In-Situ Biosequestration for Remediation of Uranium in Groundwater at the Monument Valley UMTRA Site

Abstract

The Monument Valley UMTRA Site is a former uranium mining site that is located in Cane Valley, Arizona. The mining that occurred there from 1943 to 1968 created a groundwater contaminant plume that consists of nitrate, sulfate, and uranium. There are only a few viable methods for remediation of these types of contaminants occurring in large, deep plumes. Monitored natural attenuation is a popular approach because it is a green and low-cost alternative. However, it is often ineffective without some form of supplemental enhancement. In-situ biosequestration is one method of enhanced attenuation, which involves injecting an electron- donating substrate that will promote microbial activity and sequester contaminants by bioprecipitation, biomineralization, and enhanced adsorption. Prior tests conducted at the Monument Valley site in the center of the plume using ethanol as the electron donor proved effective in the treatment of nitrate, sulfate, and uranium. Subsequent pilot scale tests are being conducted in the source zone of the Monument Valley Site to further investigate the feasibility and effectiveness of using in-situ biosequestration for treatment of uranium contaminated groundwater. The preliminary results of these tests are discussed.