MCQ
4041. The time of contact for chlorination should be at least-
5 minutes
20 minutes
1 hour
2 hours
4042. The velocity of flow in any sedimentation tank should not exceed-
0.05mm/s
5mm/s
0.5mm/s
50mm/s
4043. 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
4044. pH value is a symbol for ---concentration.
magnesium
hydrogen
calcium
sodium
4045. 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
4046. 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
4047. Sphere shaped bacteria are called-
spirilla
cocci
bacilli
trichobacteria
4048. The most common cause of acidity in water is-
hydrogen
carbon dioxide
oxygen
all of theese
4049. The maximum acidity in water will occur at a pH value of-
0
7
2
14
4050. Biochemical Oxygen Demand (BOD) of safe drinking water must be-
0
50
10
100
4051. Slow sand filter is more efficient for the removal of-
bacteria
turbidity
odour
all of these
4052. When the pH value of water is more than 7, it represents--- water.
neutral
alkaline
acidic
solt
4053. 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
4054. The coefficient of uniformity for slow sand filters is-
1.35
1.75
1.55
2.05
4055. 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
4056. Rapid sand filter can remove bacteria upto an extent of-
60 to 70%
70 to 80%
80 to 90%
90 to 99%
4057. The process of killing pathogenic bacterias from water is called-
sedimentation
coagulation
filteration
disinfection
4058. 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
4059. The max" permissible total solid content in water for domestic purposes should not exceed-
300 ppm
400 ppm
500 ppm
1000 ppm
4060. 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