Sludge Treatment and Disposal MCQ – Environmental Engineering

1. The activated sludge

  1. contains fertilizing constituents
  2. indicates the degree of aeration
  3. indicates high water content
  4. all of these
Answer
Answer. d

2. Activated sludge process is an

  1. Aerobic attached growth system
  2. Anaerobic attached growth system
  3. Anaerobic suspended growth system
  4. Aerobic suspended system
Answer
Answer. d

3. In the activated sludge process, sludge volume index is used to decide

  1. Quality of raw sewage
  2. Quality of final effluent
  3. Recirculation ratio of sludge
  4. Rate of aeration
Answer
Answer. c

4. Lower food to micro-organism ratio in a conventional activated sludge plant will mean

  1. Lower BOD removal
  2. Higher BOD removal
  3. Lower bacteria removal
  4. None of the above
Answer
Answer. b

5. In a sludge digestion tank, the gas that mainly evolves is

  1. Methane
  2. Hydrogen Sulphide
  3. Ammonia
  4. Nitrogen
Answer
Answer. a

6. In high rate activated sludge treatment, bacteria’s are removed from

  1. 20 to 40%
  2. 40 to 60%
  3. 60 to 80%
  4. 80 to 95%
Answer
Answer. d

7. The two main gases that evolve from an anaerobic sludge digestion tank include

  1. Ammonia and Carbon dioxide
  2. Methane and hydrogen sulphide
  3. Carbon dioxide and methane
  4. Ammonia and methane
  5. Carbon dioxide and Ammonia
Answer
Answer. c

8. Fresh sludge has moisture content of 99% after thickening, its moisture content is reduced to 96%. The reduction in volume of sludge is

  1. 3%
  2. 5%
  3. 75%
  4. 97.5%
Answer
Answer. c

9. Sludge treatment is mainly done in order to

  1. stabilize the organic matter
  2. destroy the pathogenic bacteria
  3. reduce the water content
  4. all of the above
Answer
Answer. d

10. The gas from sludge digestion tank is mainly composed of

  1. Nitrogen
  2. Carbon dioxide
  3. Hydrogen sulphide
  4. Methane
Answer
Answer. d

11. A B.O.D. removal efficiency of 95% can be expected from

  1. Septic tank
  2. Imhoff tank
  3. Standard filter
  4. Activated sludge plant
Answer
Answer. d

12. During sludge digestion

  1. Acidity condition should prevail
  2. Alkaline condition should prevail
  3. Acidity of alkaline condition
  4. Neutral condition should prevail
Answer
Answer. b

13. Removal of soluble organic chemicals is possible by the addition of _________ to the biological mixed liquor of an activated sludge process.

  1. alum
  2. activated carbon
  3. chlorine
  4. strong colour
Answer
Answer. b

14. Chlorine is sometimes used in sewage treatment

  1. To avoid flocculation
  2. To increase biological activated sludge
  3. To avoid bulking of activated sludge
  4. To help in grease separation
Answer
Answer. c

15. Sludge treatment is mainly done in order to

  1. stabilize the organic matter
  2. destroy the pathogenic bacteria
  3. reduce the water content
  4. all of the above
Answer
Answer. d

16. One liter of sewage, when allowed to settle for 30 minutes gives a sludge volume of 27 cm3. If the dry weight of this sludge is 3.0 grams, then its sludge volume index will be

  1. 9
  2. 24
  3. 30
  4. 81
Answer
Answer. a

17. For satisfactory working of sludge digestion tank, the pH range of digested sludge should be maintained as

  1. 4.5 to 6.0
  2. 6.0 to 8.0
  3. 8.5 to 10.0
  4. 10.5 to 20.0
Answer
Answer. b

18. Which of the following unit works in anaerobic conditions?

  1. Sludge digestion tank
  2. Sedimentation tank
  3. Activated sludge treatment
  4. Trickling filters
Answer
Answer. a

19. The hydraulic retention tinme in extended aeration activated sludge systems is

  1. 4-5 hours
  2. 4-6 hours
  3. 8-10 hours
  4. 12 – 24 hours
Answer
Answer. d

20. The dominating micro organisms in an activated sludge process reactor are

  1. Aerobic heterotrophs
  2. Anaerobic heterotrophs
  3. Autotrophs
  4. Phototrophs
Answer
Answer. a
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