The enhancement of biodegradability index of mature landfill leachate by electrochemical oxidation process using boron-doped diamond and dimensionally stable anode

Mature solid waste landfill produces stabilized leachate with extremely low biodegradability. It renders the leachate biologically untreatable. Therefore, a pretreatment aimed to increase leachate biodegradability deems necessary prior to biological treatment. The objective of this study is to investigate the effectiveness of electrochemical oxidation process in enhancing leachate's index of biodegradability, expressed as BOD₅/COD ratio. Different types of anodes were employed, namely DSA (dimensionally stable anodes) and BDD (boron-doped diamond), to represent active and non-active anode, respectively. A 2, 1.5, and 1 L leachate samples were treated in a batch recirculation reactor using an 80 mL single compartment electrochemical cell where the initial pH was set to 3, and flow rate to 5 mL s⁻¹. The reactor was operated under constant current, with current densities of 10, 30, and 50 mA cm⁻². Both DSA anode and BDD anode were successfully reached the targeted BOD₅/COD ratio above 0.5, as an indication of biological treatability of pretreated leachate. The highest BOD₅/COD ratio of 0.5759 and 0.5999 was obtained using BDD and DSA after 15 and 120 min, respectively, under the current density of 30 mA cm⁻². Under this current density, BDD and DSA capable of removing COD up to 72% and 67%, respectively, after 4-h electrochemical oxidation.