INDIRECT OXIDATION EFFECT IN ELECTROCHEMICAL OXIDATION TREATMENT OF LANDFILL LEACHATE

Treatment of a low BOD/COD ratio landfill leachate was conducted by means of electrochemical oxidation process in this investigation. Under the operating conditions of 15 A/dm(2) current density and 7500 mg/l additional chloride concentration, 92% of the COD in the landfall leachate was removed after electrolysis for 240 min with a ternary Sn-Pd-Ru oxide-coated titanium (SPR) anode. At the same time, about 2600 mg/l of ammonium in the landfill leachate was also removed completely. These results indicate that the electrochemical oxidation process is effective in removing pollutants from landfill leachate. In this investigation, the effects of operating parameters including anode material, current density, and chloride concentration on both chlorine/hypochlorite production and landfill leachate treatment efficiency were studied. It was found that the operating factors have the same effects on both chlorine/hypochlorite production efficiency and landfill leachate treatment efficiency. The results suggest that the removal of pollutants from landfill leachate by electrochemical oxidation process could be mainly attributed to the indirect oxidation effect of chlorine/hypochlorite produced during the electrolysis. Among the four anode materials investigated in this study, including graphite, PbO2/Ti, DSA(R), and SPR anodes, the SPR anode having a high electrocatalytic activity gave the best chlorine/hypochlorite production efficiency and landfill leachate treatment efficiency. In addition, the increases in both operating current density and chloride concentration also enhanced the indirect oxidation effect in the electrochemical oxidation treatment of landfill leachate.