Optimization of hydroxyl radical production using electro-Fenton method for chemical oxygen demand reduction in diluted palm oil mill effluent

Palm oil mill effluent (POME) is a well-known highly polluting wastewater due to its extremely high contents of organic matter, suspended solids and nutrients. In this study, we used electro-Fenton method to treat POME by optimizing OH• generation from hydrogen peroxide (H2O2) under low voltage input (1.5–6.0 V). A set of electro-Fenton system was set up using stainless steel as the anode and graphite as the cathode. Four parameters namely retention times, concentrations of H2O2 as well as FeSO4 catalyst and applied voltages were studied. The results were reflected in the form of removal efficiency of chemical oxygen demand (COD). The optimum conditions to degrade organic matter in POME were found to be in 4 h retention time with the respective H2O2 and FeSO4 catalyst concentrations of 0.05 and 0.10 M, and the power input of 1.5 V. Under such conditions, the maximum COD removal efficiency achieved 94%. The electro-Fenton treatment was found to have higher efficiency than the conventional Fenton treatment. Without the electrolysis, the COD removal efficiency of the conventional Fenton treatment was only 48%.