Evaluating the secondary effects of anion exchange: Focus on spatial variability and timescale

In order to avoid the adverse effects of corrosion in water distribution systems, it is necessary to evaluate the secondary effects of magnetic ion exchange (MIEX) for the removal of dissolved organic matter (DOM). As DOM concentrations in surface waters increase and surface waters become more prevalent sources of drinking water, MIEX treatment will be increasingly used. This study evaluated the effects of MIEX treatment on iron and lead corrosion potential as measured by the Larson-Skold Index (LI) and chloride-to-sulfate mass ratio (CSMR), respectively. This was accomplished by monitoring three full-scale MIEX treatment plants. It was found that MIEX treatment consistently increased the CSMR; however, the extent of the increase was dependent on variables, such as influent anion concentrations and MIEX resin regeneration. MIEX treatment had only a minor effect on the LI. Hourly samples at one of the MIEX plants revealed that both corrosion parameters were variable due to the periodic transfer of excess brine into the process train during regeneration cycles and fluctuations in raw water quality. It was also found that MIEX resin can re-release previously removed anions, such as sulfate and bicarbonate, when treating temporally variable source water. 2010