What is biological treatment

Dear Student,

Biological treatment also known as secondary treatment, is the second stage of sewage treatment in a sewage treatment plant (STP). 
This step is called biological treatment since we make use of living organisms like bacteria and fungi in treating waste water.

Following are the steps involved in the biological treatment of waste water.

STEP 1 - The primary effluent (obtained after primary or physical treatment) is passed into large aeration tanks. Constant aeration and mechanical agitation helps aerobic bacteria to flourish and form flocs (masses of bacteria associated with fungal filaments). These microbes feed upon the organic matter present in the water and in turn bring down the BOD (Biological oxygen demand).

STEP 2 - When the BOD has reduced significantly , the effluent is passed into settling tanks where the bacterial flocs are allowed to settle down. The sediment is called activated sludge .

STEP 3 -  The activated sludge is pumped into anaerobic sludge digesters.  Here anaerobic bacteria digest the aerobic bacteria and fungi and produce a mixture of gases like methane , carbon dioxide and hydrogen sulphide (BIOGAS, that is used as a form of energy).

After these steps, the effluent is free of organic matter and is released into water bodies.

Regards ,
Ruchi Bhatt

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A type of treatment that uses substances made from living organisms to treat disease. ... Types of biological therapy include immunotherapy (such as vaccines, cytokines, and some antibodies), gene therapy, and some targeted therapies. Also called biological response modifier therapy, biotherapy, and BRM therapy.
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Hope, it helps!
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