In a water softening system, which component is regenerated by the brine solution?

• A. The softening medium
• B. The chlorination unit
• C. The filtration media
• D. The storage tank

Answer: (A)

The main idea is that the resin used to soften water is recharged by a brine solution. In a water softener, the softening medium is an ion-exchange resin that captures calcium and magnesium from hard water in exchange for sodium ions. Over time the resin becomes saturated with hardness ions and can’t soften further. A concentrated brine solution is then drawn through the resin bed; the high sodium ion concentration pushes the exchange reaction, displacing calcium and magnesium and restoring the resin to its sodium form. After regeneration, a rinse flushes out the displaced hardness minerals and any excess brine. The other components aren’t regenerated by brine—chlorination handles disinfection, filtration media are cleansed or replaced rather than regenerated with brine, and the storage tank simply holds water.