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 BOD = 3.8 mg/litre

D. All of the above

Answer: Option D