Dear Ms. Anunobi, trying to give you a brief, concise answer to your question is more complicated than the question itself... Take a look over this book chapter, you will find the answer.

Dear Oluchukwu,

Please have have a look at these useful PDF attachments.

Good luck!

simply they use enzymes in their body to digest complex biodegradable compounds in ww to simple forms

Organic matter degradation in wastewater progress through hydrolysis of matter to small molecules (mostly VFA) catalysed by exoenzymes excreted by bacteria. Bacteria can then take up the smaller organic molecules and use them to form energy and new bacteria biomass.

Check the attached file

In the attached paper you can find the answers to your question.

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Vit

In the aeration basin microorganisms agglomerate in the form of flocs and develop using pollution as a substrate necessary for the production of vital energy and the synthesis of new living cells. Part of the pollutants that are not biologically degraded can be adsorbed and incorporated into the sludge flocs (BROUZES, 1973).

Many microorganisms with very different growth rates are associated with this degradation process: bacteria, algae, fungi and protozoa are usually found. Bacteria, however, remain the most involved microorganisms, they transform organic matter by means of their metabolism into microbial biomass, This process of microbial degradation can be broken down into several phases. A transport phase that brings the pollutants (soluble and insoluble) from the breast of the liquid to the surface of the bacteria. A diffusion phase during which the soluble substrate diffuses easily through the membrane, while insoluble materials (particles, colloids and large molecules) are first adsorbed on the surface of the bacterium and then hydrolyzed by exo-enzymes , before being in turn assimilated. Finally, the phase of metabolization of pollutants that takes place within the cell. This stage, much slower than the previous ones, is divided into three parts:

1) assimilation (or anabolism) which is the use of pollutants for the synthesis of new cells;

2) respiration (or catabolism) which allows the combustion of substrates to release the energy necessary for microorganisms to perform their vital functions;

3) endogenous respiration where microorganisms use their own material as a substrate.

I agree with Chandrika Priyadarshani " simply they use enzymes in their body to digest complex biodegradable compounds in ww to simple forms "