Water Treatment MCQ – Environmental Engineering

1. Which of the following processes are necessary for removing suspended solids from water?

  1. Coagulation
  2. Flocculation
  3. Sedimentation
  4. All of these
Answer. c

2. Alum acts as

  1. coagulant
  2. flocculent
  3. catalyst
  4. disinfectant
Answer. a

3. Activated carbon removes from water

  1. Organic matter
  2. Iron
  3. Manganese
  4. All of the above
Answer. d

4. For proper slow mixing in the flocculator of a water treatment plant, the temporal mean velocity gradient G needs to be of the order of

  1. 5 S-1 to 10 S-1
  2. 20 S-1 to 80 S-1
  3. 100 S-1 to 200 S-1
  4. 250 S-1 to 350 S-1
Answer. b

5. Self-purification of natural streams is caused due to

  1. Turbulence of water
  2. Dilution
  3. Oxidation-reduction
  4. All the above
Answer. d

6. In a water treatment, the optimum time of flocculation is usually given as 30 minutes. In case the time of flocculation is increased beyond this value, the flocs will

  1. become heavy and settle down in the flocculation tank itself
  2. entrap air and will float in the sedimentation tank
  3. break up and defeat the purpose of flocculation
  4. stick to the paddles
Answer. b

7. Break-point chlorination of water involves addition of chlorine in and amount sufficient to

  1. kill Guardia cysts
  2. react with any ammonia and oxidisable organic matter
  3. reduce bacterial growth
  4. react with inorganic matter
Answer. b

8. Aeration of water is done to remove

  1. Odour
  2. Colour
  3. Bacteria’s
  4. Turbidity
Answer. a

9. The most ideal disinfectant used for drinking water is

  1. Alum
  2. Chlorine
  3. Lime
  4. Nitrogen
Answer. b

10. In water treatment, rapid gravity filters are adopted to remove

  1. Dissolved organic substances
  2. Dissolved solids and gases
  3. Floating solids and dissolved inorganic solids
  4. Bacteria and colloidal solids
Answer. d

11. The treatment of water is required mainly for

  1. the removal of germs of diseases
  2. the removal of copper sulphate
  3. increasing pH value
  4. the removal of chlorides
Answer. a

12. Activated carbon is used in water treatment for

  1. disinfection
  2. removing hardness
  3. removing odour
  4. aeration
Answer. c

13. During treatment of water, sedimentation is done

  1. before filtration
  2. after filtration
  3. simultaneously with filtration
  4. along with chlorination
Answer. a

14. Self-cleansing velocity is

  1. The minimum velocity of flow required to maintain a certain amount of solids in the flow
  2. The maximum velocity of flow required to maintain a certain amount of solids in the flow
  3. Such flow velocity as would be sufficient to flush out any deposited solids in the sewer
  4. Such flow velocity as would be sufficient to ensure that sewage does not remain in the sewer
Answer. c

15. In a water supply scheme, for what purpose aeration is carried out?

  1. to remove taste and odour
  2. for complete elimination of colloidal matter
  3. for killing pathogenic bacteria
  4. for coagulation
Answer. a

16. The various treatment processes in a water treatment plant are listed below

  1. Filtration
  2. Chlorination
  3. Sedimentation
  4. Coagulation
  5. Flocculation

The correct sequence of these processes water treatment is

  1. i, ii, iii, iv, v
  2. iv, v, iii, i, ii
  3. ii, iii, i, v, iv
  4. i, ii, v, iii, iv
Answer. b

17. Which of the following treatments is the most economically effective method for controlling Schistosomiasis?

  1. Filtration
  2. Ozonation
  3. Chlorination
  4. UV radiation
Answer. c

18. Which of these is an indirect method for the determination of stream flow?

  1. Dilution techniques
  2. Slope area method
  3. Ultrasonic method
  4. Area velocity method
Answer. b

19. Consider the following unit process commonly used in water treatment; Rapid Mixing (RM), Flocculation (F), Primary Sedimentation (PS), Secondary Sedimentation (SS), Chlorination (C), and Rapid Sand Filtration (RSF). The order of these unit processes (first to last) in conventional water treatment plant is

  1. PS → RSF → F → RM → SS → C
  2. PS → F → RM → RSF → SS → C
  3. PS → F → SS → RSF → RM → C
  4. PS → RM → F → SS → RSF → C
Answer. d

20. A river is the source of water supply to a town. Its water is very turbid and polluted. The correct sequence of steps for treating the river water would be

  1. presedimentation → prechlorination → coagulation → sedimentation → filtration → post chlorination
  2. coagulation → sedimentation → prechlorination
  3. coagulation → filtration → sedimentation → prechlorination
  4. sedimentation → prechlorination
Answer. a
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