Intensified, High-Rate Reductive Immobilization of Hexavalent Chromium - PROJECT SUMMARY / ABSTRACT
Hexavalent chromium, or Cr(VI), is a highly prevalent contaminant in water resources in the U.S. and worldwide.
Research has found that high concentrations of Cr(VI) can be carcinogenic and dangerous for public health. As
a result, there is significant demand among water providers and Superfund sites for innovative technologies to
reduce Cr(VI) concentrations in water resources in a cost-effective and environmentally sustainable manner.
Current technical challenges posed by existing technologies for Cr(VI) remediation include high costs, limited
capabilities to achieve low parts-per-billion (ppb) concentrations, and the outsized effects of influent water
geochemistry on system performance. Specifically, there is a need for new technologies to reliably reduce Cr(VI)
to low parts-per-billion (ppb) levels with lower costs and better performance than existing technologies.
This proposed Phase II project builds on successful outcomes from Phase I in which a new biological process
technology was developed. The new technology is based on enhanced biological reductive immobilization in
which microorganisms reduce soluble, mobile, and highly toxic forms of specific metals to oxidation states at
which the metals are very poorly soluble and easily removed from water. In this new technology, specifically
chosen natural microorganisms are incorporated inside proprietary polymer composites called biocatalysts. The
biocatalysts are designed to retain, control, and maintain a highly active population of the chosen
microorganisms inside a bioreactor as part of a compact, high-performance water treatment system.
In Phase I support, the Cr(VI)-removal biocatalysts were developed, and a prototype bioreactor was designed,
built, and operated. Under continuous flow conditions, the removal of various influent concentrations of
Cr(VI) was consistently demonstrated, including more than 99% removal to levels below 1 μg/L, which
is well below the target concentration of five (5) μg/L. The technology was validated using actual
contaminated groundwater with co-contaminants and a technoeconomic analysis was conducted.
In Phase II, this new technology is further optimized and then scaled-up for demonstration at a contaminated
site. The Phase II project seeks to further establishes the performance and operational parameters for this new
technology. In addition, the proposed project positions the new technology for immediate implementation through
documenting the technology’s long-term operation, conducting stress testing and recovery studies, and
assessing detailed maintenance, cost and operation parameters.
This new technology addresses a critical need: the reliable treatment of Cr(VI) that cannot be removed cost-
effectively using existing technologies. This project’s success holds significant promise to become a commercial
technology-of-choice for water managers and providers to address Cr(VI) contamination, enhance water
security, and promote public health for thousands of communities in the U.S. and around the world.
