Oxidation of hydrogen sulfide by an enrichment from sour water coproduced with petroleum

We have previously demonstrated that the chemoautotroph and facultative anaerobeThiobacillus denitrificans may be readily cultured aerobically or anoxically in batch and continuous reactors on hydrogen sulfide under sulfide-limiting conditions. A sulfide-tolerant strain ofT. denitrificans (strain F) was isolated by enrichment and recently used in a successful field test of a microbial process for the treatment of sour water coproduced with petroleum at an Amoco Production Co. site in Wyoming. Prior to the initiation of this field test, it was determined that the sour water at this site contained low concentrations of indigenous autotrophs, which could grow on thiosulfate as an energy source. Samples of this sour water have now been used to produce an enrichment culture for sulfide oxidizers. This enrichment has been characterized with respect to hydrogen sulfide oxidation, response to oxygen, pH and temperature optima, and sulfide tolerance. The enrichment was shown to be strictly aerobic and to grow on sulfide as an energy source with complete oxidation of sulfide to sulfate. The enrichment has a tolerance of sulfide comparable to that ofT. denitrificans strain F. However, the enrichment has a higher optimum temperature (35°C) than strain F and was shown to oxidize sulfides over a much broader range of pH values (3.5–10).