Unit 16Conventional wastewater Treatment Processes传统污水处理过程传统污水处理过程1nConventional wastewater treatment consists of preliminaryprocesses(pumping,screening,andgritremoval),primarysettlingto remove heavy solids and floatable material, and secondarybiological aeration to metabolize and flocculate colloidal anddissolvedorganics.n传统的废水处理包括初步处理（提升，筛选和除砂），初沉去除重金属固体和漂浮物质，二级曝气生物代谢和絮凝去除胶体和溶解的有机物nWastesludgedrawnfromtheseunitoperationsisthickenedandprocessedforultimatedisposal(Fig.33).n从这些单元操作产生的污泥，被浓缩以便最终处理（图33）。
2nPreliminaryTreatmentUnitsnThefollowingpreliminaryprocessescanbeusedinmunicipalwastewatertreatment:coarsescreening(barracks),mediumscreening,comminution,flowmeasuring,pumping,gritremovalpre-aeration,flotation,flocculation,andchemicaltreatment.n以下初步处理可以在市政污水处理中使用：粗筛（格栅），中筛选，粉碎，计量泵，抽，预曝气除砂，气浮，絮凝和化学处理nThelatterthreearenotcommonindomesticwastewatertreatment.Thesepracticesaresometimesdictatedbytheindustrialpollutantsinthemunicipalwastewater.n后三种在生活污水处理是不常见的这些过程有时由城市污水所含的工业污染物决定3nFlotation is used to remove fine suspensions, grease and fats and isperformedeitherinaseparateunitorinapre-aerationtankalsousedforgritremoval.n气浮是用于去除细小悬浮物，油脂和脂肪，要么是在一个单独的处理单元或在预曝气池用于除砂。
nIf adequate pretreatment is provided by petroleum industries and meat-processingplants,flotationunitsarenotrequiredatamunicipalfacility.n在石油工业和肉类加工厂处理中，如果有足够的预处理，气浮单元在市政设施是不需要的nFlocculationwithorwithoutchemicaladditionmaybepracticedonhigh-strengthmunicipalwastestoprovideincreasedprimaryremovalandpreventexcessiveloadsonthesecondarytreatmentprocessed.n无论有没有化学添加剂的絮凝过程，高浓度的市政污水必须经过足够的预处理，防止在二级处理中有过度负荷nChlorinationofrawwastewaterissometimesusedforodorcontrolandtoimprovesettlingcharacteristicsofthewastes.n原水的氯化有时用于气味控制和提高废物的稳定特性。
4nPrimaryTreatmentUnitsnPrimarytreatmentissedimentation.Incommonusage,thoughthetermincludesthepreliminarytreatmentprocesses.n主要处理方法是沉淀在常见的用法，虽然该术语包括前处理工艺nSedimentation of rawwastewater is practiced in all largemunicipalplantsandmustprecedetrickling(biological)filtration.n在大型的市政污水厂中原水的沉淀和必须在滴滤池（生物处理）前nCompletelymixedactivated-sludgeprocessescanbeusedtotreatunsettledrawwastewater;however,thismethodisrestrictedtosmall municipalities because of the costs involved in sludgedisposalandoperation.n完全混合式活性污泥法被用来处理不沉降的原水，然而，因为污泥处理费用和操作，这个方法一般不在小的城市使用，5nSecondaryTreatmentUnitsnPrimarysedimentationremoves30%50%ofthesuspendedsolidsinrawmunicipalwastewater.n初沉池能够去除市政污水3050的悬浮固体。
nRemaining organic matter is extracted in biological secondarytreatmenttotheallowableeffluentresidualusingactivated-sludgeprocesses,tricklingfilters,orbiologicaltowers.n剩余的有机物在二级生物处理被吸附已达到出水的浓度标准，一般二级处理为活性污泥工艺，滴滤池或生物塔nIn the activated-sludge method wastewater is fed continuouslyinto an aerated tank, wheremicroorganisms synthesize theorganics.n在活性污泥法，废水被连续地送入曝气池，在这里微生物合成有机物6nTheresultingmicrobialfloc(activatedsludge)issettledfromtheaeratedmixedliquorunderquiescentconditionsinafinalclarifierandreturnedtotheaerationtank.n产生的微生物絮体（活性污泥），在沉淀池中从曝气混合液中分离出来，并返回到曝气池。
nTheplanteffluentisclearsupernatantfromsecondarysettling.n出厂水为二沉池后的上清液nAdvantagesofliquidaerationarehigh-BODremovals,abilitytotreathigh-strengthwastewater,andadaptabilityforfutureuseinplantconversiontoadvancedtreatment.7nOn the other hand, a high degree of operational control isneeded,shockloadsmayupsetthestabilityofthebiologicalprocess,andsustainedhydraulicororganicoverloadingresultsinprocessfailure.n另一方面，操作控制要求高，冲击负荷会扰乱生物处理工艺的稳定，持续的水力或者有机负荷会导致处理工艺的失败8nTricklingfiltersandrotatingbiologicalcontactorshavemediatosupportmicrobialfilms.n滴滤池和生物转盘通过媒介支撑生物膜。
nTheseslimegrowthsextractorganicsfromthewastewaterasittricklesoverthesurfaces.n这些生物膜从流过滤料的废水中吸取有机物nOxygen is supplied from air moving through voids in themedia, Excessive biological growth washes out and iscollectedinthesecondaryclarifier.n氧气从媒介中间的空隙补给产生的过量生物膜被冲洗，在二沉池中收集9nInnorthernclimatestwo-stagestone-mediatricklingfiltersareneededtoachieveefficienttreatment.n在北方的气候，两阶段的石头滤料的滴滤池被采用以实现高效处理nBiologicaltowersmaybeeithersingleortwo-stagesystems.n生物塔可以是一段或两段系统nAdvantagesoffiltrationareeaseofoperationandcapacitytoacceptshockloadsandoverloadingwithoutcausingcompletefailure.n过滤优点在于易于操作而且能够接受冲击负荷和超负荷，而不会引起失败。
10nSludgeDisposalnPrimarysedimentationandsecondarybiologicalflocculationprocesses concentrate the waste organics into a volume ofsludge significantly less than the quantity of wastewatertreated.n初沉污和二级生物絮凝过程浓缩废物，形成的污泥体积远小于被处理污水的量nBut disposal of the accumulated waste sludge is a majoreconomicfactorinwastewatertreatment.n但是，收集起来的污泥的处置费用是污水处理的主要因素nThe construction cost of a sludge processing facility isapproximatelyone-thirdthatofatreatmentplant.n污泥处理设施的建设费大约占水厂费用的1/311nFlow schemes for withdrawal, holding, and thickening raw waste sludge from sedimentation tanks are illustrated in Fig. 3-4. n图3-4示意了沉淀池中污泥排出、存储、浓缩流程图。
nThe settled solids from clarification of trickling filter effluent are frequently returned to the plant head for removal with the primary sludge (top diagram Fig. 3-4). n经生物滤池出水后的沉淀物，返回水厂头部，与初沉污泥一同被去除n Raw settlings may be stored in the primary tank。