Abstract: Disclosed is a device comprising an ozonizer (1) in the first region (1') of which container (1) ozone is formed which is dispersed into fluid by a gas feed organ (3). The thusly formed two-phase mixture flows through a second region (1") of the ozonizer (1) to a phase separating element (13). Through the arrangement and disposition of the gas feed organ (3) on the fluid entry side, the second region (1") forms and defines a flow region for the two-phase mixture resulting in the greatest possible ozone feed into the fluid. Such devices have especial application for the sterilization of drinking and bath water.