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