Abstract: A process for removing hydrocarbons such as oil from produced water entrains high concentrations of very small gas bubbles within produced water inside a vertically-oriented primary separation tank by means of aerators immersed in the water inside the tank. Oil droplets coat the gas bubbles which form a buoyant oil-rich froth phase overlying a gas-rich liquid phase. The froth phase flows out through a discharge port in a preferably conical upper section of the primary tank, for disposal or recovery of oil as appropriate. Solid contaminants not borne by the froth phase may be intermittently settled out of the liquid phase and removed for treatment or disposal through a discharge port in a preferably conical lower section of the primary tank. Clean processed water is drawn a medial region of the primary tank for re-use as appropriate. In a preferred embodiment, the froth phase passes into a secondary separation tank for further separation of contaminants by means of gravity and/or supplemental aeration.