what are flocs used in secondary sewage treatment.
Answers
When a primary effluent is passed through a large aeration tanks. Later on it is constantly agitated mechanically by pumping in of air which results in production vigorous growth of useful aerobic microbes called flocs. These microbes consume the major part of the organic matter in the effluent resulting in significant reduction of BOD of the effluent and these are basically the flocs used in sewage treatment plants
Flocs are essentially groups of bacteria which are in a sludge structure and is held together with the use of slime.
Flocs are helpful in increasing the decomposition rate and are put in the aeration tank while the secondary sewage treatment process is in effect.
This results in the sewage BOD reducing by up to approximately 15 percent before being passed on to the settlement tanks.