Waste Water Engineering

231. The normal values of over flow rates for sedimentation tanks using coagulant, 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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232. The pH value of fresh sewage is usually

1. Equal to 7
2. More than 7
3. Less than 7
4. Equal to zero

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233. The pH value of sewage is determined with the help of

1. Imhoff Cone
2. Turbid meter
3. Potentiometer
4. None of these

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234. The porosity of sediments in sewer pipes, is usually taken as

1. 0.10
2. 0.11
3. 0.12
4. 0.13

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235. The presence of free ammonia in sewage, is detected by

1. Boiling
2. Adding potassium permanganate
3. Adding sulphuric acid
4. Phenol-di-sulphuric acid

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236. The pressure exerted by

1. The sewage when running full from inside, is called internal pressure
2. The internal pressure if any, causes tensile stress in the pipe material
3. Pressure sewers are designed to be safe in tension
4. All the above

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237. The quantity of liquid waste which flows in sewers during the period of rainfall, is known

1. Sanitary sewage
2. Industrial waste
3. Storm sewage
4. None of these

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238. The rainfall at any place may be determined by

1. Its intensity
2. Its direction
3. Its frequency
4. All the above

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239. The rate of accumulation of sludge in septic tanks is recommended as

1. 30 litres/person/year
2. 25 litres/person/year
3. 30 litres/person/month
4. 25 litres/person/month

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240. The rate of accumulation of sludge per person per year, is

1. 10 litres
2. 15 litres
3. 20 litres
4. 25 litres

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