SewagetreatmentAbstractSewagetreatment,ordomesticwastewatertreatment,istheprocessofremoving\o"Contaminants"contaminantsfrom\o"Wastewater"wastewaterandhouseholdsewage,both\o"Surfacerunoff"runoff(\o"Effluents"effluents)anddomestic.Itincludesphysical,chemical,andbiologicalprocessestoremovephysical,chemicalandbiologicalcontaminants.Itsobjectiveistoproduceawastestream(ortreated\o"Effluent"effluent)andasolidwasteorsludgesuitablefordischargeorreusebackintotheenvironment.Thismaterialisofteninadvertentlycontaminatedwithmany\o"Toxic"toxicorganicandinorganiccompounds.Keywords:Sewagetreatment,fixed-filmandsuspended-growth,\o"Activatedsludge"ActivatedsludgeOriginsofsewageSewageiscreatedbyresidences,institutions,andcommercialandindustrialestablishments.Rawinfluent(sewage)includes\o"Householdwaste"householdwasteliquidfrom\o"Toilet"toilets,\o"Bathing"baths,\o"Shower"showers,\o"Kitchen"kitchens,\o"Sink"sinks,andsoforththatisdisposedofvia\o"Sanitarysewer"sewers.Inmanyareas,sewagealsoincludesliquidwastefromindustryandcommerce.Theseparationanddrainingofhouseholdwasteinto\o"Greywater"greywaterand\o"Blackwater(waste)"blackwaterisbecomingmorecommoninthedevelopedworld,withgreywaterbeingpermittedtobeusedforwateringplantsorrecycledforflushingtoilets.Alotofsewagealsoincludessomesurfacewaterfromroofsorhard-standingareas.Municipalwastewaterthereforeincludesresidential,commercial,andindustrialliquidwastedischarges,andmayinclude\o"Stormwater"stormwaterrunoff.Sewagesystemscapableofhandlingstormwaterareknownascombinedsystemsor\o"Combinedsewer"combinedsewers.Suchsystemsareusuallyavoidedsincetheycomplicateandtherebyreducetheefficiencyofsewagetreatmentplantsowingtotheirseasonality.Thevariabilityinflowalsoleadstooftenlargerthannecessary,andsubsequentlymoreexpensive,treatmentfacilities.Inaddition,heavystormsthatcontributemoreflowsthanthetreatmentplantcanhandlemayoverwhelmthesewagetreatmentsystem,causingaspilloroverflow.Itispreferabletohaveaseparate\o"Stormdrain"stormdrainsystemforstormwaterinareasthataredevelopedwithsewersystems.Asrainfallrunsoverthesurfaceofroofsandtheground,itmaypickupvariouscontaminantsincluding\o"Soil"soilparticlesandother\o"Sediment"sediment,\o"Heavymetals"heavymetals,\o"Organiccompound"organiccompounds,animalwaste,and\o"Oil"oiland\o"Petroleum"grease.Some\o"Jurisdiction"jurisdictionsrequirestormwatertoreceivesomeleveloftreatmentbeforebeingdischargeddirectlyintowaterways.Examplesoftreatmentprocessesusedforstormwaterincludesedimentationbasins,\o"Constructedwetland"wetlands,buriedconcretevaultswithvariouskindsoffilters,andvortexseparators(toremovecoarsesolids).ProcessoverviewSewagecanbetreatedclosetowhereitiscreated(in\o"Septictank"septictanks,\o"Biofilters"biofiltersor\o"Aerobictreatmentsystem"aerobictreatmentsystems),orcollectedandtransportedviaanetworkofpipesandpumpstationstoamunicipaltreatmentplant(see\o"Sanitarysewer"sewerageand\o"Sewagecollectionanddisposal"pipesandinfrastructure).Sewagecollectionandtreatmentistypicallysubjecttolocal,stateandfederalregulationsandstandards.Industrialsourcesofwastewateroftenrequirespecializedtreatmentprocesses(see\o"Industrialwastewatertreatment"Industrialwastewatertreatment).Conventionalsewagetreatmentmayinvolvethreestages,calledprimary,secondaryandtertiarytreatment.Primarytreatmentconsistsoftemporarilyholdingthesewageinaquiescentbasinwhereheavysolidscansettletothebottomwhileoil,greaseandlightersolidsfloattothesurface.Thesettledandfloatingmaterialsareremovedandtheremainingliquidmaybedischargedorsubjectedtosecondarytreatment.Secondarytreatmentremovesdissolvedandsuspendedbiologicalmatter.Secondarytreatmentistypicallyperformedby\o"Indigenous(ecology)"indigenous,water-bornemicro-organismsinamanagedhabitat.Secondarytreatmentmayrequireaseparationprocesstoremovethemicro-organismsfromthetreatedwaterpriortodischargeortertiarytreatment.Tertiarytreatmentissometimesdefinedasanythingmorethanprimaryandsecondarytreatment.Treatedwaterissometimesdisinfectedchemicallyorphysically(forexamplebylagoonsand\o"Microfiltration"microfiltration)priortodischargeintoa\o"Stream"stream,\o"River"river,\o"Bay"bay,\o"Lagoon"lagoonor\o"Wetland"wetland,oritcanbeusedforthe\o"Irrigation"irrigationofagolfcourse,greenwayorpark.Ifitissufficientlyclean,itcanalsobeusedfor\o"Groundwaterrecharge"groundwaterrechargeoragriculturalpurposes.Pre-treatmentPre-treatmentremovesmaterialsthatcanbeeasilycollectedfromtherawwastewaterbeforetheydamageorclogthepumpsandskimmersofprimarytreatmentclarifiers(trash,treelimbs,leaves,etc).ScreeningTheinfluentsewagewaterisstrainedtoremovealllargeobjectscarriedinthesewagestream.Thisismostcommonlydonewithanautomatedmechanicallyrakedbarscreeninmodernplantsservinglargepopulations,whilstinsmallerorlessmodernplantsamanuallycleanedscreenmaybeused.Therakingactionofamechanicalbarscreenistypicallypacedaccordingtotheaccumulationonthebarscreensand/orflowrate.Thesolidsarecollectedandlaterdisposedinalandfillorincinerated.GritremovalPre-treatmentmayincludeasandorgritchannelorchamberwherethevelocityoftheincomingwastewateriscarefullycontrolledtoallowsand,gritandstonestosettle.PrimarytreatmentIntheprimarysedimentationstage,sewageflowsthroughlargetanks,commonlycalled"primaryclarifiers"or"primarysedimentationtanks".Thetanksarelargeenoughthatsludgecansettleandfloatingmaterialsuchasgreaseandoilscanrisetothesurfaceandbeskimmedoff.Themainpurposeoftheprimarysedimentationstageistoproducebothagenerallyhomogeneousliquidcapableofbeingtreatedbiologicallyandasludgethatcanbeseparatelytreatedorprocessed.Primarysettlingtanksareusuallyequippedwithmechanicallydrivenscrapersthatcontinuallydrivethecollectedsludgetowardsahopperinthebaseofthetankfromwhereitcanbepumpedtofurthersludgetreatmentstages.Greaseandoilfromthefloatingmaterialcansometimesberecoveredfor\o"Saponification"saponification.SecondarytreatmentSecondarytreatmentisdesignedtosubstantiallydegradethebiologicalcontentofthesewagewhicharederivedfromhumanwaste,foodwaste,soapsanddetergent.Themajorityofmunicipalplantstreatthesettledsewageliquorusingaerobicbiologicalprocesses.Forthistobeeffective,the\o"Biota(ecology)"biotarequireboth\o"Oxygen"oxygenandasubstrateonwhichtolive.Thereareanumberofwaysinwhichthisisdone.Inallthesemethods,the\o"Bacteria"bacteriaand\o"Protozoa"protozoaconsumebiodegradablesolubleorganiccontaminants(e.g.\o"Sugar"sugars,fats,organicshort-chaincarbonmolecules,etc.)andbindmuchofthelesssolublefractionsinto\o"Flocculation"floc.Secondarytreatmentsystemsareclassifiedasfixed-filmandsuspended-growthFixed-filmORattachedgrowthsystemtreatmentprocessincluding\o"Tricklingfilter"tricklingfilterand\o"Rotatingbiologicalcontactors"rotatingbiologicalcontactorswherethebiomassgrowsonmediaandthesewagepassesoveritssurface.Insuspended-growthsystems,suchasactivatedsludge,thebiomassiswellmixedwiththesewageandcanbeoperatedinasmallerspacethanfixed-filmsystemsthattreatthesameamountofwater.However,fixed-filmsystemsaremoreabletocopewithdrasticchangesintheamountofbiologicalmaterialandcanprovidehigherremovalratesfororganicmaterialandsuspendedsolidsthansuspendedgrowthsystems.\o"Roughingfilter"Roughingfiltersareintendedtotreatparticularlystrongorvariableorganicloads,typicallyindustrial,toallowthemtothenbetreatedbyconventionalsecondarytreatmentprocesses.Characteristicsincludetypicallytall,circularfiltersfilledwithopensyntheticfiltermediatowhichwastewaterisappliedatarelativelyhighrate.Theyaredesignedtoallowhighhydraulicloadingandahighflow-throughofair.Onlargerinstallations,airisforcedthroughthemediausingblowers.Theresultantwastewaterisusuallywithinthenormalrangeforconventionaltreatmentprocesses.\o"Enlarge"ActivatedsludgeMainarticle:\o"Activatedsludge"ActivatedsludgeIngeneral,activatedsludgeplantsencompassavarietyofmechanismsandprocessesthatusedissolvedoxygentopromotethegrowthofbiologicalflocthatsubstantiallyremovesorganicmaterial.Theprocesstrapsparticulatematerialandcan,underidealconditions,convert\o"Ammonia"ammoniato\o"Nitrite"nitriteand\o"Nitrate"nitrateandultimatelyto\o"Nitrogen"nitrogengas,(seealso\o"Denitrification"denitrification).Surface-aeratedbasinsMostbiologicaloxidationprocessesfortreatingindustrialwastewatershaveincommontheuseofoxygen(orair)andmicrobialaction.Surface-aeratedbasinsachieve80to90%removalof\o"BiochemicalOxygenDemand"BiochemicalOxygenDemandwithretentiontimesof1to10days.Thebasinsmayrangeindepthfrom1.5to5.0metresandusemotor-drivenaeratorsfloatingonthesurfaceofthewastewater.Inanaeratedbasinsystem,theaeratorsprovidetwofunctions:theytransferairintothebasinsrequiredbythebiologicaloxidationreactions,andtheyprovidethemixingrequiredfordispersingtheairandforcontactingthereactants(thatis,oxygen,wastewaterandmicrobes).Typically,thefloatingsurfaceaeratorsareratedtodelivertheamountofairequivalentto1.8to2.7

kg\o"Oxygen"O2/\o"Watt-hour"kW·h.However,theydonotprovideasgoodmixingasisnormallyachievedinactivatedsludgesystemsandthereforeaeratedbasinsdonotachievethesameperformancelevelasactivatedsludgeunits.Biologicaloxidationprocessesaresensitivetotemperatureand,between0°Cand40°C,therateofbiologicalreactionsincreasewithtemperature.Mostsurfaceaeratedvesselsoperateatbetween4°Cand32°C.Filterbeds(oxidizingbeds)Mainarticle:\o"Tricklingfilter"TricklingfilterInolderplantsandplantsreceivingmorevariableloads,\o"Tricklingfilter"tricklingfilterbedsareusedwherethesettledsewageliquorisspreadontothesurfaceofadeepbedmadeupof\o"Coke(fuel)"coke(carbonizedcoal),\o"Limestone"limestonechipsorspeciallyfabricatedplasticmedia.Suchmediamusthavehighsurfaceareastosupportthebiofilsthatform.Theliquorisdistributedthroughperforatedrotatingarmsradiatingfromacentralpivot.Thedistributedliquortricklesthroughthisbedandiscollectedindrainsatthebase.Thesedrainsalsoprovideasourceofairwhichpercolatesupthroughthebed,keepingitaerobic.Biologicalfilmsofbacteria,protozoaandfungiformonthemedia’ssurfacesandeatorotherwisereducetheorganiccontent.This\o"Biofilm"biofilmisgrazedbyinsectlarvaeandwormswhichhelpmaintainanoptimalthickness.Overloadingofbedsincreasesthethicknessofthefilmleadingtocloggingofthefiltermediaandpondingonthesurface.BiologicalaeratedfiltersBiologicalAerated(orAnoxic)Filter(BAF)orBiofilterscombinefiltrationwithbiologicalcarbonreduction,\o"Nitrification"nitrificationordenitrification.BAFusuallyincludesareactorfilledwitha\o"Filter(water)"filtermedia.Themediaiseitherinsuspensionorsupportedbyagravellayeratthefootofthefilter.Thedualpurposeofthismediaistosupporthighlyactivebiomassthatisattachedtoitandtofiltersuspendedsolids.Carbonreductionandammoniaconversionoccursinaerobicmodeandsometimeachievedinasinglereactorwhilenitrateconversionoccursin\o"Hypoxia(environmental)"anoxicmode.BAFisoperatedeitherinupflowordownflowconfigurationdependingondesignspecifiedbymanufacturer.Membranebioreactors\o"Membranebioreactor"Membranebioreactors(MBR)combineactivatedsludgetreatmentwithamembraneliquid-solidseparationprocess.Themembranecomponentuseslowpressuremicrofiltrationorultrafiltrationmembranesandeliminatestheneedforclarificationandtertiaryfiltration.Themembranesaretypicallyimmersedintheaerationtank;however,someapplicationsutilizeaseparatemembranetank.OneofthekeybenefitsofanMBRsystemisthatiteffectivelyovercomesthelimitationsassociatedwithpoorsettlingofsludgeinconventional\o"Activatedsludge"activatedsludge(CAS)processes.Thetechnologypermitsbioreactoroperationwithconsiderablyhighermixedliquorsuspendedsolids(MLSS)concentrationthanCASsystems,whicharelimitedbysludgesettling.TheprocessistypicallyoperatedatMLSSintherangeof8,000–12,000

mg/L,whileCASareoperatedintherangeof2,000–3,000

mg/L.TheelevatedbiomassconcentrationintheMBRprocessallowsforveryeffectiveremovalofbothsolubleandparticulatebiodegradablematerialsathigherloadingrates.ThusincreasedSludgeRetentionTimes(SRTs)—usuallyexceeding15days—ensurecompletenitrificationeveninextremelycoldweather.ThecostofbuildingandoperatinganMBRisusuallyhigherthanconventionalwastewatertreatment.Membranefilterscanbeblindedwithgreaseorabradedbysuspendedgritandlackaclarifier'sflexibilitytopasspeakflows.Thetechnologyhasbecomeincreasinglypopularforreliablypretreatedwastestreamsandhasgainedwideracceptancewhereinfiltrationandinflowhavebeencontrolled,however,andthelife-cyclecostshavebeensteadilydecreasing.ThesmallfootprintofMBRsystems,andthehighqualityeffluentproduced,makethemparticularlyusefulforwaterreuseapplications.ThereareMBRplantsbeingbuiltthroughouttheworld,includingNorthLibrty,Iowa,Georgia,andCanada.SecondarysedimentationThefinalstepinthesecondarytreatmentstageistosettleoutthebiologicalflocorfiltermaterialandproducesewagewatercontainingverylowlevelsoforganicmaterialandsuspendedmatter.RotatingbiologicalcontactorsMainarticle:\o"Rotatingbiologicalcontactor"RotatingbiologicalcontactorRotatingbiologicalcontactors(RBCs)aremechanicalsecondarytreatmentsystems,whicharerobustandcapableofwithstandingsurgesinorganicload.RBCswerefirstinstalledin\o"Germany"Germanyin1960andhavesincebeendevelopedandrefinedintoareliableoperatingunit.Therotatingdiskssupportthegrowthofbacteriaandmicro-organismspresentinthesewage,whichbreakdownandstabiliseorganicpollutants.Tobesuccessful,micro-organismsneedbothoxygentoliveandfoodtogrow.Oxygenisobtainedfromtheatmosphereasthedisksrotate.Asthemicro-organismsgrow,theybuilduponthemediauntiltheyaresloughedoffduetoshearforcesprovidedbytherotatingdiscsinthesewage.EffluentfromtheRBCisthenpassedthroughfinalclarifierswherethemicro-organismsinsuspensionsettleasasludge.Thesludgeiswithdrawnfromtheclarifierforfurthertreatment.Afunctionallysimilarbiologicalfilteringsystemhasbecomepopularaspartofhome\o"Aquarium"aquariumfiltrationandpurification.Theaquariumwaterisdrawnupoutofthetankandthencascadedoverafreelyspinningcorrugatedfiber-meshwheelbeforepassingthroughamediafilterandbackintotheaquarium.Thespinningmeshwheeldevelopsa\o"Biofilm"biofilmcoatingofmicroorganismsthatfeedonthesuspendedwastesintheaquariumwaterandarealsoexposedtotheatmosphereasthewheelrotates.Thisisespeciallygoodatremovingwasteureaandammoniaurinatedintotheaquariumwaterbythefishandotheranimals.

