Analysis of water hardness and residual chlorine

Introduction: Regardless of where it is located, as a drinking water source, it will surely contain a certain amount of calcium and magnesium ions. Residual chlorine is the only substance in tap water that must be added artificially and must retain a certain amount of residual substances. It can be considered as a disinfectant residue. How can we understand and look at the water hardness and residual chlorine?

Water hardness:

Regardless of where it is located, as a source of drinking water, it will certainly contain a certain amount of calcium and magnesium ions (the sum of calcium and magnesium ions is the definition of total water hardness, and the total hardness of water in different countries and industries has different equivalents and units. Different equivalents and units can be freely converted).

Calcium and magnesium ions are harmless to the human body, and even they are essential elements for the human body. However, depending on the region, excessively high hardness of water can also have a negative impact on drinking water or food. For the beverage industry, the most direct influence is the taste of water. In GB5749-2006, the proposed limit for the hardness of tap water is less than 450mg/L. This standard will not exceed the standard in the southern region in general, but in the northern or mountainous regions. In particular, where groundwater is used as source water, there may be problems with excessive water hardness.

This may happen in everyday life. After boiling the water, there is a large amount of white precipitate in the kettle. This is because the calcium and magnesium ions in the water precipitate out as carbonates, which is also known as temporary hardness. (Temporary hardness: It refers to the hardness of bicarbonate ion and carbonate ion as the temporary hardness. This part of hardness can be removed by heating and boiling. Durability: After heating and boiling natural water, calcium ions still remain in the water. The amount of magnesium ion is called permanent hardness)

Need to monitor the hardness of water regularly

1. In the aspect of industrial water, excessive water hardness may affect the normal operation of equipment and pipelines due to the precipitation of scale, especially in the circulating water, boiler and other industries, and some other precision instruments use water with hardness requirements. .

2, the general household water without excessive worry about the hardness of drinking water. However, with the improvement of living standards, some households will install household water treatment equipment. These household water treatment equipment can generally achieve the effect of softening the hardness of water. At this time, the hardness of raw water and effluent can be properly detected to evaluate the water purification soft water. Whether the effect is achieved and whether replacement of the accessory is required.

3, some food industry water will have requirements for water quality, such as making tea or coffee, water is often considered to be better in a certain hardness range of water, rather than completely non-hard water.

Residual chlorine:

The only substance in tap water that has to be added to the human body and must retain a certain amount of residue is considered to be a disinfectant residue (of course, it can also be other types of disinfectants, such as chlorine dioxide, ozone, etc.) ),

The strict meaning of residual chlorine includes free residual chlorine and combined residual chlorine. Free residual chlorine refers to Cl2, HOCl, and OCl in aqueous solution in water, which are collectively referred to as free residual chlorine, and have good antivirus effect and strong oxidizing property. In addition, chlorine and ammonium react to produce chloramine (monochloramine, dichloramine, trichloramine) known as combined chlorine. (The residual chlorine in this department refers specifically to free residual chlorine)

Now many news reports have mentioned the problem of excess chlorine. As the core issue of food safety, drinking water safety has always affected the nerves of consumers. In fact, residual chlorine itself will not bring serious safety problems, because residual chlorine is very easy. By boiling or leaving it for a long time to remove it, the problem is that excessive chlorine residues react with organic matter in the water to produce toxic and harmful substances. At the same time, high residual chlorine will lead to water odor and some skin allergies allergic reactions to chlorine in the water.

However, the residual chlorine in water can not exist, because it is under the current technical conditions to ensure that the tap water in the water pipe in the process of transporting the bacteria does not exceed the standard of super bodyguard “motivation”, based on this special attribute, residual chlorine in daily water monitoring is particularly important . In the tap water production process, the tap water company must strictly comply with the requirements of GB5749-2006 so that the residual chlorine value of the factory water reaches the national standard limit (not less than 0.3mg/L), and the water quality of the faucet effluent still meets the standard (not less than 0.05 Mg/L) must also meet the maximum limit (less than 4mg/L).

However, for industrial water users, the “super bodyguard” of the residual chlorine in the process of transportation is redundant in the water use process. The main reason is that the residual chlorine may have a certain impact on the industrial water treatment membrane, and the industrial production water will also be The presence of residual chlorine produces an unfavorable chemical reaction, so at this point the user must detect the residual chlorine to confirm if it is completely removed before use.

When domestic water is used, the chlorine used to control the growth of bacteria has no meaning in the tap. Excessive chlorine in addition to odor and by-products, it is gratifying that almost all household-grade water purification equipment can now Remove residual chlorine completely.

Source: Guangdong Huankai Microbial Technology Co., Ltd.