question_answer 26)

  What would happen if oxygen availability to activated sludge floes is reduced? (a) I will slow down the rate of degradation of organic matter (b) The center of floes will become anoxic, which would cause death of bacteria and eventually breakage offices (c) Floes would increase in size as an aerobicbacterial would grow around floes (d) Protozoa would grow in large numbers      

Answer:

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