Applicability of electrochemical methods to carwash wastewaters for reuse. Part 1: Anodic oxidation with diamond and lead dioxide anodes

The anodic oxidation of a real carwash wastewater has been comparatively studied using lead dioxide (PbO2) and boron-doped diamond (BDD) anodes in an electrolytic flow cell. The influence of several operating parameters such as current (from 1A to 3A), liquid flow rate (from 100 to 300 dm3 h−1) and temperature (25 °C and 40 °C) on the performance of both systems with a stainless steel cathode has been studied and the energy consumption has been also evaluated. Surfactants concentration and COD have been monitored during the treatment. Galvanostatic electrolyses always lead to complete COD removal due to the high amounts of effective hydroxyl radicals generated from water oxidation at each anode and the COD removal rate increases with rising applied current and liquid flow rate, while it as almost unaffected by temperature. The performance of the BDD anode is always better than that of PbO2, requiring shorter electrolysis time to reach overall mineralization, thus leading to remarkably higher current efficiency and lower specific energy consumption, that was 375 kWh m−3 and 770 kWh m−3 for BDD and PbO2, respectively.