Waste Water Engineering

191. The detention period for plain sedimentation water tanks, is usually

  1. 4 to 8 hours
  2. 8 to 16 hours
  3. 16 to 24 hours
  4. 24 to 36 hours

Correct answer: (A)
4 to 8 hours

192. The detention time (t) of a settling tank, may be defined as the time required for

  1. A particle to travel along its length
  2. A particle to travel from top surface to bottom sludge zone
  3. The flow of sewage to fill the tank
  4. None of these

Correct answer: (C)
The flow of sewage to fill the tank

193. The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is

  1. d2 (0.011d + 0.785H)/Q
  2. d (0.022d + 0.085H)/Q
  3. d (0.785d + 0.011H)/Q
  4. d (0.285d + 0.011H)/Q

Correct answer: (A)
d2 (0.011d + 0.785H)/Q

194. The digested sludge from septic tanks, is removed after a maximum period of

  1. 3 years
  2. 3.5 years
  3. 4 years
  4. 5 years

Correct answer: (A)
3 years

195. 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

  1. 204 cu.m
  2. 208 cu.m
  3. 212 cu.m
  4. 216 cu.m

Correct answer: (D)
216 cu.m

196. The discharge per unit plan area of a sedimentation tank, is generally called

  1. Over flow rate
  2. Surface loading
  3. Over flow velocity
  4. All the above

Correct answer: (D)
All the above

197. The disintegrating pump in which solid matter is broken up before passing out, is

  1. Centrifugal pump
  2. Reciprocating pump
  3. Pneumatic ejector
  4. None of these

Correct answer: (A)
Centrifugal pump

198. 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 Ps = 900/(t + 60) the maximum run off is

  1. 0.10 cumec
  2. 0.12 cumec
  3. 0.15 cumec
  4. 0.20 cumec

Correct answer: (C)
0.15 cumec

199. The drop man holes are generally provided in sewers for

  1. Industrial areas
  2. Large town ships
  3. Hilly town ships
  4. Cities in plains

Correct answer: (C)
Hilly town ships

200. The effluent of a septic tank is

  1. Fit for discharge into any open drain
  2. Foul and contains dissolved and suspended solids
  3. As good as that from a complete treatment
  4. None of these

Correct answer: (A)
Fit for discharge into any open drain

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