The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening.

The purpose of this work was to provide an empirical foundation for decisions regarding regenerant brine management in anion exchange systems for the removal of compounds that absorb ultraviolet (UV) light at a wavelength of 254 nm (UV 254 ) in drinking water treatment. Regenerant performance was assessed for fresh regenerant brine, reused regenerant brine, and used brine that had been treated with aluminum sulfate (alum) before reuse. Jar tests were conducted to examine the UV 254 reduction achieved by resins treated with each of these regenerants. Over three regeneration cycles, resin treated with continuously reused regenerant did not display a significant decline in UV 254 reduction. While treatment with alum was effective for removing UV 254 -absorbing compounds from used regenerant brine, this treatment did not improve the brine's performance as a regenerant. These results demonstrate that regenerant brine may be reused several times without any intermediate treatment, which provides a cost-saving solution for treatment plants seeking to install anion exchange systems.

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