The release of municipal wastewater and industrial waste into our natural water bodies is causing disastrous effect to the aquatic life. Explain the biological treatment that should be given to it before releasing into the natural water bodies

The primary effluent is passed into large aeration tanks where it is mechanically constantly agitated and air is pumped into it, this allow growth of useful aerobic microbes into Flocs / masses of bacteria associated with fungal filaments , these microbes consume major part of organic matter in the effluent reducing BOD , effluent is passed into settling tanks where Flocs are allowed to sediment called activated sludge , a small part of this is pumped back into the aeration tank to serve as the inoculum, The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters where anaerobic bacteria digest the bacteria and the fungi in the sludge. (During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbondioxide.)