Trickle Bed Air Biofilter (TBAB) could be an attractive treatment option for removal of hydrophobic Volatile Organic Compounds (VOCs) from air streams. In this study, three independent parallel laboratory-scale TBABs were run simultaneously to degrade n-hexane, a hydrophobic VOC known to be difficult to degrade. The loading rate of n-hexane varied from 13.4 and 47.7 g/(m(3) h) (1.14-4.04 kg COD/(m(3) day)). The experimental plan was designed to operate one TBAB at pH 7, another at pH 7 utilizing surfactant for enhancing the solubility of n-hexane, and finally a third one operating at pH 4 to promote fungi growth. Elimination capacities up to 38.7 g/(m(3) h) (3.28 kg COD/(m(3) day)) were observed with a removal efficiency of 90% for the TBAB operating at pH 4. The operating conditions for the TBABs include 120 s of Empty Bed Residence Time (EBRT). 1.4 L/min air flow rate and fixed temperature of 20 degrees C. Biomass control within the TBAB was investigated through two strategies, namely, stagnation (off flow for 2 days/week) and flow switching. (C) 2010 Elsevier B.V. All rights reserved.