Assessing the impact of packaging materials on anoxic biotrickling filtration of siloxanes in biogas: Effectiveness of activated carbon in removal performance

Siloxanes (VMS) represent a class of organosilicon compounds known for their adverse effects on both the environment and human health. Their presence in biogas significantly hinders its economic valorisation, highlighting the need for effective treatment methods. This study investigates the performance of three different packing materials in the anoxic biofiltration of VMS (L2, L3, D4 and D5). The materials evaluated included plastic rings (BTF-1), polyurethane foam (BTF-2) and plastic rings combined with activated carbon (80:20) (BTF-3). Among them, BTF-3 exhibited superior performance, achieving maximum VMS removal efficiencies (REs) of 90%, including the complete elimination of L3 and D4, and ∼80% removal of D5, attributed to the presence of activated carbon. However, the abatement of L2 was inferior to that of other VMS (<80%), which was attributed to the activated carbon's affinity for larger molecular weights and critical diameters. In contrast, BTF-1 and BTF-2 supported maximum VMS removals of 40%. Notably, neither increasing the trickling liquid velocity from 2 to 4.5 m h⁻¹ nor adding Fe-carbon nanoparticles to the solution had any impact on the BTFs' performance. Following the successful results observed in BTF-3, gas residence time was reduced from 60 to 42 min, consequently leading to an increase in the EC from 366 to 509 mg m^-3 h^-1 (corresponding to an RE = 87%). Despite the different performance of the BTFs, comparable bacterial communities were identified, dominated by the genera Thermomonas, Corynebacterium, Aquimonas, Thauera and Parvibaculum. The results obtained in this study highlighted the potential of activated carbon as packing material for enhancing abatement performance during biotrickling filtration and identified new bacterial genera with potential for VMS degradation.