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

Secondary sewage treatment reduces effluent BOD via these mechanisms:
- Organic matter consumption: Aerobic microbes in the effluent utilize organic matter. 
- Floc formation: Microbial action creates flocs, which are bacterial and fungal aggregates. 
- Organic matter decomposition: Organic substances are broken down into simple compounds like carbon dioxide and water. 
- Activated sludge separation: Flocs sediment as activated sludge, diminishing the organic load.