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 biofil tration of air circulated within the space. A biofilter with living botanic al matter as the packing medium reduced concentrations of toluene, ethylben zene, and o-xylene concurrently present at parts per billion (volume)in ind oor air. The greatest reduction in concentrations per pass was under the sl owest influent air flux (0.025 m s(-1)); however, the maximum amount remove d 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. Contr ary to biofilters subjected to higher influent concentrations, the optimal temperatures for removal by this biofilter decreased to less than 20 degree sC at the most rapid flux for all three compounds. Microbial activity was d ecreased at these cooler temperatures suggesting the biofilter was not micr obially limited but rather was limited by the availability of substrate. Th e cooler temperatures allowed greater partitioning of the VOCs into the wat er column which had a greater impact on removal than its reduction in micro bial activity.