水污染 英文版.ppt

Waterpollution,Itcovers71%oftheearthssurfaceandmakesup65%ofourbodies.Withouttheseeminglyinvaluablecompoundcomprisedofhydrogenandoxygen,lifeonEarthwouldbenon-existent,WaterisEssentialforLife,ThreefourthsofthesurfaceoftheEarthiscoveredwithwater.Nearly98%ofthewateronEarth,though,isseawaterunfitfordrinkingandnotevensuitableformostindustrialpurposes.Somethinglessthan2%ofthewaterisfrozeninthepolaricecaps,leavinglessthan1%availableasfreshwater.,Water:UnusualProperties,Manychemicalsubstancesaresolubleinwater.Thus,theyareeasilydispersedandeventuallyarescatteredtonearlyinfinitedilutionintheocean.Thosepropertiesofwaterthatmakeituniquelysuitedforthesupportoflifealsomakeiteasytopollute.,NaturalWaterIsntAllH2O,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:anicmaterials-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,AerobicbacteriathatliveinwateruseoxygengasdissolvedinthewaterwhentheyconsumetheirfoodAerobicmicroorganisms-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,whichdepletethewatersoxygensupply.,Suspendedmatter,Particulatematter,consistofmuchlarger-butstillverysmall-particleswhicharejustsuspendedinthewaterTheywilleventuallysettleoutandformsiltormudatthebottom:sediments,Water-bornedisease,Pathogenswhichincludevirus,bacteria,protozoa,andparasiticwormsaredisease-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,anaer