218.  The gas evolved in sewers is
A. Carbondioxide
B. Hydrogen sulphide
C. Methane
D. All &these.

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219. Lead acetate test in sewer manhole is done to test the presence of
A. Methane gas
B. Hydrogen sulphide
C. Carbondioxide gas
D. Diesel vapours.

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220. . A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of
A. Carbondioxide gas
B. Hydrogen sulphide gas
C. Methane gas
D. Petrol vapours.

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221.  Inter-distance between ventilation columns in a sewer line is kept
A. 25 to 50 m
B. 50 m to 100 m
C. 100 m to 150 m
D. 150 m tO 300 m.

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222. Which of the following pumps in used to pump sewage solids with liquid sewage without clogging the pump is
A. centrifugal pump
B. pneumatic ejector
C. reciprocating pump
D. none of these.

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223.  Pick up the correct statement from the following :
A. anaerobic bacteria flourish in the absence of oxygen
B. aerobic bacteria flourish in the presence of oxygen
C. facultative bacteria flourish with or without oxygen
D. all the above.

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224. A well oxidized sewage contains nitrogen mainly as
A. nitrates
B. nitrites
C. free ammonia
D. none of these.

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