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 ppm_v. This study assessed the performance of two bench-scale biotrickling filters (BTFs) treating synthetic sulfide-rich acidogenic off-gas (7000 ppm_v) from mesophilic sugarcane vinasse fermentation. The systems were packed with materials of high (950 m² m^-3, BTF_H) and low (460 m² m^-3, BTF_L) 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, BTF_H 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.