Biological removal of high concentrations of H2S was studied using the immobilized Thiobacillus denitrificans with peat moss, wood chip, ceramic and granular activated carbon (GAC) separately. Experiments on the physical adsorption capacity of matrix, retention time and pressure drop were carried out; the ability of bioreactor to buffer shock loading and the removal efficiency with different packing materials were also investigated. Besides, the kinetics of single-stage biodesulfuration was analyzed. The results showed that GAC provided higher bacteria adsorption capacity, showed a more resistance to shock loading and allowed better operational control with respect to pressure drop than other inert carriers. When the retention time was changed from 30 to 100 s at an influent concentration of 100 mg/ L of H2S, the removal efficiencies were above 98%; when the inlet concentration of H2S were changed from 110 to 120 mg/L, an average 96.8% removal efficiency was achieved during the long-term operation for GAC bioreactor. Next to GAC, wood chip was found to be a good packing material; however, peat moss and ceramic had limited effectiveness and their removal efficiencies were less of 90%. The kinetic analysis showed that the maximum removal rate and the half-saturation constant of the GAC bioreactor were 666.7 mg (H2S)/(L (.) d) and 20.8 mg/L, respectively. (c) 2005 Elsevier Ltd. All rights reserved.