- (A) Are large shallow artificial lakes also known as clarification lakes, maturation ponds or oxidation ponds
- (B) Use micro-organisms/bacteria in presence of dissolved oxygen
- (C) Gives an excellent final effluent (with 3 to 4 lagoons arranged in series) having suspended solid < 1 mg/litre and BO
- (D) = 3.8 mg/litre
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- (A) Sedimentation tank
- (B) Circular clarifier
- (C) Mechanical flocculation
- (D) Chemical coagulation
- (A) Ferrous sulphate
- (B) Alum
- (C) Lime
- (D) Hydrazine
- (A) 100
- (B) 1000
- (C) 400
- (D) 4000
- (A) Poor visibility due to sky darkening
- (B) Irritation in eyes
- (C) Respiratory trouble
- (D) All
- (A) Forestation
- (B) Rain
- (C) Green house effect
- (D) Vegetation
- (A) 0.1 to 1
- (B) 3 to 6
- (C) 10 to 15
- (D) 15 to 20
- (A) Industrial chimney exhaust
- (B) Forest fire
- (C) Automobiles exhaust
- (D) Photochemical oxidation of organic matter
- (A) Incineration
- (B) Biological oxidation
- (C) Composting
- (D) None of these
- (A) SO2 & SO3
- (B) NO2
- (C) NH3
- (D) CO
