Secondary treatment is the heart of the wastewater treatment process. Secondary Treatment at the Norwalk WPCF is carried out in aeration tanks, which use helpful microorganisms or “bugs” within the wastewater (known as “activated sludge”) to breakdown contaminants and biologically remove nutrients (known as a “BNR” process) in the wastewater. Air is supplied in selected zones of the aeration tanks (whereas other zones are not aerated) to facilitate the growth of different microorganisms which remove various wastes.

Aeration Tanks