Sand Filter MCQ and Rapid Sand Filter MCQ – Environmental Engineering

1. Consider the correct statements regarding the quantities of sand used for filtration

  1. Free from dirt and other impurities
  2. Uniform size
  3. Soft and collective
  4. It loses at least 10% of its weight when immersed in hydrochloric acid for 24 hours.

Of these statements:

  1. i alone is correct
  2. ii alone is correct
  3. i and ii are corect
  4. iii and iv are correct
Answer
Answer. c

2. In comparing slow sand filters (SSF) and rapid sand filters (RSF), which of the following is an incorrect statement?

  1. SSF require larger area for its installation
  2. Cost of operation of RSF is lower
  3. Depreciation of SSF is lower
  4. SSF cannot meet variations in the demand
  5. SSF requires cleaning at a frequency of one month
Answer
Answer. b

3. After cleaning a slow sand filter, the filtered water is not used for

  1. 6 hours to 12 hours
  2. 12 hours to 18 hours
  3. 18 hours to 24 hours
  4. 24 hours to 36 hours
  5. 48 hours
Answer
Answer. d

4. Which of the following is incorrect regarding a slow sand filter?

  1. Incoming water should not be treated by coagulants
  2. Depth of water should be double the depth of filter sand
  3. Loss of head is limited to a maximum of 1.2 m
  4. Cleaning should not be done by back washing
Answer
Answer. b

5. The cleaning of slow sand filter is done by

  1. Reversing the direction of flow of water
  2. Passing air through the filter
  3. Passing a solution of alum and lime through the filter
  4. Scrapping off top layer of sand admitting water
Answer
Answer. d

6. Which one of the following filters will produce water of high quality with respect to the bacteriological parameter?

  1. Slow sand filter
  2. Rapid sand filter
  3. Pressure filter
  4. Dual media filter
Answer
Answer. a

7. Slow sand filters require

  1. Finer sand
  2. Coarse sand media
  3. Medium sand media
  4. Any type of sand media
Answer
Answer. a

8. In which treatment unit is Schmutzdecke formed

  1. Sedimentation tank
  2. Rapid sand filter
  3. Slow sand filter
  4. Coagulation tank
Answer
Answer. c

9. Design period for slow sand filters as suggested

  1. 30 years
  2. 50 years
  3. 10 years
  4. 25 years
Answer
Answer. c

10. The rate of filtration of a slow sand filter ranges from

  1. 10 to 100 L/h/m2
  2. 100 to 200 L/h/m2
  3. 200 to 400 L/h/m2
  4. 400 to 1000 L/h/m2
Answer
Answer. b

11. After cleaning a slow sand filter filtered water is not used for

  1. 6 hours to 12 hours
  2. 12 hours to 10 hours
  3. 18 hours to 24 hours
  4. 24 hours to 36 hours
Answer
Answer. d

12. The eifective size of sand particles used in slow sand filters is

  1. 0.25 to 0.35 mm
  2. 0.35 to 0.60 mm
  3. 0.60 to 1.00 mm
  4. 1.00 to 1.80 mm
Answer
Answer. a

13. The cleaning of slow sand filter is done by

  1. Scraping off top layers of sand and admiting water
  2. Passing air through the filter
  3. Passing a solution of air and lime through the filter
  4. Reversing the direction of flow of water
Answer
Answer. a

14. Which one of the following filters will produce water of higher bacteriological quality?

  1. Rapid sand filter
  2. Slow sand filter
  3. Dual media filter
  4. Pressure filter
Answer
Answer. b

15. Standard rate of filtration in slow sand filters is

  1. 25-50 ltr/hr
  2. 50-90 ltr/hr
  3. 100-150 ltr/hr
  4. 160-200 ltr/hr
Answer
Answer. c

16. The slow sand filter is more efficient in removing bacteria because

  1. effective size of sand grains in small
  2. uniformity co-efficient of sand grains is small
  3. water is pretreated
  4. size of filter bed is large
Answer
Answer. c

17. Slow sand filters remove bacteria as much as

  1. 80 to 90%
  2. 70 to 80%
  3. 98 to 99%
  4. 90 to 95%
Answer
Answer. c

18. For which of the following considerations, slow sand filters are better than rapid sand filters used for water purification?

  1. Compactness
  2. Construction
  3. Rate of filtration
  4. Flexibility
Answer
Answer. b

19. The area requirement in sq.m of a rapid sand filter bed (rate of filtration is 5 m3/h) for a town having a population of 50000 with an average water demand of 200 l/day/head will be. Assume that the filter bed is utilized for 24 h/day.

  1. 125
  2. 25
  3. 10000
  4. 2083
  5. 50
Answer
Answer. a

20. Air binding in rapid sand filters is encountered when

  1. the water is subjected to prolonged aeration
  2. the water contains high dissolved aeration
  3. the filter bed comprises largely of coarse sand
  4. there is excessive negative head
Answer
Answer. d
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