A view of the secondary sedimentation basins. The final step in the secondary treatment process at the Oneonta plant is Disinfection . Disinfection is done by chlorination. Chlorine gas kills bacteria that may cause disease. Chlorinating is done only during the summer in order to minimize environmental damage.
Chlorine is generally toxic to fish and other aquatic life.
While the liquid effluent resulting from Primary Treatment is sent on to Secondary Treatment, the solids, or sludge, goes through further treatment as well. This sludge consists of raw sewage solids and is the most offensive of the sludge. The purpose of sludge treatment is to reduce the volume, offensiveness, and number of pathogens in sewage solids. The first step is Thickening which reduces the volume of the sludge so that it will be less expensive to treat. The second step is Sludge Stabilization which reduces the pungency of smell, volume, and the number of pathogens.