The present invention comprises a process and apparatus for separation of hydrocarbons from hydrocarbon-containing produced water, wherein in a water tank two chambers are formed by a separation plate (30): an upper chamber (29) and a lower chamber (33) so as to carry out a 2-stage process. In stage 1 the hydrocarbon-containing produced water is supplied with a gas-containing component, whereupon a gas- and hydrocarbon-containing produced water mixture is fed to an inlet tube (22) in the center of a tank, whereupon the said mixture is tangentially distributed via at least one nozzle (7) and at least one baffle plate (8.1). The separated hydrocarbons are conveyed to at least one upper oil outlet (10) from the tank and partially cleaned water is directed to stage 2 in the lower chamber (33). Separated oil is discharged from this lower chamber (33) via a second outlet (36) and the cleaned water is conveyed to an outlet (12) from the tank.