The feasibility of removing ammonium from landfill leachates by electrochemical oxidation was studied. Raw leachates and biologically/physico-chemically pretreated leachates from a municipal landfill site were treated. Boron doped diamond was used as anode and stainless steel as cathode, both electrodes with an area of 70cm(2). The effects of the applied current density (15-90 mA cm(-2)), the initial ammonium concentration (480-2000 mg L-1), and the initial chloride concentration were experimentally studied. Total ammonium removal was obtained after 360 min of processing and almost half of the initial ammonium nitrogen was oxidized to nitrate. On the other hand, the concentration of chloride enhanced the rate of ammonium oxidation. In addition, the amount of N-NH4+ transformed into N-NO3- decreased when additional chloride was provided. (c) 2007 Elsevier B.V. All rights reserved.