MCQ
16281. Rapid sand filter can remove bacteria upto an extent of-
60 to 70%
70 to 80%
80 to 90%
90 to 99%
16282. 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
16283. 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
16284. When the pH value of water is more than 7, it represents--- water.
neutral
alkaline
acidic
solt
16285. pH value is a symbol for ---concentration.
magnesium
hydrogen
calcium
sodium
16286. The maximum permissible colour for domestic supplies, on platinum cobalt scale is-
5 to 10 ppm
10 to 20 ppm
20 to 30 ppm
30 to 40 ppm
16287. The most common cause of acidity in water is-
hydrogen
carbon dioxide
oxygen
all of theese
16288. 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
16289. The maximum acidity in water will occur at a pH value of-
0
7
2
14
16290. Biochemical Oxygen Demand (BOD) of safe drinking water must be-
0
50
10
100
16291. 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
16292. The maximum permissible temperature for domestic supply is-
5 to 10°C
10 to 15°C
15 to 20°C
20 to 25°C
16293. Sphere shaped bacteria are called-
spirilla
cocci
bacilli
trichobacteria
16294. Slow sand filter is more efficient for the removal of-
bacteria
turbidity
odour
all of these
16295. The presence of hydrogen sulphide in water causes-
softening
acidity
alkalinity
bad taste
16296. 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
16297. The velocity of flow in any sedimentation tank should not exceed-
0.05mm/s
5mm/s
0.5mm/s
50mm/s
16298. The maximum permissible turbidity for domestic supplies, on silica scale is-
5 to 10 ppm
20 to 30 ppm
10 to 20 ppm
30 to 40 ppm
16299. The max" permissible total solid content in water for domestic purposes should not exceed-
300 ppm
400 ppm
500 ppm
1000 ppm
16300. The coefficient of uniformity for slow sand filters is-
1.35
1.75
1.55
2.05