295. In a sludge tank, the gas mainly produced. Is
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide

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296.  For house drainage minimum gradient is
A. 1 in 60
B. 1 in 80
C. 1 in 10
D. 1 in 400.

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297. Removal of oil and grease from sewage, is known
A. screening
B. skinning
C. filtration
D. none of these.

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298. In septic tanks, decomposition of organic bacteria, is done by
A. anaerobic bacteria
B. aerobic bacteria
C. both types of bacterias
D. none of these.

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299.  The self-cleansing velocity of water flowing through pipe lines, is
A. 2 metres/sec
B. 1 metre/sec
C. 0.5 metre/sec
D. 0.25 metre/sec.

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300. Dry water flow in a combined sewer, is
A. industrial sewage
B. domestic sewage
C. storm water
D. inclusive of domestic and industrial sewage but excludes storm water.

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301.  Drop manholes at the junctions of sewer lines, are provided if
A. invert level of a branch sewer is more than 60 cm that of the main sewer
B. sewer line runs along a main road
C. ordinary manhole cannot be built
D. two sewer lines intersect.

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