What would happen if oxygen availability to activated sludge flocs is reduced?

Options

A. It will slow down the rate of degradation of organic matter.
B. The centre of flocs will become anoxic, which would cause death of bacteria and eventually breakage of flocs.
C. Flocs would increase in size as anaerobic bacteria would grow around flocs.
D. Protozoa would grow in large numbers

Answer

B

Explanation

Activated sludge micro-organisms need oxygen as they oxidise wastes to obtain energy for growth. Insufficient oxygen will slow down or kill off aerobic micro-organisms, make facultative organisms work less efficiently and ultimately lead to the breakage of flocs. It will also result in the production of the foul-smelling byproducts of anaerobic decomposition. So, sufficient oxygen must always be sustained in the aeration tank to ensure complete waste stabilisation.