Degradation of biologically treated landfill leachate by using electrochemical process combined with UV irradiation

Leachate originated from landfills, where municipal solid wastes (MSWs) were disposed, was of complex compositions that could have a high environmental impact. The primary aim of this work was to provide a feasible and effective way to remove biorefractory organics and ammonium-nitrogen from landfill leachate by electrochemical process combined with UV irradiation. A nonphotoactive RuO2/Ti electrode was selected as anode and comparative treatments were investigated. At the natural pH and without addition of electrolyte, about 100% of color and NH3-N, and 80% of TOC in the leachate were removed with a current density of 50 mA cm−2 followed by a final COD reduction from 560 mg L−1 to less than 50 mg L−1, which was by far better than single electrochemical process. Moreover, the kinetic analysis also proved that a synergetic effect was observed by combining UV irradiation with electrochemical process in the treatment of landfill leachate. The variations of active chlorine and ESR results together indicated that the in situ electrogenerated active chlorine and in situ photogenerated radical species in the bulk of solution should be responsible for the synergetic effect. In addition, excitation emission matrix (EEM) and gel permeation chromatography (GPC) spectra indicated that the humic and fulvic substances in the leachate were preferentially degraded.