Final answer:
Hard water contains high levels of dissolved calcium and magnesium, which causes issues like limescale buildup in water heaters. Hard water is mitigated using techniques such as lime softening and ion-exchange resins. Moreover, consuming mineral-rich water can positively contribute to the intake of important minerals.
Step-by-step explanation:
Hard water is water that contains relatively large amounts of dissolved calcium and magnesium. Minerals usually dissolve in natural water bodies, including lakes, rivers, and underground waterways. One common compound found in the Earth crust and dissolved in water is calcium carbonate (CaCO₃), which can lead to hard water.
One illustration of the issue with hard water is the tank-type water heater commonly used in the United States. When water is heated, the dissolved calcium carbonate can precipitate out, forming what is known as limescale. This limescale can reduce the efficiency of the water heater, revealing why water with high mineral content, particularly calcium and magnesium, requires treatment such as lime softening or the use of ion-exchange resins.
In the context of health, natural mineral-rich waters can be beneficial because they provide a substantive contribution to the dietary intake of calcium and magnesium. The World Health Organization has acknowledged the significance of these minerals in drinking water for public health.