Nowadays due to large amounts of wastewaters containing petroleum compounds that are discharged to water resources and also fastidious criteria approved by agencies, effective treatment of these kinds of wastewaters seems to be important. Treatment for these kinds of wastewater is accomplished in two stages. First, a series of pre-treatment steps, in which suspended matters, oil and grease are reduced, and an advanced stage, in which wastewater contaminants are decreased to certain acceptable discharge limits. However, applying conventional processes are inadequate when the wastewater contains highly toxic and recalcitrant compounds. In this case more advanced techniques must be used to degrade these compounds. Advanced oxidation processes are powerful methods to degrade these pollutants and have been increasingly used in recent years. Fenton based are promising methods among advanced oxidation processes that have been applied in treatment of bio-refractory compounds. Unfortunately most of studies related to treatment of wastewaters containing petroleum compounds are focused on treatment singular contaminants or simulated wastewaters. The main purpose of this research is evaluation of Fenton and Photo Fenton in reduction of COD for a wastewater containing petroleum compounds using scrap iron. In order to optimize the process, mass ratios of H2O2 to COD and H2O2 to Fe and pH were used as parameters and COD reduction was considered as the response. At this stage all the experiments were conducted within 90 minutes. All experiments were conducted in batch mode and Response Surface Methodology (RSM) was used for design of experiments. At the next stage, by exerting the optimal conditions on processes, the effect of time on processes and kinetics of reactions were investigated. The results from analysis of variance revealed that all the parameters were statistically significant. More than 83.6% and 91.3 of COD removal were achieved under optimal conditions for Fenton and Photo Fenton processes respectively. According to the experiments, the Photo Fenton process was faster and needed fewer amounts of Fe and hydrogen peroxide in compare to the Fenton process. Kinetics investigation revealed that both Fenton and Photo Fenton processes could be described by a second order reaction model. Overall, this study showed that both Fenton and Photo Fenton processes are capable of deceasing COD and also scrap iron powder could be used as iron salts in processes. Keywords: Petroleum compounds, Fenton based, scrap iron, RSM
