Water Supply Engineering

261. The most commonly used chemical for de-chlorination of water, is

1. Sodium thiosulphate
2. Sodium bisulphate
3. Sodium sulphite
4. Sulphur-dioxide

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262. The most ideal disinfectant used for drinking water throughout the world, is

1. Alum
2. Lime
3. Chlorine
4. Nitrogen

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263. The most important and widely used tube well in India, is

1. Strainer well
2. Cavity well
3. Slotted well
4. Perforated pipe well

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264. The nitrate concentration in domestic water supplies, is generally limited to

1. 10 ppm
2. 15 ppm
3. 30 ppm
4. 45 ppm

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265. The order of existence of three portions of water in a reservoir from the bottom to top is

1. Useful storage + surcharge storage + dead storage
2. Useful storage + dead storage + surcharge storage
3. Dead storage + useful storage + surcharge storage
4. Surcharge storage + useful storage + dead storage

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266. The percentage of chlorine in fresh bleaching powder is roughly

1. 50 to 60
2. 30 to 35
3. 40 to 50
4. 20 to 25

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267. The period of cleaning of a slow sand filter, is usually

1. 5 to 10 days
2. Two weeks to three weeks
3. One month to three months
4. Three months to six months

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268. The permissible amount of nitrites present in potable water, is

1. 10 ppm
2. 15 ppm
3. 45 ppm
4. Nil

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269. The permissible pH value for public water supplies may range between

1. 4.5 to 5.5
2. 5.5 to 6.5
3. 6.5 to 8.5
4. 8.5 to 10.5

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270. The pH value of water fit for drinking, is

1. 13
2. 11
3. 9
4. 7

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