Apparatus and process for aerating a liquid with gas, the apparatus comprising a pressure vessel including a lower section containing the liquid and an upper section containing a volume of the gas. A pressure connection in the upper section of the pressure vessel adapted receives the gas. A nozzle in the upper section of the pressure vessel receives the liquid. An injector extends from the upper section of the pressure vessel to the lower section of the pressure vessel and has a head in fluid communication with the nozzle. Part of the gas volume is sucked in by the vacuum generated by the liquid injected, carried along together with the liquid and mixed intimately with the liquid at the same time.