The methods for softening water include:
① Lime soda process. First, measure the hardness of the water, then add a certain amount of calcium hydroxide and sodium carbonate, and the calcium and magnesium ions in the hard water will precipitate.
Ca（HCO3）2＋Ca（OH）2=2CaCO3 ↓＋2H2O
② Phosphate water softening method. For boiler water, sodium hypophosphite (NaPO3) can be added as a water softener, which forms complexes with calcium and magnesium ions. When water boils, calcium and magnesium will not precipitate, thus preventing the formation of scale. This method is not suitable for softening drinking water.
Mg（HCO3）2＋2Ca（OH）2=Mg（OH）2 ↓＋2CaCO3↓＋2H2O
③ Ion exchange method. Although both zeolites and ion exchangers are insoluble in water, the sodium and hydrogen ions can undergo exchange reactions with calcium and magnesium ions in hard water, causing them to be adsorbed and removed by zeolites, artificial zeolites, and ion exchangers. Zeolite and ion exchangers that fail after long-term use can be regenerated and reused, making it an economical and efficient soft water method.
CaSO4+Na2CO3=CaCO3↓+Na2SO4
4. Dosing method: Scale inhibitors added to water can alter the binding characteristics of calcium and magnesium ions with carbonate ions, thereby preventing the precipitation and deposition of scale. There are many scale inhibitors currently available for industrial use. The characteristics of this method are: less one-time investment and wide adaptability; However, when the water volume is soft and large, the operating cost is high. Due to the addition of chemicals, the application of water is greatly limited and generally cannot be used for drinking, food processing, industrial production, and other purposes. It is also rarely used in the civilian field.
Electromagnetic method: By adding a certain electric or magnetic field to water to change the characteristics of ions, the deposition rate and physical properties of calcium carbonate (magnesium carbonate) are altered to prevent the formation of hard scale. Its characteristics are: small equipment investment, easy installation, and low operating costs; However, the effect is not stable enough, there is no unified measurement standard, and because the main function is only to affect the physical properties of scale within a certain range, the use time and distance of the treated water are limited to a certain extent. It is mainly used for the treatment of circulating cooling water in commercial applications such as central air conditioning, and cannot be applied to industrial production or boiler feedwater treatment (at the same time, the mechanism of this equipment has not been truly theoretically proven).
Membrane separation method: Both nanofiltration membrane (NF) and reverse osmosis membrane (RO) can intercept calcium and magnesium ions in water, thereby fundamentally reducing the hardness of water. The characteristic of this method is that the effect is obvious and stable, and the treated water has a wide range of applicability; However, there are high requirements for inlet pressure, and equipment investment and operating costs are also high. It is generally less used and more commonly used for specialized softening treatment.
Benefits of using soft water
Soft water makes your hair smooth and your skin delicate;
• Soft water can prevent the incidence rate of lithiasis and maintain health;
Soft wash clothes, saving 50% to 80% of various detergents;
Soft water reduces the wear and tear of clothing, making it soft after washing and maintaining its color for a longer period of time;
Soft water reduces the maintenance of water heaters and improves thermal efficiency;
• Maintenance and repair of soft water pipelines;
Soft water reduces the generation of dirt on sanitary ware.
Special attention: Industrial treated softened water should not be consumed by people due to cost issues. Generally, industrial softened water treatment uses sodium ions to replace calcium and magnesium ions. If people drink water containing high sodium salts for a long time, they are prone to cardiovascular and cerebrovascular diseases. For example: hypertension, coronary heart disease, cerebral thrombosis, etc.