AWWA JAW27595

This article, the second in a series, focuses on the results of bench- and pilot-scale studies of ion exchange processes for radium removal from groundwater in Lemont, Ill. (The first article in the series, "Evaluating Various Adsorbents and Membranes for Removing Radium from Groundwater," appeared in the July 1988 issue of Journal AWWA.) Batch and column studies indicated a very high resin selectivity for radium compared with common cations. Exhaustion-regeneration studies with a variety of resins showed that a standard gel-type strongacid cation exchanger is most suitable for radium removal in cyclic operation. Because the ion exchange softening process, operated to hardness breakthrough (300-360 bed volumes (BV)), removes radium but does not fully utilize the resin capacity, cyclic runs were made with resins exhausted to radium breakthrough (2,500-3,000 BV) and regenerated with sodium and calcium salts. But because of the poor radium regenerability of the exhausted resins, simultaneous breakthrough of radium and hardness occurred during the subsequent exhaustion run of the sodium cycle, and high radium leakage was observed on the calcium cycle. Use of very high regenerant dosages (up to 20 times stoichiometric) could desorb 75-90 percent of the adsorbed radium. The sodium ion exchange softening process (operated to hardness breakthrough without regenerant reuse) continues to be an appropriate technology for the removal of radium. Includes 29 references, tables, figures.