# Civil Engineering - Waste Water Engineering

### Exercise :: Waste Water Engineering - Section 4

36.

In sewers the velocity of flow should not be

 A. more than the self-cleansing velocity B. less than the self-cleansing velocity C. less than 10 m/sec D. more than 20 m/sec.

Answer: Option B

Explanation:

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37.

If D is the diameter of a circular sewer and D' is the top horizontal diameter of an equivalent egg shaped section, the relationship which holds good, is

 A. D' = 0.64 D B. D' = 0.74 D C. D' = 0.84 D D. D' = 0.94 D.

Answer: Option C

Explanation:

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38.

If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains

 A. Hydrogen sulphide B. Carbon dioxide C. Methane D. Oxygen E. None of these.

Answer: Option A

Explanation:

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39.

The design period of sewage treatment works in normally

 A. 5 - 10 years B. 15 - 20 years C. 30 - 40 years D. 40 - 50 years.

Answer: Option B

Explanation:

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40.

The porosity of sediments in sewer pipes, is usually taken as

 A. 0.01 B. 0.011 C. 0.012 D. 0.013 E. 0.02

Answer: Option D

Explanation:

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