水污染 英文版.ppt

Waterpollution Itcovers71 oftheearth ssurfaceandmakesup65 ofourbodies Withouttheseeminglyinvaluablecompoundcomprisedofhydrogenandoxygen lifeonEarthwouldbenon existent WaterisEssentialforLife ThreefourthsofthesurfaceoftheEarthiscoveredwithwater Nearly98 ofthewateronEarth though isseawater unfitfordrinkingandnotevensuitableformostindustrialpurposes Somethinglessthan2 ofthewaterisfrozeninthepolaricecaps leavinglessthan1 availableasfreshwater Water UnusualProperties Manychemicalsubstancesaresolubleinwater Thus theyareeasilydispersedandeventuallyarescatteredtonearlyinfinitedilutionintheocean Thosepropertiesofwaterthatmakeituniquelysuitedforthesupportoflifealsomakeiteasytopollute NaturalWaterIsn tAllH2O Rainwatercarriesdustparticlesfromtheatmospheretotheground Rainwateralsodissolvesalittleoxygen nitrogen andcarbondioxideasitfallsthroughtheatmosphere Duringelectricalstorms lightningcausesnitrogen oxygen andwatervaportocombinetoformnitricacid AswatermovesalongorbeneaththesurfaceoftheEarth itdissolvesmineralsandmatterfromdecayingplantsandanimals Theprincipalpositiveions cations innaturalwateraresodium Na potassium K calcium Ca2 magnesium Mg2 andsometimesiron Fe2 orFe3 Thenegativeions anions areusuallysulfate SO42 bicarbonate HCO3 andchloride Cl hardwater Watercontainingthesecalcium magnesium andironionsiscalledhardwater Thepositiveionsreactwiththenegativeionsinsoaptoformascumthatclingstoclothesandleavesthemdingylooking Waterpollution Waterpollutionisanychemical physicalorbiologicalchangeinthequalityofwaterthathasaharmfuleffectonanylivingthingWaterpollutioncausedbyhumanactivitiesisalargesetofadverseeffectsuponwaterbodiessuchaslakes rivers oceans andgroundwaterPollutantsinwaterincludeawideofchemicals pathogens病原体 andphysicalchemistryorsensorychanges Waterpollution Waterpollutionistheleadingworldwidecauseofdeathsanddiseases andthatitaccountsforthedeathsofmorethan14 000peopledaily Effectsofwaterpollutionincludepoisonousdrinkingwater poisonousfoodanimals unbalancedriverandlakeecosystems deforestationandmanyothereffects Sourcesofwaterpollution Theusedwaterofacommunityiscalledwastewater orsewage Ifitisnottreatedbeforebeingdischargedintowaterways seriouspollutionistheresult Therearetwosortsofsources pointandnonpointsources Pointsourcesdischargepollutantsatspecificlocationsthroughpipelinesorsewers下水道intothesurfacewater Nonpointsources非点 污染 源aresourcesthatcannotbetracedtoasinglesiteofdischarge FactoriesAgricultureTransportationHousehold Sourcesofwaterpollution Domesticsewage Domesticsewagereferstowastewaterthatisdiscardedfromhouseholds Alsoreferredtoassanitarysewage Domesticsewagecontainsawidevarietyofdissolvedandsuspendedimpurities a organicmaterials foodandvegetablewasteb plantnutrients chemicalsoaps washingpowdersc disease causingmicrobes微生物 HouseholdChemicals Example substancesusedforhousesclean SoapandsyntheticdetergentsWaxPaintsandpaintremoversBleachesDisinfectants消毒剂Polishes AgriculturalRunoff Fertilizers nitrate phosphatesPesticides phenol chlorinediphenylEutrophication富营养作用 nutrientsartificiallysupplementedresultsinanabnormalincreaseinthegrowthofwaterplants IndustrialPollution Industrialeffluentofmanykindsofwaste isdischargedintostreams lakes oroceans whichinturndispersethepollutingsubstances Thepollutantsincludegrit asbestos石棉 phosphatesandnitrates mercury lead causticsodaandothersodiumcompounds sulfurandsulfuricacid oils andpetrochemicals Example Chromeplatingonbumpers grills andornamentsisasourceofpollution Pollutantsfromvariousindustries Thetextileindustrydumpsconditioners dyes bleaches andwatereffluentscontainingoils dirt andotherorganicdebris Meat packingplantsdumpblood thecontentsofentrails内脏 andotheranimalwastes Otherfood processingplantsdischargefruitandvegetableskins seeds leaves stems andothervegetablewastes Refineries精炼厂releasedyes oils acids盐水 sulfurcompounds andotherwastes Chemicalsplantsproduceavarietyofwastematerials Oilspills OilspillsfromtankersatseaorleaksfromundergroundstoragetanksonlandareverydifficulttocontrolOilspillsatseadecreasetheoxygenlevelinthewaterandcausegraveharmtothecreatureslivinginthesea