What increases when hard water is softened using the ion exchange method?

When hard water is softened using the ion exchange method, the concentration of sodium increases. This method involves exchanging calcium and magnesium ions, which are responsible for water hardness, with sodium ions. As hard water passes through the ion exchange resin, the resin captures the calcium and magnesium ions and releases sodium ions into the water, thus replacing hardness ions with sodium ions.

The increase in sodium concentration is significant because while it ameliorates the issues associated with hard water—such as scale buildup and reduced soap effectiveness—it can also have implications for individuals on sodium-restricted diets. Understanding this process is crucial for sanitarians as they assess water quality and its impacts on health and infrastructure.