Applicability of electrochemical methods to carwash wastewaters for reuse. Part 2: Electrocoagulation and anodic oxidation integrated process.

In this work a combined two-step process consisting in the electrochemical coagulation with iron anodes and the electrochemical oxidation with boron-doped diamond anode (BDD) was developed for the treatment of a real carwash wastewater. The effects of important operating parameters such as current density, electrolysis time and pH on the surfactants oxidation, COD removal and energy consumptions during electrocoagulation have been explored. Furthermore, the effect of current density on the performance of anodic oxidation has been studied. The experimental results revealed that in the optimal experimental conditions (actual pH 6.4, electrolysis time 6 minutes and applied current 2 mA cm-2) the electrocoagulation method is able to remove 75% of COD in with low energy consumption, about 0.14 kWh m-3. The complete COD removal of the wastewater was achieved by the overall combined process where the residual organics coming from the electrocoagulation are degraded by electrochemical oxidation applying a current of 10 mA cm-2. The energy consumption and the electrolysis time for the complete mineralization of the carwash wastewater were 12 kWh m-3 and 100 minutes, respectively.