Treatment of O2-free toluene emissions by anoxic biotrickling filtration

Toluene biotrickling filtration under anoxic denitrifying conditions was evaluated in two identical bioreactors (R1 and R2) operated at liquid recycling rates of 1.3, 2.7 and 5.3 m h(-1) and liquid renewal rates of 0 and 0.17 d(-1). R1 and R2 achieved a similar maximum elimination capacity (EC similar to 30 g m(-3) h(-1)) at the same toluene inlet load (similar to 50 g m(-3) h(-1)), which was approximately 7 times higher compared with available literature on continuous toluene removal under anoxic conditions. Nevertheless, higher metabolite accumulation was observed in the bioreactor operated without periodical liquid phase renewal (R2), leading to intermittent drops in its toluene removal performance. This is the first work operating an anoxic biotrickling filter at empty bed residence time of 3 min, which is comparable with those employed in conventional aerobic systems. A characterization of the metabolites accumulated in the liquid phase revealed a dynamic metabolite production and degradation. (C) 2014 Elsevier Ltd. All rights reserved.