Apparatus and method for treating sewage

Claim 1

A sewage treatment apparatus comprising: a. a primary receiving and mixing tank for receiving raw sewage; b. means in said primary receiving tank for separating larger solids from the sewage; c. a vertical cylindrical aeration tank containing a series of downwardly inclined baffles arranged to trap pockets of air and to circulate sewage along a tortuous path across the air pockets, said baffles including a first truncated inverted conical baffle in a lower region extending inwardly and downwardly from the cylindrical wall and forming an axial opening, a second truncated inverted conical baffle in an upper central region of the aerator having a cylindrical extension connected to the lower end thereof for collecting aerated sewage in an upper region of the aerator and carrying it downwardly through the axial opening of the first baffle and at least one further truncated conical baffle extending outwardly and downwardly from an upper region of said second baffle; d. pump means for pumping a stream of said sewage from the primary receiving tank into a bottom region of the aeration tank beneath said first baffle; e. a venturi aerator for introducing air into the stream of sewage being pumped into the aeration tank; f. means for recycling a portion of aerated sewage from an upper region of said aeration tank to said primary receiving tank for mixing with un-aerated sewage; g. a settling tank in fluid communication with said aeration tank for receiving aerated sewage from an upper region of said aeration tank and separating activated sludge from the liquid portion of the sewage; and h. means for returning said activated sludge to said aeration tank at a location beneath said first baffle for mixing with said aerated sewage.