Water hardness refers to the presence of certain minerals, primarily calcium and magnesium, in water. These minerals can cause problems in household appliances and plumbing, as well as affect the taste and lathering properties of soap. Hard water can be classified as temporary or permanent, depending on the type of minerals present and how they are dissolved in the water.
Temporary hardness, also known as carbonate hardness, is caused by the presence of dissolved bicarbonate minerals, such as calcium bicarbonate and magnesium bicarbonate. These minerals are present in water as a result of the dissolution of limestone and other rock formations. When water containing temporary hardness is heated, the bicarbonate minerals decompose and release carbon dioxide, resulting in the formation of insoluble calcium and magnesium carbonates. This process is called "temporary" because the hardness can be removed by boiling the water, causing the minerals to precipitate out of the solution.
Permanent hardness, on the other hand, is caused by the presence of dissolved calcium and magnesium sulfates and chlorides. These minerals are not affected by boiling and cannot be removed from the water by this method. Permanent hardness is more difficult to treat and requires the use of specialized water softening systems, such as ion exchange or reverse osmosis, to remove the excess minerals.
The level of water hardness varies depending on the source and treatment of the water. Hard water is more common in areas with high levels of limestone and other rock formations, as these minerals can leach into the water supply. Water treatment plants can also contribute to water hardness by adding chemicals, such as calcium or magnesium, to the water for various purposes.
In conclusion, temporary and permanent hardness of water are caused by the presence of different types of dissolved minerals, with temporary hardness being caused by bicarbonates and permanent hardness being caused by sulfates and chlorides. The level of hardness in water can vary depending on its source and treatment, and different methods are needed to remove the excess minerals.