5-200 μm size particles are called__________________?
(A) Colloids or aerosols
(B) Powder
(C) Dust
(D) Smoke
Lagoons used for purification of polluted water_______________?
(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
Which of the following is the most efficient for removal of very finely divided suspended solids and colloidal matter from the polluted water stream ?
(A) Sedimentation tank
(B) Circular clarifier
(C) Mechanical flocculation
(D) Chemical coagulation
The most commonly used chemical coagulant in water treatment is________________?
(A) Ferrous sulphate
(B) Alum
(C) Lime
(D) Hydrazine
Hazardous/polluting chemical industries should have an ‘exclusion zone’ with a green belt and general public access prohibited around it, covering a radius of _____________ metres?
(A) 100
(B) 1000
(C) 400
(D) 4000
Sooty and sulphurous smog formed due to combustion of fossil fuels particularly in winter, continues throughout the day and night. When the moist atmospheric air’s water vapor condenses on the solid particles of smoke thereby forming smog (smoke + fog), it causes_________________?
(A) Poor visibility due to sky darkening
(B) Irritation in eyes
(C) Respiratory trouble
(D) All
Oceans act as sinks for atmospheric gases including carbon dioxide whose concentration in the atmosphere is increased by the_______________?
(A) Forestation
(B) Rain
(C) Green house effect
(D) Vegetation
Water filtration rate in a rapid sand filter ranges from ______________ kilolitres/m2/hr?
(A) 0.1 to 1
(B) 3 to 6
(C) 10 to 15
(D) 15 to 20
Which of the following sources is responsible for maximum air pollution ?
(A) Industrial chimney exhaust
(B) Forest fire
(C) Automobiles exhaust
(D) Photochemical oxidation of organic matter
The biological decomposition of organic substances in wastes controlled conditions is called_________________?
(A) Incineration
(B) Biological oxidation
(C) Composting
(D) None of these