Optimizing electrocoagulation and electro-Fenton process for treating car wash wastewater

Background: Car wash wastewater contains several contaminants such as organic matter, oil, grease, detergents and phosphates, all of which are harmful for the environment. In this study, the applicationof electrocoagulation (EC) to treat car wash wastewater has been studied, and the operating parametersoptimized. The electro-Fenton (EF) for further contaminant removal was also investigated. Methods: In EC process, the effect of pH, current density, and the reaction time of the removalefficiency of chemical oxygen demand (COD), phosphate, and turbidity were investigated using the response surface methodology (RSM). The electrochemical cell consisted of four iron electrodes thatwere connected to a power supply using a monopolar arrangement. In the EF process, the effect of pH, reaction time, and hydrogen peroxide concentration on COD removal efficiency were probed.Results: The optimum pH, current density, and the reaction time for the EC process were 7.3, 4.2 mA cm-2 and 20.3 minutes, respectively. Under these conditions, the COD, phosphate, and turbidity removalpercentages were 80.8%, 94.9% and 85.5%, respectively, and the specific energy consumption was 1.5 kWh m-3. For the EF process, the optimum pH, reaction time, current and hydrogen peroxide dosagewere 3, 10 minutes, 2 A and 500 mg L-1, respectively. The EF showed higher COD removal efficiency (85.6%) with a lower specific energy consumption (0.5 kWh m-3) and reaction time compared to the EC. Conclusion: This study shows that both EC and EF can effectively treat car wash wastewater with high removal efficiency within a short reaction time.