A comparative, kinetic study on cork and activated carbon biofilters for VOC degradation

Abstract

Two bio-filters packed with cork, an organic macroporous material and activated carbon, an inorganic microporous one were compared in terms of operative performance on biological degradation of VOC, which was a mixture of benzene, toluene, ethylbenzene and xylene (BTEX) vapors. Two filters were successfully operated for 4 months with three different periods. In general, the bio-filter with packed cork in the long thin glass was distinguishably better than the one with biological activated carbon (BAC). During the first period in which 150 ppm of the gas was flown in at 90 s of empty bed retention time (EBRT), the cork bio-filter performed better except for the first 2 weeks, the biological adaptation phase, which provided the BAC bio-filter with its much greater adsorption capacity as to lead to nearly perfect removal. Despite the shorter breakthrough point for cork, however, the cork bio-filter overwhelmed the BAC after that; even three times higher BTEX load at the shorter EBRT guaranteed the cork filter 90% or more removal. The maximum elimination capacities were 86 g/(m 3 h) for the cork and 67 g/(m 3 h) for the BAC around 94 g/(m 3 h) of inlet load. The higher biomass in the cork column could be resulted from organic surfaces, pore structure with sufficient room for sound microbial film or clumps even though its specific surface area was only 1/12 of BAC. This finding was supported by the model calculation in which the effective surface area of cork bed turned out to be 33% more than that of BAC. The derived relationship between consumption of BTEX and growing cell mass was found to be logarithmically proportional to each other, which was confirmed experimentally in here. We also found that through one-third of the whole length of the packed columns, as much as 79% of the inlet concentration of BTEX gas in the cork bio-filter was eliminated, which well agreed to our data and model depicting concentration versus column height, showing 1st order gradient.