Reverse osmosis (RO) series

Introduction of reverse osmosis technology
     Reverse osmosis is currently the most advanced, energy-saving and effective separation technology in the world. Principle of the technology: Under force exceeding the osmotic pressure of solvent, impurities can be separated from water because such substances can not penetrate semi-permeable membrane. Since pore diameter of reverse osmosis is extremely small (only around 10A), so 97%-98% of dissolved salt, colloid, microorganism and organic matters in water can be effectively filtered. Reverse osmosis is the most widely adopted desalination technology in high purity water treatment equipment at present. It targets at organic ions and organic matters of molecular weight of several hundred. Reverse osmosis (RO), ultrafiltration (UF), micro-filtration (MF) and electrodialysis (EDI) technology all belong to membrane separation technology.

In recent three decades, RO, EDI, UF and MF technologies have been applied industries such as electronics, chemical, foodstuff, pharmaceutical and drinking water.

Working principle of reverse osmosis technology
1. Osmosis and osmotic pressure
     Osmosis is a common phenomenon in the nature. For example, if you put a cucumber in water, the cucumber will lose water and shrink. The process of water molecules entering salt water solution is referred to as osmosis. If we use a membrane that allow water molecules to pass to divide a water tank into two halves, and infuse pure water and salt water to the same height at the two sides respectively, after a while, we can discover that the water level at the pure water side increases, while the water level at the other side decreases. However, the water level at the salt water side will not increase limitlessly. Instead, it will reach an equilibrium point at a certain height. Then the pressure represented by water surface level difference between the two sides is called osmotic pressure, which is directly related to concentration of salt water.
2. Reverse osmosis phenomenon and reverse osmosis water purifying technology
    When the set-up above reaches an equilibrium point, if certain pressure is applied on the salt water side, then water molecules will migrate from the salt water side to the pure water side. This phenomenon is called reverse osmosis. If salt water is infused at one side of the set-up and pressure exceeding the osmotic pressure of the salt water is applied, we can obtain pure water at the other side. This is the principle of reverse osmosis water purification.
    There are two key factors of pure water production by reverse osmosis equipment: one is a selective membrane which is called semi-permeable membrane, while the other is certain pressure. To put it simple, there are numerous pores on reverse osmosis semi-permeable membrane, the size of which is equivalent to that of water molecules. Because bacteria, virus and most of organic pollutants and aquo ions are much larger than water molecules, they can not penetrate reverse osmosis semi-permeable membrane so as to separate from water molecules capable of penetrating the reverse osmosis membrane. Among numerous impurities in water, dissolved salt is most difficult to get rid of. Therefore, salt removal rate is often used to determine the effect of reverse osmosis water purification, while the salt removal rate is mainly decided by the selectivity of reverse osmosis semi-permeable membrane. Currently, salt removal rate of good reverse osmosis semi-permeable membrane can reach as high as 99.7%.

Small-sized reverse osmosis main machine	Medium-sized reverse osmosis main machine	Large-sized reverse osmosis main machine

Two-level reverse osmosis process chart