ABSTRACT
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The contamination of soil and groundwater by metals and metalloids* represents a significant
threat to drinking water supplies and human health. Methods currently employed to manage
such contamination — excavation, pump-and-treat, and immobilization using zero-valent
iron as a reducing agent — are often expensive, have restricted ranges of application, and
generate large volumes of hazardous waste for transport and disposal. As such, there is
considerable interest in alternative treatment techniques for metal contamination. Use of
bioremediation to immobilize metals in situ is attractive because microorganisms can trans-
form metals into sparingly soluble forms, thus removing them from groundwater and allevi-
ating the need for waste disposal. Microbial populations with the requisite capabilities are
ubiquitous, so remediation efforts can usually focus on the addition of chemicals to stimulate
the growth and activity of extant populations.
