In this work, pre-ozonation for degradation, decolourization and detoxicifying of a raw textile wastewater collected in a textile fininshing industry, Istanbul (Turkey) is investigated. Differing from the previous studies, a low ozone (O3) flow rate (9.6 mg min-1) was applied at original pH of the wastewater. The effect of pH varying from 5 to 11 and the H2O2 dose of 600 mg l-1 on ozone oxidation were also investigated. The acute toxicity of raw and treated wastewater samples were measured

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... 24 h newborn Daphnia magna. COD, colour in APHA Pt-Co (platin-cobalt) unit and absorbance at 450, 500 and 550 nm wave lengths which were coinciding the peak absorbance band of the raw wastewater were analyzed in treated samples. A 60% of acute toxicity, 92% of and 50% of total COD removal were obtained at original pH of wastewater by applying ozone for 30 min. Absorbed ozone dose was 105 mg l-1 with a ozone transfer rate of 3.5 mg l-1. Varying pH did not improve toxicity removal, however, soluble COD removal increased at 3 and 6% respectively for 9.0 and 11.0 values while colour removal increased (7%) only at 11.0 pH. Adding 600 mg l-1 of H2O2 increased COD removal at 10% after 20 min oxidation. Colour removal increase was more significant in O3/H2O2 oxidation in parallel with the increase in absorbance kinetics. All over results obtained this study are expected to contribute to control the textile industry wastewater pollution and to protect aquatic environment.