A biofiltration system was developed to treat benzene, toluene, ethylbenzene, and xylene (BTEX) and Hg�
vapour from a petrochemical waste stream during overhaul maintenance. The biofilter compost bed was
inoculated with a microbial consortium provided by a petrochemical wastewater treatment plant. The
effect of the a BTEX concentration (192.6e973.8 g/m3h) and empty bed residence time (EBRT) of 20
e100 s were studied under the conditions of steady state, transient, shock BTEX-loading, and off-restart.
The findings revealed that during a biofilter start-up, an increase in the influent BTEX concentration to
around 334.3 g/m3h did not notably affect the biofiltration function at an EBRT of 100 s, and the removal
efficiency was higher than 98%. Further, the low EBRT of 60 s did not have adverse effects on the BTEX
and Hg� biofiltration (the removal efficiency in both was >93%). For the biofiltration system, the BTEX
and Hg� critical attenuation capacity were obtained as 663 gBTEX/m3h and 12.6 gHg�/m3h respectively. A
maximum attenuation capacity of 774.5 gBTEX/m3h was achieved in the biofilter when the BTEX loading
rate was 973.8 gBTEX/m3h. The parameters of km and rmax of the MichaeliseMenten kinetic model were
obtained as 0.099 g/m3 and 0.578 g/m3min respectively. Both BTEX and mercury vapours were
completely mass balanced during a continuous biofiltration test. In general, the developed treatment
system exhibited a good performance in the treatment of the BTEX stream containing Hg� vapour in the
off-gas of a petrochemical compan
