A post-denitrification (PDN) is an interesting option for compact biological nitrogen removal scheme in a biofilm-MBR (BF-MBR). Stable nitrogen removal rates were obtained by applying a C/N ratio of 4.5. Fouling potential of effluent and overall performance of a PDN configuration is investigated and compared with the performance of a nitrification (NR) configuration. Higher fouling potential of colloidal organic matter was indentified to dominate in the PDN configuration. Furthermore, stable settling characteristics of concentrate resulted in better solids separation. Periodical backwashing with moderate air scouring rates was found to be a promising strategy for fouling control in BF-MBR with a post-denitrification configuration. (C) 2011 Elsevier B.V. All rights reserved.