In this paper, a car wash wastewater (CW) was treated by an economic and eco-friendly method called electro-Fenton (EF) technique. The experiments were conducted to investigate the effect of five important variables including reaction time, current density, pH, H2O2/Fe2+ molar ratio and H2O2/Car wash wastewater (mL/L) on the quality characteristics of wastewater such as COD, BOD5, TOC, TSS, heavy metals, EC, surfactants and hardness. By applying Box-Behnken design (BBD) and response surface methodology (RSM), the optimum operating conditions were obtained. The optimum conditions for COD [as a main factor in a wastewater (according to the environmental protocols)] removal of 68.72% were experimentally found at reaction time of 75.80 min, current density of 58.81 mA/cm2, pH of 3.02, volume ratio of H2O2/CW of 1.62 mL/L, H2O2/Fe2+ molar ratio of 3.66.
