In this study, the use of a cocurrent downflow jet pump contactor for possible ozone disinfection was demonstrated. The results showed that this type of reactor has an advantage over conventional contactors such as bubble columns and U-tube columns since it showed a high mass transfer coefficient. Interestingly, the mass transfer coefficient is found to be nearly independent of the gas to liquid volumetric flow ratio (QG/QL). The explanation and the empirical correlation for mass transfer coefficient (kLa) also are described in this paper.