Mesophilic and thermophilic BTEX substrate interactions for a toluene-acclimatized biofilter.

Benzene, toluene, ethylbenzene and xylene (BTEX) substrate interactions for a mesophilic (25 degrees C) and thermophilic (50 degrees C) toluene-acclimatized composted pine bark biofilter were investigated. Toluene, benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies, both individually and in paired mixtures with toluene (1:1 ratio), were determined at a total loading rate of 18.1 g m(-3) h(-1) and retention time ranges of 0.5-3.0 min and 0.6-3.8 min for mesophilic and thermophilic biofilters, respectively. Overall, toluene degradation rates under mesophilic conditions were superior to degradation rates of individual BEX compounds. With the exception of p-xylene, higher removal efficiencies were achieved for individual BEX compounds compared to toluene under thermophilic conditions. Overall BEX compound degradation under mesophilic conditions was ranked as ethylbenzene >benzene > o-xylene > m-xylene > p-xylene. Under thermophilic conditions overall BEX compound degradation was ranked as benzene > o-xylene >ethylbenzene > m-xylene > p-xylene. With the exception of o-xylene, the presence of toluene in paired mixtures with BEX compounds resulted in enhanced removal efficiencies of BEX compounds, under both mesophilic and thermophilic conditions. A substrate interaction index was calculated to compare removal efficiencies at a retention time of 0.8 min (50 s). A reduction in toluene removal efficiencies (negative interaction) in the presence of individual BEX compounds was observed under mesophilic conditions, while enhanced toluene removal efficiency was achieved in the presence of other BEX compounds, with the exception of p-xylene under thermophilic conditions.