Environmental Engineering Reference
In-Depth Information
1.2 Remediation Technologies
Generally, environmental remediation deals with the removal of pollution or
contaminants from the environment, including soils, groundwater, sediment and
surface water, for the protection of human health and the environment or for the
redevelopment of brownfield sites. Various remediation technologies are avail-
able, including the more traditional physical and chemical approaches, such as
“excavation and disposal” and “pump and treat,” and the biological approaches,
such as bioremediation and phytoremediation. The remediation technologies
that have been used for uranium remediation are discussed in the following
sections.
1.2.1 Physical and Chemical Remediation of Uranium
Among the physical and chemical remediation technologies, the pump and treat and
permeable reactive barriers (PRBs) methods have been used in the field for uranium
remediation [4]. In the pump and treat method, polluted groundwater is pumped to
the surface, where it can be treated more easily. This traditional
ex situ
remedia-
tion approach has been used by the EPA at over 500 Superfund sites (hazardous
waste sites placed on the EPA National Priority List based on a scoring process that
rates current and potential health impacts) [20]. However, its application in uranium
remediation is limited by poor extraction efficiency, the generation of large volumes
of toxic uranium waste, and the increased public health and safety risks of bringing
uranium contaminants up to the surface [18].
PRBs provide a relatively quick, economical
in situ
groundwater cleanup
method. Reactive barriers such as zero-valent iron and phosphate minerals are
placed in the subsurface to intercept a plume of contaminated groundwater that
moves through it as it flows, typically on its natural gradient. As the contaminants
move through the material, they are transformed into less harmful or immo-
bile species. PRBs have been installed at more than 40 sites in the U.S. and
Canada. This
in situ
remediation method has been applied to uranium-contaminated
sites [21, 22, 23, 24]. However, when uranium is present at a high concen-
tration, it precipitates and/or is absorbed in such large quantities that it causes
the diversion of subsurface groundwater flow paths, exacerbating the subsur-
face containment issues by increasing the region influenced by the contaminant
plume [25].
Although pump and treat methods and PRBs have been used in the field, their
application on a large scale is limited by their high cost and low sustainability [4].
Thus, to circumvent the issues associated with these methods, bioremediation -
the strategy of harnessing indigenous microbial processes for cleanup - has been
extensively studied in the past decade. It is a cost-effective technology with mini-
mal environmental disruption and has been utilized to achieve the goal of uranium
remediation [18, 26, 27].
