Which ions are removed by the water softener to prevent hardness in dialysis water?

• A. Calcium and Magnesium
• B. Sodium and Potassium
• C. Chloride and Bicarbonate
• D. Phosphate and Sulfate

Answer: (A)

Hardness in water comes from dissolved calcium and magnesium ions. A water softener uses an ion-exchange process that swaps these multivalent Ca2+ and Mg2+ ions for sodium (or potassium) ions, removing the hard, scale-forming ions from the water used in dialysis. Without removing calcium and magnesium, the water can form scale on equipment and membranes, compromising performance and safety. The other ions listed (sodium, potassium, chloride, bicarbonate, phosphate, sulfate) are not the primary contributors to hardness, so they aren’t the ions targeted to remove for softening.