Phase III lasted from day 99 to 114. As shown in Fig. 1, BTEX removal
efficiencies of phase III decreased from 99.50 to 69.48%,
99.01 to 70.63%, 97. 66 to 70.0% and 98.18 to 71.69%, respectively.
Flow rate of the gas mixture and average concentration of BTEX
were maintained at 5 L min1 (EBRT of 1.84 min) and at 0.3026,
0.3006, 0.3001 and 0.3009 g m3, respectively so that the average
organic loading rate to the biofilter was increased to 39.270 g m3 -
h1.