Water is quickly becoming both scarce and very expensive. Thus, it has become necessary for every industry to examine proposals for the purification and re-use of their wastewater and effluent streams. The Textile industry is one of the largest industrial consumers of water. Predominantly. wastewater from textile industry contains large amounts of dye and dyeing agents, as well as mordant and sizing agents. Current advanced oxidation processes (AOPs) which include ozone, photochemical and photo catalytic oxidation are techniques used for the treatment of such wastewater. Although AOPs are relatively expensive, they appear to be the most likely candidates for full-scale dye house effluent decolouration. The ozonation of wastewater containing four different textile reactive dyestuffs in a semi-batch reactor have been studied. Various ozonation conditions - ozone dose, ozone consumption efficiency, etc. - were explored and studied for these various types of dyestuffs. The mass transfer coefficient of ozone in water and its relationship to the ozone efficiency was studied. Pseudo-first order decolouration rate constants for all dyestuffs were determined experimentally. (C) 2010 Elsevier B.V. All rights reserved.