The aim of this study was to compare the performance of coagulation, Fenton's oxidation (Fe2+/H2O2) ozonation for the removal of chemical oxygen demand (COD) and colour from biologically pretreated textile wastewater. FeSO4 and FeCl3 were used as coagulants at varying doses and varying colour removal efficiency was measured. For the Fenton process, COD and colour removal efficiencies were found to be 78% and 95% for the Fenton process, and to be 64% and 71% for the Fenton-like process (Fe3+/H2O2), respectively. Ozonation experiments were conducted at different initial pH values and fixed ozone doses. Ozonation resulted in 43% COD and 97% colour removal whereas these rates increased to 54% and 99% when 5 mg/l hydrogen peroxide was added to the wastewater before ozonation at the same dose. The operating costs of all proposed treatment systems were also evaluated in this study. © 2006 The Authors. Journal compilation © 2006 Society of Dyers and Colourists.