Grit Chambers MCQ – Environmental Engineering

1. A velocity control device has to be provided in a

  1. slow and filter
  2. aeration tank
  3. flow equalization tank
  4. grit chamber
Answer. d

2. Grit chambers of a sewage plant are usually changed after

  1. 1 week
  2. 1 day
  3. 4 weeks
  4. 2 weeks
Answer. d

3. A grit chamber of dimensions 12.0 m × 0.80 m liquid depth has a flow of 720 m3/hr. Its surface loading rate and detention time are respectively

  1. 4000 m3/hr/m2 and 1.2 minute
  2. 40000 Lph/m2 and 40 minute
  3. 40 m3/hr/m2 and 12 minute
  4. 4000 Lph/m2 and 1.2 minute
Answer. c

4. Parshall flume is primarily provided in the downstream side of the grit chamber of act as device

  1. oxygenation
  2. velocity control
  3. floating material removal
  4. putrescible material removal
Answer. b

5. The purpose of proportional weir at the effluent end of a channel type grit removal unit is to

  1. provide easy passage of solid particles
  2. measure the rate of flow in the channel
  3. keep the depth of flow in the channel above a certain value
  4. maintain constant mean velocity in the channel
Answer. d

6. During treatment of sewage, removal of sand and grit is done by

  1. screening
  2. skimming tank
  3. digestion tank
  4. detritus tank
Answer. d

7. Which one of the following sewage treatment units has a parshall flume?

  1. Aeration tank
  2. Trickling filter
  3. Oxidation pond
  4. Grit chamber
Answer. d

8. Grit chamber has a detention period of

  1. 20 min to 30 min
  2. 2 hrs to 4 hrs
  3. 45 sec to 90 sec
  4. 2 min to 5 min
Answer. c

9. In a sewage treatment system, a grit chamber of dimensions 10 m × 1.5 m × 0.75 m liquid depth has a flow of 750 m3/hr. The surface loading rate and detention time of the grit chamber are respectively

  1. 5000 l/h/m2; 9 min
  2. 50000 l/h/m2; 0.9 min
  3. 50 m3/h/m2; 1.8 min
  4. 5 m3/h/m2; 0.89 min
Answer. b

10. Why is proportional flow weir provided in a grit chamber?

  1. To reduce the suspended solids entering the grit chamber
  2. To maintain constant flow velocity in the grit chamber over a certain depth range
  3. To maintain constant flow depth in the grit chamber
  4. To allow sewage a fresh into the grit chamber
Answer. b

11. In a conventional sewage treatment plant employing trickling filters the grit chamber is placed

  1. ahead of primary setting tank
  2. ahead of the trickling filter
  3. ahead the secondary setting tank
  4. following the secondary setting tank
Answer. b

12. Detention time for Design of Grit chamber is

  1. 20 to 70 sec.
  2. 40 to 60 sec.
  3. 50 to 100 sec.
  4. 80 to 120 sec.
Answer. b

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