The transient behavior of hybrid system composed of a photo-catalytic reactor and a biofilter was observed at the height of each sampling port to treat waste-air containing hydrogen sulfide highly concentrated up to 1000 ppmv with high loading. The biofilter packed with mixed media (of granular activated carbon and compost) was inoculated with a pure culture of Thiobacillus sp. IW, while the photo-catalytic reactor was composed of 15 W UV-A lamps and annular pyrex tubes packed with glass beads coated with TiO2 sol before calcination. The maximum elimination capacity of a biofilter-only process was 95 g/m(3)/h. On the other hand, the maximum elimination capacity of a hybrid system was observed to be 140 g/m(3)/h. The contribution of the photo-catalytic process to the increment of the elimination capacity of the applied hybrid system was composed of the direct contribution of photo-catalytic process and its indirect contribution to the increment of the elimination capacity of subsequent process, a biofilter. The contributions of the photo-catalytic process to the hybrid system-elimination capacity turned out to consist of a direct (37-55%) one and an indirect (45-63%) one for the removal of highly concentrated hydrogen sulfide with high loading of 232 g/m(3)/h. However, the indirect contribution of the photocatalytic process could not be estimated for the stages of lowly-loaded hybrid system run. Consequently, the percent-fraction of the indirect contribution of photo-catalytic process for the removal of hydrogen sulfide is reported to be smaller than that for the removal of VOCs.