155.  The settlement velocity of a solid (diameter 0.5 mm, specific gravity 2.5) in water having temperature 10?C, is
A. 213.5 cm/sec
B. 313.5 cm/sec
C. 413.5 cm/sec
D. 500 cm/sec.

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156. For a continuous flow type of sedimentation tanks
A. width of the tank is normally kept about 6 m
B. length of the tank is normally kept 4 to 5 times the width
C. maximum horizontal flow velocity is limited to 0.3 m/minute
D. capacity of the tank for 24 hours, is kept equal to maximum daily flow of sewage

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157. The detention period for plain sedimentation water tanks, is usually
A. 4 to 8 hours
B. 8 to 16 hours
C. 16 to 24 hours
D. 24 to 36 hours.

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158.  The discharge per unit plan area of a sedimentation tank, is generally called
A. over flow rate
B. surface loading
C. over flow velocity
D. all the above.

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159. The normal value of over flow rates for plain primary sedimentation tanks, ranges bet-ween
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

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160.  The normal values of over flow rates for sedimentation tanks using coagulent, 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

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161. The normal values of over flow rates for secondary sedimentation tanks, ranges bet-ween
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 10,000 litres/sqm/day

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