Biological treatment of domestic sewage was accomplished in a pilot-scale modified sequencing batch biofilm reactor (SBBR) bio-augmented with consortium of 5 strains of indigenous bacteria (genus Pseudomonas and Bacillus). The reactor consisted of fibrous filler in the upper and ceramsite filter media in the bottom. It demonstrated to have a short hydraulic residence time (HRT) for 10 h and good quality effluent to cope with low C/N ratio domestic wastewater. The biofilm attached fibrous fillers mainly contributed to contaminants removal. Bio-augmentation dramatically enhanced the removal efficiency of chemical oxygen demand (COD), total phosphorus (TP), and especially total nitrogen (TN), which increased respectively from 80.3%, 58.1% and 41.3% to 83.7%, 67.8% and 58.7%. Polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) technique indicated the 5 strains' survival in the reactor and that Bacillus cereus strain ZQN2 was the most dominant bacteria. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.