Abstract
Two laboratory‐scale biofilters filled with the same type of packing material were operated at different gas flow rates and influent concentrations of toluene and xylene in order to investigate their performance in treating waste gas streams. The columns contained a mixture of municipal compost as a base material and wood chips as a bulking agent in an 80:20 ratio; the porosity was 54%. Microbial acclimation was achieved by addition of nutrient‐enriched solution along with pollutants for a week by daily mixing and natural aeration. During the start‐up of the systems with inlet concentrations of 20 and 70 ppm for toluene and xylene, respectively, high biomass growth resulted in pressure drops in excess of 2000 Pam^−1^. Under steady state conditions, the response of each biofilter to variations in contaminant mass loading was studied by either changing the influent concentration or flow rate of the inlet waste stream. The results show that organic loading rates of up to 110 and 150 gm^−3^h^−1^ can be handled without any indication of the elimination capacity being saturated. However, maintaining the pressure drop below 1000 Pam^−1^ to avoid operational problems, optimal organic loading rates for toluene and xylene of 78 ± 8 and 80 ± 14 gm^−3^h^−1^ respectively are suggested for an HRT value of 60 s. Under these conditions, elimination capacities of 73 ± 4 and 73 ± 14 gm^−3^h^−1^ and removal efficiencies of 94 ± 6% and 91 ± 8% were achieved for toluene and xylene, respectively. Copyright © 2003 Society of Chemical Industry