The origin of reverse osmosis water treatment equipment
Reverse osmosis water treatment, also known as reverse osmosis, is a membrane separation operation that uses pressure difference as the driving force to separate the solvent from the solution. Because it is opposite to the direction of natural infiltration, it is called reverse osmosis. According to the different osmotic pressures of various materials, a reverse osmosis pressure greater than the osmotic pressure, that is, reverse osmosis method, can be used to achieve the purpose of separation, extraction, purification and concentration.
Reverse osmosis water treatment equipment usually consists of three parts: raw water pretreatment system, reverse osmosis purification system, and ultra-purification post-treatment system. The main purpose of pretreatment is to make the raw water meet the influent requirements of the reverse osmosis membrane separation module, and the stable operation of the reverse osmosis purification system. The reverse osmosis membrane system is an economical purification method to remove more than 98% of ions, organic matter and 99% of microorganisms (theoretically) in raw water. The ultra-purification post-treatment system further removes trace ions, organic matter and other impurities remaining in reverse osmosis pure water through a variety of integrated technologies to meet the water quality index requirements for different purposes.
Reverse osmosis is an ultra-precise membrane liquid separation technology. The operating pressure is applied on the influent (concentrated solution) side to overcome the natural osmotic pressure. When the operating pressure higher than the natural osmotic pressure is applied to the concentrated solution side, the flow of natural osmosis of water molecules The direction will be reversed, and the water molecules in the influent (concentrated solution) will pass through the reverse osmosis membrane to become the purified water on the dilute solution side; the reverse osmosis equipment can block all dissolved salts and organic substances with a molecular weight greater than 100, but allow water molecules. The desalination rate of reverse osmosis composite membranes is generally greater than 98%. They are widely used in the preparation of industrial pure water and electronic ultrapure water, the production of drinking pure water, boiler feed water and other processes. The use of reverse osmosis equipment before ion exchange can greatly reduce the amount of salt. bottom operating water and wastewater discharge.
The pretreatment system of reverse osmosis water treatment equipment usually consists of polypropylene fiber (PP) filter and activated carbon (AC) filter. For raw water with higher hardness, a softening resin filter needs to be installed. The PP filter element can remove pollutants such as mechanical particle impurities, rust and large colloids above 5μm in the raw water, and protect the subsequent filter. It is characterized by large dirt holding capacity and low price. AC activated carbon filter can absorb residual chlorine and some organic substances and colloids in raw water, and protect polyamide reverse osmosis composite membrane from residual chlorine oxidation. The softening resin can remove most of the calcium and magnesium ions in the raw water, prevent the subsequent RO membrane surface fouling and blockage, and improve the water recovery rate.
Reverse osmosis is a high-tech membrane separation technology driven by pressure difference. It has the characteristics of high separation, no phase change and simplicity. The "pore size" of the reverse osmosis membrane is as small as nanometers (1nm=10-9m), and any "filtering" pores on the surface cannot be seen under the scanning electron microscope. Under the operating pressure higher than the osmotic pressure of the raw water, water molecules can reverse osmosis through the RO semipermeable membrane to produce pure water, while a large number of inorganic ions, organic matter, colloids, microorganisms, pyrogens, etc. in the raw water are retained by the RO membrane.
Usually, when the conductivity of raw water is less than 200μS/cm, the conductivity of first-grade RO pure water is less than or equal to 5μs/cm, which meets the standard of laboratory third-grade water. For areas with high electrical conductivity of raw water, in order to save the cost of subsequent mixed bed ion exchange resin replacement and improve the quality of pure water, customers can consider choosing a secondary reverse osmosis purification system. Raw water quality. The principle of reverse osmosis: put the same volume of dilute solution (such as fresh water) and concentrated solution (such as seawater or salt water) on both sides of a container, with a semi-permeable membrane in the middle, and the solvent in the dilute solution will naturally penetrate. After passing through the semipermeable membrane and flowing to the concentrated solution side, the liquid level of the concentrated solution side will be higher than the liquid level of the dilute solution by a certain height, forming a pressure difference and reaching a state of osmotic equilibrium. This pressure difference is the size of the osmotic pressure. Depending on the type of dope, the concentration and temperature are independent of the properties of the semipermeable membrane. If a pressure greater than the osmotic pressure is applied on the concentrated solution side, the solvent in the concentrated solution will flow to the dilute solution, and the flow direction of this solvent is opposite to the original infiltration direction. This process is called reverse osmosis.
Generally, after the tap water or groundwater is treated by the primary reverse osmosis water treatment equipment, the conductivity of the produced water is less than 10 μS/cm, and the conductivity of the produced water after the secondary reverse osmosis water treatment equipment is less than 5 μS/cm or even lower. The water treatment equipment system is supplemented by ion exchange equipment or EDI equipment to prepare ultrapure water, so that the resistivity can reach 18 megohms (conductivity = 1/resistivity). Reverse osmosis is to use sufficient pressure to make the solvent in the solution (generally Often referred to as water), it is separated out through a reverse osmosis membrane (a semi-permeable membrane) in the opposite direction of osmosis, and a reverse osmosis method greater than osmotic pressure can be used to separate, purify and concentrate the solution. The main separation object of the reverse osmosis membrane is the range of ions in the solution.
