The application of a nanofiltration membrane bioreactor (NF-MBR) has been investigated for the treatment of two pharmaceutical compounds (cyclophosphamide and ciprofloxacine). A new type of ceramic nanofiltration (NF) membrane has been employed for the filtration of acclimated activated sludge artificially doped by these antibiotics. The performance of the NF-MBR was monitored during approximately 4 months, in order to evaluate the long term operational stability of the system and the potential effect of the high sludge retention time on antibiotics degradation. The hypothesis of this study lies in the development of NF membrane and its cut-off support in order to (i) retain micropollutants and (ii) increase micropollutant concentration in the bioreactor. The two antibiotics are weakly degraded even with acclimated sludge, and only a small fraction of these compounds was retained when the fouling of the membrane increased. COD, total suspended solids (TSS) and colour were effectively removed. No unclogging operation was necessary (4 months of operation without chemical cleaning). The biodegradability, retention and adsorption mechanisms have been also studied. (C) 2012 Elsevier B.V. All rights reserved.