Abstract
Many kinds of volatile organic compounds (VOCs) have been treated in the biofilters based on the degradation of VOCs by the biolayer on the surface of packing media. Such a bed is easily subjected to compaction or clogging due to separation of biolayer and hence to an increase in pressure drop of gas flow. To overcome the drawbacks, our previous study has proposed the packed column containing the immobilized activated sludge gel beads together with the hollow plastic balls to avoid the bed compaction. In this study, a single VOC such as benzene, toluene or ethylbenzene is treated in the biofilter. The gel beads are the same as in our previous works on the acetaldehyde and propionaldehyde removal. The acclimation of the gel beads to the VOC is accomplished in the packed column during the earlier stage of the removal operation. The gel beads are durable, stable and reproducible for removing the VOCs for several months to one year. The rate of each VOC degradation by the gel beads is represented by the Michaelis-Menten type rate expression as in the case of the single aldehyde above. The Henry's law constant of the present VOC depends on its concentration or partial pressure in the dilute range as opposed to that of the aldehyde. The design equation similar to that in the aldehyde removal predicts the observed removal using the degradation kinetic parameters and the Henry's law constant modified considering the above concentration dependency as well as a higher affinity of the VOC to gel phase than to water.
