Stimulating the in situ activity of Geobacter species to remove uranium from the groundwater of a uranium-contaminated aquifer.
The potential for removing uranium from contaminated groundwater by stimulating the in situ activity of dissimilatory metal-reducing microorganisms was evaluated in a uranium-contaminated aquifer located in Rifle, Colo. Acetate (1 to 3 mM) was injected into the subsurface over a 3-month period via an injection gallery composed of 20 injection wells, which was installed upgradient from a series of 15 monitoring wells. U(VI) concentrations decreased in as little as 9 days after acetate injection was initiated, and within 50 days uranium had declined below the prescribed treatment level of 0.18 micro M in some of the monitoring wells. Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone. Fe(II) in the groundwater also increased during this period, suggesting that U(VI) reduction was coincident with Fe(III) reduction. As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed. Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community. This apparent switch from Fe(III) reduction to sulfate reduction as the terminal electron accepting process for the oxidation of the injected acetate was associated with an increase in uranium concentration in the groundwater. These results demonstrate that in situ bioremediation of uranium-contaminated groundwater is feasible but suggest that the strategy should be optimized to better maintain long-term activity of Geobacter species.
Anderson
Robert T
RT
Department of Microbiology, University of Massachusetts, Morrill Science Center, Amherst, Massachusetts 01003, USA. rtanders@microbio.umass.edu
Vrionis
Helen A
HA
Ortiz-Bernad
Irene
I
Resch
Charles T
CT
Long
Philip E
PE
Dayvault
Richard
R
Karp
Ken
K
Marutzky
Sam
S
Metzler
Donald R
DR
Peacock
Aaron
A
White
David C
DC
Lowe
Mary
M
Lovley
Derek R
DR
D000085:Acetates / Q000378:metabolism* / Q000494:pharmacology; D004275:DNA, Ribosomal / Q000032:analysis; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis; D005290:Ferric Compounds / Q000378:metabolism; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D045302:Geobacter / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D008906:Mining; D010084:Oxidation-Reduction; D010743:Phospholipids / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013431:Sulfates / Q000378:metabolism; D014501:Uranium / Q000378:metabolism*; D014877:Water Pollution, Chemical
D000085:Acetates; D004275:DNA, Ribosomal; D005227:Fatty Acids; D005290:Ferric Compounds; D010743:Phospholipids; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D014501:Uranium