Secondary treatment of sewage

During the secondary treatment of sewage, bacteria are used to reduce nutrients in the wastewater. This occurs in the activated sludge plant, where different types of bacteria exist in aerobic (with added oxygen) and anoxic (without added oxygen) environments, which are side by side. These micro-organisms break down organic materials and remove ammonia at both the Eastern Treatment Plant and the Western Treatment Plant. Ammonia is first converted to nitrates and finally to nitrogen gas that is released into our air. The water then passes through sedimentation tanks where more sludge is removed and treated secondary effluent is produced.