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Abstract

An apparatus and method for treating wastewater is provided including a cylindrical tank having a top, a bottom, an outer wall and a cylindrical inner wall. The inner wall extends from the bottom of the tank to a point above a desired water level. The inner wall, the top and the bottom define an inner aerobic zone. The inner wall, the outer wall, the top and the bottom define an outer anaerobic zone. Wastewater may pass from the outer anaerobic zone to the inner aerobic zone through holes in the inner wall. An open ended conical hopper is positioned within the inner aerobic zone with its smaller end pointed toward the bottom of the tank. Several radially spaced air outlet pipes connected to a compressed air source extend downward into the inner aerobic zone where air is discharged through the open ends of the outlet pipes. An inlet line connected to the tank opens into the outer anaerobic zone of the tank. An outlet line is positioned within the clarification zone to remove purified water from the tank. Wastewater is treated by anaerobic bacteria in the outer anaerobic zone and by aerobic bacteria in the inner aerobic zone. Aerobic bacteria, forced through holes in the inner wall by aeration occurring in the inner aerobic zone, denitrify the wastewater as they are starved of oxygen in the outer anaerobic zone. Finally, suspended solids settle out of solution in the clarification zone prior to the purified water leaving the tank.

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