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The main pollutant in waste water discharged from a petroleum refinery is oil (both in free and emulsified form). Free oil is removed by_________________? A. Biological oxygen pond B. Aerated lagoons C. Trickling filtersD. Gravity separator having oil skimming devices
Noise emitted by a ventilation fan at a distance of 3 metres is about _____________ decibels? A. 85B. 105 C. 125 D. 145
Presence of ____________ in water stream are deleterious to aquatic life? A. Soluble and toxic organics B. Suspended solids C. Heavy metals and cyanidesD. All A., B. & C.
Tolerable limit of nitrogen oxides in air is _____________ ppm? A. 0.1 B. 1C. 5 D. 25
BOD of raw municipal sewage may be in the range of about _____________ mg/litre? A. 1-2 B. 5-10C. 150-300 D. 2000-3000
Iron & manganese present in the polluted water is removed by __________________? A. Simple filtrationB. Oxidation followed by settling & filtration C. Chemical coagulation D. Chlorination only
TLV of aldrin in public water supply system is about ____________ μg/litre? A. 0.5B. 17 C. 357 D. 1097
Aerobic biological oxidation ponds used for the purification of polluted water__________________? A. Destroys/removes pathogen from the sewage B. Is not very effective for non-biodegradable substances (e.g. ABS) containing effluents C. Destroys/removes pathogen much more effectively if the sewage is chlorinatedD. All A., B. & C.
Presence of excess fluorine in water causes__________________? A. Dental cavity B. Tooth decayC. Fluorosis D. Respiratory disease
Direct reaction of unsaturated hydrocarbons with either NO or NO2 produces an eye irritating pollutant compound known as________________? A. Photochemical smogB. Peroxyacetyl nitrate (PAN) or methyl nitrite C. Benzopyrene D. Polyacrylonitrile