Textile processing industries are widespread in developing countries. Among the various processes in the textile industry, the dyeing process uses large volumes of water for dyeing, fixing and washing. Textile industry wastewater is characterized by suspended particles, salts, high pH and high chemical oxygen demand (COD) concentrations that discarding of these toxic wastewaters to the environment will cause a major problem. In this study, electrochemical oxidation of Reactive Black 5 (RB5) dye using bipolar trickle tower (BTT) reactor and Raschig ring shaped boron-doped diamond (BDD) electrodes in recirculated batch mode was fulfilled. Experimental parameters like flow rate, sodium sulfate concentration (Na2SO4) as supporting electrolyte, initial pH, current density and initial dye concentration were examined. The best experimental conditions obtained were as follows: current density 1 mA cm(-2), natural pH, flow rate 100 mL min(-1), Na2SO4 concentration 0.02 mol L-1. Under these conditions, 97% color, similar to 51% COD and 29.3% TOC removal were achieved. Toxicity of RB5 solution was also decreased relatively to its initial toxicity value at the same conditions. (C) 2011 Elsevier B.V. All rights reserved.