288.  A five day B.O.D. at 15?C of the sewage of a town is 100 kg/day. If the 5 day B.O.D. per head at 15?C for standard sewage is 0.1 kg/day, the population equivalent is
A.100
B.1000
C.5000
D.10000

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289. Disposal to sewage in large cities, is done in
A. irrigation
B. dilution
C. oxidation
D. putrifaction.

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290.  A nuisance is experienced in diluting water if dilution factor is less than
A.100
B.60
C.40
D.20

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291.  The sewage in oxidation ponds, is treated by
A. aerobic bacteria action
B. sedimentation
C. action of algae
D. both A and (c).

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292. In a trickling filter
A. filtration process is used
B. biological action is used
C. neither A nor B
D. both A and B.

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293. In trickling filter, B.O.D. is reduced to
A. 30 to 40%
B. 40 to 60%
C. 60 to 80%
D. 80 to 90%

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294.  In normal conditions, the period for sludge digestion, is
A. 10 days
B. 20 days
C. 30 days
D. 60 days

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