Hard water
Hardness is the most common water quality problem which can removed only by a water softener plant . The term “hard” began to characterize the water after washing with the use of conventional soaps based on fatty acids, the laundry became harsh.
Today this is one of the main problems of water, both for technological and for domestic use.
By stiffness, the total amount of dissolved alkaline earth metal ions usually takes into account calcium Ca 2+ and magnesium Mg 2+ , since they make up at least 98-99% of all compounds. To a small extent, Beryllium, Strontium and Barium are responsible for it. These metals belong to the group of heavy ones; therefore, they are separately regulated by more stringent standards.
Hardness indicators:
Numerically, hardness is represented as the sum of the concentrations of magnesium and calcium. The unit that is recommended in the SI system to express this indicator is a mole per cubic meter (mol / m³), but, in Ukraine, milligram equivalents per liter (mEq / l) are more often used. In weakly mineralized waters, high calcium hardness. With increasing mineralization, the content of calcium ions decreases rapidly, and usually does not exceed 1 g / l. The content of magnesium ions in highly mineralized – can reach several grams, and in saline – several tens of grams.
Types of Stiffness:
1. Temporary or carbonate got its name because it is removed by boiling and consists mainly of calcium and magnesium carbonates and hydrogen carbonates – Ca (НСО 3 ) 2 and Mg (НСО 3 ) 2 .
Their solubility is inversely proportional to temperature. This means that the higher the temperature, the lower the solubility. Accordingly, with increasing temperature, the equilibrium of the system shifts towards the formation of sediment and, as a result, we obtain limescale and scale.
2. Permanent hardness is formed by sulfates and chlorides of tungsten metals, these include CaSO 4 , CaCl 2 , MgSO 4 , MgCl 2 .
Such water does not form precipitation, but this parameter is important for some technological operations.
Where does it come from?
The main route of calcium and magnesium ions are natural minerals: dolomite, calcite, volastonite, etc. Water moves through the layers to contain these rocks and leaches a certain amount of minerals. Therefore, all natural water contains hardness salts.
There are also anthropogenic sources, such as the anomalous rigidity of chemical production as a result of amber mining, etc.
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