Radium Removal from Potable Water Supplies

There has been intense interest in radium removal from potable water supplies in the last few years, driven by the radium MCL issued by the US EPA. Although the compliance cycle for large systems ended a few years ago, the cycle for small systems ended in Dec 2016, even small systems are now required to take action if samples exceed the MCL.

Although radium can be reduced by membrane processes such as RO, this treatment method produces a waste stream of significant volume that contains the radium in more concentrated form. Radium is removed by water softening resins so long as hardness ions are also removed but it is neither desirable nor cost effective to soften potable water. Highly crosslinked cation resins have high affinity for radium compared to other cations such as calcium, magnesium, and sodium and can be effectively applied in single use applications where the TDS and hardness are modest. For higher TDS and hardness waters, the radium selective complexer hybrid cation provides high throughput capacities for single use applications.

This paper discusses the relative merits of the various radium removal processes, presents operating data for both the single use highly crosslinked cation resin and for the radium selective complexer hybrid. Some of the operational difficulties associated with the used of radium removal by ion exchange are also discussed.