Effect of saponins on n-hexane removal in biotrickling filters

• The effect of saponins on n-hexane removal is examined in biotrickling filters.
• Saponins can considerably enhance biotrickling filter removal performance.
• Saponins can decrease biomass accumulation rate in packing media.
• Removal mechanisms are examined in biofilters at the existence of saponins.

Saponins was applied to enhance the removal of n-hexane in a biotrickling filter (BTF) in this study. Comparison experiments were carried out to examine the effect of saponins on n-hexane removal in two BTFs at various saponins concentrations, n-hexane loading rates (LRs) and gas empty bed contact times (EBCTs). Results show that the optimum concentration of saponins in nutrient feed was 50.0 mg L−1. When organic LR of n-hexane increased from 47.8 to 120.0 g m−3 h−1, the removal efficiency (RE) for BTF1 (with saponins) and BTF2 (without saponins) decreased from 91.3% to 83.3% and from 62.8% to 56.8%, respectively. As gas EBCT decreased from 30.0 to 7.5 s, the RE declined from 88.4% to 64.5% for BTF1 and from 61.4% to 38.3% for BTF2. Saponins could also decrease the biomass accumulation rate within the medium bed. These results could be referred in the design and operation of BTFs for hydrophobic VOC removal.