Regarding the purification and filtration of the drinking water end, the materials used are not complicated. There are mainly stainless steel strainers, PP cotton, activated carbon and various filter membranes. The first three materials cannot remove some bacteria, viruses and water-soluble salts due to their large pore size. And heavy metal ions, so the protagonist of clean water filtration is mainly the last various filter membranes.
At present, there are mainly three kinds of filter membrane technologies on the market, namely ultrafiltration, nanofiltration and RO reverse osmosis. The difference between the first three membranes is mainly that the pore size of the membrane is different, and the substances that can be filtered are different.
1, ultrafiltration, nanofiltration
Ultrafiltration membranes filter most of the impurities in the water, but they are still free of heavy metal ions. Nanofiltration is a filtration method between ultrafiltration and RO reverse osmosis. This membrane has a negative charge and can repel the negatively charged heavy metal ions outside the membrane, while retaining the positively charged calcium and magnesium in the water. Trace elements such as sodium, in principle, can remove harmful heavy metals and retain substances beneficial to the human body.
Since the nanofiltration has a small pore size, it is also required to be energized and pressurized, and a part of the wastewater is generated. However, compared to RO reverse osmosis, the nanofiltration pore size is still much larger, so the pressure required is less, the proportion of wastewater is less, and the water output speed will be faster.
Advantages: low cost, fast water delivery, no need to run on power
Disadvantages: unable to completely filter heavy metal ions
Advantages: retain beneficial trace elements and filter most harmful substances
Disadvantages: need to be energized to produce wastewater
2. Reverse osmosis is to pressurize the tap water at one end of the RO membrane. When the pressure reaches a certain level, the water molecules will reversely penetrate against the direction of natural penetration, thereby obtaining pure water. The theory is not important, let's talk about the effect.
RO reverse osmosis technology is different from general filtration technology in that the water purifier using reverse osmosis filtration needs to be energized, and the wastewater will be generated during the filtration process. The ratio of waste water to purified water is about 1:1 to 1:3. So every time you filter, you will waste more than half of the water.
RO reverse osmosis
Advantages: The purified water is basically pure water.
Disadvantages: Waste water, electricity, and water are very slow.