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, SACUV254nm 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.
Keywords: Mature landfill leachate; O3/UV/H2O2; advanced oxidation processes; electrochemical oxidation; electrocoagulation.