The study focused on using a biofilter to remove hydrogen sulfide from odor gas. By enriching sulfur bacteria, researchers found that the biofilter could remove over 98% of H2S when certain conditions were met. These conditions included a specific flow rate, gas retention time, and H2S concentration. The biofilter was also able to handle sudden increases in H2S levels without losing efficiency. Overall, the study showed that biofilters are effective in treating hydrogen sulfide gas.