Over the past decade, environmental scientists and engineers have discovered that it is very difficult to restore polluted groundwater to pre-contamination conditions.  Environmental engineers at the University at Buffalo have explored a number of innovative strategies to improve the cost-effectiveness of groundwater remediation programs.  Recently a “permeable reactive barrier” (PRB) was deployed at the West Valley Demonstration Project, a former nuclear reprocessing facility located in Western New York, to remediate a large plume of groundwater contaminated by the radionuclide strontium-90.  The PRB strategy involves the placement of engineered materials that allow the passage of groundwater but retain or transform the target contaminants.

UB researchers worked together with scientists at West Valley Nuclear Services and the Department of Energy to assess the performance of the proposed barrier material – clinoptilolite, a natural zeolite mineral - using a combination of physical and mathematical modeling.  Physical modeling was conducted by operating laboratory-scale reactors constructed to mimic the subsurface conditions expected at the West Valley facility.  The results from these short-term experiments were then extrapolated using sophisticated numerical computer models developed to simulate the complex chemical process by which strontium is removed by the zeolite.  The primary chemical reaction – termed ion exchange – exploits a unique property of the zeolite that preferentially retains strontium and releases other naturally occurring ions such as sodium and calcium.

In addition to supporting the deployment of the first passive zeolite barrier in late 1999, the UB study produced a computer model that can be applied to characterize the potential performance of zeolite barriers at other radioactive sites.   Further work is ongoing to develop an improved understanding of the influence of PRBs on regional groundwater movement.