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1、1,Unit 16Conventional wastewater Treatment Processes,传统污水处理过程,2,Conventional wastewater treatment consists of preliminary processes (pumping, screening, and grit removal), primary settling to remove heavy solids and floatable material, and secondary biological aeration to metabolize and flocculate c
2、olloidal and dissolved organics. 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。Waste sludge drawn from these unit operations is thickened and processed for ultimate disposal (Fig.33).从这些单元操作产生的污泥，被浓缩以便最终处理（图33）。,3,Preliminary Treatment UnitsThe following preliminary processes can be
3、used in municipal wastewater treatment: coarse screening (bar racks), medium screening, comminution, flow measuring, pumping, grit removal pre-aeration, flotation, flocculation, and chemical treatment. 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。The latter three are not common in domesti
4、c wastewater treatment. These practices are sometimes dictated by the industrial pollutants in the municipal wastewater. 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。,4,Flotation is used to remove fine suspensions, grease and fats and is performed either in a separate unit or in a pre-aeration tank also us
5、ed for grit removal. 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。If adequate pretreatment is provided by petroleum industries and meat-processing plants, flotation units are not required at a municipal facility. 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。Flocculation with or without chemical addition ma
6、y be practiced on high-strength municipal wastes to provide increased primary removal and prevent excessive loads on the secondary treatment processed. 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。Chlorination of raw wastewater is sometimes used for odor control and to improve settling character
7、istics of the wastes.原水的氯化有时用于气味控制和提高废物的稳定特性。,5,Primary Treatment UnitsPrimary treatment is sedimentation. In common usage, though the term includes the preliminary treatment processes. 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。Sedimentation of rawwastewater is practiced in all large municipal plants and must p
8、recede trickling (biological) filtration. 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。Completelymixed activated-sludge processes can be used to treat unsettled raw wastewater; however, this method is restricted to small municipalities because of the costs involved in sludge disposal and operation. 完全混合式活性污泥法被用来处理
9、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，,6,Secondary Treatment UnitsPrimary sedimentation removes 30%50% of the suspended solids in raw municipal wastewater. 初沉池能够去除市政污水30 50的悬浮固体。Remaining organic matter is extracted in biological secondary treatment to the allowable effluent residual using activated-
10、sludge processes, trickling filters, or biological towers. 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。In the activated-sludge method wastewater is fed continuously into an aerated tank, wheremicroorganisms synthesize the organics. 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。,7,The resultingmicrobial floc (
11、activated sludge) is settled from the aerated mixed liquor under quiescent conditions in a final clarifier and returned to the aeration tank. 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。The plant effluent is clear supernatant from secondary settling. 出厂水为二沉池后的上清液。Advantages of liquid aeration are high-B
12、OD removals, ability to treat high-strength wastewater, and adaptability for future use in plant conversion to advanced treatment.,8,On the other hand, a high degree of operational control is needed, shock loads may upset the stability of the biological process, and sustained hydraulic or organic ov
13、erloading results in process failure.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。,9,Trickling filters and rotating biological contactors have media to support microbial films. 滴滤池和生物转盘通过媒介支撑生物膜。These slime growths extract organics from the wastewater as it trickles over the surfaces. 这些生物膜从流
14、过滤料的废水中吸取有机物。Oxygen is supplied from air moving through voids in the media, Excessive biological growth washes out and is collected in the secondary clarifier. 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。,10,In northern climates two-stage stone-media trickling filters are needed to achieve efficient treatment.
