Question

how do the microorganisms help in sewage treatment plants??

Answer 1

Aerobic bacteria are used in most new treatment plants in an aerated environment. This means that there is dissolved oxygen available for the respiration of the bacteria. They use the free oxygen in the water to degrade the pollutants in the incoming wastewater into energy they can use for growth and reproduction.
A wastewater treatment plant is a microbiological zoo that houses bacteria, protozoa, metazoa and other microlife. The microorganisms do the actual breakdown and removal of nutrients and organic material in the wastewater. ... It is the task of the operator to provide a favorable environment for the microorganisms.
Microorganisms breaks down the chemical and biological waste present in the sewage, digesting the organic matter present in it. They feed on the organic matter and releases an enzyme which helps in its degradation removing the organic matter from thesewage.