Immobilization of uranium in groundwater using biofilms

Abstract

Uranium is one of the most common radionuclides in soils, sediments, and groundwater at radionuclides-contaminated sites. At these contaminated sites, uranium leaches into the groundwater, which has become a widespread problem at mining and milling sites across North America, South America, and Eastern Europe. The movement of groundwater usually transports soluble uranium contaminants beyond their original boundaries, causing a global problem in aquifers, water supplies, and related ecosystems and posing a serious threat to human health and the natural environment. In order to meet the EPA standards, extensive efforts have been made to assess and remediate uranium-contaminated sites. As a cost-effective technology with minimal disruption to the environment, bioremediation harnessing indigenous microbial processes for cleanup has been utilized for uranium remediation. In the first part of this chapter, various uranium remediation technologies are discussed. Emphasis is placed on the principles and mechanisms of uranium bioremediation and the key factors affecting it. The second part of this chapter focuses on the use of biofilms for uranium immobilization in groundwater from subsurface environments. Most of the literature studies on uranium bioremediation have been conducted with suspended microorganisms or enriched sediments, which were eventually spiked with micro-or nano-particles of other minerals. However, biofilms are the commonly found microbial growth pattern in natural soils and water-sediment interfaces. With heterogeneous and complex biotic, abiotic and redox conditions significantly different from those in bulk conditions, biofilms pose challenges in predicting the mobility of uranium. Although previous studies have improved our understanding of uranium immobilization processes in biofilms, in order to efficiently and sustainably immobilize uranium at contaminated sites using indigenous biofilms, more knowledge is needed on the complex interactions among uranium, biofilms, and various redox-sensitive minerals during in situ uranium bioremediation. © 2010 Springer Science+Business Media B.V.