Purification

The processes, generally employed in making water safe for water supply, include coagulation, filtration, and disinfection. Water from some sources must be treated also for the removal of color, taste, and odor. Coagulation is commonly effected by adding to water a salt of aluminum (usually aluminum sulphate) or ferric iron. A precipitate forms and causes a clumping of the bacteria and other foreign particles which then settle out during several hours of sedimentation; in this way 85 per cent or more of the bacteria and suspended particles can be removed.

Activated carbon is sometimes added before sedimentation to remove tastes and odors. In the process of filtration water is allowed to pass through layers of fine sand to remove remaining germs and particles. Chlorine is commonly used to destroy harmful bacteria persisting in a municipal water supply after the other treatments. Chlorine dioxide has more recently been found effective as a destroyer of bacteria as well as a means of removing unwanted tastes and odors.

Other means of destroying germs include the use of ozone and ultraviolet light. Some water supplies are aerated, i.e., exposed to the action of air and sunlight either through sprays or by running over coarse gravel; taste and odor are improved and some germs are destroyed.

Notes to the text:

1) a means of – средство

2) i.e. = id est (лат.) – то есть

Упр. 5. Подберите в правом столбике подходящий перевод к английским словам и выражениям.

1) chlorine dioxide а) удалять оставшиеся микробы

2) ferric iron б) активированный уголь

3) to make water safe в) пропускать сквозь грубый гравий

4) foreign particles г) двуокись хлора

5) suspended particles д) тонкий слой песка

6) activated carbon е) трехвалентное железо

7) fine sand ж) инородные частицы

8) to remove remaining germs з) взвешенные частицы

9) to run over coarse gravel и) обезопасить воду

Упр. 6. Какое из данных предложений выражает главную мысль текста?

1) The processes generally employed in making water safe for water supply include coagulation, filtration, and disinfection.

2) In the process of filtration water is allowed to pass through layers of fine sand to remove remaining germs and particles.

3) Some water supplies are aerated.

Упр. 7. Расположите предложения согласно последовательности изложения.

1) Coagulation is commonly effected by adding to water a salt of aluminum or ferric iron.

2) In the process of filtration water is allowed to pass through layers of fine sand to remove remaining germs and particles.

3) Chlorine is commonly used to destroy harmful bacteria persisting in a municipal water supply after the other treatments.

4) The processes generally employed in making water safe for water supply include coagulation, filtration, and disinfection.

Упр. 8. Составьте план к тексту.

Упр. 9. Ответьте на вопросы более чем одним высказыванием.

1) What processes make water safe?

2) What is the process of coagulation?

3) What happens in the process of filtration?

4) How can water be disinfected?

Упр. 10. Перескажите текст по-английски, используя материал упр. 5, 6, 7, 8, 9.