Wastewater treatment through a hybrid electrocoagulation and electro-Fenton process with a porous graphite air-diffusion cathode

Wastewater from hospitals is a major source of pollution, and its treatment to protect the environment is a challenge. Different traditional methods have been applied to treat hospital wastewater (HW). Recently, hybrid processes, such as electrocoagulation (EC) with the electro-Fenton (EF) process, have been found to outperform traditional methods in terms of their high removal rate, low sludge generation and energy consumption and environmental sustainability. Herein, a combined EF process integrated with EC was successfully applied to reduce the chemical O demand (COD) of HW. A batch tubular electrochemical reactor composed of a microporous graphite air diffusion cathode and a hollow cylinder Al anode was used as a new design to remove pollutants from HW. Response surface methodology was adopted to explore the effects of operating factors, which were represented by current density, Fe2+ concentration and time, on COD removal and identify their interactions. The best operating conditions were a current density of 20 mA/cm2, an Fe2+ concentration of 6 mM and a reaction time of 63 min. These conditions yielded a COD removal efficiency (RE %) of 93.5 % with an energy consumption of 18.325 kWh/kg COD. Time had the main effect on the RE % due to the synergistic effect of EC and EF. The hybrid system had higher efficiency and lower energy consumption and sludge production than individual EC or EF. Therefore, combining EC with EF could be a promising approach for the treatment of HW.