H 2 S biotreatment with sulfide-oxidizing heterotrophic bacteria.

Many industrial activities produce H2 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 H2 S to thiosulfate and sulfite. These bacteria may also potentially be used in H2 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 H2 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 H2 S biotreatment. The immobilized bacteria removed H2 S as efficiently as the bacteria in suspension, and the inclusion of Fe3 O4 nanoparticles during immobilization resulted in increased efficiency for sulfide removal, in part due to chemical oxidation H2 S by Fe3 O4 . Thus, heterotrophic bacteria may be used for H2 S biotreatment under aerobic conditions.