The performance of a trickle-bed air biofilter (TBAB) treating isopropyl alcohol (IPA) and acetone (ACE) mixtures was investigated under different gas flow rates and influent concentrations. In pseudo-steady-state conditions, the elimination capacities of IPA and ACE increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of IPA were higher than those of ACE, indicating that IPA is a preferred substrate in the IPA and ACE mixtures. More than 90% removal efficiencies were achieved with influent carbon loadings of IPA and ACE below 80 and 53 g/m(3.)h, respectively. The TBAB appears efficient for controlling mixed IPA and ACE emission with low to medium carbon loadings. Applicable operating conditions of TBAB for treating mixed IPA and ACE emission were suggested. (C) 2003 Elsevier Science Ltd. All rights reserved.