Use of sulfur-oxidizing bacteria enriched from sewage sludge to biologically remove H2S from biogas at an industrial-scale biogas plant

Anaerobic digestion has been widely used for organic waste and wastewater treatment to produce renewable energy, especially biogas. Hydrogen sulfide (H2S) being harmful to human beings and the environment is one of the highly toxic compounds in the biogas. For the sake of health and safety, removal of H2S from biogas is necessary before further utilization. In this study, sewage sludge was used to enrich sulfur-oxidizing bacteria (SOB) quickly under weak alkaline condition (pH = 7.5-8.2) in the laboratory and then applied in an industrial-scale desulfurization system. The SOB was successfully enriched in the system within 10 days by addition of Na2S. The optimal dissolved oxygen (DO) for producing elemental surfer (S0) in the regeneration tank was 0.8-1.2 mg/L. The performance shows that the outlet H2S concentration could be reduced to the safety limit of 200 ppm after 2 months' operation, achieving a stable H2S removal up to 95%.