An Affordable Solution for Water Hardness Determination
What is the total hardness of water?
Total hardness in water refers to the combined concentration of polyvalent cations, primarily calcium (Ca²⁺) and magnesium (Mg²⁺), dissolved in the water. It is typically expressed as the equivalent amount of calcium carbonate (CaCO₃) in milligrams per liter (mg/L). This parameter is crucial for determining water quality for both drinking and industrial use. According to WHO guidelines, the acceptable range for total hardness in drinking water is between 10 and 500 mg/L. Although the EPA has not set specific permissible limits, common classifications for water hardness are: Soft (0-60 mg/L), Moderately hard (61-120 mg/L), Hard (121-180 mg/L), and Very hard (above 180 mg/L). While hardness ions are generally not harmful to health unless they include heavy metals, very hard water can cause scaling and cloudiness in water distribution systems, and very soft water may lead to pipe corrosion, increasing leaching of metals like iron.
How to determine the total hardness of water?
The determination of total hardness is done through a complexometric titration method using EDTA-Na₂ as the titrant. The titration is monitored potentiometrically by employing a perfectION combined calcium ion selective electrode (Ca-ISE) which helps in detecting the equivalence point accurately. The process involves adding a buffer solution (pH 10) to the water sample and titrating it with the EDTA solution until the endpoint is reached, indicating the total concentration of calcium and magnesium ions in the sample.
