Question

List the events that reduce the Biochemical Oxygen Demand (BOD) of a primary effluent during sewage treatment.

Hint:

A decrease in BOD during sewage treatment reflects the removal of organic pollutants, ensuring cleaner water for reuse or discharge.

Answer 1

During secondary treatment of sewage, the BOD of the effluent is reduced through the following processes: 
- Consumption of organic matter: Aerobic microorganisms in the effluent consume the organic matter. 
- Formation of flocs: Microbial activity leads to the formation of flocs, which are aggregations of bacteria and fungi. 
- Decomposition of organic matter: Organic matter is broken down into simpler substances like carbon dioxide and water. 
- Separation of activated sludge: The flocs settle down as activated sludge, further reducing the organic load.