Water Hardness

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

Water is classified as soft water or hard water. Water containing little or no calcium and magnesium ions is called soft water, while water with abundant calcium and magnesium ions is called hard water. If the hardness is caused by sodium bicarbonate or magnesium bicarbonate, it is temporary hard water (boiling temporarily hard water decomposes the sodium bicarbonate, forming insoluble carbonates that precipitate, thus softening the water). If the hardness is caused by calcium and magnesium sulfates or chlorides, it is permanent hard water, which cannot be removed by boiling. Both types of hardness are collectively called total hardness. Based on the total hardness value, water with a total hardness of 0-30 ppm is considered soft water, and water with a total hardness above 60 ppm is considered hard water. High-quality drinking water has a total hardness of no more than 25 ppm, and high-quality soft water has a total hardness below 10 ppm. In natural water sources, rainwater and snowmelt from unpolluted areas far from cities are considered soft water; spring water, stream water, river water, and reservoir water are mostly temporarily hard water, while some groundwater is highly hard water.

When water droplets condense in the atmosphere, they dissolve carbon dioxide to form carbonic acid. This carbonic acid eventually falls to the ground with rainwater, then seeps through the soil to the rock layer, dissolving limestone (calcium carbonate and magnesium carbonate) to produce temporarily hard water. This is how hard water forms in and near some caves.

Advantages and Disadvantages of Hard Water

Hard water has many disadvantages: 1. When it reacts with soap, it produces insoluble precipitates, reducing washing effectiveness. (This can also be used to distinguish between hard and soft water.) 2. In industry, the precipitation of calcium and magnesium salts can cause scale buildup in boilers, hindering heat conduction and, in severe cases, leading to boiler explosions. Due to hard water problems, industries spend tens of millions of yuan annually on equipment and pipeline maintenance and replacement. 3. Drinking hard water can also have certain impacts on human health and daily life. For those who don't regularly drink hard water, occasional consumption can cause gastrointestinal upset, a condition known as "water and soil incompatibility." Cooking fish, meat, and vegetables with hard water can make them difficult to cook thoroughly, damaging or reducing their nutritional value. Brewing tea with hard water alters its color, aroma, and flavor, lowering its overall drinking value. Making tofu with hard water not only reduces yield but also affects the tofu's nutritional composition.

So, is hard water completely useless? Not at all, otherwise why would so many people buy bottled water? Calcium and magnesium are essential macro-elements for life. Scientists and medical researchers have found that the mortality rate from certain cardiovascular diseases, such as hypertension and arteriosclerotic heart disease, is inversely proportional to the hardness of drinking water; lower water hardness is associated with higher mortality rates. In fact, long-term consumption of excessively hard or soft water is detrimental to health. my country stipulates that the hardness of drinking water should not exceed 25 degrees.