Sewerage. General Considerations



Unit 3.1 Sewerage. Historic background.

Discuss in pairs:

1) What time do sanitary sewers date to?

2) What improvement caused a sharp decline in the urban death rate?

Read the text and see if your ideas are right.

Remains of sanitary sewers are to be found in the ruins of the ancient cities of Crete and Assyria. Rome also had sewers, but they were primarily drains to carry away storm water. It was the practice to deposit all sorts of refuse in the streets, and accordingly the storm sewers also carried much organic matter at times. Sewerage was practically unknown during the Middle Ages, and construction of sewers was not resumed until modern times. At first, these were storm sewers not intended to carry domestic sewage. As late as 1850, the discharge of household wastes into the sewers of London was forbidden. The water courses in or near towns apparently were used as convenient places of refuse disposal, for many writers comment upon the offensive condition of the London brooks, with their burden of dead dogs and filth of all sorts. In the course of time it was recognized that sanitation would best be served by permitting the use of sewers to convey human excreta away from dwellings as promptly as possible, and the original storm drains became combined sewers which carried both storm-water runoff and the liquid wastes from occupied buildings. The development of water supplies, of course, played a large part in the greater use of plumbing systems with water-flush toilets. The commonly used vault toilets, which frequently overflowed and always produced odors, were soon legislated out of existence in the larger cities in favor of the water-carried system. This improvement together with safer water supplies caused a sharp decline in the urban death rate.

When the problem of sewage treatment first attracted attention, a difference of opinion existed among engineers, as to the completeness of treatment that should be given to sewage before discharge into a body of water. Some engineers main­tained that the public interest required the most complete treatment possible. Others held the opinion that treatment should be based upon local conditions and that no more treatment need be provided than would give reasonable assurance, with a factor of safety, that danger and nuisance would not exist. So far as safety of water supplies is concerned, this viewpoint placed upon the waterworks authori­ties some of the burden of safeguarding and treating their raw water. When it is considered that water of streams and lakes may often be polluted or made unsuit­able for use otherwise than by city sewage, it is obviously inequitable to require all cities to produce a sewage treatment plant effluent comparable to drinking water. Therefore, sewage treatment has been based upon local conditions rather than idealistic standards.

Present regulations in the United States establish which bodies of water are quality, and which effluent limited. Those waters which are of a quality suitable for their highest intended use are defined as effluent limited. Wastes discharged into such waters must be treated to the degree obtained in secondary systems. Waters which are not suitable for their highest intended use under such effluent limitations are governed by water quality and are analyzed to establish the allow­able total pollution load which can be assimilated without degradation. This allowable waste load is then allocated to present and future discharges. Treatment at each discharge point is then tailored to meet this waste load allocation. Treat­ment to a level less than that provided by secondary systems is never permitted under either system.

1. Notes to the text:

drain – сточная канава

refuse – отходы

disposal – сброс, удаление нечистот

to pollute – загрязнять

2. Match  the words in two columns and make the collocations:

1) sanitary                a) matter

2) storm                   b) wastes

3) to deposit                      c) sewage

4) organic                 d) sewers

5) domestic              e) water

6) household            f) refuse

3. Match the following English expressions to their Russian ones:

1) to carry domestic sewage a) сброс отходов домашнего хозяйства
2) discharge of household waste b) жидкие отходы
3) storm water runoff c) запах
4) liquid waste d) переносить бытовые отходы
5) odor  e) ливневый сток

4. Read the text again and answer the questions:

1) What type of sewers did Rome have?

2) Was sewerage known in the Middle Ages?

3) What were storm sewers intended to carry?

4) When was the discharge of household wastes into the sewers of London forbidden?

5) What were the combined sewers intended for?

6) What development played a large part in use of plumbing system?

5. Read the following statements and say whether they are true or false (T/F). If they are false correct them. Use the following phrases:

• That’s right…

• No objections…

• I don’t think it’s  right…

• That’s wrong…

• According to the text…

1) Vault toilets existed in large cities for a long time.

2) Water-carried system didn’t improve town sanitation.

3) Sewage treatment has been based upon local conditions.

4) Waters which are of a quality suitable for their highest intended use are defined as effluent limited.

6. Look through the text and find in the text English equivalents for the following words and word combinations:

1) остатки канализационных систем

2) складировать все виды отходов

3) ливневая канализация

4) канализация бытовых отходов

5) первые ливневые стоки

6) водопроводная система

7) уровень смертности в городе

8) полная очистка

7. Discuss in pairs:

1) Different types of ancient sewers.

2) Different engineer’s views on sewage treatment.

 


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