Device comprises an inlet chamber (2) and an outlet chamber (3), which are separated from each other by a partition wall with an inlet (7) and an outlet, and an injection (12) with the ozone-containing gas. At least one inflow channel is arranged in the inlet chamber, which exhibits horizontally arranged edge region submerging with respect to water level (6) and the edge regions are provided with many adjacently arranged, upwardly open recesses. The recesses extend upward in a direction parallel to the water level from a lower deepest point.
