Removal of hydrogen sulfide from gas streams using biological processes - A review

Syed, M., Soreanu, G., Falletta, P. and Béland M. 2006. Removal of hydrogen sulfide from gas streams using biological processes A review. Canadian Biosystems Engineering/Le génie des biosystèmes au Canada 48: 2.1 2.14. Hydrogen sulfide (H2S) is a toxic and odorous compound present in biogas produced by the anaerobic digestion of biosolids and other organic materials. Due to its corrosive nature in internal combustion engines, biological hydrogen sulfide removal processes are being investigated to overcome the chemical and disposal costs associated with existing chemically-based removal processes. Both phototrophic and chemotrophic bacteria are suitable candidate microorganisms for hydrogen sulfide bioxidation. Phototrophic C. limicola is an ideal bacterium in these biological removal processes due to its ability to grow under anaerobic conditions using only inorganic substrates and a light source and its efficient extracellular production of elemental sulfur from H2S. Phototrophic fixed-film reactors are an interesting concept for cost-effective H2S removal from biogas due to their ability to operate for long periods of time without requiring a biomass separation step and their ability to operate under higher and variable loadings. However, a light source is one of the key constraints for this process. Chemotrophic bacteria can also be used in fixed-film reactors to produce elemental sulfur instead of sulfate under controlled oxygen conditions. These bioscrubbers are gaining acceptance for treating hydrogen sulfide containing gases from a wide variety of sources such as biogas, off-gases from wastewater treatment plants, livestock farms, etc. The biofilter medium is inexpensive and may contain sufficient micro-nutrients for the microbial communities. Future research needs include the optimization of the anaerobic biofiltration process, the development of a system combining the advantages of phototrophic and chemotrophic bacteria and the possible co-removal of siloxanes within this process.