Civil Engineering - Waste Water Engineering

21. 

Acid regression stage of sludge digestion at a temperature 21°C extends over a period of

A. 15 days
B. 30 days
C. 60 days
D. 90 days.

Answer: Option D

Explanation:

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22. 

If the pH value of sewage is 7

A. it is acidic
B. it is alkaline
C. it is neutral
D. none of these.

Answer: Option C

Explanation:

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23. 

Pick up the correct statement from the following :

A. Maximum daily flow = 2 times the average daily flow
B. Maximum daily flow = x average daily flow
C. Sewers are designed for minimum permissible velocity at minimum flow
D. All the above.

Answer: Option D

Explanation:

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24. 

Pick up the incorrect statement from the following :

A. The mixture of water and waste products, is called sewage
B. The treated sewage effluents, are generally used for irrigating the crops
C. The process of collecting, treating and disposing off the sewage, is called sewerage
D. The old convergency system was definitely better than water carried sewerage system
E. None of these.

Answer: Option D

Explanation:

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25. 

Pick up the correct statement from the following :

A. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
B. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
C. Solubility of oxygen in sewage is 95% of that of distilled water
D. Dissolved oxygen content of sewage, may be determined by Winkler's method
E. All the above.

Answer: Option E

Explanation:

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