Comparative assessment of two biotrickling filters for siloxanes removal: Effect of the addition of an organic phase

Biogas produced at wastewater treatment plants and landfills contains trace levels of volatile methyl siloxanes (VMS) that are responsible for abrasion, corrosion and erosion of equipment during biogas storage and combustion. This research comparatively evaluated the removal of the most common VMS (L2, L3, D4, and D5) under aerobic conditions in a conventional biotrickling filter (BTF) and a two-phase partitioning BTF (TP-BTF) with silicone oil (at 30%) as organic phase. The TP-BTF showed a superior performance compared to the conventional BTF, increasing the total VMS removal from <30% in the BTF up to ∼70% in the TP-BTF. The highest REs in the TP-BTF were recorded for D4 and D5, reaching values of 80–90%, corresponding to ECs between 0.12 and 0.17 g m −3 .h −1 . Slightly lower values were obtained for L3 (70–80%), and the lowest performance was recorded for L2 (20–60%) due to the high vapor pressure of this siloxane and therefore its lower affinity by the organic phase. Surprisingly, despite the different inocula used, a similar microbial community was found by the end of operation of both BTFs, with KMBC-112 , Reynarella and Chitinophaga as the dominant genera. • The addition of silicon oil boosted siloxanes abatement in a conventional BTF. • The two-phase BTF exhibited a 5× increase in the siloxanes elimination capacity. • The highest removals were recorded for D4 and D5 reaching values between 80 and 90%. • The high vapor pressure of L2 hindered its mass transfer and therefore its removal. • The genera KMBC-112, Reynarella and Chitinophaga were retrieved from both BTFs.