David Llewellyn^1,2, Alan Darlington^2,3, Jeff Mallany² and Michael Dixon²

ABSTRACT
Biofiltration is a promising alternative to ventilation for maintaining indoor air quality. Researchers at the University of Guelph have developed a thin-layer trickle-bed biofiltration system that is capable of removing a variety of volatile organic compounds (VOCs) at very low concentrations and high airflow rates. This study investigated the removal of toluene and methylethylketone (MEK) at airflows from 0.025 to 0.4 m s^-1. Influent VOC concentrations followed a diurnal pattern; ranging from 10 to 80 ppbv, the resulting loading rates (per VOC) ranged from 0.5 to 10 g m-3 hr-1. The packing materials consisted of a range of synthetic polyester fibre materials and a coconut fibre mat.Ê The biofilters operated under first order kinetics for MEK elimination over the range of airflow. However, the biofilters switched from first order to zero order toluene elimination at airflows over 0.1 m s^-1. This suggests that, under higher loading rates, toluene elimination became microbially limiting whereas MEK was substrate limited. The biofilters attained maximum elimination rates of 4.0 and 1.6 g m^-3 h^-1 for MEK and toluene respectively. In recirculating air streams, elimination rates are more critical than single-pass removal efficiency. Hence, airflow should be adjusted towards attaining maximum elimination rates. These results will help define the optimum engineering specifications for incorporation of this technology into conventional building air handling systems.

² Division of Horticultural Science, Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada, N1G 2W1

³ Air Quality Solutions Ltd., 55 Callander Dr., Guelph, Ontario, Canada, N1E 4H6