148. Flow through period, in sedimentation tanks, is
A. equal to detention period
B. more than detention period
C. less than detention period
D. detention period divided by displacement efficiency
149. Alum is chemically
A. Copper sulphate
B. Aluminium sulphate
C. Ferrous sulphate
D. Ferric sulphate.
150. The process of passing water through beds of granular materials, is called
A. screening
B. sedimentation
C. filtration
D. none of these.
151. Filtration of water is done to remove
A. colour
B. odour
C. turbidity
D. pathogenic bacteria
152. The main process to purify water by filtration, is
A. mechanical straining
B. flocculation and sedimentation
C. biological metabolism
D. all the above.
153. An ideal sand for filters should be
A. free from dirt and other impurities
B. uniform in nature and size
C. hard and resistant
D. all the above.
154. The U.C.60 .C. (uniformity coefficient) Dio for the best filter media sand should be
A.2
B.3
C.4
D.5
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