Total Organic Carbon Treatment Through Ion Exchange
With regulations in place for trihalomethanes and haloacetic acids, reducing disinfection by-products in community drinking water is a priority. Total Organic Carbon (TOC) reduction can be achieved through various treatment options. Many of these treatment options also decrease the formation of disinfection by-products. Ion exchange technology continues to be a popular treatment option with low capital cost, decreased operation and maintenance expenses and overall ease of operation, compared to alternative treatment methods.
Ion exchange is a process in which ions are exchanged between a solution and an insoluble (usually resinous) solid. For TOC removal, ion exchange technology takes advantage of the negatively charged carboxylic functional groups of the TOC molecules that result from an oxygen double bonded with carbon. This negative charge allows the TOC to exchange on an anion resin with another anion of less selectivity, or charge. During the process of TOC removal, TOC molecules are exchanged on the resin surface for chloride ions. In addition to the exchange removal mechanism, utilizing a macroporous resin allows for surface adsorption to occur.
As water containing TOC continues to be treated by the resin, more of the exchange sites are appropriated with TOC, finally reaching a point of break-through. Prior to the break-through point, dependent on the amount of water treated, the resin is regenerated with salt (namely the Cl ion) to displace the TOC from the resin sites. Periodic alkaline-brine cleanings may also be required to regenerate the resin, based on water quality.
TOC varies across water sources, making it imperative to perform a pilot study to determine the performance of the ion exchange process for each water source. Completing a pilot study will also identify other operational parameters necessary to design a full-scale system including loading rates, regeneration frequency and operation and maintenance costs.
Learn more about our ion exchange treatment options.