Thermophilic biofiltration of H₂S and isolation of a thermophilic and heterotrophic H₂S-degrading bacterium, Bacillus sp. TSO3

Thermophilic biofiltration of H₂S-containing gas was studied at 60 °C using polyurethane (PU) cubes and as a packing material and compost as a source of thermophilic microorganisms. The performance of biofilter was enhanced by pH control and addition of yeast extract (YE). With YE supplement and pH control, H₂S removal efficiency remained above 95% up to an inlet concentration of 950 ppmv at a space velocity (SV) of 50 h^-1 (residence time = 1.2 min). H₂S removal efficiency strongly correlated with the inverse of H₂S inlet concentrations and gas flow rates. Thermophilic, sulfur-oxidizing bacteria, TSO3, were isolated from the biofilter and identified as Bacillus sp., which had high similarity value (99%) with Bacillus thermoleovorans. The isolate TSO3 was able to degrade H₂S without a lag period at 60 °C in liquid cultures as well as in the biofilter. High H₂S removal efficiencies were sustained with a periodic addition of YE. This study demonstrated that an application of thermophilic microorganism for a treatment of hot gases may be an economically attractive option since expensive pre-cooling of gases to accommodate mesophilic processes is not required.