A Combined Electrocoagulation-Electrooxidation Process for Carwash Wastewater Reclamation

Wastewater from a carwash was treated by a combined electrocoagulation and electrooxidation process. Electrocoagulation is effective at reducing organics, but even more so when coupled with electrooxidation. Electrocoagulation with iron and aluminum produced similar results, but iron imparted color to the solution, so aluminum was used. Aluminum electrocoagulation at pH 7 with a current density of 150 A/m2 for 60 min reduced turbidity by 98%, color by 96%, oils by 92%, chemical oxygen demand by 76%, biochemical oxygen demand by 74%, and methylene blue active substances by 56%. The electrooxidation process with BDD electrodes at 210 A/m2 for 120 min was effective in reducing chemical oxygen demand 82%, color 81%, methylene blue active substances 81%, biochemical oxygen demand 73%, and chlorides 72%. The combined process was very effective in reducing oils 100%, color 99.3%, turbidity 98.4%, chemical oxygen demand 96%, biochemical oxygen demand 93% and methylene blue active substances 92%. Finally, the organic characteristics of the wastewater are well below the limits set by the governments of Mexico and the US. However, it could also be reused as wash water in the carwash.