Современные проблемы промышленного и гражданского строительства на занятиях английского языка. Кузьмина Е.В. - 51 стр.

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concentrated before dewatering. The settler overflow, or supernatant, is

recycled to the influent line of the filtration process.

TEXT E. SEWERAGE

The problem of protecting natural water resources has grown very

pressing for many countries since the beginning of the second half of the 20

century. The development of human society, the growth of civilization and

social and technical progress has resulted in the changing of the composition of

natural water resources. The rivers, lakes and groundwaters contain today a

considerable amount of the products of mechanical, chemical and biological

pollution.

The waste products that result from the daily activities in a community

are of two general types: namely, the liquid waste, known as sewage and the

solid wastes, known as refuse. The different wastes of which sewage is

composed are the following: the wastes from lavatories, baths, sinks, and

laundry tanks in residences, institutions, and business buildings; certain liquid

wastes from various types of manufacturing or industrial plants, and, in many

communities, the surface run-off that results from storms or street-flushing

operations.

Sewage may also be divided according to its source into the following

three classes. The sewage from residences, institutions and business buildings is

called domestic sewage, sanitary sewage or house sewage; that resulting from

manufacturing or industrial processes is known as industrial waste; and that

from run-off during or immediately following storms is called storm sewage. A

combination of domestic sewage, industrial waste and storm water is called

combined sewage.

Both sewage and refuse must be removed promptly in order to avoid

endangering the health of the community and also prevent decomposition of the

materials of animal or vegetable origin and the subsequent production of

nuisances and odours.

The removal of all kinds of sewage is usually accomplished by means of

sewers. The sewers are placed in the streets at several feet below the ground