The current mainstream reverse osmosis membrane is made of fully aromatic and highly cross-linked polyamide. Reverse osmosis technology is widely used for seawater desalination. This is the only known way to effectively replenish fresh water at sea besides collecting rainwater. Of course, there are special desalination membranes for seawater desalination, but the principle is the same. The largest application of seawater desalination in China is In Changdao, Shandong, because there is no fresh water supply on the island, all fresh water is obtained through seawater desalination. The daily processing capacity reaches tens of thousands of tons, and the comprehensive cost is between 8 and 10 yuan per ton, which is quite economical. Then, reverse osmosis technology was widely used for sewage treatment. Some people may ask, how can reverse osmosis be used in sewage? In fact, many wastewater pollutants in industry are very serious, including various highly toxic substances. If they are directly discharged into natural water bodies, it may cause very serious consequences. The advantage of reverse osmosis is that it removes most dissolved substances from water. Generally speaking, the desalination rate of a qualified reverse osmosis membrane system is about 95% to 98%. Therefore, after sewage is pretreated and then reverse osmosis is carried out, the water that comes out can basically meet the requirements for direct discharge. Since I am a non-professional, I also have a question. Although sewage can be treated by reverse osmosis, concentrated water still appears. When used at home, it is drained with tap water. So in sewage treatment, where is the water that exceeds the treatment limit of the reverse osmosis membrane? I hope professionals can answer this question. Next, let’s look at water used in the pharmaceutical and food industries. Both of these require reverse osmosis treatment to remove pollutants. In the pharmaceutical industry, ultrapure water is used, which needs to undergo reverse osmosis treatment twice, and then be further processed by EDI ultrapure water equipment. After three-level treatment, it can reach a level without any impurities and bacteria (0.00x ppm). The food industry is not so strict. Generally, it goes through a first-level reverse osmosis to remove most (more than 95%) of the impurities and bacteria and viruses in it. Reverse osmosis water treatment is also widely used in the electroplating industry, mainly to remove salt in the water. The presence of salt will affect the effect of electroplating. This is a necessity for the electroplating industry.