Elimination of high concentration hydrogen sulfide and biogas purification by chemical-biological process

A chemical-biological process was performed to remove a high concentration of H₂S in biogas. The high iron concentration tolerance (20gL^-1) of Acidithiobacillus ferrooxidans CP9 provided sufficient ferric iron level for stable and efficient H₂S elimination. A laboratory-scale apparatus was setup for a 45 d operation to analyze the optimal conditions. The results reveal that the H₂S removal efficiency reached 98% for 1500ppm H₂S. The optimal ferric iron concentration was kept between 9 and 11gL^-1 with a cell density of 10⁸CFUg^-1 granular activated carbon and a loading of 15gSm^-3h^-1. In pilot-scale studies for biogas purification, the average inlet H₂S concentration was 1645ppm with a removal efficiency of up to 97% for a 311d operation and an inlet loading 40.8gSm^-3h^-1. When 0.1% glucose was added, the cell density increased twofold under the loading of 65.1gSm^-3h^-1 with an H₂S removal efficiency still above 96%. The analysis results of the distribution of microorganisms in the biological reactor by DGGE show that microorganism populations of 96.7% and 62.7% were identical to the original strain at day 200 and day 311, respectively. These results clearly demonstrate that ferric iron reduction by H₂S and ferrous iron oxidation by A. ferrooxidans CP9 are feasible processes for the removal of H₂S from biogas.