Air-driven contact filter

Claim 1

In a rotary contact filter for use in a system for biological cleaning of waste water including a rotor having at least one spiral channel through which air and waste water pass partially submerged in a body of water to be treated and rotatable about a horizontal axis at the central portion of the rotor, the improvement comprising: a mixing chamber in the central portion of said rotor through which the axis of rotation extends; a central hollow pipe extending through said mixing chamber and having a longitudinal axis coincident with the axis of rotation and being closed at one end thereof; a source of compressed air connected to the other end of said pipe for feeding air into said pipe; holes in said pipe for the passage of air from the inside of said pipe to said mixing chamber; an inner end on said at least one spiral channel communicating with said mixing chamber; an outer end on said at least one spiral channel passing above the surface of the water during part of the revolution of the rotor; said rotor having gable plates between which said at least one spiral channel extends; and openings in said gable plates for the passage of water into said rotor; said central pipe being disposed below the surface of the water so that said compressed air injected into said pipe passes through said holes into said mixing chamber and into said inlet end of said at least one spiral channel and displaces water in said one spiral channel into a part of said channel on substantially the opposite side of said rotor relative to the axis of rotation from said channel inlet causing said rotor to rotate in the direction opposite to the direction in which the spiral channel extends from the inner end to the outer end thereof.