Water purifiers, also known as water purifying machines, can be categorized based on their structural composition into RO (Reverse Osmosis) reverse osmosis water purifiers, ultrafiltration membrane water purifiers, energy water purifiers, and ceramic water purifiers, among others.

Generally, reverse osmosis water purifiers use a 5-stage filtration process. As shown in the figure below:

In simple terms, its technical principle mainly utilizes membrane separation filtration technology driven by a pressure gauge. This technology originated in the 1960s and was initially used for aerospace research. As technology has continuously developed and updated, it has gradually been adapted for household use and is now widely applied in various fields.

The RO reverse osmosis membrane has a pore size as small as the nanometer level (1 nanometer = 10^-9 meters), which is one-millionth the diameter of a hair strand and invisible to the naked eye. Bacteria and viruses are 5000 times larger than it. Under certain pressure, H2O molecules can pass through the RO membrane, while inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses, and other impurities in the source water cannot pass through the RO membrane. This strictly separates the permeable pure water from the impermeable concentrated water, thus achieving the purpose of water purification.

RO reverse osmosis water purifiers produce pure water that is fresher, more hygienic, and safer compared to bottled water. They have a wide range of applications for water brands: the water can be consumed directly or boiled for drinking, and the most prominent feature in this regard is that kettles or electric kettles will no longer scale; using pure water for cooking makes the food more hygienic and more delicious; bathing with pure water can remove impurities from the skin, moisturize the skin, and achieve a natural beautifying effect; the water from water purifiers and purifying machines can provide the water needed for small appliances such as humidifiers, steam irons, and beauty devices, and there will be no annoying scale; the water produced by water purification equipment using this technology, when used with ice-making machines, produces crystal-clear ice cubes without any odor.

Currently, there is a claim in society that "RO reverse osmosis water purifiers filter out all the minerals beneficial to the human body, and the pure water produced does not contain minerals, which is not suitable for excessive consumption, as it may lead to rickets."

According to researcher E Xueli from the Environmental and Health Related Product Safety Institute of the Chinese Center for Disease Control and Prevention, this claim seems to have some merit at first glance, but upon careful analysis, it is found to be scientifically unfounded.

He explains that the role of water in the human body is: 1. Food digestion, 2. Nutrient transport, 3. Blood circulation, 4. Waste excretion, 5. Body temperature regulation. We have never heard of a doctor advising a patient to drink water to supplement nutrients when they lack nutrition and vitamins.

The nutrients and minerals that the human body extracts from water account for only 1%, while 99% of nutrients and minerals are obtained from grains, fruits and vegetables, chicken, eggs, and milk, not from water.

For example, molybdenum is beneficial to the human heart muscle. If one wants to obtain enough molybdenum through water, they would have to drink 160 tons of water a day, but eating a potato or a handful of melon seeds can meet the body's need for molybdenum.

Furthermore, a cup of milk contains as much calcium as 1200 cups of water, a pound of beef contains as much iron as 8300 cups of water, and a cup of orange juice contains as much vitamin as 3200 cups of water; therefore, people lacking nutrients can only supplement through food, not water.

Moreover, the organic minerals in water cannot be directly absorbed by the human body. Only by consuming the edible parts of animals or plants that have absorbed these minerals can the human body absorb them.

Have we ever heard of someone lacking a certain vitamin being advised to supplement by drinking water? No! Cleanliness is a hundred times better than pollution. It is unwise to drink dirty water for the sake of obtaining a small amount of nutrition.