Middle-thermophilic sulfur-oxidizing bacteria Thiomonas sp RAN5 strain for hydrogen sulfide removal

Hydrogen sulfide (H(2)S) is one of the most toxic and offensively odorous gases and is generated in anaerobic bioreactors. A middle-thermophilic sulfur-oxidizing bacterium (SOB), Thiomonas sp. strain RAN5, was isolated and applied for H(2)S removal from both artificial and anaerobically digested gas. When a bioreactor containing medium inoculated with RAN5 was aerated continuously with artificial gas (containing 100 ppm H(2)S) at 45 degrees C for 156 hr, the H(2)S concentration in the vented gas was reduced by 99%. This was not affected by the presence of other microbes in the bioreactor. The H(2)S removal efficiency of the RAN5 bioreactor for anaerobically digested gas was greater than 99% at influent H(2)S concentrations ranging from 2 to 1800 ppm; the efficiency decreased to 90% at influent H(2)S concentrations greater than 2000 ppm. Thiomonas sp. strain RAN5 cannot survive at room temperature, and thus its leakage from a wastewater treatment plant would not damage sewage systems. These data suggest that Thiomonas sp. strain RAN5 may be a useful microorganism for H(2)S removal. Implications: The hydrogen sulfide removal efficiency of the RAN5 bioreactor was greater than 99% over the long term, for influent H(2)S concentrations of up to 2000 ppm. Removal was not affected by the presence of other microbes. Leakage of strain RAN5 would not damage sewage systems.