The biofilter Fig. 1 was made from a transparent Plexiglas tube having a 15.3-cm internal diameter. It
was divided into three 45-cm high sections, each section being filled to a height of 33-cm with equal amounts
of the prepared filter-bed material. In order to support the filter-bed and to ensure homogeneous radial distribution
of the input gas, a stainless steel mesh was installed at the base of each section. These supports
were reinforced with stainless steel rods in order to bear the weight of the wet filter material. The biofilter
was fed by a measured primary airflow, provided by a continuous compressed air source, the delivered air
flowing through a water column in order to become fully saturated. A secondary fraction of the main airflow was directed to a ‘bubbler’ unit containing the liquid toluene reagent (Fischer Scientific, 99.9% pure).
The now ‘pollutant’-saturated gas was carried through Teflon-internally-coated tubing in order to prevent
toluene reaction with the tube material. The previous separate gas flows were then mixed together and the
resultant polluted humid input gas mixture was carried to the base of the biofilter