Using anion exchange resins to remove THM precursors

This study investigated the control of trihalomethanes (THMs) with ion exchange by comparing the THM formation potentials of the organic fractions in the influent to three column systems. The results showed that the smallest organic fraction, <0.5 K apparent molecular weight (AMW), was most reactive with free available chlorine. With the ion exchange system, the 1--5K-, 0.5K--1K-, and < 0.5-AMW organic fractions produced the majority of THMs, whereas with the granular activated carbon (GAC) and the combined ion exchange-GAC systems, the <0.5-AMW fraction produced most of the THMs. The authors conclude that regeneration of the resin of the ion exchange column at sulfate breakthrough, in combination with a GAC column, will produce a water very low in THM formation potential.