Systems and methods for dissolving ozone gas in a liquid. An embodiment can comprise a tank having an upper region, a lower region, and a discharge outlet, all disposed in a specified geometry. A pump can be coupled with a liquid inlet in order to receive a liquid therefrom and to deliver the liquid via a pipe to the upper region of the tank. The pump can be coupled with the lower region of the tank in order to receive the liquid from the tank and to recirculate the liquid to the upper region of the tank. The apparatus can include an ozone inlet to receive ozone into the tank. The ozone inlet can comprise a venturi inlet disposed on the pipe downstream of the pump. The liquid can be released from the tank and depressurized, thereby providing for the ozone to emerge from the liquid as gas bubbles. The released liquid can be selected for a two-stage gas and aqueous cleaning process.
