An innovative biofiltration technology based on anoxic biodegradation was proposed in this work for the treatment of inert VOC-laden emissions from the petrochemical industry. Anoxic biofiltration does not require conventional O2 supply to mineralize VOCs, which increases process safety and allows for the reuse of the residual gas for inertization purposes in plant. The potential of this technology was evaluated in a biotrickling filter using toluene as a model VOC at loads of 3, 5, 12 and 34 g m−3 h−1 (corresponding to empty bed residence times of 16, 8, 4 and 1.3 min) with a maximum elimination capacity of ∼3 g m−3 h−1. However, significant differences in the nature and number of metabolites accumulated at each toluene load tested were observed, o- and p-cresol being detected only at 34 g m−3 h−1, while benzyl alcohol, benzaldehyde and phenol were detected at lower loads. A complete toluene removal was maintained after increasing the inlet toluene concentration from 0.5 to 1 g m−3 (which entailed a loading rate increase from 3 to 6 g m−3 h−1), indicating that the system was limited by mass transfer rather than by biological activity. A high bacterial diversity was observed, the predominant phyla being Actinobacteria and Proteobacteria.
