Abstract: Liquid effluent from a conventional septic tank is passed successively through a filter tank and a plurality of spaced ozonating tanks, at least one of which has an activated charcoal filter located intermediate its ends. The filtered liquid passes from the last ozonating tank into a reservoir, and finally through an overflow outlet to a surrounding leach field. Perforated diffusers in the lower ends of the ozonating tanks are connected to an ozone generator which intermittently supplies ozone gas to the diffusers. Excess ozone gas is piped from the upper ends of the ozonating tanks back to the septic tank to increase the effectiveness of the septic tank. Dimethyl sulfoxide is added to the septic tank to prevent sludge formation.

Abstract: Placed in the ground adjacent a conventional septic tank are a purification tank, which contains a smaller, cylindrical filter tank, and a plurality of spaced, parallel, vertically-disposed ozonating tanks, which are located in an annular space between the filter tank and the purification tank. Perforated diffusers in the lower ends of the ozonating tanks are connected to an ozone generator which intermittently supplies ozone gas to the diffusers. Liquid effluent from the septic tank is fed to the lower end of the filter tank and passes upwardly through a removable, porous filter, then successively through the ozonating tanks, then into the space or reservoir formed in the purification tank around the outsides of the filter tank and ozonating tanks, and finally through an overflow outlet to a surrounding leach field. Excess ozone gas is piped from the upper ends of the ozonating tanks back to the septic tank to increase the effectiveness of the septic tank.