Water treatment system knowledge: soft water and hard water

September 10, 2021

Water treatment system knowledge: soft water and hard water treatment system knowledge: soft water and hard water

Water treatment system knowledge: soft water and hard water

Water hardness

The hardness of water refers to the concentration of calcium and magnesium ions in water. The unit of hardness is ppm, and 1 ppm represents the calcium carbonate content of 1 mg/L (mg/L).

Soft and hard water

Water is divided into soft water and hard water. Any water that does not contain or contain a small amount of calcium and magnesium ions is called soft water, and vice versa. The hardness component of water, if it is caused by sodium bicarbonate or magnesium bicarbonate, is temporary hard water (boiled temporary hard water, decomposed sodium bicarbonate, precipitated insoluble carbonate, and water changes from hard water to soft water) If it is caused by h2so4 salt or chloride containing calcium or magnesium, it is permanent hard water and cannot be removed after boiling. The above two hardnesses are collectively referred to as total hardness. According to the total hardness value of water, the total hardness is 0-30ppm, which is called soft water. The total hardness is 60ppm or more, which is called hard water. The high-quality drinking water does not exceed 25ppm, and the high-quality soft water has a total hardness of 10ppm or less. In natural water, away from the city, unpolluted rainwater and snowwater are soft water; spring water, stream water, river water, and reservoir water are mostly temporary hard water, and some groundwater is high hardness water.

When water droplets condense in the atmosphere, carbon dioxide in the air is dissolved to form carbonic acid. Carbonic acid eventually falls on the ground with rain and then seeps through the soil to the rock layer, dissolving lime (calcium carbonate and magnesium carbonate) to produce temporary hard water. The hard water near the caves and caves in some areas is formed in this way.

The pros and cons of hard water

Hard water has many disadvantages: 1. It produces an insoluble precipitate when reacted with soap to reduce the washing effect. (Using this point can also distinguish between hard water and soft water.) 2. Industrially, the precipitation of calcium salt and magnesium salt will cause scale, hinder heat transfer, and in serious cases, the boiler will explode. Due to the hard water problem, the industry will cost tens of millions of yuan each year for the repair and replacement of equipment and pipelines. 3. Drinking hard water will also have a certain impact on human health and daily life. People who do not drink hard water occasionally drink hard water, which can cause gastrointestinal dysfunction, the so-called "water and soil dissatisfaction"; cooking fish and vegetables with hard water will destroy or reduce the nutritional value of food because it is not easy to cook; use hard water to make tea Changing the color and aroma of tea reduces its drinking value; making tofu with hard water not only reduces the yield but also affects the nutrients of the tofu.

So hard water is nothing? No, otherwise how can there be so many people buying mineral water to drink? It turns out that both calcium and magnesium are macroscopic metal elements in essential elements of life. Scientists and medical scientists have found that the mortality rate of certain cardiovascular diseases, such as hypertension and arteriosclerotic heart disease, is inversely proportional to the hardness of drinking water. The water hardness is low and the mortality rate is high. In fact, long-term drinking of hard or soft water is unfavorable to human health.

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