A team of researchers from Washington University in St Louis, Missouri, has helped discover a new chemical method to immobilise uranium in contaminated groundwater, which could lead to more precise and successful water remediation efforts at former nuclear sites.
Researchers in the lab of Daniel Giammar, the Walter E. Browne Professor of Environmental Engineering in the School of Engineering & Applied Science, ran a series of experiments in a laboratory setting using water containing uranium – present in contaminated groundwater at various sites in the United States as a legacy of Cold War-era processing and waste disposal activities associated with nuclear materials production.
Calcium and phosphate work together chemically to immobilise uranium, which is shown to lead to increased cancer risk and liver damage in humans when ingested. Past field studies, including one at the Hanford Site in the state of Washington, focused on an in-situ solution that injected phosphates directly into contaminated groundwater. Remediation efforts were not fully successful, because the scale of overlap for the calcium, uranium and phosphates was limited.
"A challenge with subsurface remediation is finding the right way to bring the necessary ingredients together in a poorly-mixed system," Giammar said. "In the field-scale test, much of the added phosphate never reached the uranium because it precipitated out near the injection well. The solution is to figure out scenarios where it is possible to send the phosphate to where the uranium is, and other scenarios where the phosphate can be added to a location where the natural groundwater flow will bring the uranium into contact with it."