给水排水专业英语课件(李田)7

1Unit7SelectionofWaterTreatmentProcesses2Newwordsandexpressionswatershedn.流域分水岭screenn.筛子vt.筛分presedimentationn.预沉降desiltv.挖除淤泥沉砂pretreatvt.预先处理,预处理coagulationn.混凝coagulant混凝剂bacterialadj.细菌的bacteriumn.细菌pl.bacteria.polyelectrolyte[ˌpɔliiˈlektrəuˌlait]n.聚合(高分子)电解质alumn.明矾,矾aluminium铝sulfiden.硫化物hydrogensulfidetasteandodor嗅味chlorinen.氯气氯chlorinedioxide二氧化氯3Newwordsandexpressionspotassium[pəˈtæsiəm]n.钾permanganaten.高锰酸高锰酸盐trihalomethanen.三卤甲烷oxidizev.(使)氧化flexibilityn.弹性,适应性,机动性,挠性feedlinen.进料管线feedern.进料器投加装置land-runoffn.地表径流eutrophic[ju:'trɔfik]adj.富营养的suppressvt.镇压抑制suppressasmile.aeratorn.通风装置曝气器trayaeratorflocn.絮凝体絮状物filtern.滤池过滤器vt.过滤4Newwordsandexpressionsammonian.氨水氨ammonium铵.amine[ə'mi:n,'æmin]胺residualadj.剩余的残留的n.残留残余物freechlorineresidualn.自由性余氯Combinedchlorineresidualn.化合性余氯fluosilicicacidn.氟硅酸manganese['mæŋɡə,ni:s,,mæŋɡə'ni:z]n.锰limesofteningn.石灰软化flocculationn.絮凝fluoriden.氟化物plainsedimentationn.自然沉淀简单沉降scalen.结垢垢层vi.生水垢refractoryadj.难降解的难控制的难溶的short-circuitvt.使短5Watershedmanagementshouldbeconsideredpartoftheoperationofawater-supplysystem,whichisveryimportanttoprotectrawwaterquality.Behindanintakestructure,therecomeswatertreatmentprocess.1-16Currentpretreatmentprocessesinmunicipalwatertreatmentarescreening,presedimentationordesilting,chemicaladdition,andaeration.Screeningispracticedinpretreatingsurfacewaters.Presedimentationisregularlyusedtoremovesuspendedmatterfromriverwater.2-17Chemicaltreatment,inadvanceofin-plantcoagulation,ismostfrequentlyappliedtoimprovepresedimentation,topretreathard-to-removesubstances,suchastasteandodorcompoundsandcolor,andtoreducehighbacterialconcentrations.2-28Conventionalchemicalsusedwithpresedimentationarethepolyelectrolytesandalum.Aerationiscustomarilythefirststepintreatmentfortheremovalofironandmanganesefromwellwatersandastandardwaytoseparatedissolvedgasessuchashydrogensulfideandcarbondioxide.2-39Treatmentprocessesusedinwaterplantsdependontheraw-watersourceandqualityoffinishedwaterdesired.Thespecificchemicalsselectedfortreatmentarebasedontheireffectivenesstoperformthedesiredreactionandcost.3-110Forexample,activatedcarbon,chlorine,chlorinedioxide,andpotassiumpermanganateareallusedfortasteandodorcontrol.Excesschlorination,althoughleastexpensive,cancreateundesiredtrihalomethanes;activatedcarbonisthemosteffectivechemical.3-211Insurface-watertreatmentplantsequipmentforfeedingtwoorthreetaste-andodor-removalchemicalsisusuallyprovided,sotheoperatorcanselectthemosteffectiveandeconomicchemicalapplications.3-312Thereisnofixedruleforcolorremovalapplicabletoallwaters.Alumcoagulationwithadequatepretreatment,andapplyingoxidizingchemicalsoractivatedcarbon,mayprovidesatisfactoryremoval.Ontheotherhand,amoreexpensivecoagulantmightprovetobemoreeffectiveandreduceoverallchemicalcosts.3-413Perhapsthemostimportantconsiderationindesigningwatertreatmentprocessesistoprovideflexibility.Theoperatorshouldhavethemeanstochangethepointofapplicationofcertainchemicals.Forexample,chlorinefeedlinesarenormallyprovidedforpre-,intermediate-,andpostchlorination.4-114Multiplechemicalfeedersandstoragetanksshouldbesuppliedsothatvariouschemicalscanbeemployedinthetreatmentprocess.Degradationoftheraw-waterquality,orchangesincostsofchemicals,maydictateachangeinthetypeofcoagulantorauxiliarychemicalsusedincoagulation.4-215Inthecaseofsurface-watertreatmentplantsitisdesirabletoprovidespacefortheconstructionofadditionalpretreatmentfacilities.Theflowinrivermaychangeduetoconstructionofdams,channelimprovements,orupstreamwateruse.4-316Thequalityofwaterchangesduetohumanalterationandoccupationofthewatershed.Concentrationsofpollutantsfromdisposalofmunicipalandindustrialwastesandagriculturalland-runoffmayincrease.Lakescanbecomemoreeutrophic.4-41718ThetreatmentplantdescribedinFig.2-2isagroundwaterplantwithprovisionsforironandmanganeseremovalandlimesoftening.5-119SandfilterWellsChlorine:tosuppressgrowthofironbacteriainpipesandinitateoxidationofFeandMnChlorine:tooxidereducedMnremainingAeration:toincreasedissolvedoxygen,oxidizeFeandMnandreduceCO2RemovalofFeandMnflocTrayaeratorContactordetectiontankDetention:toallowforcompleteoxidationammonia:toconvertfreechlorineresidualtocombinedchlorineresidualtocombinedchlorineFluosilicicacid:forfluoridation20Afterinstallation,theplantcapacityhasbeenexpandedandthetreatmentprocessconvertedtoonlyironandmanganeseremovalbyincreasingtheaeratorcapacity,addingchlorinefeedaftertheaeration,andusingthesettlingbasinasadetentiontank.5-221Atpresentthisplantisonlycapableofperformingoxidationbyaerationandchlorinationforironandmanganeseremovalanddisinfection.Finishedwaterqualityisexcellentallyearroundbecauseofthestablecharacterofthewellsupply.5-322ThetreatmentplantinFig.2-3isatypicalconventionalplantforsurfacewatertreatmentbuiltin1950's.Sincethenthelake-watersourcehasbecomeincreasinglyeutrophic,andadditionalfacilitiesfortasteandodorcontrolhavebeenprovided.6-123Activatedcarbon,chlorinedioxide,andvariousauxiliarychemicalsforimprovedchemica