This study investigated the reduction of the chemical oxygen demand from the Kermanshah oil refinery wastewater using Fenton and Photo-Fenton processes. The study investigated the effects of operating variables such as ultraviolet light intensity in values of 0, 15, and 30 W, ferrous ion concentration in values of 10, 50, and 90 mg/l, hydrogen peroxide concentration in values of 100, 500 and, 900 mg/l, and treatment time in values of 30, 90, and 150 min on the reduction of the chemical oxygen demand percentage from this industrial wastewater. All the experiments were carried out in a glass reactor at a temperature of 25 ℃ under a stirrer speed of 350 rpm. Using the Box-Behnken experimental method, 27 experiments were performed randomly. Then, using the least-squares error method, an experimental quadratic model was achieved. Analysis of variance of the model showed that the proposed model had a high level of accuracy. Finally, we obtained the optimum conditions for maximizing the percentage of the chemical oxygen demand removal from the wastewater. The optimal conditions were Fe2+ concentration of 89.2 mg/l, H2O2 concentration of 119.9 mg/l, and treatment time of 135.9 min for the Fenton process. Also, these conditions were Fe2+ concentration of 35.1 mg/l, H2O2 concentration of 110.2 mg/l, treatment time of 92.8 min, and ultraviolet light intensity of 30 W, for the photo-Fenton process. Under these conditions, the percentage of chemical oxygen demand removal using the proposed model was 96.61 % and 92.82 % for the Fenton and photo-Fenton processes, respectively.
