Abstract: An apparatus for treating and purifying waste water containing organic pollutants and includes a vertical tank for receiving waste water and discharging treated water, a vertical clarifying structure located within the tank and connected to the tank having sidewalls which diverge from a bottom opening to a larger top opening, a series of air injecting pipes connected to the tank and located inside the tank for injecting air into the lower portion of the tank to aerate the waste water in the tank, an inlet located in the upper portion of the tank for supplying waste water to the tank, and an output connected to the tank for removing treated water from the tank, the outlet being located in the upper portion of the clarifier, the outlet being a horizontal pipe having a vertical pipe connected to the end hereof, the top of the vertical pipe extending above the level of the waste water and treated water in the clarifier and the bottom of the vertical pipe extending beneath the level of any scum blanket on waste wa