During phase I, the gas flow rate was kept constant at 3 L min1 corresponding to EBRT of 3.06 min. The inlet concentrations of BTEX were increased gradually in the range of 0.2975–0.3063, 0.2926–0.3057, 0.2949–0.3059 and 0.2993–0.3033, respectively and were maintained constant to stabilized steady state.