Environmental Engineering Reference
In-Depth Information
Table 1.4
Selected field studies on the
in situ
bioremediation of U(VI)
Testing site
Method
Results/comments
References
An aquifer in
Norman,
Oklahoma
Push-pull test by injecting test solution containing
U(VI) and bromide
Injected U(VI) (1.5
M) was reduced in three days in the
absence of an additional electron donor. The ability of
indigenous aquifer bacteria to reduce U(VI) was
demonstrated. This was not a typical U(VI)-contaminated
aquifer because it had an established low redox potential
but no preexisting contamination.
μ
[59]
U(VI)-contaminated
aquifer in a site at
Rifle, Colorado
Biostimulation by injecting acetate
An initial growth of
Geobacter
species and decrease in
U(VI) with the addition of acetate was followed by sulfate
reduction associated with an increase in U(VI).
Heterogeneity was a dominant control: local differences
in hydrology led to an uneven distribution of the electron
donor, microbial activity and U(VI) reduction. The
microorganisms actively incorporating acetate into
biomass and the bacteria involved in U(VI) reduction
were identified.
[148, 149, 4, 8,
150]
U(VI)- and nitrate-
contaminated
aquifer in a site at
Oak Ridge,
Tennessee
Preconditioning using bicarbonate followed by
biostimulation
In contaminated zones with a high level of nitrate
(>100 mM) and low pH (˜3.5), with the addition of
adequate electron donor, denitrification followed by
U(VI) depletion was observed.
Anaeromyxobacter
dominated before stimulation, and both
Anaeromyxobacter
and
Geobacter
were stimulated by the
addition of the electron donor.
[85, 151, 152,
153, 59]
Three-step approach: (i) nitrate removal from aquifer
(acidic flush); (ii) nitrate removal from flush water;
and (iii) reinjection of treated groundwater into
aquifer in conjunction with the addition of an
electron donor to stimulate
in situ
U(VI) reduction
Column studies demonstrated the feasibility of this
three-step strategy and concluded that nitrate leaching out
of the immobile pore space must be removed
continuously by
in situ
denitrification to maintain
favorable conditions for microbial U(VI) reduction.
[60, 154, 155]
