Biofiltration of BTEX by the fungus Paecilomyces variotii

Benzene, toluene, ethyl benzene and xylenes, known collectively as BTEX, are widespread contaminants, commonly found in soil, aquifers, and the atmosphere. BTEX degradation was evaluated as separate substrates and in mixtures, in liquid culture, and in packed biofilters with the filamentous fungus Paecilomyces variotii CBS115145. BTEX were differentially utilized by P. variotii: toluene was completely degraded, followed by ethyl benzene; benzene was partially assimilated (45%), similarly to m- and p-xylenes, while o-xylene was only 30% metabolized in liquid culture. Carbon recoveries as CO2 were 48, 40, and 53% for toluene, benzene, and ethyl benzene, respectively. Initial toluene addition allowed complete elimination of m-xylene in 12 days. In mixtures of toluene–benzene and ethyl benzene–benzene, the toluene degradation rate (0.27 mg l−3 h−1) was lower than the rate obtained with only toluene (0.37 mg l−3 h−1), while for ethyl benzene the rate was 0.15 mg l−3 h−1 as single substrate and 0.10 mg l−3 h−1 in the ethyl benzene–benzene mixture. Benzene degradation was also negatively affected by both toluene and ethyl benzene. Enzymatic analyses showed benzene oxidation activity. In biofiltration experiments average total carbon elimination capacities (TCECs) of 70 gC m−3 h−1 and a maximum of around 110 gC m−3 h−1 for the BTEX mixture were attained. Toluene, ethyl benzene, and benzene ECs were around 70 gC m−3 h−1, 40 gC m−3 h−1, and 10 gC m−3 h−1, respectively.