A biofilter column inoculated with Pseudontonas putida F1 was operated to study cometabolic biodegradation of trichloroethylene (TCE) gas using toluene as a primary substrate. Variations in the efficiency and capacity of TCE elimination with different inlet concentrations of toluene and TCE were investigated in order to understand the competitive inhibition between toluene and TCE. Two toluene feeding methods, stage feeding along the column and cyclic feeding, were examined as strategies to enhance TCE cometabolic biodegradation by avoiding the toluene inhibition of TCE biodegradation and the toxic effect of TCE on cells and toluene dioxygenase enzymes. It was concluded that both methods are promising and that the determination of a suitable feeding frequency, recovery period, and inlet toluene concentration was required to optimize cyclic feeding in the cometabolic biodegradation of TCE.