Waste Water Engineering

1. ¾th or ¼th extra space is left in sewer pipes at maximum discharge for

1. Low estimates of the average and maximum flows
2. Large scale infiltration of storm water
3. Unexpected increase in population
4. All the above

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2. 1000 kg of sewage contains

1. 0.112 kg in suspension
2. 0.112 kg in solution
3. 0.225 kg in solution
4. Both (a) and (c) of above

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3. 3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the D.O. concentration was 5 mg/l. The BOD of raw sewerage is

1. 100 mg/l
2. 200 mg/l
3. 300 mg/l
4. 400 mg/l

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4. 5 days-biochemical oxygen demand (BOD₅) is taken at a temperature of

1. 0°C
2. 15°C
3. 20°C
4. 25°C

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5. A circular sewer section is preferred to because

1. It is cheaper in construction
2. It provides maximum area for a given perimeter
3. It provides maximum hydraulic mean depth
4. All the above

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6. A cylindrical ejector having its height 2 m fills after every 10 minutes with a peak sewage discharge of 0.0157 cumec. The diameter of the ejector chamber, is

1. 2.30 m
2. 2.40 m
3. 2.45 m
4. 2.50 m

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7. A drop manhole is provided if

1. A sewer drops from a height
2. A branch sewer joins the main sewer at higher level
3. A lamp is inserted to check obstruction
4. None of these

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8. 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

1. 100
2. 1000
3. 5000
4. 10000

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9. A manhole is classified as shallow if its depth is between

1. 0.4 to 0.5 m
2. 0.5 to 0.7 m
3. 0.7 to 0.9 m
4. 0.9 to 1.20 m

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10. A manhole is generally provided at each

1. Bend
2. Junction
3. Change of gradient
4. All the above

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