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 BOD = 3.8 mg/litre
D. All A., B. & C.
Related Mcqs:
- 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 chlorinated
D. All A., B. & C. - The amount of chemical coagulant added for treatment of polluted water ______________ with increase in temperature of the polluted water to be treated?
A. Decreases
B. Increases
C. Remain constant
D. May increase or decrease; depends on the chemical characteristics of polluted water - 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 - Replenishment of dissolved oxygen in water stream polluted with industrial waste occurs by________________?
A. Natural aeration of water stream
B. Photosynthetic action of algae
C. Both A. & B.
D. Neither A. nor B. - Waste/polluted water discharged from electroplating, blast furnace and coal mining industries contain mainly _____________ substances?
A. Radioactive
B. Organic
C. Inorganic
D. None of these - Iron & manganese present in the polluted water is removed by __________________?
A. Simple filtration
B. Oxidation followed by settling & filtration
C. Chemical coagulation
D. Chlorination only - Biological oxidation ponds remove organic matters present in the polluted water by _______________?
A. Using the activities of bacteria and other micro organisms
B. Aerobic oxidation
C. Both A. & B.
D. Neither A. nor B. - Which is the most practical and economical method for removal of suspended solid matter from polluted water ?
A. Sedimentation
B. Skimming off
C. Chlorination
D. Biological oxidation - Which is the best and the most effective method for the removal of organic contaminant present in the polluted water in very small quantity (say < 200 mg/litre) ?
A. Lagooning
B. Activated carbon adsorption
C. Biological oxidation pond
D. Chemical coagulation - Bacterial aerobic oxidation of polluted water in biological oxidation ponds is done to purify it. Presence of bacteria helps in____________________?
A. Coagulation and flocculation of colloids
B. Oxidation of carbonaceous matter to CO2
C. Nitrification or oxidation of ammonia derived from breakdown of nitrogenous organic matter
to the nitrite and eventually to the nitrate
D. All A., B. and C.
