Many groundwater sources used for drinking water in the United States contain naturally occurring gross alpha emitting radium-226 that exceeds the National Drinking Water Standards maximum contaminant level. The health risks associated with continuous and intermittent exposure to these low levels of naturally occurring radioactive material (NORM) over long periods of time can cause genetic damage which may lead to effects such as cancer.

The EPA identifies ion exchange resins as a best available technology (BAT) in radium-226 removals. This determination has resulted in an increased need for knowledge about the characteristics of these resins. The ability of the resins to remove radium-226, their the life expectancy, and, in particular, the point at which resins can no longer be conventionally disposed of need to be determined to minimize the potential for inadvertent environmental and/or health risks.

The purpose of this study was to investigate the effectiveness of the brine cleaning solutions used to remove naturally occurring radium-226 from cation exchange resins used in drinking water treatment. Using the information found from this study, water treatment operators may adjust their cleaning practices to minimize hazardous buildup of naturally occurring radioactive material on these resins and increase the life expectancy.

Two cation resins used to treat groundwater at a site in Pelham, New Hampshire that was identified by New Hampshire Department of Environmental Services (NHDES) to contain trace levels of radium-226 was evaluated. The resins were cleaned in a series of batch studies using various brine cleaning solutions. The optimal cleaning solution was then used to clean aged resin from two ion exchange treatment systems in current field-scale use.

The cleaning solution with the highest radium-226 activity removals from resins found in this study include high salt concentrations, low pH, and high resin to brine contact time. Higher salt mass loadings show a significant impact on radium-226 and hardness recoveries, but showed diminishing contaminant removals after 85%. This indicates there may be irreversible fouling occurring with resins that have been in service for lengthy periods of time and may impact the overall effectiveness of the resin to remove target contaminants.