Decolorization of 1-amino-4-bromoanthraquinone-2-sulfonic acid (ABAS) in a Sphingomonas xenophaga-augmented membrane bioreactor was investigated. The results showed that sequencing bioaugmented membrane bioreactor (SMBR) could run stably for 60 days. During the process. over 99% ABAS (570 mg/L) was decolorized and 60% COD was removed. Moreover, the yellow intermediate produced in continuous operation mode was not detected in SMBR. It was probably a dimer resulting from the autoxidation of 2-amino-3-hydroxy-5-bromobenzenesulfonic acid. Ribosomal intergenic sequence analysis (RISA) of the sludge in SMBR suggested that bioaugmentation resulted in large decrease or increase of certain population and Strain QYY can persist in SMBR. The biomass of membrane surface in SMBR could be further divided into a cake layer and a dense layer. The former is mainly composed of coccus, bacillus and filamentous bacteria, which is different from suspended sludge flocs with predominant bacillus. (C) 2009 Elsevier Ltd. All rights reserved.