In sewage treatment, the detention period allowed for oxidation ponds ranges from __________ weeks.
A. 1 to 2
B. 4 to 5
C. 9 to 10
D. 15 to 20
Answer: Option B
A. 1 to 2
B. 4 to 5
C. 9 to 10
D. 15 to 20
Answer: Option B
Fluorosis is caused due to the presence of excessive amount of __________ in drinking water.
A. Mercury
B. Lead
C. Fluoride
D. Arsenic
Smog is not formed due to the presence of __________ in the atmosphere.
A. SO2
B. NOx
C. CO2
D. Any of these
Dose of chlorine for disinfection of water is about __________ mg/litre of water.
A. 0.01
B. 0.1
C. 0.3
D. 1
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