In this paper, a technique of hydrogen recovery from an electrocoagulation process treating dye-containing wastewater is presented. The electrocoagulation system used consists of a continuous-mode electrocoagulator connected with a gas separation tank and two sedimenters. It is shown that a significant amount of hydrogen can be harvested using the gas separation tank whose configuration follows that of a conventional upflow anaerobic sludge bed. The experimental hydrogen yields obtained were comparable with those calculated from theory. The electrical energy demand of the electrocoagulation process for treating Reactive Blue 140 and Direct Red 23 was 1.42 and 0.69 kWh(e) m(-3), respectively, while the energy yield of harvested hydrogen was 0.2 kWh m(-3). The quality of water treated by the electrocoagulation system was satisfactory, i.e., the color, COD and TS removal were 99%, 93% and 89%, respectively. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.