This work aimed to study the decolorization of dye wastewater by ozonation membrane contacting process. Three different dyes, i.e., Direct red 23, Acid blue 113 and Reactive red 120 were selected to be used in this work. The effects of operating parameters which were gas and liquid velocity, liquid phase temperature, dye auxiliary reagents were investigated along with the mass transfer study. Membranes used in this work were PVDF and PTFE hollow fiber membranes. The ozone mass transfer performance and long term performance in ozonation by these two different types of membrane were studied. In addition, decolorization performance and kinetic study of ozonation in the batch system with various operating parameters and dye types were investigated. From the results, the ozone mass transfer increased with increasing liquid velocity, liquid phase temperature, and with the presence of Na2CO3. On the contrary, the ozone flux was not influenced by gas velocity. PVDF membrane provided higher ozone flux than PTFE, but PTFE membrane gave more stable and higher flux than PVDF for a long operation period. The ozone flux of different types of dye was in the following order: Direct red 23> Reactive red 120> Acid blue 113. Conversely, the decolorization performance of Acid blue 113 was higher than those of Direct red 23 and Reactive red 120. Kinetic analysis showed that decolorization of dyes followed the first order kinetics and the rate constants were in the following order: Acid blue 113> Reactive red 120> Direct red 23. (C) 2010 Elsevier B.V. All rights reserved.