求助,环境专业英语翻译
发布网友
共1个回答
热心网友
Municipal wastewater, also called sewage, is a complex mixture containing water usually over 99 percent) together with organic and inorganic contaminants, both suspended and dissolved.The concentration of these contaminants is normally very low and is expressed in mg/L,that is ,milligrams of contaminant per liter of the mixture.This is a weight-to-volume ratio used to indicate concentrations of constituents in water ,wastewater , industrial wastes, and other dilute solutions.
The amount of organic matter in water or wastewater can be measured directly (as TOC ,for example ) but this doesn’t tell us whether the organics are biodegradable or not.To measure the amount of oxygen by a growing microbial populayion to convert (oxidize)organic matter to CO2 and H2O in a closed system. .The oxygen consumed,or biochemical oxygen demand (BOD),is proportional to the organic matter converted ,and therefore BOD is a relative measure of the biologically degradable organic matter present in the system . Because biological oxidation continues indefinitely , the test for ultimate BOD has been arbitrarily limited to 20 days , when perhaps 95 percent or more the oxygen requirement has been met . Even this period ,however,is too long to make measurement of BOD useful, so a five-day test ,BOD5 ,carried out at 20℃, has become standard .The rate of the BOD reaction depends on the type of waste present and the temperature and is assumed to vary directly with the amount of organic matter (organic carbon) present.
An alternative technique is the activated sludge process. Here the sewage ,after primary treatment ,is pumped into an aeration tank , where it is mixed for several hours with air and bacteria-laden sludge .The biological action is similar to that which occurs in the trickling filter .The sludge bacteria metabolize the organic nutrients ; the protozoa , as secondary consumers ,feed on the bacteria.The treated waters then flow to a sedimentation tank , where the bacteria-landen solids settle out and are retuened to the aerator. Some of the sludge must be remove to maintain steady-state conditions .The activated sludge process requires less land space than the trickling filters, and ,since it exposes less area to the atmosphere ,it does not stink so much.
Screening, coagulation/flocculation ,sedimentation, filtration, and disinfection are the main unit operations involved in the treatment of surface water. Water treatment operations fulfill one or more of three key tasks :remvval of particulate substances such as sand and clay , organic matter ,bacteria, and algae ;removal of dissolved substances such as those causing color and hardness ; and removal or destruction of pathogenic bacteria and viruses. The actual selection of treatment processes depends on the type of water source and the desired water quality.
城市废水，也称为污水，是一项复杂的混合物载水通常超过99 ％ ） ，连同有机和无机的污染物，无论是暂停和dissolved.the浓度的这些污染物通常是非常低，是表示在毫克/升，即是毫克每升污染物的mixture.this是一个重量到货量的比例，用来表明浓度的选民在水，废水，工业废料，及其他稀溶液。
数额中有机质的水或废水可直接测量（ TOC的，例如） ，但这并没有告诉我们是否可生物降解的有机物或not.to措施的金额氧气越来越多微生物populayion转换（氧化）有机质，以CO2和H2O在一个封闭的系统。 。氧消耗量，或生化需氧量（ BOD ） ，是成正比的有机质转换，因此，生化需氧量是一个相对的措施，生物可降解的有机物，目前在该系统。因为生物氧化继续下去，测试的最终生化需氧量一直任意有限至20天，当也许是95 ％或更多的氧气的要求已经得到满足。即使这期间，不过，太长，使测量的生化需氧量有用的，因此，进行为期5天的测试，生化需氧量，进行了在20 ℃ ，已成为标准。率的BOD反应取决于该类型的废物当前和温度和假设不同，直接与金额的有机物（有机碳） 。
另一种技术是活性污泥法处理。这里的污水，经过初级处理，是注入一曝气池，在那里是混合了几个小时，与空气和细菌-拉登的污泥。生物的行动是类似即是发生在生物滤池。污泥细菌代谢有机养分;原生动物，作为中学的消费者，饲料对bacteria.the治疗水域，然后流至沉淀池，那里的细菌- landen固体和解，并retuened向曝气器。一些污泥，必须删除，以维持稳定状态的条件。活性污泥的过程中需要较少的土地空间比滴过滤器，和，因为它暴露了少面积的气氛，它不臭了这么多。
筛选，混凝/絮凝，沉淀，过滤和消毒是主要的操作单元所涉及的治疗地表水。水处理行动履行一个或一个以上的三个主要任务： remvval的微粒物质，例如沙子和粘土，有机质，细菌和藻类;去除溶解物质，例如那些造成的颜色和硬度;去除溶解物质，例如那些造成的颜色和硬度;和排除或销毁的致病细菌及病毒。实际选择的处理过程依赖于类型的水源和理想的水质。
