1. Presence of fluoride in water greater than permissible level of 1.5 mg/L causes _____.

[A] methemoglobinemia
[B] dental fluorosis
[C] hepatitis
[D] cardiovascular disease

Answer: Option B

2. An inverted siphon is a ______.

[A] derive for preventing crown corrosion of sewer
[B] section of sewer which is dropped below the hydraulic grade line in order to avoid an obstacle
[C] device for preventing overflow from elevated water storage tank
[D] device for distributing septic tank effluent to a soil absorption system

Answer: Option B


3. Symbiosis, the beneficial association between algae and bacteria is used for treatment of waste water in _____ unit.

[A] Rotating biological disc
[B] Oxidation pond
[C] Activated sludge
[D] Anaerobic digestor

Answer: Option B

4. The atmospheric layer closest to the earth surface is ______.
[A] stratosphere
[B] troposphere
[C] thermosphere
[D] mesosphere

Answer: Option B


5. If total hardness and alkalinity of a water sample are 200 mg/l as CaCO3 and 260 mg/l as CaCO3, respectively, what are the values of carbonate hardness and non-carbonate hardness?

[A] Zero and 200 mg/l
[B] Zero and 60 mg/l
[C] 60 mg/l and zero
[D] 200 mg/l and zero

Answer: Option D


CH = min(TH, alkalinity)

      = min{200, 260) = 200 mg/l

NCH = TH – alkalinity = 200 – 260 = -60 (negative) i.e. NCH = 0


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