Comparing Hydrogen Sulfide Removal Efficiency in a Field-Scale Digester Using Microaeration and Iron Filters

Biological desulfurization of biogas from a field-scale anaerobic digester in Peru was tested using air injection (microaeration) in separate duplicate vessels and chemical desulfurization using duplicate iron filters to compare hydrogen sulfide (H 2 S) reduction, feasibility, and cost. Microaeration was tested after biogas retention times of 2 and 4 h after a single injection of ambient air at 2 L/min. The microaeration vessels contained digester sludge to seed sulfur-oxidizing bacteria and facilitate H 2 S removal. The average H 2 S removal efficiency using iron filters was 32.91%, with a maximum of 70.21%. The average H 2 S removal efficiency by iron filters was significantly lower than microaeration after 2 and 4 h retention times (91.5% and 99.8%, respectively). The longer retention time (4 h) resulted in a higher average removal efficiency (99.8%) compared to 2 h (91.5%). The sulfur concentration in the microaeration treatment vessel was 493% higher after 50 days of treatments, indicating that the bacterial community present in the liquid phase of the vessels effectively sequestered the sulfur compounds from the biogas. The H 2 S removal cost for microaeration (2 h: $29/m 3 H 2 S removed; and 4 h: $27/m 3 H 2 S removed) was an order of magnitude lower than for the iron filter ($382/m 3 H 2 S removed). In the small-scale anaerobic digestion system in Peru, microaeration was more efficient and cost effective for desulfurizing the biogas than the use of iron filters.