Influence of Varying Concentration of Toluene in a Soil Biofilter with Water Content Control

Contaminant concentration affects rate of removal of air contaminant in biofiltration. In this study, extent of degradation rate at varying concentrations of toluene (from 50 to 700 ppm) as the air contaminant in terms of elimination capacity (EC) was measured in a soil biofilter with water content control ran for 215 days. Results showed that no inhibition or oxygen limitation was observed at 700 ppm as EC went higher at this concentration reaching 58 g m-3 hr-1. At low concentrations in the gas stream, toluene was degraded faster than it could diffuse into the biofilm while at high toluene concentrations, the whole biofilm was fully penetrated and there was no increase in EC due to biological activity limitation. Oxygen limitation may influence removal rates even if oxygen is not completely depleted in the biofilm with biofilm thickness as another factor in oxygen limitation. There was growth in the biofilm but it did not produce a biofilm thick enough to give rise to oxygen limitation. Though toluene inhibition and/or oxygen limitation could eventually become influencing factors, biofiltration may be used as an air pollution control technology at varying contaminant concentration.