Abstract

The effect of a non-ionic surfactant, Tween-20, on xylene removal performance of a previously acclimated scoria-compost-based biofilter was evaluated. In the presence of the surfactant, the maximum elimination capacities (ECmax) of 71.0, 84.1, and 93.6 gm(-3) h(-1) were obtained for xylene inlet loading rates (ILRs) of 114.9, 124.1, and 197.1 gm(-3) h(-1) at empty bed residence times (EBRTs) of 40, 60, and 90 s, respectively. When the biofilter was fed the nutrient solution with Tween-20, the average removal efficiency (REavg) was increased approximately 13 and 14 at EBRTs of 40 s (ILRavg of 43-47 gm(-3) h(-1)) and 60 s (ILRavg of 61 gm(-3) h(-1)), respectively. This indicates that the surfactant improved the performance of the biofilter at moderate ILRs. However, the removal of xylene was not significantly affected by the surfactant at high ILRs, around which ECmax was achieved. This means that the non-ionic surfactant probably had a positive effect on the biofiltration of xylene when the diffusion through the biofilm, rather than biodegradation rates, appears to be the main process governing the performance of biofilter. Overall, this study showed that Tween-20, in terms of xylene removal efficiency, may not have similar effects on the performance of biofilter at various loading conditions.