Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of waste waters rich in organic matter? Discuss.

(N/A) Secondary treatment or biological treatment is essential for large volumes of wastewater because aerobic microbes are highly efficient at breaking down organic matter.
$1$. In aeration tanks,constant agitation and air supply promote the growth of aerobic microbes into 'flocs' (masses of bacteria associated with fungal filaments).
$2$. These microbes consume the major part of the organic matter,which significantly reduces the $BOD$ (Biochemical Oxygen Demand) of the effluent.
$3$. $BOD$ is a measure of the organic matter present in the water; the greater the $BOD$,the higher the polluting potential.
$4$. Aerobic degradation is faster and more effective at reducing high levels of organic pollutants compared to anaerobic processes,which are typically used later for sludge digestion.
$5$. Once $BOD$ is reduced,the effluent is passed into a settling tank where flocs sediment as 'activated sludge'.
$6$. The remaining sludge is then treated in anaerobic sludge digesters to produce biogas (methane,hydrogen sulphide,and carbon dioxide),which serves as an energy source.