The chemical treatability of a nonbiodegradable textile dye carrier by single ozonation and ozonation enhanced by ferrous iron salt (FeSO4 (.) 7H(2)O) and granular activated carbon (GAC) addition has been reported. First, the single effects of Fe2+ and Fe3+ salts (100-1,000 mg L-1 at pH = 11) and GAC (1-10 g L-1 at pH = 3) addition have been examined to explain their effects in combination with ozone. Thereafter, the investigated pollutant has been subjected to oxidative treatment via direct ozonation at pH = 3 (the natural PH of carrier added textile dye-baths) to reduce its chemical oxygen demand (COD) and thereby to improve its biodegradability in terms of the 5-day biochemical oxygen demand (BOD5), which is a useful sum parameter for biological treatability evaluation. A kinetic study was also conducted in which time-dependent changes in COD as well as in outlet partial ozone pressure have been measured throughout the ozonation process. These have been used to determine k(COD), the bimolecular reaction rate constant for COD abatement that has been found as 81 M-1 min(-1). Finally, it could established that the addition of only 1 mM (56 mg L-1) Fe2+ considerably enhanced COD abatement, speculatively by acting as a redox catalyst, whereas the effect of GAC was rather additive. The biodegradability of the textile dye carrier (initial BOD5 approximate to 0) increased to 70, 109, and 140 mg L-1 after oxidative treatment with O-3, Fe(II)/O-3, and GAC/O-3, respectively, supporting the possibility of chemical pretreatment with enhanced ozonation process at reasonable ozone doses (0.7 mgO(3) mg L-1 CODo).