Sulfide removal is a significant problem in the oil and gas industry. Some of the problems presented by sulfides include environmental compliance, toxicity, corrosion, reduced efficiency of fluid handling equipment, offensive odor, reduced value of products, and increased operation costs. Microbial oxidation of sulfides offers the potential for a safe, cost-effective method of removing sulfides from natural gas, sour water, spent-sulfidic caustic, etc. The purpose of this study is the development of an efficient and economically viable bioreactor system for sulfide oxidation. The application of immediate interest is the removal of H2S from "stranded" natural gas.

The immobilization matrix Bio-Sep® has previously been used for successful biotreatment of BTEX-contaminated groundwater. In this study, a special sorbent has been added to Bio-Sep® to adsorb sulfide while still maintaining the desirable physical properties of the original beads. Thiobacillus denitrificans is a sulfide-oxidizing autotroph which may use either oxygen or nitrate as a terminal electron acceptor. Thiosulfate, elemental sulfur, or sulfide may be used as an energy source for T. denitrificans and each are oxidized to sulfate. Previously, suspended cultures of T. denitrificans were shown to remove H2S from a gas stream with 1-2 s of gas-liquid contact time. However, the volumetric productivity of suspended cultures was insufficient to lead to an economically viable bioreactor design due to low biomass concentrations. In order to increase biomass concentration and volumetric productivity T. denitrificans has been immobilized in both standard Bio-Sep® and the new sulfide-sorbing version (Bio-Sep®S). The two matrices will be compared according to their ability to immobilize this sulfide-oxidizing culture and increase biomass concentration and volumetric productivity.

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