Water purification information

Introduction of various indexes of reverse osmosis membrane

Update time : 2021-09-27 17:47:07

1. Desalination rate and salt permeability of reverse osmosis membrane

Salt permeability = product water concentration / influent water concentration × 100%

Desalination rate = (1-salt content of product water / salt content of influent water) × 100%

Salt penetration rate = 100%-desalination rate

The desalination rate of the 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 membrane element. The denser the desalination layer, the higher the desalination rate and the lower the water production.

The desalination rate of different substances by reverse osmosis 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 ions, potassium ions, and chloride ions is slightly lower. , But it also exceeds 98%; the removal rate of organics with a molecular weight greater than 100 can also exceed 98%, but the removal rate of organics with a molecular weight of less than 100 is low.

2. Water production of reverse osmosis membrane

Water production-refers to the water production capacity of the reverse osmosis system, that is, the amount of water permeating the membrane per unit time, usually expressed in tons/hour or gallons/day.

Permeation flow rate-is also an important indicator of the water production of reverse osmosis membrane elements. 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 membrane surface to increase, which will aggravate membrane fouling.

3. Recovery rate of reverse osmosis membrane

Recovery rate-refers to the percentage of feed water converted into product water or permeate in the membrane system. