The gas absorption characteristics of the Karman contactor fitted with a static Kannan mixer and an ejector, was investigated under various gas and liquid flow rates. The rates of ozone absorption increased with the increase of gas and liquid flow rates, owing to small bubbles generated by the Karman mixer. To evaluate the practicability of the Karman contactor as an ozonation unit, the volumetric mass transfer coefficient of ozone was compared between the Karman contactor and the other contactors reported. The Karman contactor was evaluated as a desirable small-scale ozonation unit. (C) 2004 Elsevier B.V. All rights reserved.