Ion Exchange Ion exchange works by exchanging a compound in the water for a chemical on the filter resin. It is effective for treatment of ions or charged contaminants. Most inorganic compounds can be removed by ion exchange, however, most common organic compounds cannot effectively be removed. Ion exchange is most commonly used to remove compounds which are of esthetic rather than health concern. Water softeners are the best known examples of ion exchange systems.
Water softeners soften water by removal of calcium and magnesium which make water hard.
The water softener will no longer be effective when all sodium ions on the resin have been replaced by hardness ions. At this time, it is necessary to recharge the resin with sodium. There may be some health risks associated with consuming the exchanged sodium ions from home water softeners for people with high blood pressure and heart disease. These people should check with health profes- sionals to determine if their maximum allowable intake of sodium will be exceeded by using a home water softerner. Ion exchange systems have also been developed for removing nonhardness chemical ions, such as nitrate and metals.