Contact Stabilization

Contact stabilization uses two separate tanks for the treatment of the wastewater and the stabilization of the activated sludge. The stabilized activated sludge is merged along with the influent (either raw or settled) wastewater in a contact tank. The mixed liquor is settled within a secondary settling tank and return sludge is aerated separately in a re-aeration basin for stabilization of the organic matter. Aeration volume needs are typically 50% less than in the case of conventional plug flow. BOD removal efficiency varies between 80-90%.