1. In slow sand filter effective size of particle is _____.

[A] 0.35 – 0.40 mm
[B] 0.45 – 0.75 mm
[C] 0.45 – 0.60 mm
[D] 0.20 – 0.30 mm

Answer: Option D

2. As per Indian Standard (IS 10500:2012) iron in drinking water should not exceed _____.

[A] 0.3 mg/L
[B] 0.5 mg/L
[C] 0.2 mg/L
[D] 0.1 mg/L

Answer: Option A


3. For old town / city which water distribution system is useful?

[A] Ring system
[B] Dead end system
[C] Grid system
[D] None of above

Answer: Option B

4. At lower pH, the contact period required for chlorination is _____.

[A] Higher
[B] Lower
[C] Remains same
[D] None

Answer: Option B

Explanation:  When chlorine is added in water, it reacts at pH of water greater than 5 and results in the formation of highly unstable HOCl. So, at Lower pH (5-7) it exists in HOCI form and hence needs less contact period.


5. The acceptable limits of total dissolved salts for drinking water is ____.

[A] 1000 mg/l
[B] 500 mg/l
[C] 250 mg/l
[D] 200 mg/l

Answer: Option B


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