Onlandcrudeistransportedthroughpipelinesortankerswhichcangetdamagedandspewoutcrudeoilovertheland Oilspillsareverydifficulttocontrolasoiltendstospreadveryfast affectingalargeareainaveryshorttime Groundwateranditscontamination Groundwaterarecontaminatedwithheavymetals persistentorganicpollutants andnutrientsPesticides Run offfromfarms backyards andgolfcoursesLeachate沥出液fromlandfillsitesUntreatedorinadequatelytreatedmunicipalsewage organicmaterial microbialpathogenNutrients phosphorusandnitrogenSyntheticorganics industrialchemicalsandpesticides Chemicalsindrinkingwater ChemicalsindrinkingwatercanbebothnaturallyoccurringorintroducedbyhumaninterferenceFluorideArsenicPetrochemicalsChlorinatedsolventsSalts Differenttypesofwaterpollution Microbiological Disease causing pathogenic microorganisms likebacteria virusesandprotozoa原生动物 Chemicals Awholevarietyofchemicalsfromindustry suchasmetals solventsandacids Oxygen depletingSubstancesManywastesarebiodegradable theycanbebrokendownandusedasfoodbymicroorganismslikebacteria Toomuchbiodegradablematerialcancausetheseriousproblemofoxygendepletioninwaters Aerobicbacteria Aerobicbacteriathatliveinwateruseoxygengasdissolvedinthewaterwhentheyconsumetheir food Aerobicmicroorganisms whichusedissolvedoxygen convertthenitrogen sulfur andcarboncompoundspresentinthewastewaterintoodorless andrelativelyharmless oxygenatedformslikenitrates sulfatesandcarbonates Anaerobicbacteria Oncetheoxygenisdepleted other anaerobic bacteriathatdonotneeddissolvedoxygentakeoverAnaerobicmicroorganismsproducetoxicandsmellyammonia amines andsulfides andflammablemethane swampgas Biochemicaloxygendemand orBOD BODistheamountofoxygenrequiredbymicro organismstodecomposetheorganicsubstancesinsewage Themoreorganicmaterialthereisinthesewage thehighertheBOD Nutrients Water solublenitratesandphosphatesthatcauseexcessivegrowthofalgaeandotherwaterplants whichdepletethewater soxygensupply Suspendedmatter Particulatematter consistofmuchlarger butstillverysmall particleswhicharejustsuspendedinthewaterTheywilleventuallysettleoutandformsiltormudatthebottom sediments Water bornedisease Pathogens whichincludevirus bacteria protozoa andparasiticworms aredisease producingagentsfoundinthefaecesofinfectedpersons Hepatitis肝炎 cholera霍乱 dysentery痢疾 diarrhoea腹泻 skinirritation andtyphoid伤寒症arecommonwater bornediseases Howdowepreventwaterpollution Inurbanareas thewastewaterfromhomes businessesandfactoriesiscollectedbyasystemofundergroundpipes sewerswhichcarryittooneormorecentraltreatmentfacilities Homesinnon urbanareasthatarenotconnectedtoasewerareusuallyrequiredbytheirtowntohaveon sitetreatmentsystems Wastewatertreatmentplants Consistsofatrainofindividualunitprocesses withtheoutput effluent ofoneprocessbecomingtheinput influent ofthenextprocess Biologicalplantsaremorecommonlyusedtotreatdomesticorcombineddomesticandindustrialwastewaterfromamunicipality Physical chemicalplantsaremoreoftenusedtotreatindustrialwastewatersdirectly becausetheyoftencontainpollutantswhichcannotberemovedefficientlybymicroorganisms Atypicaltreatmentplant Thefirststageswillbemadeupofphysicalprocessesthattakeouteasilyremovablepollutants Theremainingpollutantsaregenerallytreatedfurtherbybiologicalorchemicalprocesses physicalprocess Aphysicalprocessusuallytreatssuspended ratherthandissolvedpollutantsflocculationFiltration Ultrafiltration andreverseosmosisadsorptiononactivatedcharcoalAirorsteamstripping Desalinationofseawaterbyreverseosmosis Acommonsetofprocesses Preliminarytreatment grinders barscreens andgritchannels Toremovelargeorhardsolidsthatmightclogordamageotherequipment Primarysettlingbasins Thewaterflowsslowlyforuptoafewhours toalloworganicsuspendedmattertosettleoutorfloattothesurface Secondarytreatment toremovetheremainingdissolvedorcolloidalorganicmatterusingusuallybiologicalmethod Themostcommontypeofbiologicaltreatmentprocess Activatedsludgeprocess Activatedsludgeprocess consistsoftwoparts anaerationtankandasettlingtank Theaerationta