TREATMENT of sewage effluents that reduces the biochemical oxygen demand of wastewater and may reduce the toxicity of some impurities. Secondary treatment by oxidation of dissolved and colloidal organic compounds is widely used in sewage treatment and is applicable to some agricultural and industrial wastewaters. BIOLOGICAL oxidation will preferentially REMOVE organic compounds useful as a FOOD supply for the treatment ecosystem. The concentration of some less digestible compounds may be reduced by co-metabolism. Removal efficiency is limited by the minimum food concentration required to sustain the treatment ecosystem.Chlorination: Chlorination plays a key role in the wastewater treatment process by removing pathogens and other physical and chemical impurities. Chlorine's important benefits to wastewater treatment are:DisinfectionControlling odorScum and grease removalRemoves ammoniaDestroying CYANIDES and phenols