MCQ
17841. Slow sand filter is more efficient for the removal of-
bacteria
turbidity
odour
all of these
17842. The velocity of flow in any sedimentation tank should not exceed-
0.05mm/s
5mm/s
0.5mm/s
50mm/s
17843. 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
17844. The pH value of water for public supplies is limited from-
2.5 to 6.5
8 to 10.5
6.5 to 8.5
10.5 to 15
17845. 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
17846. 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
17847. The total count of bacteria per cubic centimeter for domestic purposes varies from-
0 to 100
150 to 200
100 to 150
200 to 250
17848. By lime soda process, hardness can be reduced to less than
50 ppm
75 ppm
150 ppm
100 ppm
17849. Biochemical Oxygen Demand (BOD) of safe drinking water must be-
0
50
10
100
17850. The aeration of water is done to remove--
colour
taste
odour
all of these
17851. The coefficient of uniformity for slow sand filters is-
1.35
1.75
1.55
2.05
17852. The time of contact for chlorination should be at least-
5 minutes
20 minutes
1 hour
2 hours
17853. The most common cause of acidity in water is-
hydrogen
carbon dioxide
oxygen
all of theese
17854. The process of killing pathogenic bacterias from water is called-
sedimentation
coagulation
filteration
disinfection
17855. 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
17856. The percentage of chlorine in fresh bleaching powder is-
20 to 25%
25 to 30%
30 to 35%
35 to 40%
17857. Sphere shaped bacteria are called-
spirilla
cocci
bacilli
trichobacteria
17858. When the pH value of water is more than 7, it represents--- water.
neutral
alkaline
acidic
solt
17859. Rapid sand filter can remove bacteria upto an extent of-
60 to 70%
70 to 80%
80 to 90%
90 to 99%
17860. 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