Treatment of petroleum refinery wastewater by electrochemical methods

Direct and indirect electrochemical oxidation by using boron doped diamond anode (BDD), direct electrochemical oxidation by using ruthenium mixed metal oxide (Ru-MMO) electrode, and electrofenton and electrocoagulation by using iron electrode were investigated for the treatment of petroleum refinery wastewater (PRW). The results have been given at the best operational conditions which were obtained for each electrochemical method. The results obtained from electrochemical methods were compared to each other. Complete phenol and COD removal can be achieved in almost all electrochemical methods, except electrocoagulation, provided that electrolysis time is prolonged. The most efficient method was the electrofenton process followed by the electrochemical oxidation using BDD anode. Phenol removal of 98.74% was achieved in 6 min of electrolysis and COD removal of 75.71% was reached after 9 min of electrolysis in electrofenton. Additionally, 99.53% phenol and 96.04% COD removal were obtained in direct electrochemical oxidation at the current density of 5 mA/cm2. Initial phenol concentration was reduced to final phenol concentration of 0.91 mg/L after 40 min of electrolysis, and initial COD decreased to 36.7 mg/L and 23.3 mg/L after 60 min and 75 min of electrolysis, respectively. Electrocoagulation was found to be ineffective for the treatment of PRW.