waste water engineering MCQs – Page 7

Practise focused waste water engineering questions with marked answers for exam preparation and subject revision.

waste water engineering Mcqs
121. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20C, B.O.D. of the sewage is_________________?
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A. 250 mg/l

B. 150 mg/l

C. 50 mg/l

D. 100 mg/l

122. An inverted siphon is designed generally for____________________?
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A. Three pipes

B. One pipe

C. Two pipes

D. Four pipes

123. The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is________________?
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A. d (0.285d + 0.011H)/Q

B. d (0.011d + 0.785H)/Q

C. d (0.022d + 0.085H)/Q

D. d (0.785d + 0.011H)/Q

124. For detecting the nitrites in the sewage, the matching colour may be developed by adding_________________?
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A. None of these

B. Potassium permanganate

C. Sulphuric acid and napthamine

D. Phenol-di -sulphuric acid potassium hydroxide

125. In case of Imhoff tanks_____________________?
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A. Detention period is 2 hours

B. The velocity of flow is restricted to 0.30 m/minute

C. The shape is rectangular

D. All the above
126. running partially full with central angle , For a circular sewer of diameter__________________?
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A. r/R = [1

B. d/D = (1

C. a/A

D. All the above
127. Chlorination of water is done for the removal of____________________?
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A. Hardness

B. Sediments

C. Suspended solids

D. Bacterias
128. For design purposes, the normal rate of infiltration of ground water into the sewer, is___________________?
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A. 1500 litres/km/cm

B. 1000 litres/km/cm

C. 2000 litres/km/cm

D. 500 litres/km/cm

129. The liquid wastes from kitchens, bath rooms and wash basins, is not called________________?
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A. Sullage

B. Sewage

C. None of these

D. Liquid waste

130. For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed________________?
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A. 4 ppm

B. 3 ppm

C. 5 ppm

D. 10 ppm

131. Lead caulked joints are used for laying____________________?
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A. G.I. pipes

B. Stone ware pipes

C. Earthenware pipes

D. C.I. pipes

132. It is customary to design a sewer for D.W.F. on the basis of________________?
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A. Four times the average demand

B. Average demand

C. Twice the average demand

D. Thrice the average demand
133. The dimensions of a rectangular settling tank are: length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is_____________________?
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A. 216 cu.m

B. 212 cu.m

C. 204 cu.m

D. 208 cu.m

134. Ventilating shafts are provided to a sewer line at every__________________?
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A. 150 m

B. 100 m

C. 200 m

D. 300 m
135. A sewer running partially full and hurried with back filled, fails in compression due to_________________?
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A. Weight of the back fill

B. All the above

C. Weight of the pipe

D. Superimposed traffic loads

136. In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time?
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A. All of these

B. 225 mm dia.

C. 100 mm dia.

D. 150 mm dia.

137. Hazens formula VS = 418 (GS Gw)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter______________________?
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A. Greater than 0.1 mm

B. Less than 0.01 mm

C. Less than 0.05 mm

D. Less than 0.1 mm

138. Nitrogen cycle of sewage, is____________________?
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A. Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia

B. Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates

C. Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen

D. Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates

139. A rainfall may be classified as acidic if its pH value is less or equal to________________?
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A. 6

B. 6.5

C. 7

D. 5
140. Which one of the following statements regarding septic tanks is wrong ?
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A. The depth of tank is kept equal to its width

B. The outlet invert level is kept 5 to 7.5 cm below the inlet invert level

C. A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided

D. The minimum width of septic level is 90 cm