Assessment of aerobic-anoxic biotrickling filtration for the desulfurization of high-strength H2S streams from sugarcane vinasse fermentation.

The increasing demand for renewable energy has heightened interest in biogas production from agro-industrial residues, such as sugarcane vinasse-a byproduct of ethanol production. During vinasse fermentation, sulfate reduction generates biogas with high hydrogen sulfide (H2S) concentrations, reaching up to 50,000 ppmv. This study assessed the performance of two bench-scale biotrickling filters (BTFs) treating synthetic sulfide-rich acidogenic off-gas (7000 ppmv) from mesophilic sugarcane vinasse fermentation. The systems were packed with materials of high (950 m2 m-3, BTFH) and low (460 m2 m-3, BTFL) specific surface areas and inoculated with sulfur-oxidizing bacteria (SOB). Operational conditions included decreasing empty bed residence times (EBRTs) of 9, 6, and 4 min and nitrate-to-sulfur ratios of 0.1, 0.3, and 0.5, respectively. Both BTFs achieved complete H2S removal at the shortest EBRT, with elimination capacities (ECs) exceeding 140 g S-H2S m-3 h-1. However, BTFH exhibited reduced EC at higher H2S loads due to elemental sulfur (S⁰) accumulation, resulting in clogging, pH instability, and diminished denitrification activity. Despite these challenges, the system demonstrated resilience by restoring nitrate reduction and H2S oxidation. This study underscores the efficacy of hybrid aerobic-anoxic BTFs for treating H2S-rich biogas and highlights the critical role of packing material selection and nitrogen-to-sulfur ratio control for long-term operational stability.