. Introduction
The activated sludge process is widely used in wastewater treatment plants to reduce effluent levels in contaminated
wastewaters originating from both the municipal and industrial sectors. The process generally occurs in two units: an
aerated biological reactor, in which bacteria are used to degrade pollutants, and a settling unit (or clarifier), in which the
activated sludge settles to the bottom of the unit. Activated sludge, along with mixed liquor, is recycled from the bottom of
the clarifier into the biological reactor