Question

The aeration tank of a sewage treatment plant is not functioning properly. Explain in detail the impact of this on the treatment of sewage and BOD of the effluent.

Answer 1

• It will adversely affect the secondary treatment or biological treatment of sewage.
• When the aeration tank is not functional, the air will not be pumped into it.
• This will not allow the vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures).
• Thus, the major part of the organic matter in the effluent will not be consumed by these bacteria.
• The BOD (biochemical oxygen demand) of the effluent will not be reduced. BOD refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria.
• The greater the BOD of wastewater, the more its polluting potential. Thus, the effluent will remain polluted with a high amount of organic matter and high BOD.