High loading toluene treatment in a compost based biofilter using up-flow and down-flow swing operation

A compost/ceramic (1:1, v/v) three section laboratory-scale biofilter inoculated with acclimated activated sludge was examined to treat high loading toluene vapors from a synthetic gas stream. The biofilter was operated continuously at different gas flow rates, 0.108-0.15 m3 h−1, with inlet toluene concentrations ranging 0.5-13 g m−3. The overall performance of the biofilter was divided to seven stages according to the mode of operation (down-flow and up-flow) over a period of 102 days. Removal efficiencies ranging from 48 to 100% and elimination capacities ranging from 26 to 180 g m−3 h−1 were observed depending on the initial loading rates and the mode of operations. A maximum elimination capacity of 180 g m−3 h−1 was observed in the last period at an inlet toluene concentration of about 13 g m−3. The results showed that changing the mode of operation (up-flow and down-flow) periodically will improve the performance of the biofilter under high inlet toluene concentration (higher than 4 g m−3). Results obtained in this study provide insight into the possibility of the biofilter to treat high inlet concentrations rather than low concentrations well known in the literature.