With the development of science and technology, human civilization has become more and more prosperous, and social life has been prolonged. In the long river of history, we have gained a lot of lessons. Today, the average life expectancy of human beings is from 15 years old in BC to 35 years old in the Renaissance, 60 years old in the last century, and now 80 years old. The biggest reason may be the improvement of medical standards. Still, it must be said that the ever-increasing quality of life has also contributed significantly to the extension of life. There is an old saying in China called “Disease from the mouth”. Take drinking water as an example. Let’s discuss this issue.


The direct drinking water flowing out of the water pipe needs several processes like coagulation, sedimentation, filtration, and disinfection. Because the raw water contains impurities due to various natural and human factors, these impurities can be classified into three categories: suspended solids, colloids, and dissolved materials.

First, a chemical coagulant (such as iron salt, aluminum salt, or polymer) is added to the raw water and stirred slowly. The fluctuating water causes the particles to collide with each other and fuse into larger and more easily removable floes.

The water after the coagulation process flows into the sedimentation tank, the particles in the water sink to the bottom of the pool and are periodically discharged outside the pool. Then the sedimented water needs filtering, and the direct drinking water is filtered differently than the tap water and needs to be screened several times.


The first step is rough filtration, the granular filter layer with voids such as quartz sand intercepts the suspended particles in the water, and removes the large particulate impurities of various suspended materials.


Then there is ultrafiltration, which filters out some colloids, fine impurities, and macromolecular organics, including some E. coli and so on.

The third step is activated carbon filtration, which could remove some of the color’s, special taste, residual chlorine, and chlorine-containing by-products. The concentration of trihalomethane in the final effluent can be deficient through this step, and there is no odor of chlorine disinfection. The turbidity of the water is further reduced after filtration, and the residual bacteria, viruses, and the like are also lost to the protection or attachment, thereby creating favorable conditions for post-filtration sterilization.

The tap water disinfection depends on hypochlorous acid produced by the reaction of chlorine and water oxidizes inside the bacteria to cause the bacteria to die. However, drinking water is much more complicated. After filtration, it is UV-sterilized and then passed through a security filter.

The most pivotal is the filtration of the reverse osmosis membrane, according to the principle of reverse osmosis to remove various ions, organic matter, suspended matter, and the like in the water. Moreover, this step could reduce the calcium and magnesium ions in the water, which can reduce the hardness of the water and improve the mouthfeel. What’s more, it also removes nitrate from the water and heavy metal ions that may be present in the water. Finally, ozone sterilization.

From the filtration process, it can be concluded that after repeated filtration and disinfection, the drinking water is not contaminated with other pollutant components, such as pathogenic pyrogens, total organic carbon, or dissolved solids. This dramatically reduces the likelihood that many water users will get sick. In addition to water, many of the liquids that enter our mouth are also filtered to make the liquid purer. Milk, juice, mineral water, honey, wine, spirits, beer, liquor, cooking oil, syrup, and other products like these.

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