What is Hard Water
Hard water means mainly when the ions of chloride, sulfate and bicarbonate of calcium and magnesium are dissolved in water. Ferrous iron can also be present; in presence of oxygen it turns into ferric iron. These minerals dissolve in water depends on pressure, temperature, turbulence and PH levels. The main source of hard water is ground water. Rain water is purely soft water. But as the water travels through soil and rock, it dissolves a little amount of minerals like salt of calcium and magnesium and holds in solution. Therefore water becomes hard. Water is universal solvent and easily contaminant. Rain water absorbs carbon di-oxide from the air and that is making the water acidic (very weak carbonic acid). This rain water reacts with the limestone, dolomite and chalk rocks on earth and form water soluble bicarbonate ions. The equation for the reaction is:
Water + carbon di-oxide + calcium carbonate = calcium bicarbonate
H2O (l) + CO2 (g) + CaCO3 (s) → Ca(HCO3)2 (aq)
The degree of hardness increases if the calcium and magnesium content enlarge.
Basically hardness is two types; permanent hardness and temporary hardness.
Temporary Hardness
Temporary hardness occurs when the bicarbonate of calcium and magnesium is presence in water. This temporary hardness can be easily removed by boiling the water. When water is boiled the bicarbonate convert in to carbonate; this is insoluble in water. As a result it is easily removed and water becomes soften.
Permanent Hardness
Permanent hardness cannot be removed by boiling the water. It is generally caused by the ions of chloride and sulfate of calcium and magnesium. To removed permanent hardness needs chemical processing (using a water softener or ion exchange column).
Total Permanent Hardness = Calcium Hardness + Magnesium Hardness
Total permanent water hardness calculated as equivalent of calcium carbonate.