Electrochemical treatment of landfill leachate:: Oxidation at Ti/PbO2 and Ti/SnO2 anodes

Leachate originating in landfills where municipal solid wastes are disposed is a wastewater with a complex composition that could have a high environmental impact. The primary goal of this research was to investigate the feasibility of removing refractory organic pollutants and ammonium nitrogen from landfill leachate by electrochemical oxidation. The effects of current density, pH, and chloride concentration on the removal of both chemical oxygen demand (COD) and ammonium nitrogen were investigated. Titanium coated with lead dioxide (PbO2) or tin dioxide (SnO2) was used as the anode. An effective process was achieved in which the leachate was decolorized, COD was removed up to a value of 100 mg L-1, and ammonia was totally eliminated. Average current efficiency of about 30% was measured for a decrease of COD from 1200 to 150 mg L-1, while efficiency of about 10% was measured for a near complete removal of ammonium nitrogen, starting from an initial value of 380 mg L-1. Results indicated that the organic load was removed by both direct and indirect oxidation. Indirect oxidation by chlorine or hypochlorite originating from oxidation of chlorides is believed to be mainly responsible for the nitrogen removal.