Performance of peat biofilter: Impact of the empty bed residence time, temperature and toluene loading

The performance of a pilot-scale peat biofilter in the treatment of air contaminated with toluene has been evaluated in this study. The operational parameters investigated were the empty bed residence time (EBRT), temperature and toluene loading. The EBRT tests were performed at a constant toluene loading of 0.71 kg COD m^-3 per day and a temperature of 11°C. Removal efficiencies over 99% were achieved at an EBRT of 12 min. The removal efficiency exhibited a decreasing trend at lower EBRTs, with the efficiency dropping to as low as 75% at an EBRT of 2 min. The performance of the biofilter was found to be sensitive to temperature. For a toluene loading of 0.45 kg COD m^-3 per day and an EBRT of 2 min, the removal efficiency was 99% at 32.2°C. The removal efficiency data collected at different temperatures correlated reasonably well with a van't Hoff-Arrhenius-type equation. As the toluene loading was increased at the optimal operational temperature, the removal efficiency decreased to as low as 57% at a toluene loading of 1.57 kg COD m^-3 per day. An adequate moisture content (55%-60%) and mineral nutrients for microbial activity in organic media were found to contribute significantly in the consistent long-term performance of the biofilter.