污水處理摘要自然或生活污水處理，是指去除包含家庭排放和地面徑流在內(nèi)污水廢水和地面污染物過程。它包含物理，化學(xué)和生物過程，消除物理，化學(xué)和生物污染物。其目標(biāo)是集中產(chǎn)生廢物流（或經(jīng)處理污水）以及固體廢物或污泥進(jìn)行處理或再進(jìn)入環(huán)境。這種污物通常是在無意中受到了許多有毒有機(jī)和無機(jī)物污染。關(guān)鍵詞：污水處理;生物膜處理法和停頓增加生物處理法;活性污泥法污水起源污水是由個人住宅，機(jī)關(guān)，商業(yè)和工業(yè)機(jī)構(gòu)產(chǎn)生。原進(jìn)水（污水）包含家庭廁所，浴室，淋浴，廚房，水槽廢液等等，這些水將經(jīng)過污水管排放。在許多地域，污水也包含工業(yè)和商業(yè)污水。在發(fā)達(dá)國家，家居分別將污水排放為灰水和黑水已經(jīng)越來越普遍，因為灰水能夠用于澆灌植物或回收用來沖馬桶。大量污水還包含一些屋頂流下水以及地表水。所以城市廢水包含住宅，商業(yè)和工業(yè)排放廢水，且可能包含雨水徑流。具備處理雨水能力污水處理系統(tǒng)被稱為合流排水系統(tǒng)。這種系統(tǒng)通常是不被普遍采取，因為它們復(fù)雜化而且因為其季節(jié)性，降低了污水處理廠效率。因為流量經(jīng)常改變，也造成處理量往往大于必需，因而使處理設(shè)施更昂貴。另外，當(dāng)遭遇暴雨時，過量雨水會造成污水處理能力不足，因而引發(fā)溢流。所以在設(shè)計排水管網(wǎng)時最好采取雨污分流系統(tǒng)。因為降雨流經(jīng)屋頂和地面時，會帶走包含土壤顆粒和其余沉積物，重金屬，有機(jī)物，動物排泄物，污油和油脂等各種污染物質(zhì)。所以有些地方會有法律要求在雨水排入河道之前要進(jìn)行一些一定水平處理。比如以下對雨水進(jìn)行處理：盆地沉淀處理，濕地過濾處理，混凝土地窖過濾處理，和旋渦分離器（去除粗固體）。過程概述污水能夠在以下構(gòu)筑物(化糞池，生物過濾器或好氧處理系統(tǒng)）附近被處理，或搜集并經(jīng)過排水管網(wǎng)和泵站送至城市污水處理廠（見污水處理和管道和基礎(chǔ)設(shè)施）。污水搜集和處理，通常取決于當(dāng)?shù)刂莺吐?lián)邦法規(guī)和標(biāo)準(zhǔn)。起源于工業(yè)廢水，往往需要專門處理過程（見工業(yè)廢水處理）。常規(guī)污水處理可能包括三個階段，一級處理，二級處理和三級處理。一級處理包含在沉淀池中短時停留，這么比較重固體就會沉到池底，而油，油脂，更輕固體則浮到水面。沉淀和浮動材料都將被去除，其余液體可被釋放或繼續(xù)二級處理。二級處理能夠去除溶解和懸浮生物物質(zhì)。二級處理通常由好氧或厭氧微生物進(jìn)行。二級處理還可能需要一個分離過程，以去除殘余微生物或進(jìn)行三級處理。三級處理有時被界定為與一級和二級不一樣過程。受處理水在排放到河流，海灣，瀉湖或濕地前有時需要化學(xué)消毒或物理（比如瀉湖和微濾）處理，或者能夠用于澆灌高爾夫球場，綠色道路或公園。假如它足夠清潔，也能夠用于地下水回灌或農(nóng)業(yè)用途。預(yù)處理預(yù)處理能夠從原始廢水除去垃圾，樹枝，樹葉等比較輕易搜集物質(zhì)，以預(yù)防其損壞或阻塞水泵和一級處理澄清池處理。篩選進(jìn)水污水必須消除隨污水流進(jìn)行大污染物。在服務(wù)大量人口當(dāng)代化處理廠，經(jīng)慣用自動傾斜格柵來達(dá)成這個目標(biāo)。而小處理廠可能采取手動格柵。機(jī)械式格柵清污是經(jīng)典以格柵污物積累或流量積累來進(jìn)行。搜集到固體將被進(jìn)行填埋或焚燒處理。除砂預(yù)處理可使包含沙子或砂礫在內(nèi)物質(zhì)經(jīng)過控制速度在渠道或廳室內(nèi)旋轉(zhuǎn)流動，使砂，砂礫和石塊沉淀。初級處理在初級沉淀階段，污水流經(jīng)一個大池子，俗稱“初級澄清池”或“初級沉淀池”。這些池子需要足夠大以令污泥能夠沉淀而油和油脂等漂浮物能夠上升到表面，并掠出池子。在初級沉淀階段主要目標(biāo)是提供一個均勻液態(tài)環(huán)境使微生物和污泥都能被處理。初級沉淀池，通常裝配有機(jī)械驅(qū)動刮削泥器，不停推進(jìn)將污泥搜集到底部污泥斗，從那里能夠抽取污泥進(jìn)行深入處理。油脂和石油漂浮物有時會回收進(jìn)行皂化。二級處理二級處理設(shè)計是為了降低了污水中那些來自人類垃圾，食物渣滓，肥皂和洗滌劑產(chǎn)生生化生物污染。大多數(shù)市政都打算采取好氧生物方法處理污水處理問題。為了達(dá)成這個目標(biāo)，生物既需要氧也需要生活底物。有多個方式來達(dá)成這個目標(biāo)。在全部這些方法中，細(xì)菌和原生動物生物都能夠降解消耗水中水溶性有機(jī)污染物（如糖，脂肪，有機(jī)短鏈碳分子等），將大部分可溶性組分結(jié)合成絮狀。二級處理系統(tǒng)被分為生物膜處理法和停頓增加生物處理法。生物膜處理法和停頓增加生物處理法系統(tǒng)處理流程包含生物濾池和生物轉(zhuǎn)盤，它們提供生物生長媒體以使污水流過時進(jìn)行處理。在停頓增加生物處理法如活性污泥系統(tǒng)中，生物質(zhì)能夠與與污水充分混合，而且在處理等量污水時能夠比膜系統(tǒng)采取更小空間操作。