水坑tuberculosisn.肺结核launderv洗涤，洗熨virala.滤过型病毒的oxygenn氧气hepatitisn.肝炎oxidizev氧化dysenteryn.痢疾acclimatev.适应环境organismn有机体生物体微生物degradev降解intestinea.内部的.n.肠ultimatea最终的根本的definitionn.定义arbitrarilya.专横的residulen.剩余残渣co2carbondioxide