The biofiltration of indoor air: Air flux and temperature influences the removal of toluene, ethylbenzene, and xylene

AN alternative approach to maintaining indoor air quality may be the biofiltration of air circulated within the space. A biofilter with living botanical matter as the packing medium reduced concentrations of toluene, ethylbenzene, and o-xylene concurrently present at parts per billion (volume)in indoor air. The greatest reduction in concentrations per pass was under the slowest influent air flux (0.025 m s(-1)); however, the maximum amount removed per unit time occurred under the most rapid flux (0.2 m s(-1)). There was little difference between the different compounds with removal capacities of between 1.3 and 2.4 mu mol m(-3) (biofilter) s(-1) (between 0.5 and 0.9 g m(biofilter)(-3) h(-1)) depending on influent flux and temperature. Contrary to biofilters subjected to higher influent concentrations, the optimal temperatures for removal by this biofilter decreased to less than 20 degreesC at the most rapid flux for all three compounds. Microbial activity was decreased at these cooler temperatures suggesting the biofilter was not microbially limited but rather was limited by the availability of substrate. The cooler temperatures allowed greater partitioning of the VOCs into the water column which had a greater impact on removal than its reduction in microbial activity.