A REVIEW OF POTENTIAL BIOTECHNOLOGIES FOR REMEDIATION OF URANIUM MILL TAILINGS

One environmental concern from the mining and milling of uranium is the byproduct called Uranium Mill Tailings (UMT), which are the residues remaining after the extraction of uranium from ore in the earth’s crust. The principle concerns with uranium mill tailings are the release of radon and the potential contamination of surface and ground water from the closed or abandoned UMT stacks. These environmental impacts have led to the Uranium Mill Tailings Radiation Control Act (UMTRCA) and to investigations of remediation technologies for the UMT stacks. Remediation technologies range from physical remediation by capping the stacks with clay to potential application of biotechnologies. Biotransformation of trace metals in the environment has been demonstrated by processes such as mobilization by oxidation and reduction reactions, biosorption, and hyperaccumulation. Potential remediation strategies applicable to UMT include: microbial reduction of radium sulfate (insoluble) to radium sulfide (soluble), leaching and subsequent microbial oxidation or biosorption as a means to concentrate the radioactive material. Phytoremediation utilizes plants for in-situ hyperaccumulation of radionuclides, followed by harvesting of biomass as a means of limiting radon emission. Application of biotechnologies appears to be an alternative to physical and/or chemical remediation techniques, although has not yet been demonstrated on a full-scale basis.