Ozone integrated with internal micro-electrolysis (O-3/IE) was applied to electrochemically oxidize reactive red X-3B owing to its well-established synergetic effect in the present study. The final removal rates of color, COD, TOC and AOX were found to be 99%, 85%, 59%, and 74%, respectively, when the following optimal conditions were used: dyestuff concentration of 1 g/L with a pH of 9.0, a reaction temperature of 60 degrees C, 400g of iron scraps with the diameter in the range of 0.9-2.0 mm and 10 g/h ozone flow rate. The dominant degradation mechanism of reactive red X-3B was elucidated by the addition of radical scavenger/enhancer. The results indicated that the formation of hydroxyl radicals in the presence of ozone was the major contributing factor in O-3/IE system. (C) 2010 Elsevier B.V. All rights reserved.