Gaseous toluene removal by pine-cone/compost biofilter: setup, performance, and optimization

Toluene is one of the most important volatile organic compounds that threaten human health and introduce many environmental problems. Therefore, the present study aims to determine the performance of a biofilter based on pine cones/compost to remove toluene vapors from polluted air streams.

In this research, a biofilter with a volume of 19.468 L was designed and built. The biofilter bed consisted of two parts 26 cm in height and packed with a mixture of compost and pine cones in 1:1 volumetric ratio. After inoculating the bed with sludge from a municipal wastewater treatment plant and making it compatible with toluene, the performance of the biofilter in different parts of the bed was investigated at the inlet toluene concentrations of 2.5-5.5 g/m3 and Empty Bed Retention Times (EBRTs) of 1.3, 1.7, and 2.43 min. Also, the results were analyzed statistically.

At EBRT of 2.43 min and different inlet toluene concentrations of 2.5-5.5 g/m3, the removal efficiency reached 100 percent. Also, the removal efficiency decreased with the reduction of EBRT. The results showed that removal efficiency was higher in the first part of the biofilter bed relate to the second part. At an inlet toluene concentration of 2.62 g/m3 and EBRT of 1.7 min, the maximum elimination capacity (ECmax) of 2.74 g/m3.min was obtained.

In all experimental conditions the outlet concentration of pine-cone/compost biofilter was below the WHO standard (260 µg/m3). Also, the high elimination capacity of biofilter verified its capability toward toluene removal from polluted gas streams.