This work seeks to improve the robustness of vapour phase bioscrubbing by applying an absorber prior to a bioscrubber during the dynamic treatment of sequentially alternating loads of inhibitory pollutants. Rhizobiales sp. strain F11 and Xanthobacter autotrophicus sp. GJ10, exhibiting specific degradation capabilities for fluorobenzene (FB) and 1,2-dichloroethane (DCE), respectively, were used as a compound-strain model system. The stability of a combined oil-absorber-bioscrubber (OAB) was compared to the stability of a bioscrubber only (BO) system, during sequentially alternating periods (duration 3-6d) of FB and DCE in the gas feed. The OAB achieved > 66% degradation of FB, while in the BO system the FB removal efficiency dropped to 0% upon restoring FB feed after a 3 d FB starvation period. Following 6 d of FB starvation the BO failed to recover within 10 d, while the OAB required only 2 d to recover. In contrast, during the DCE treatment periods the OAB system did not show any advantage over the BO system. Further investigation showed that the F- (a main metabolic product from FB degradation) has a strong inhibitory effect on strain GJ10 even at concentrations below 50mg L-1. In the OAB system the inhibitory effect persisted for longer periods due to the absorber, which continued to supply FB to the system, and caused deterioration in the DCE removal efficiency. The inhibition of the microbial culture was confirmed by fluorescence in situ hybridisation (FISH), which showed that the activity of cells was reduced when only FB was fed. The results of this study have shown that in the presence of an inhibitory metabolic product the OAB system may not effectively improve the biological treatment of waste gas during sequential alternations in the feed of inhibitory pollutants. (C) 2007 Elsevier Ltd. All rights reserved.