Abstract: A system for dissolved air floatation treatment of a liquid stream where the system includes a pump having an impeller cavity with input and output ports, and an impeller with an eye disposed adjacent the input port. The impeller draws liquid through the input port and drives the liquid toward the output port and creates a subatmospheric pressure zone in the cavity away from the eye. The pump includes an air introduction port opening into the subatmospheric zone to introduce significant quantities of air into the cavity for mixing with the liquid stream. The system also includes a tank adapted to receive the liquid stream from the pump with dissolved air introduced therein.