The electrocoagulation process is an effective, fast and economic technique for the treatment of water and wastewater. In this paper, electrocoagulation (EC) has been used for the removal of COD, total nitrogen, color, turbidity and bacteria from the Oued Smar (north of Algeria) town landfill leachate, characterized by high chemical oxygen demand, high concentration of nitrogen and black color. Firstly, the effects of process variables such as inter-electrode distance, magnetic stirring speed, current density and electrode material on the treatment efficiency, sludge volume production, pH and temperature evolution during the EC process were studied. Secondly, energy consumption and operating costs were calculated with aluminium and iron electrodes under the same experimental conditions. The findings, in this study show that an increase in current density (125-500 A/m(2)) enhanced the speed of treatment significantly, the inter-electrode distance was 2.8 cm and the stirring speed was 150 rpm for the studied leachate. The removal efficiencies of COD, total nitrogen, color and turbidity were respectively 70%, 24%, 56%, and 60% with Al electrodes and 68%, 15%, 28%, and 16% with Fe electrodes. Electrical energy consumption and operating cost with Al electrodes were 0.022 (kWh/L), 0.54 (USS/m(leachate treated)(3)), respectively, and 0.019 (kWh/L), 0.47 (US$/m(3)) with Fe electrodes. (C) 2011 Elsevier B.V. All rights reserved.