Simultaneous acidic air biofiltration of toluene and styrene mixture in the presence of rhamnolipids: Performance evaluation and neural model analysis

Abstract

Biotrickling filters (BTFs) supplied with di-rhamnolipids have been proven to improve biodegradability and bioavailability of singly fed hydrophobic volatile organic compounds (VOCs). However, BTFs performance could be significantly impacted for multi-component mixtures. Herein, the performance of lab-scale fungal-BTF was evaluated for the co-treatment of toluene-styrene gas-phase mixture and compared to previous single runs of both VOCs. For equal ratios of the VOCs, the total removal efficiencies (REtotal) ranged from 89.1% to 74% by varying the total inlet loading rates (LRtotal) from 199.1 to 295.2 g m−3 h−1 at empty bed residence times (EBRT) of 90 and 60 s. Both VOCs were efficiently removed (up to RE 90%) at 199.1 g m−3 h−1 inlet LRtotal and 90 s EBRT. Shortening EBRT to 60 s revealed that styrene degradation was kinetic-limited, whereas toluene was less impacted, indicating styrene inhibition and preferential toluene utilization. Increasing toluene:styrene ratio to 2:1 (v./v.) improved styrene biodegradation and mineralization. Neural network model was developed for the binary mixture which highlighted the interaction effects between input and output variables. The model provided high predictive accuracy (R2-0.993) and revealed significant information towards improving future BTFs design.