污水处理外文翻译---废水处理方法发展(编辑修改稿)

污水处理外文翻译---废水处理方法发展(编辑修改稿)内容摘要：

er 169。 2020 Elsevier . All rights reserved doi。 I. Introduction Water covers 71% of the earth39。 s surface and makes up 65% of our bodies. Everyone wants clean water to drink, for recreation, and just to enjoy looking at. If water bees polluted, it loses its value to us economically and aesthetically, and can bee a threat to our health and to the survival of the fish living in it and the wildlife that depend on it. The pollution of rivers and streams with chemical contaminants is one of the most crucial environmental problems. Waterborne chemical pollution entering rivers and streams causes tremendous amounts of destruction. Although some kinds of water pollution can occur through natural processes, it is mostly a result of human activities. We use water daily in our homes and industries. The water we use is taken from lakes and rivers and from underground (groundwater)。 and after we have used it and contaminated it most of it returns to these locations. This used water is called wastewater. If it is not treated before being discharged into waterways, serious pollution is the result. Wastewater may be defined as a bination of liquid or watercarried waste removed fro residences, institutions, and mercial and industrial establishments, together with ground water, surface water and storm water. It generally contains a high load of oxygen demanding wastes, pathogenic or diseasecausing agents,organic materials, nutrients that stimulate plant growth, inorganic chemicals and minerals and sediments. It may also contain toxic pounds[1]. Wastewater may be classified into four categories: • domestic: wastewater discharged from residences and mercial institutions and similar facilities。 • industrial: wastewater in which industrial waste predominates。 • infiltration/inflow: extraneous water that enters the sewer system through indirect and direct means such as through leaking joints, cracks, or porous walls. Inflow is storm water that enters the sewer system from storm drain connections, roof headers, foundation and basement drains or through manhole covers。 • storm water: runoff resulting from flooding due to rainfall. For many years the main goal of treating municipal wastewater was simply to reduce its content of suspended solids, oxygendemanding materials, dissolved inorganic pounds, and harmful bacteria. In recent years, however, more stress has been placed on improving means of disposal of the solid residues from the municipal treatment processes. The basic methods of treating municipal wastewater fall into three stages:primary treatment, including grit removal,screening, grinding, and sedimentation。 secondary treatment, which entails oxidation of dis solved organic matter by means of using biologically active sludge, which is then filtered off。 and tertiary treatment, in which advanced biological methods of nitrogen removal and chemical and physical methods such as granular filtration and activated carbon absorption are employed [2]. The characteristics of industrial wastewaters can differ considerably both within and among industries. The impact of industrial discharges depends not only on their collective characteristics such as biochemical oxygen demand and the amount of suspended solids, but also on their content of specific inorganic and organic substances. Three options are available in controlling industrial wastewater. Control can take place at the point of generation in the plant。 wastewater can be pretreated for discharge to municipal treatment sources。 or wastewater can be treated pletely at the plant and either reused or discharged directly into receiving waters. Industrial wastewaters are the discharge of industrial plants and manufacturing wastewaters can represent, collectively, an important part of munity wastewaters and must be considered for successful wastewater treatment plant operation. In some locations industrial wastewater discharge is collected together with other munity wastewaters and the mixed wastes are treated together. In other instances, industries may provide some pre treatment or partial treatment of their wastewaters prior to discharge to the municipal sewers. In still other situations, the volume and character of the industrial waste are such that separate collection and disposal are necessary. Industrial wastewaters vary widely in position, strength, flow and volume, depending on the specific industry or manufacturing establishment in the munity. The specific position and volume of the industrial waste will, of course,depend on the use to which the water has been put. Typical industries which produce significant volumes of wastewaters include paper and fiber plants, steel mills, refining and petrochemical operations, chemical and fertilizer plants, meat packers and poultry processors, vegetable and fruit packing operations and many more. Industrial discharges may consist of very strong organic wastewaters with a high oxygen demand or contain undesirable chemicals that can damage sewers and other structures. They may contain pounds, which resist biological degradation,or toxic ponents, which interfere with satisfactory operation of the wastewater treatment plant. A less obvious source, which must be considered an industrial waste, is thermal discharge since it lowers dissolved oxygen values. Many industries use large quantities of cooling water, with the electric power industry being the largest , the primary metal and chemical industries also use substantial quantities of cooling waters. 2. Conventional wastewater treatment processes Conventional wastewater treatment consists of a bination of physical, chemical, and biological processes and operations to remove solids,organic matter and, sometimes, nutrients from wastewater. General terms used to describe dif ferent deg。