The correct answer is: A. Oxidation pond
Oxidation ponds are the most efficient type of wastewater treatment system for removing BOD. They are large, shallow ponds that are filled with microorganisms that break down organic matter. Oxidation ponds are typically used to treat wastewater from small communities or industries.
Oxidation ditches are also effective at removing BOD, but they are not as efficient as oxidation ponds. Oxidation ditches are long, narrow channels that are filled with microorganisms. The microorganisms are mixed with the wastewater by a rotating arm. Oxidation ditches are typically used to treat wastewater from larger communities or industries.
Aerated lagoons are less efficient at removing BOD than oxidation ponds or oxidation ditches. Aerated lagoons are large, shallow ponds that are filled with microorganisms. The microorganisms are mixed with the wastewater by aeration. Aerated lagoons are typically used to treat wastewater from small communities or industries.
Trickling filters are the least efficient type of wastewater treatment system for removing BOD. Trickling filters are filled with a bed of rocks or other material. The wastewater is sprayed over the rocks, and the microorganisms on the rocks break down the organic matter. Trickling filters are typically used to treat wastewater from small communities or industries.
In conclusion, the maximum efficiency of BOD removal is achieved in oxidation ponds. Oxidation ponds are large, shallow ponds that are filled with microorganisms that break down organic matter. Oxidation ponds are typically used to treat wastewater from small communities or industries.