Waste Water Engineering

221. The minimum recommended diameter of sewers, is

1. 5 cm
2. 10 cm
3. 15 cm
4. 20 cm

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222. The moisture content of sludge is reduced from 90% to 80% in a sludge digestion tank. The percentage decrease in the volume of sludge, is

1. 25 %
2. 50 %
3. 10 %
4. 5 %

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223. The most dangerous pollutant in vehicular emissions is

1. CO
2. SO2
3. CO2
4. O3

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224. The most effective arrangement for diverting excess storm water into a natural drainage, is

1. Leaping weir
2. Overflow weir
3. Siphon spill way
4. None of these

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225. The most efficient cross section of sewers in a separate sewerage system is

1. Parabolic
2. Circular
3. Rectangular
4. New egged

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226. The most efficient cross-section of sewers in a combined sewerage system is

1. Parabolic
2. Circular
3. Rectangular
4. New egged

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227. The most widely used pump for lifting sewage is

1. Centrifugal pump
2. Reciprocating pump
3. Pneumatic ejector
4. Air pressure pump

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228. The non-clog pump which permits solid matter to pass out with the liquid sewage, is

1. Centrifugal pump
2. Reciprocating pump
3. Pneumatic ejector
4. None of these

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229. The normal value of over flow rates for plain primary sedimentation tanks, ranges between

1. 25,000 to 35,000 litres/sqm/day
2. 40,000 to 50,000 litres/sqm/day
3. 50,000 to 60,000 litres/sqm/day
4. 80,000 to 100,000 litres/sqm/day

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230. The normal values of over flow rates for secondary sedimentation tanks, ranges between

1. 25,000 to 35,000 litres/sqm/day
2. 40,000 to 50,000 litres/sqm/day
3. 50,000 to 60,000 litres/sqm/day
4. 80,000 to 10,000 litres/sqm/day

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