Microbial
Plugging of Uranium Mine Tailings to Prevent Acid Mine Drainage
- Final Report
Mine Environment Neutral Drainage at CANMET-MMSL |
MEND Report
2.44.1
December 1992
SUMMARY
Four test conditions
and a set of controls were used to examine the best conditions for
microbial cap formation. The following conditions were executed
in triplicate (1) inoculation of three columns with Ultramicrobacteria
(UMB's) and addition of liquid nutrient (BHI + sucrose); (2) inoculation
with UMB's, liquid and solid nutrients (Stillage concentrate), (3)
addition of the same as the previous set plus calcium and (4) only
liquid nutrient was added. The control maintained a constant pH
around 3, an Eh higher than 415 mV, an oxygen level always higher
than 5.1 mg/L. However, the Fe content in general decreased over
time which was unexpected. The series with UMB's, liquid and solid
nutrients maintained a lower Eh than the other series for the longest
period of time followed by the series of columns with liquid nutrient
only. Al1 conditions tested were generally better than the controls
in increasing the pH and also in reducing the Eh of the effluent
but nothing can be concluded with respect to the dissolved oxygen
and iron contents due to continuous variations in the results. There
was a significant decrease in the redox potential of the permeates,
however none of the conditions tested completely reduced the permeability
of the tailings over a long period of time. The scavenging of the
oxygen and the increase in pH by the heterotrophs help reduce AMD
generation by preventing growth of Thiobacillus ferrooxidans.
The use of the UMB, Klebsiella oxytoca a heterotrophic strain,
is not essential since the results of uninoculated columns with
liquid nutrient only were equivalent to the columns with liquid
nutrients and UMB's. It is likely that the nutrients increased the
metabolic activity of the indigenous heterotrophs already present
in the tailings.
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