Environmental Engineering Reference
In-Depth Information
Chapter 1
Immobilization of Uranium in Groundwater
Using Biofilms
Bin Cao, Bulbul Ahmed, and Haluk Beyenal
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 contam-
inants 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 reme-
diation. 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.
