Innovative polishing stage in biogas upgrading: Siloxanes abatement in an anoxic two-phase partitioning biotrickling filter

The present work investigated for the first time the feasibility of the anoxic biodegradation of siloxanes (hexamethyldisiloxane, L2; octamethyltrisiloxane, L3; octamethylcyclotetrasiloxane, D4; and decamethylcyclopentasiloxane, D5) in a two-phase partitioning biotrickling filter (TP-BTF) using silicone oil as the organic phase. The influence of the silicone oil ratio and the inlet concentration of siloxanes were also evaluated. The highest removals were obtained for D4 (41–54%) and D5 (48–73%). Lower removals were recorded for L2 (12–15%) and L3 (22–38%) as a consequence of their higher volatility. The best performance was obtained at a silicone oil content of 45%. Doubling the inlet load enhanced the elimination capacity of the TP-BTF by 50%, although the removal efficiencies did not vary. A specialized bacteria consortium dominated by the genera Parvibaculum, Zarvaz inia, KCM-B-11, Arenimonas, Moraxellaceae and Luteimonas was related to anoxic siloxanes degradation.