SULFATE-REDUCING BACTERIA AND IMMOBILIZATION OF METALS

The subaqueous disposal of sulfide-rich mine tailings appears to minim ize the release of solubilized metals from these deposits. As well as inhibiting oxidation of the tailings, and consequent release of trace metals, burial of failings results in the immobilization of metals as insoluble sulfides. Dissolved sulfide is generated by sulfate-reducing bacteria (SRB) a diverse group of microorganisms responsible for the bulk of organic carbon mineralization in sediments. They can metaboliz e a wide variety of organic compounds, although they require low-molec ular-weight compounds, nearly all of which are fermentation products f rom the anaerobic bacterial degradation of more complex substrates. Th ese bacteria are universally distributed and are found in greatest num bers in anoxic sediments, although they are able to withstand long exp osure to oxygen. SRB are adaptable to almost arty environment and can grow at temperatures of -5 to 75 degrees C, pH's of 5 to 9.5, and at v irtually any salinity and pressure.