The evolution patterns of temperature, pH, and voltage during the removal of chemical oxygen demand from a landfill leachate using electrocoagulation under different conditions

Evaluation of electrochemical and O3/UV/H2O2 methods at various combinations during treatment of mature landfill leachate

In this study, electrochemical treatment and application of O₃/UV/H₂O₂ in various combinations were evaluated in respect to their efficiency to depurate mature landfill leachate. Based on preliminary experiments, electrochemical treatment using stainless-steel electrodes at 2 cm gap was performed optimally at 50 mA/cm² and pH 6, while application of O₃ at 120 L/h, UV at 991 J/cm² and H₂O₂ concentration of 1 g/L was carried out. Electrochemical treatment and O₃/UV/H₂O₂ under optimal conditions were applied as follows: I) electrochemical treatment, followed by O₃/UV/H₂O₂ and solids precipitation, II) electrochemical treatment, followed by precipitation and then by O₃/UV/H₂O₂ treatment, and III) O₃/UV/H₂O₂, followed by electrochemical treatment. A low performance was observed when O₃/UV/H₂O₂ preceding electrochemical treatment. Solids, TKN and total COD (tCON) removal was primarily achieved through electrocoagulation, whereas color and soluble COD (sCOD) reduction was mainly attributed to electrochemical oxidation. Experimental setup I was the most efficient treatment scheme, resulting in tCOD, sCOD, TKN, TSS, SAC_UV254nm and color number reduction of 73%, 80%, 76%, 79%, 94% and 98%, respectively. Indeed, O₃/UV/H₂O₂ step could be omitted since its effectiveness was restricted during landfill leachate treatment. In conclusion, electrochemical treatment followed by precipitation could result in effective reduction of nutrients and color.