15、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。Biological towers may be either singleor two-stage systems.生物塔可以是一段或两段系统。Advantages of filtration are ease of operation and capacity to accept shock loads and overloading without causing complete failure.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。,11,Sludge Disposal Primary sedim
16、entation and secondary biological flocculation processes concentrate the waste organics into a volume of sludge significantly less than the quantity of wastewater treated. 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。But disposal of the accumulated waste sludge is a major economic factor in wastewater treatme
17、nt. 但是，收集起来的污泥的处置费用是污水处理的主要因素。The construction cost of a sludge processing facility is approximately one-third that of a treatment plant.污泥处理设施的建设费大约占水厂费用的1/3。,12,Flow schemes for withdrawal, holding, and thickening raw waste sludge from sedimentation tanks are illustrated in Fig. 3-4. 图3-4示意了沉淀池中污泥
18、排出、存储、浓缩流程图。The 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). 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。 Raw settlings may be stored in the primary tank bottom until processed or pumped into a
19、 holding tank for storage. 初沉池底部的沉淀物通过泵抽取到污泥池。,13,The withdrawn sludge may be concentrated in a thickener, usuallya gravity-type unit, prior to processing. 排出的污泥在浓缩池中浓缩。 In the bottom diagram of Fig. 3-4, waste-activated sludge is mixed with primary residue after withdrawal. 在图3-4的下面的示意图中，剩余活性污泥与初沉污
20、泥混合处理。 A holding tank is commonly used in this system arrangement, along with a thickener. 在浓缩池之前，存在一个污泥存储池。The waste activated may be thickened separately or the combined sludge thickened prior to processing.剩余活性污泥有可能被单独浓缩，也有可能与其他污泥联合浓缩。,14,Common alternatives for processing and disposal of raw slu
21、dge are anaerobic digestion and mechanical dewatering by vacuum or pressure filtration. 常见的方法处理和处置生污泥厌氧消化和机械脱水是由真空或压力过滤。 Centrifugation and wet combustion are less often employed. 离心和湿式燃烧更经常使用。 Conventional methods of disposal include burial in landfill, incineration, production of soil conditioner,
22、 and barging to sea. 常规方法处理包括埋葬在垃圾填埋、焚烧、生产的土壤改良剂，和驳运到海洋。 For coastal cities ocean dumping is often least expensive, whereas burial is regularly practiced if landfill area is available. 对于沿海城市海洋倾倒往往是最便宜的，如果垃圾填埋区是可用的，填埋经常采用。 Incinerationalthough more costly, is frequently the only feasible method of d
23、isposal in urbanized areas. 焚烧，虽然更昂贵，通常是唯一可行的处置方法在城市化的地区。,15,All possible sludge-disposal processes for a municipal treatment plant must be givencareful consideration. 对所有的污泥处置方式，污水厂必须仔细衡量。 The method selected should be the most economical process, if it is best, with due regard to environmental con
24、ditions. Attention must be given to such factors as trucking sludge through residential areas, future use of landfill areas, groundwater pollution, air pollution, other potential public health hazards, and esthetics.必须注意通过居住区的污泥运输等因素，将来使用垃圾的地区，地下水污染、空气污染、其他潜在的公共卫生风险，和美学。,16,Advanced wastewater treat
25、ment Phosphorus removal is practiced in processing wastewater that discharged to receiving waters subject to eutrophication including lakes, reservoirs, and slow-moving rivers acting like impoundments. 磷是污水处理的主要去除物，因为磷排入受纳水体，如河流、水库以及水流较慢的河流，会引起水体富营养化。Since nitrogen removal is much more difficult and
26、 costly, it is rarely performed, although nitrification to reduce the ammonia content is sometimes done to control the oxygen demand and toxicity of the plant effluent. 因为氮的去除相对困难和昂贵，很难实现。尽管硝化作用能够降低氨氮的浓度，控制需氧量和出水毒性。,17,Water reclamation is achieved in varying degrees by many plants depending on the local environmental concerns; however, only a few large-scale plants are reclaiming water to near original quality. Advanced wastewater treatment processes are discussed later on.许多水厂在不同程度上实现了水的再生，这些取决于当地的环境状况。然后，只有很少的大型水厂能够再生水达到原水水质。污水的深度处理在滞后进行探讨。,18,Thanks！,
