# Civil Engineering - Waste Water Engineering

### Exercise :: Waste Water Engineering - Section 6

16.

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

 A. 25, 000 to 35, 000 litres/sqm/day B. 40, 000 to 50, 000 litres/sqm/day C. 50, 000 to 60, 000 litres/sqm/day D. 80, 000 to 100, 000 litres/sqm/day E. none of these.

Explanation:

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17.

The asbestos cement sewers are

 A. light in weight B. not structurally strong to bear large compressive stress C. susceptible to corrosion by sulphuric acid D. All the above.

Explanation:

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18.

Bottom openings 15 cm x 15 cm in the standing baffle wall are provided

 A. 15 cm c/c B. 22.5 cm c/c C. 30 cm c/c D. 50 cm c/c.

Explanation:

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19.

Faculative bacterias survive in

 A. the presence of oxygen B. the absence of oxygen C. both cases (a) and (b) D. neither (a) nor (b).

Explanation:

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20.

The ratio of maximum sewage flow to average sewage flow for trunk mains having diameters more than 1.25 m, is

 A. 1.5 B. 2 C. 3 D. 4