Comparative Analysis of Sequential Electrooxidation and Electrocoagulation Processes for Leachate Treatment

This study aims to improve the removal efficiency of chemical oxygen demand (COD), NH₃-N, and turbidity from Bingöl leachate through a sequential electrochemical process. This process includes electrooxidation (EO) with Ti/PdO-CoO anodes and stainless-steel cathodes, followed by electrocoagulation (EC) with aluminum anodes and stainless-steel cathodes. The sequential electrochemical process lasted 400 min, consisting of 360 min of EO followed by 40 min of EC process. At pH 5, COD and turbidity reached optimal removal efficiencies of 89% and 99.9%, respectively, while NH₃-N achieved 88.5% at pH 9.5. These results indicate that the sequential electrochemical process was most effective under these pH values for removing organic matter, nitrogen, and suspended solids. The sequential electrochemical process led to significant improvements in the removal efficiencies of COD, NH₃-N, and turbidity, with increases of 32.5%, 44%, and 6.9%, respectively, compared to the EO process. The sequential electrochemical process showed improvements of 9.5% in COD and NH₃-N removal, and 1.2% in turbidity removal, compared to the results of the EC process. The pseudo-first-order (PFO) reaction rates for the EO and EC processes were determined, resulting in high R2 values (0.98–0.99). Additionally, the total consumption cost of the EO process was higher than that of the EC process. After the sequential electrochemical process, the consumption cost increased from $13.586/kg COD to $24.332/kg COD as the current density increased from 15 mA/cm2 to 25 mA/cm2.