Process for dissolved gas flotation in anaerobic wastewater treatment

Abstract

A process for gas entrainment of wastewater in an anaerobic wastewater treatment system includes the steps of withdrawing wastewater from an anaerobic digester and piping it into a flotation container. Thereafter the wastewater is pumped into a free standing tank having pressure in the tank maintained at a predetermined level through the injection into the tank of compressed gas generated by anaerobic digestion occurring in the treatment system. The wastewater is removed from the tank and pumped through a multiple jet configuration wherein gas from the tank is entrained in the wastewater as the water is injected back into the tank. The gas entrained water is then discharged from the tank back into the flotation container where the gas bubbles particles to the surface of the water to form a sludge layer. The sludge layer formed on the surface of the water in the flotation container is recycled to the digester for further increased digestion, thereby providing an efficient flotation process with increased wastewater clarification, reduced disturbance of the anaerobic bacterial sludge layer, and efficient utilization of the gas generated by anaerobic digestion in the system.