Waste Water Engineering

281. The value of Chezy's constant C = 157.6/(1.81 + K/√r) is used in

1. Chezy's formula
2. Bazin's formula
3. Kutter's formula
4. Manning's formula

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282. The water carried sewerage system removes

1. Domestic sewage
2. Industrial sewage
3. Storm sewage
4. All the above

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283. The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is

1. 0.68 m
2. 0.88 m
3. 1.36 m
4. 1.76 m

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284. The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is

1. 5 m
2. 5.5 m
3. 6.5 m
4. 7 m

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285. To maintain aerobic biological activity, the moisture content of the compost mass should be about

1. 45 %
2. 50 %
3. 55 %
4. 60 %

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286. To prevent settling down of sewage both at the bottom and on the sides of a large sewer, selfcleaning velocity recommended for Indian conditions, is

1. 0.50 m/sec
2. 0.60 m/sec
3. 0.70 m/sec
4. 0.75 m/sec

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287. To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of

1. Hydrochloric acid
2. Sulphuric acid
3. Nitric acid
4. Citric acid

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288. Traps

1. Are water seals which prevent the entry of foul gases
2. Are used to trap the rats entering sewers
3. Dissolve the foul gases
4. Create symphonic action to increase the quick disposal of sewerage

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289. Ventilating shafts are provided to a sewer line at every

1. 100 m
2. 150 m
3. 200 m
4. 300 m

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290. w is the unit weight of water, 'r' the hydraulic mean depth of the sewer and 'S' the bed slope of the sewer, then the tractive force exerted by flowing water, is

1. γ_w r S
2. γ_w r^½ S
3. γ_w r
4. γ_w r^⅔ S

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