If the hardness of water is temporary, after the water is boiled, the calcium bicarbonate or magnesium bicarbonate contained in the water will be decomposed into water-insoluble calcium carbonate and water-insoluble magnesium hydroxide precipitate. When these precipitates are precipitated, the hardness of water can be reduced, thus softening the water with higher hardness. If the hardness of water is permanent, the following methods are usually used.
1. ion exchange method: using a specific cation exchange resin, calcium and magnesium ions in water are replaced by sodium ions. Due to the high solubility of sodium salt, scaling with the increase of temperature is avoided. This method is the most commonly used standard method at present.
2. Membrane separation method: Both nanofiltration membrane (NF) and reverse osmosis membrane (RO) can intercept calcium and magnesium ions in water, thus fundamentally reducing the hardness of water.
3. Lime method: adding lime to water is mainly used to treat water with high hardness and large flow, and the hardness can only be reduced to a certain range.
4. Electromagnetic method: adding a certain electric field or magnetic field to water to change the characteristics of ions, thus changing the deposition speed and physical characteristics of calcium carbonate (magnesium carbonate) and preventing the formation of hard scales.
5. Dosing method: Adding special scale inhibitor to water can change the characteristics of combining calcium and magnesium ions with carbonate ions, so that scale can not be deposited. At present, there are many scale inhibitors that can be used in industry.