In this study, a biotrickling filter reactor was set up and used to treat high concentrations of gaseousH2S. Inoculation was carried out at an inlet H2S concentration of 1,000 ppmv (27.8 g H2S m-3 h-1)and sludge from a municipal wastewater treatment plant (MWWTP) was used as inoculum. After 3days, removal efficiency (RE) above 98 % was achieved even after the loading rate (LR) wasincreased up to 55.6 g H2S m-3 h-1 (2,000 ppmv). Operation at such LR, with an empty bed residencetime (EBRT) of 180 s and controlled pH of 6.5-7 was carried out during 3 months. The start-upphase, the effect of decreasing EBRTs at constant inlet concentration and the composition of theprocess end-products in relation to the supplied O2/H2S ratio were studied. Also, a carbon massbalance under steady state conditions was calculated.Peer ReviewedPostprint (published version