Aerobic and Anaerobic organisms play a vital role in sewage treatment plant. Justify the statement.

Dear Student

Secondary treatment of wastewater is also called as biological treatment.

Primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped to it. Due to this, useful aerobic microbes grow rapidly and form flocs and growing these microbes consume the major part of the organic matter in the effluent. This reduces the BOD of the effluent. When BOD of sewage or waste water is reduced, the effluent is then passed into settling tank where bacteria flocs are allowed to sediment. This sediment is called activated sludge.
A small part of this activated sludge is pumped back into the aeration tank to serve as the inoculum.The remaining part is passed into large tanks called anaerobic sludge digesters. Here, heterotrophic microbes anaerobically digest bacteria and fungi in sludge producing mixture of gases such as methane, H₂S, CO₂ .

These gases form the biogas and can be used as source of energy as it is inflammable. The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.

Hence, aerobic and anaerobic organisms plays a vital role in sewage treatment plant.

Regards