H 2 S biotreatment with sulfide-oxidizing heterotrophic bacteria

Many industrial activities produce H 2 S, which is toxic at high levels and odorous at even very low levels. Chemolithotrophic sulfur-oxidizing bacteria are often used in its remediation. Recently, we have reported that many heterotrophic bacteria can use sulfide:quinone oxidoreductase and persulfide dioxygenase to oxidize H 2 S to thiosulfate and sulfite. These bacteria may also potentially be used in H 2 S biotreatment. Here we report how various heterotrophic bacteria with these enzymes were cultured with organic compounds and the cells were able to rapidly oxidize H 2 S to zero-valence sulfur and thiosulfate, causing no apparent acidification. Some also converted the produced thiosulfate to tetrathionate. The rates of sulfide oxidation by some of the tested bacteria in suspension, ranging from 8 to 50 µmol min −1 g −1 of cell dry weight at pH 7.4, sufficient for H 2 S biotreatment. The immobilized bacteria removed H 2 S as efficiently as the bacteria in suspension, and the inclusion of Fe 3 O 4 nanoparticles during immobilization resulted in increased efficiency for sulfide removal, in part due to chemical oxidation H 2 S by Fe 3 O 4 . Thus, heterotrophic bacteria may be used for H 2 S biotreatment under aerobic conditions.