Applications of advanced oxidation processes (Electro‑Fenton and sono‑electro‑Fenton) for COD removal from hospital wastewater: Optimization using response surface methodology

Abstract

This study investigates the feasibility of applying electro-Fenton (EF) and sono-electro-Fenton (SEF) processes for the removal of chemical oxygen demand (COD) from the hospital wastewater generated by the Al-Diwaniyah hospital located in Iraq. The effect of various operational parameters on COD removal was studied based on the response surface methodology (RSM). The optimal conditions for maximum removal of COD using EF were found to be a current density of 19.293 mA/cm2, an H2O2/COD ratio of 1.4, and a time duration of 46.67 min, in which 96.27% COD removal was obtained at a specific energy consumption rate of 7.325 kWh/kg COD. In the EF process, results showed that the H2O2/COD ratio has the most effect on COD removal, with a 61.76% contribution, followed by the current density, which contributed 22.78%. The suitability of the model equation was confirmed by its high R2 value (98.90%). For the SEF system, the best operating conditions were found to be a current density of 10 mA/cm2, an H2O2/COD ratio of 0.2, and a time duration of 46.67 min, in which 88.31% COD removal was obtained at a specific energy consumption of 2.082kWh/kg COD. Adopting the SEF process showed that the specific energy, H2O2, and iron consumptions are lowered by 1/3.5, 1/7, and 1/2, respectively, compared to those observed at the optimum conditions for maximizing EF alone. Results revealed a significant improvement in the EF system when combined with the ultrasonic (US) technique, wherein a considerable amount of COD removal with a final value of COD less than 100 ppm was observed at a lower cost in terms of energy consumption and the chemicals used, thus confirming the role of SEF for treating hospital wastewater using a more efficient and cost-effective approach.