[EN]Fresh water sources are under pressure globally by the increasing population and consequently increasing production, which increases the water demand day by day. Thus, decreasing the industrial fresh water demand and wastewater production became crucial both for the water availability in the future and for its impact to the environment. This study examined the ozone-based treatments as the possible solution to a refinery to treat the effluent already treated by the traditional techniques to reach the final requirements for reuse and recycle purposes. The screening tests performed by fractional factorial design revealed that the significant parameters for the treatment were ozone feed ratio, H2O2 amount and processing time while pH was found insignificant for this case. Based on the box-Behnken response surface methodology for effluent collected after biological treatment, the significant parameters were optimized as the ozone ratio of 0.9 g/h, H2O2 amount of 47 mg/L and 60 min duration. However, in case of increasing the H2O2 amount to 80 mg/L the duration can be minimized to 37.5 min decreasing the energy and reagent consumption costs by a 37%, reaching a final total organic carbon (TOC) under 4 mg/L, that is the target for reuse possibilities.
