Water purification information

What is reverse osmosis membrane

Update time : 2021-10-15 16:29:06

Reverse osmosis membrane is an artificial semi-permeable membrane with certain characteristics made by simulating biological semi-permeable membrane, and it is the core component of reverse osmosis technology. The principle of reverse osmosis technology is that under the action of higher than the osmotic pressure of the solution, other substances cannot pass through the semi-permeable membrane and these substances and moisture are removed. The membrane pore size of the reverse osmosis membrane is very small, so it can effectively remove dissolved salts, colloids, microorganisms, and organic matter in the water. The system has the advantages of good water quality, low energy consumption, no pollution, simple process and easy operation.

Customers often ask what performance indicators we need to consider when we choose reverse osmosis RO membranes. Usually divided into three: desalination rate, water production, recovery rate.

1. Desalination rate and salt permeability of RO reverse osmosis membrane
The desalination rate of the RO reverse osmosis membrane element is determined when it is manufactured and formed. The desalination rate depends on the density of the ultra-thin desalination layer on the surface of the reverse osmosis RO membrane element. The denser the desalination layer, the higher the desalination rate and the greater the water production. Low. The desalination rate of different substances of reverse osmosis membrane is mainly determined by the structure and molecular weight of the substance. The desalination rate of high-valent ions and complex monovalent ions can exceed 99%, and the desalination rate of monovalent ions such as sodium, potassium, and chloride is slightly Low, but it can also exceed 98% (the longer the reverse osmosis membrane is used, the more the number of chemical cleanings, the lower the salt rejection rate of the reverse osmosis membrane). The removal rate of organic matter with a molecular weight greater than 100 can also exceed 98%. The removal rate of organic matter with molecular weight less than 100 is low.
Calculation method of salt rejection and salt permeability of reverse osmosis membrane:
Salt permeability of RO membrane = RO membrane product water concentration / influent water concentration × 100%
RO membrane desalination rate = (1-RO membrane water salt content / influent salt content) × 100%
Salt penetration rate of RO membrane = 100%-desalination rate
2. Water production and permeate flow rate of RO reverse osmosis membrane
RO membrane water production-refers to the water production capacity of the reverse osmosis system, that is, the amount of water passing through the RO membrane per unit time, usually expressed in tons/hour or gallons/day.
The permeate flow rate of the RO membrane is also an important indicator of the water production of the reverse osmosis membrane element. Refers to the flow rate of permeate per unit membrane area, usually expressed in gallons per square foot per day (GFD). Too high permeate flow rate will cause the water velocity perpendicular to the surface of the RO membrane to increase, which will aggravate membrane fouling.
3. Recovery rate of RO reverse osmosis membrane
The recovery rate of RO membrane-refers to the percentage of feed water converted into product water or permeate in the reverse osmosis membrane system. Depends on the pretreatment influent water quality and water requirements in the reverse osmosis system. The recovery rate of the RO membrane system has been determined at the time of design.
(1) Recovery rate of RO membrane = (Production water flow rate of RO membrane/Inlet water flow rate) × 100%
(2) The calculation formulas for the recovery rate, salt permeability and desalination rate of reverse osmosis (nanofiltration) membrane modules are as follows:
Recovery rate of reverse osmosis membrane module = RO membrane module water production/intake water×100%
Salt permeability of reverse osmosis membrane module = RO membrane module product water concentration/influent water concentration × 100%

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