Unit 9 Text a. Sewerage.

I

Man’s sewerage practice has been known from ancient times. Explorations revealed sewers in Babylon dating from the 7-th century before our era. Remains of sanitary sewers are to be found in the ruins of the prehistoric cities of Crete and the ancient cities of Assyria. Rome also had sewers, but they were primarily drains to carry away storm water. It was practice to deposit all sorts of refuse in the street gutters and accordingly the storm sewers also carried much organic matter at times. Sewerage was practically unknown during the middle ages, and not until modern times the construction of sewers was resumed. At first, however, they were storm sewers not designed to carry domestic sewage.

The water courses in or near towns apparently were used as convenient places of refuse disposal. The offensive and dangerous materials were discharged into streams where they decomposed to cause discomfort and danger to rural populations or to cities located downstreams. Most cities, therefore, soon found it necessary to treat the sewage before releasing it.

II

The history of the progress of sanitation in London probably shows a typical picture of what took place quite generally about the middle of 19-th century in the largest cities of Great Britain and the United States. Sanitation was little considered and execution of sewage work was impossible. There were hundreds of streets in London that had no sewers. All through London’s history until modern time, the question of water supply continued to be a problem. In the 18-th century even with the appearance of larger water companies the water supply was far from being satisfactory. Water taken from the river Thames was offensive to the sight as the intake was only three yards from the outlet of a great sewer. But the feeling that public health depends largely upon sewerage was the deciding factor in the growing recognition of good sewerage system. In 1885 after two outbreaks of cholera British Parliament passed an act which laid the basis for the sanitation of London. On the continent a marked progress in sewerage began in 1842 when a severe fire destroyed the old part of Hamburg. It was decided to rebuild this part according to the modern ideas of convenience. As a result Hamburg was the first city which had a compete systematic sewerage system throughout built according to modern ideas.

Выучите слова.

I

sewerage - канализация

sewage - сточные воды

exploration - исследование

reveal- обнаружить, открыть

primarily - в основном, первоначально

drain - сток

deposit – осаждать(ся), осадок

refuse – отходы, отбросы

gutter – сточная канава, желоб

resume – возобновлять, продолжать

storm sewage – ливневая вода

apparently – несомненно

disposal – удаление, устранение

offensive – неприятный, имеющий запах

discharge – выпускать, спускать

cause – причинять, причина

treat – обрабатывать

release – выпускать, выпуск

II

execution – выполнение

intake – входной канал

depend on (upon) – зависеть

outbreak – вспышка

considerable – значительный

destroy – разрушать

purity – чистота

resources – запасы

amount – количество

confine – ограничивать

safeguard – охранять

pollution – загрязнение

according to – согласно, в соответствии

a number of – ряд

until – до, до тех пор пока

therefore – поэтому, следовательно

through – сквозь, через

both… and – как… так и

same – тот же самый

Задание 1. Ответьте на вопросы.

1. Where are the ruins of prehistoric sanitary sewers to be found? 2. Did Rome have sewers? 3.What were drains used for? 4. Was sewerage practically known in Middle Ages? 5. Where were the offensive and dangerous materials discharged? 6. Was there any sewage system in medieval cities? 7.What did most cities decide to treat? 8. Why was it necessary to treat the sewage before discharging it?

Задание 2. Переведите предложения, обращая внимание на функцию “that”

1. That system was built some years ago. 2. Water that is absolutely pure is not found in nature. 3. The problems of good sanitation is closely connected with that of protecting the purity of natural water supply. 4. That this method of controlling waste water produced good results is well known. 5. It was found that the local sources of water supply were inadequate to meet the sanitary requirements. 6. Some of the suspended matter is so small that its removal by sedimentation is impracticable. 7. The system of conduits that conveys water is known as the distribution system.

Задание 3. Переведите предложения, обращая внимание на модальные глаголы.

1. We can live without food for several weeks. 2. These pipes must be protected against corrosion. 3. Water can be obtained from different natural sources on the earth. 4. Sewage must be treated prior to disposal. 5. Students may leave the lab if the work is done. 6. Quite often pipelines must be built over long distances to obtain water supplies.

Задание 4. Переведите предложения, обращая внимание на формы с окончанием “ing”.

1. Most cities soon found it necessary to treat the sewage before releasing.

2. The important effects of water works and sewerage upon cities are not confined to the safeguarding of health. 3. Street cleaning and flushing are possible. 4. Swimming pools and other recreational uses of water are commonplace. 5. Many cities had a difficultly in carrying away their waste waters . 6. Ancient cities deposited their refuse into the street gutters instead of constructing sewers for the removal of wastes. 7. Improving the methods of water treatment we improve the water quality. 8. The main function of water supply systems is to supply the population with safe water for drinking.

Text B. Don’t Forget Fire Protection.

In addition to providing supply for general service , most public systems provide supply for another very important service : fire protection. Although the volume of water required for fire fighting, in comparison to that used for general service during the course of a year normally insignificant, the rate at which water must by supplied, when needed is quite substantial. Depending on the fire hazards within a particular community, fire flow requirements may vary from 500 gpm to over 12000 gpm. As a general rule, the smaller the community, the greater the impact of fire capacity requirements on the overall system capacity required. However, in a larger community where bigger mains are required to meet general service demands, the additional capacity required for fire flow is not as significant. It should also be noted that, in general, fire flow requirements are more severe in an industrially or commercially-oriented community than in a residential community. Industrial and commercial buildings are generally more of a fire hazard than residential buildings and therefore more water is required for control of fire.

Notes:

gpm – галлонов в минуту

Text C. Purification of Water.

If the water of a source doesn’t meet specified requirements, it is subjected to purification and treatment. Water is purified in specially constructed purification plants. The water purification methods are as follows: clarification, serving to reduce turbidity, – to disinfection eliminate pathogenic bacteria softening serving to reduce the content of salts etc.

Clarification of water, i.e. removal of suspended substances is attained by the processes of sedimentation and filtration. Water is treated by sedimentation in special sedimentation tanks through which the treated water flows at a rate of 1-2 mm/sec. During the time the treated water remains in the basin (from 9 to 18 hr) fine particles settle on the bottom of the sedimentation tank. A more thorough treatment is attained by adding chemical substances to the treated water. These substances form flocs which accumulate the suspended particles and rapidly settle on the bottom of the sedimentation tank. At the outlet of the sedimentation bank water still contains a certain amount of fine suspended matter and drinking water is therefore subjected to additional filtration.