Sludge Treatment and Disposal MCQ – Environmental Engineering

21. Chlorine is sometimes used in sewage treatment

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

22. In an Activated Sludge process (ASP), the sludge volume Index of a good sludge range between

  1. 10 to 50 ml/gm
  2. 50 to 100 ml/gm
  3. 100 to 150 ml/gm
  4. 150 to 200 ml/gm
Answer. b

23. The MLSS concentration in an aeration tank is 2500 mg/L and the settled sludge volume is 215 ml, the sludge volume index is

  1. 86 ml/g
  2. 8.6 ml/g
  3. 6.8 g/ml
  4. 68 g/ml
Answer. a

24. A sample of mixed liquor was found to have suspended solids (SS) = 4500 mg/L and after setting for 30 minutes in a 1 L cylinder, it occupied 300 mL. The Sludge Volume Index (SVI) is

  1. 67
  2. 150
  3. 1500
  4. 75
Answer. a

25. For conventional activated sludge process, the F/M ratio should range between

  1. 0.1-0.2
  2. 0.5-1.0
  3. 0.3-0.4
  4. 0.05-0.10
Answer. c

26. Generally, for the satisfactory working of a Sludge digestion unit, the pH range of a digested sludge shall be maintained as

  1. 10.5 to 12.0
  2. 6.5 to 8.0
  3. 4.5 to 6.0
  4. 8.5 to 10.0
Answer. b

27. Which of the following unit work on the principle of anaerobic decomposition?

  1. Oxidation ditch
  2. Tickling filter
  3. Activated sludge process
  4. Sludge digestion tank
Answer. d

28. The correct sequence of the sludge digestion steps is

  1. Methanogenesis, Acidogenesis, Hydrolysis
  2. Acidogenesis, Methanogenesis, Pyrolysis
  3. Hydrolysis, Acidogenesis, Methanogenesis
  4. Hydrolysis, Methanogenesis, Acidogenesis
Answer. c

29. The most important type of species involved in degradation of organic matter in the case of activated sludge process is

  1. hetrotrophs
  2. autotrophs
  3. photo-autotrophs
  4. prototrophs
Answer. a

30. Lower (F/M) ratio in a conventional activated sludge treatment plant will mean

  1. Lower BOD removal
  2. Higher BOD removal
  3. No effect on BOD removal
  4. Sometimes is lower and sometimes higher removal
Answer. b

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