Sulfide microbial

The decreasing redox potential favors the reduction of iron-3-phosphate to iron-2-phosphate, which is dissolved from the sediments causing a strong increase of phosphate in the anoxic deepwater. Nitrate and nitrite are unstable under these conditions. Ammonium resulting from the microbial decomposition of organic compounds is the only stable nitrogen compound in the presence of hydrogen sulfide. Microbial processes also seem to be responsible for the accumulation of silicate in anoxic deep waters. 

Many of the by-products of microbial metaboHsm, including organic acids and hydrogen sulfide, are corrosive. These materials can concentrate in the biofilm, causing accelerated metal attack. Corrosion tends to be self-limiting due to the buildup of corrosion reaction products. However, microbes can absorb some of these materials in their metaboHsm, thereby removing them from the anodic or cathodic site. The removal of reaction products, termed depolari tion stimulates further corrosion. Figure 10 shows a typical result of microbial corrosion. The surface exhibits scattered areas of localized corrosion, unrelated to flow pattern. The corrosion appears to spread in a somewhat circular pattern from the site of initial colonization. 

Sodium chlorite has also been used for treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans. Chlorine dioxide from chlorite is also useful for microbial and slime control in paper mills and alkaline paper machine systems (164,165). The use of sodium chlorite in textile bleaching and stripping is well known. Cotton is not degraded by sodium chlorite because the oxidation reactions are specific for the hemiceUulose and lignin components of the fibers. 

A relatively high degree of corrosion arises from microbial reduction of sulfates in anaerobic soils [20]. Here an anodic partial reaction is stimulated and the formation of electrically conductive iron sulfide deposits also favors the cathodic partial reaction. 

R. W. FairbriiXjE, Encyclopedia of Geochemistry and Environmental Sciences, Van Nostrand, New York, 1972.. See sections on Geochemical Classification of the Elements Sulfates Sulfate Reduction-Microbial Sulfides Sulfosalts Sulfur Sulfur Cycle Sulfur Isotope Fractionation in Biological Processes, etc., pp. 1123 - 58. 

If the pH level of drilling fluid drops and the hydrogen sulfide test result is negative, there is a good possibility that carbon dioxide will be present. Positive results of microbial activity tests (described later) also indicate the possibility of carbon dioxide presence. Carbon dioxide meters are also available commercially and can be used. 

A number of studies describing the oxidation of sulfides to sulfoxides by biological oxidizing agents have been published over the years2 9,13,107- Microbial systems are often... 

Interest in the possible persistence of aliphatic sulfides has arisen since they are produced in marine anaerobic sediments, and dimethylsulfide may be implicated in climate alteration (Charlson et al. 1987). Dimethylsnlfoniopropionate is produced by marine algae as an osmolyte, and has aronsed attention for several reasons. It can be the source of climatically active dimethylsulfide (Yoch 2002), so the role of specific bacteria has been considered in limiting its flux from the ocean and deflecting the prodncts of its transformation into the microbial sulfur cycle (Howard et al. 2006). 

Enantiomerically pure alkyl aryl sulfoxides have been obtained by the microbial oxidation of the corresponding sulfides (Holland 1988). Both Corynebacterium equi, and fungi... 

Besides adding biocides to wells, another approach seems to be promising— modifying the reservoir ecology. The production of sulfide can be decreased, and its concentration is reduced by the establishment and growth of an indigenous microbial population that replaces the population of sulfate-reducing bacteria. 

M. J. Mclnemey, A. D. Montgomery, and K. L. Sublette. Microbial control of the production of sulfide. In E. C. Donaldson, editor. Microbial enhancement of oil recovery recent advances Proceedings of the 1990 International Conference on Microbial Enhancement of Oil Recovery, volume 31 of Developments in Petroleum Science, pages 441-449. Elsevier Science Ltd, 1991. 

Biochemical waste transformation occurred at low waste concentrations, resulting in the production of methane. Additional microbial degradation of the waste resulted in the reduction of sulfates to sulfides and ferric ions to ferrous ions. 

Hydrogen sulfide is produced in the large intestine of mammals by metabolism of sulfhydryl proteins by anaerobic bacteria, and may compose 0-10% of intestinal gases (Beauchamp et al. 1984 EPA 1978). It is produced in the human mouth by microbial petrification (Rosenberg et al. 1991). 

Tyagi RD, Tran FT, Polprasert C. 1988. Bioconversion of lignosulphonate into lignin and hydrogen sulfide by mutualistic bacterial system. Journal of Microbial Biotechnology 3 90-98. 

A class of enzymes capable of removing sulfur from alkane sulfonates exists, which may have relevance in microbial desulfurization of alkyl sulfides. A gene cluster ssuEADCB was identified in E. coli. The enzyme SsuD was capable of conversion of pentane sulfonic acid to pentaldehyde and sulfite. It was reported to be capable of conversion of alkyl sulfonates from C2 to CIO, as well as substituted ethanesulfonates and sulfonated buffers. The SsuE was a flavin-reducing enzyme that provided FMNH2 to the SsuD. 

A microbial contacting process for the oxidation of H2S was disclosed [22], in which a chemoautotrophic bacterium T. thiooxidants or T. ferroxidans) is used to remove sulfides from gaseous streams, at aerobic conditions and low pH. The low pH is preferred since the optimum pH for growth of the bacteria is below 4.0. and for the elimination of undesired contaminant bacterial strains. A contactor is employed, the flow of the sulfur-containing stream is contacted counter-currently with the biocatalytic aqueous solution. The sulfate is recovered from the aqueous solution, which contains the biocatalyst, as well. 

The genus Thiobacillus, especially the species T. denitrificans catalyzed the oxidation reactions of hydrogen sulfide yielding soluble hydrosulfide compounds, elemental sulfur, and sulfuric acid. Carbonyl sulfide and carbon disulfide are converted to hydrogen sulfide by hydrolysis. Additionally, they are oxidized to SOx and sulfates via microbial action. The reported oxidation reactions of thiosulfate using nitrate as electron acceptor are ... 

Bioleaching, particularly of sulfidic ores, has received much attention since the early 1980s. The conditions needed and mechanisms for such processes have been reviewed. Microbial processes involve complete oxidation of sulfide to sulfate, e.g.,... 

Suzuki, I. Microbial leaching of metals from sulfide minerals. Biotechnol. Adv. 2001, 19, 119-132. 

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