Question

How are microbes helpful in treating wastewater sewage?

Answer 1

Microbes are central to the biological stages of sewage treatment, where they break down organic pollutants.

1. Primary treatment: Filtration and sedimentation physically remove debris, grit and suspended solids. The resulting effluent still contains organic matter and microbes.
2. Secondary treatment: The effluent is aerated and mixed with aerobic microbes. They grow into flocs and consume organic matter, reducing the biochemical oxygen demand (BOD). The flocs settle as activated sludge; some is recycled to the aeration tank as inoculum.
3. Anaerobic digestion: The remaining sludge is treated by anaerobic microbes. They decompose biodegradable matter, reduce foul odour and produce biogas containing methane, carbon dioxide and hydrogen sulphide.
4. Tertiary treatment: The water may receive further physical and chemical treatment to remove remaining pollutants and harmful microbes before discharge.

Microbial treatment makes sewage less polluting and can also yield biogas.