English for Architecture & Civil Engineering I
Prepared by Indra Tj-2004
I.Reading
Water Treatment
People need water which is clear and free from disease-causing organisms.
They also desire water which is soft, free from tastes and odors, and does not
discolor plumbing fixtures or corrode metals. Industry requires water that will not
interfere with its processes. Recently there has been an increasing concern
about the presence of minute quantities of organic material, particularly
chlorinated hydrocarbons, which are thought to be causative agents of a variety
of diseases. Such contaminants are known to be present in many water supplies
although their effect upon health is unknown. Standard disinfection practice using
chlorine contributes to the production of these compounds.
Chlorine In Water
Disinfection of water is the killing of disease-causing microorganisms that it
may contain. In the process, bacteria are reduced in number. Complete
sterilization, however, is not ordinarily obtained nor necessary. Chlorine in its
various forms has been widely used in disinfecting water. It is cheap, reliable
and presents no' great difficulty in handling.
Chlorine is a very active element and when added to water as free chlorine it will
combine with organic and inorganic matter and oxidize some organic and
inorganic compounds. Free available chlorine reacts with ammonia and many
organic amines to form chloramines. Chlorine is used in water treatment for
disinfection, prevention and destruction of odors, iron removal and color removal.
While its principal use is as a disinfectant the mechanism of its bactericidal action
is uncertain. It is likely that the chlorine destroys the extracellular enzymes of the
bacterlal cells, and possible that it actually passes through the cell wall to attack
intracellular systems. The bactericidal efficiency of chlorine is reduced by
increased pH values and low temperatures.
Chlorination of water is practiced for the purposes listed above, and the various
needs may be satisfied simultaneously. It is extremely important as the principal,
if not the only safeguard, against disease. Untreated waters are likely to be rather
high in inorgartic matter and require high dosages and long contact periods for
maximum safety. The chlorine may be added to the water in the pipe leading
from an impounding reservoir to the city.
Prechlorination is done before any other treatment. The chlorine may be added
in the suction pipes of "raw-water pumps or to the water as it enters the mixing
chamber. Its use in this manner has several advantages. lt may improve
coagulation and will reduce tastes and odors caused by organic sludge in the
English for Architecture & Civil Engineering I
Prepared by Indra Tj-2004
sedimentation tank. By reducing algae and other organisms it may keep the
filter sand cleaner and increase the length of filter runs.
("General Engineering", 1992)
II.
Vocabulary preview
Disease – causing organism
Soft(water)
Tastes
Discolor
Plumbing fixtures
Concern
Minute [mainju:t]
Contaminants
Disinfection
Simultaneously
Impounding
coagulation
Jasad renik penyebab penyakit
(air)lunak,tidak mengandung kapur
Rasa payau
Mengotori,menghitamkan
Perlengkapan kran air
Keprihatinan
Sangat kecil
Zat pencemar
Pembasmian hama
Sekaligus
Tersendiri
Waduk
Penggumpalan
III.Reading Comprehension
1. What properties should a good water supply have?
2. What is one kind of organic material, present in many water supplies,
which is thought to cause disease?
3. What two factors can reduce the efficiency of chlorine as a bactericide?
4. What word, words, or phrases do the 12 underlined words each refer to?
IV. Decide whether. the following statements are true or false according to the
facts in the passage:
1. The public requires that their water supply be clean and safe to drink.
2. There has been some anxiety about organic materials which could cause
disease.
3. It is certain that chlorine kills the extracellular enzymes of bacterial ceils.
4. Industry requires water that will have an effect on its processes.
5. Large quantities of organic material are found in mains water.
6. Chlorinated hydrocarbons are absent in the water supply.
7. Standard disinfection practice prevent the production of these compounds.
8. The bactericidal efficiency of chlorine is increased by increased pH values.
9. A pH smaller than 7 is acid, and larger than 7 is alkaline.
10. Chlorine is used in water treatment for disinfection, destruction of odors and
English for Architecture & Civil Engineering I
Prepared by Indra Tj-2004
iron addition.