What is typically the composition of hard water?

The composition of hard water is characterized by high levels of calcium and magnesium ions. These minerals dissolve in water as it passes through limestone and other mineral-rich geological formations, leading to increased concentrations in the water supply. The presence of these ions is significant because they can have various effects on water's suitability for consumption, its interaction with soap and detergents, and its ability to support aquatic life.

In contrast, other options refer to different characteristics of water. For instance, high levels of sodium and potassium are typically found in saline or brackish water rather than hard water. Low levels of dissolved minerals indicate soft water, which lacks the high concentrations of calcium and magnesium that define hard water. Lastly, high levels of dissolved organic matter would relate to water quality issues such as pollution and nutrient enrichment, rather than the minerals that characterize hard water. Understanding the defining elements of hard water is essential for managing its effects on plumbing, appliances, and aquatic ecosystems.