MCQ
21. Cleaning period for a rapid sand filter is taken as-
2 to 3 hours
2 to 3 days
2 to 3 weeks
2 to 3 months
22. The velocity of flow in any sedimentation tank should not exceed-
0.05mm/s
5mm/s
0.5mm/s
50mm/s
23. Rapid sand filter can remove turbidity from water upto an extent of-
15 to 25 ppm
25 to 35 ppm
35 to 40 ppm
40 to 50 ppm
24. The process of killing pathogenic bacterias from water is called-
sedimentation
coagulation
filteration
disinfection
25. Slow sand filter is more efficient for the removal of-
bacteria
turbidity
odour
all of these
26. Rapid sand filter can remove bacteria upto an extent of-
60 to 70%
70 to 80%
80 to 90%
90 to 99%
27. The internal diameter of the sewer should not be less than-
15cm
25cm
50cm
75cm
28. The aeration of water is done to remove--
colour
taste
odour
all of these
29. The percentage of chlorine in fresh bleaching powder is-
20 to 25%
25 to 30%
30 to 35%
35 to 40%
30. The minimum diameter of a manhole cover should be-
25cm
50cm
75cm
100cm
31. The water from kitchens, bathrooms, wash basins is called-
sewage
raw sewage
sullage
none of this
32. The minimum size of a fire hydrant is--
5cm
10cm
15cm
20cm
33. The coefficient of uniformity for slow sand filters is-
1.35
1.75
1.55
2.05
34. The time of contact for chlorination should be at least-
5 minutes
20 minutes
1 hour
2 hours
35. The amount of chlorine used for plain b chlorination of water is about-
0.2 ppm
0.3 ppm
0.4 ppm
0.5 ppm
36. The effective size of sand particles for slow sand filters varies from- 0.3 to 0.35mm 0.35 to 0.5mm 0.5 to 0.65mm 0.65 to 0.75mm
0.3 to 0.35mm
0.35 to 0.5mm
0.5 to 0.65mm
0.65 to 0.75mm
37. The human excreta is a ---waste.
dry
liquid
semi-liquid
solid
38. The cross-section recommended for separate system of sewerage is--
circular
rectangular
egg-shaped
none of these
39. The detention time for an ordinary plain sedimentation tank is-
1 to 2 hours
6 to 8 hours
2 to 4 hours
20 to 24 hours
40. By lime soda process, hardness can be reduced to less than
50 ppm
75 ppm
150 ppm
100 ppm