The recommended detention period for grit chambers is 1 minute 2 minutes 3 minut

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Question
The recommended detention period for grit chambers is
Options
A. 1 minute
B. 2 minutes
C. 3 minutes
D. 5 minutes.

Correct Answer

1 minute

Waste Water Engineering problems

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1. The drainage area of a town is 12 hectares. Its 40% area is hard pavement (K = 0.85), the 40% area is unpaved streets (K = 0.20) and the remaining is wooded areas (K = 0.15). Assuming the time of concentration for the areas as 30 minutes and using the formula the maximum run off is
Options
A. 0.10 cumec
B. 0.12 cumec
C. 0.15 cumec
D. 0.20 cumec.

2. Nitrogen cycle of sewage, is
Options
A. Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
B. Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
C. Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
D. Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates
E. None of these.

3. A drop manhole is provided if
Options
A. a sewer drops from a height
B. a branch sewer joins the main sewer at higher level
C. a lamp is inserted to check obstruction
D. none of these.

4. During preliminary treatment of a sewage
Options
A. Oil and grease are removed from skimming tanks
B. Floating materials are removed by screening
C. Girt and sand are removed by girt chambers
D. All the above.

5. The clarigesters are
Options
A. circular septic tanks
B. rectangular septic tanks
C. circular Imhoff double tanks with bottom hoppers
D. circular Imhoff double storey tanks without bottom hoppers.

8. For design purposes, the normal rate of infiltration of ground water into the sewer, is
Options
A. 500 litres/km/cm
B. 1000 litres/km/cm
C. 1500 litres/km/cm
D. 2000 litres/km/cm
E. 2500 litres/km/cm.

9. Pick up the incorrect statement from the following :
Options
A. Septic tanks are horizontal continuous flow type of sedimentation tanks
B. Septic tanks are generally provided a detention period of 12 to 36 hours
C. Septic tanks are completely covered and high vent shafts are provided for the escape of foul gases
D. Septic tanks are generally classified as tanks which work on the principle of anaerobic decomposition
E. None of these.

10. For providing an Indian type W.C., the R.C.C. slabs in the toilet portion
Options
A. should be sunk by 20 cm
B. should be kept 20 cm above the adjacent portion
C. should be sunk by 50 cm
D. need not be sunk.

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