Lagoons used for purification of polluted water Are large shallow artificial lakes also known as clarification lakes, maturation ponds or oxidation ponds Gives an excellent final effluent (with 3 to 4 lagoons arranged in series) having suspended solid < 1 mg/litre and BOD = 3.8 mg/litre Use micro-organisms/bacteria in presence of dissolved oxygen All of these TRUE ANSWER : ? YOUR ANSWER : ?
There are five concentric layers within the atmosphere which is differentiated on the basis of temperature. The atmospheric layer which lies close to the earth's surface in which human being along with other organisms live is called troposphere. The rate at which air temperature in the troposphere gradually decreases with height is about __________ °C/km. 15 1 6.5 0.05 TRUE ANSWER : ? YOUR ANSWER : ?
World's worst radioactive pollution was caused by nuclear reactor disaster which occured in Chernobyl (undivided U.S.S.R.) Arizona (U.S.A.) Moscow (U.S.S.R.) Pensylvania (U.S.A.) TRUE ANSWER : ? YOUR ANSWER : ?
Shouting by a man at his full voice corresponds to a voice level of about __________ decibels. 120 25 80 50 TRUE ANSWER : ? YOUR ANSWER : ?
Presence of nitrogen in high concentration in contaminated air reduces partial pressure of oxygen in lungs, thereby causing asphyxia (suffocation) leading to death from oxygen deficiency. Concentration of N₂ in contaminated air at which it acts as a natural asphyxant is ≥ __________ percent. 92 80 84 88 TRUE ANSWER : ? YOUR ANSWER : ?
The upper layer of atmosphere is called the None of these Troposphere Stratosphere Ionosphere TRUE ANSWER : ? YOUR ANSWER : ?
Septic tanks are used for the __________ of the deposited solids. Aerobic decomposition None of these Separation Anaerobic decomposition TRUE ANSWER : ? YOUR ANSWER : ?
In a sedimentation tank, the detention period for water ranges from __________ hours. 2 to 4 16 to 20 8 to 12 24 to 32 TRUE ANSWER : ? YOUR ANSWER : ?
Which of the following fine dust removal equipments is the most efficient? Bag filter Cyclone separator Scrubber Electrostatic precipitator TRUE ANSWER : ? YOUR ANSWER : ?
Which of the following is not a natural source of air pollution? Biological decay of vegetable matter Photochemical oxidation of organic matter Volcanic eruptions and lightening discharges None of these TRUE ANSWER : ? YOUR ANSWER : ?