Three laboratory-scale sequence batch reactors were set up in this study. It was found that a successfully established sulfate-reducing system - operating at COD/SO42- ratio of 5.0 - could speed up the start-up process, leading to a high performance. It took about 100 and 60 days, respectively, for a non-sulfate-reducing system and a sulfate-reducing control system to achieve stable and high removal of NB. However, it maintained a complete NB removal in sulfate-reducing system throughout the study. Rapid and stable NB reduction was coupled to the on-going sulfate reducing process. Denaturing gradient gel electrophoresis profile demonstrated that the predominant bacterial groups in the non-sulfate-reducing system and the sulfate-reducing control system were affiliated to Deltaproteobacterium and Acinetobacter. while in the sulfate-reducing system were sulfate-reducing and sulfur-oxidizing bacteria. (C) 2012 Elsevier Ltd. All rights reserved.