Intensified, High-Rate Reductive Immobilization of Hexavalent Chromium - Project Summary / Abstract
Hexavalent chromium, or Cr(VI), is among the most widespread contaminants in water resources in the U.S. and
around the world. Cr(VI) has been found in at least 1,127 of the 1,699 current or former National Priority List
(NPL) sites, which have been identified by the U.S. Environmental Protection Agency (EPA) as the most serious
hazardous waste sites in the nation and are the highest priority targets for long-term federal cleanup activities.
Toxicological research has found that high concentrations of Cr(VI) can contribute to stomach cancers, kidney
and liver damage, and reproductive harm. As a result, there is significant demand among water providers and
managers of Superfund sites for innovative technologies to address Cr(VI) contamination in a cost-effective and
environmentally sustainable manner.
The lack of cost-effective technologies to reduce Cr(VI) levels in water are due to technical challenges associated
with existing physical/chemical approaches, including high cost, the need for disposal of secondary waste
streams, and performance that can be vulnerable to influent water geochemistry. Specifically, there is a need for
new technologies to reliably reduce Cr(VI) to very low parts-per-billion levels with lower costs and less waste
than existing physical or chemical treatment technologies.
This project seeks to address this need through a novel combination of materials science and bacterial reductive
immobilization. In contrast to conventional physical or chemical technologies, this new technology does not
produce a hazardous secondary waste stream. Moreover, the proposed technology offers unique redox flexibility,
which allows it to remain effective even while hydrogeological characteristics may change. These and other
advantages help position the proposed technology as a highly effective ex-situ or in-situ treatment approach to
achieve low concentrations of Cr(VI) in water.
In the proposed project, a prototype of the proposed technology is developed through comprehensive kinetic
studies under various operating conditions supported by whole-genome transcriptional studies. In addition to
developing optimum parameters for the treatment system, the project will also provide insights into the unique
physiology employed to achieve reductive immobilization of Cr(VI). Development of material composites to
deploy a high density of the targeted culture proceeds in an iterative manner to ultimately select one composite
to evaluate in a continuous-flow reactor study using both synthetic and actual contaminated groundwater.
The outcome of this project will be the proof-of-concept of a new technology for efficient, environmentally friendly,
and cost-effective Cr(VI) treatment. As a result, this project holds significant promise to provide a critically
necessary tool for protecting and remediating drinking water supplies from chromium contamination, thus
promoting public safety and environmental health.
