BACKGROUND: Textile industries generate considerable amounts of waste-water, which may contain strong colour, suspended particles, salts, high pH and high chemical oxygen demand (COD) concentration. The disposal of these coloured wastewaters poses a major problem for the industry as well as a threat to the environment. In this study, electrochemical oxidation of Basic Blue 3 (BB3) dye was studied in a bipolar trickle tower (BTT) reactor using Raschig ring shaped boron-doped diamond (BDD) electrodes in recirculated batch mode. The effects of current density, temperature, flow rate, sodium sulfate concentration (Na2SO4) as supporting electrolyte, and initial dye concentration were investigated. RESULTS: The best experimental conditions obtained were as follows: current density 0.875 mA cm(-2), temperature 30 degrees C, flow rate 109.5 ml min(-1), Na2SO4 concentration 0.01 mol L-1. Under these conditions, 99% colour and 86.7% COD removal were achieved. Toxicity tests were also performed on BB3 solutions under the best experimental conditions. CONCLUSION: Based on these results, the BDD anode was found to be very successful for the simultaneous degradation of BB3 and removal of COD. Additional toxicity test results also showed that electrochemical treatment using a BDD Raschig ring anode in a BTT reactor is an effective way of reducing toxicity as well as removing colour and COD. (C) 2010 Society of Chemical Industry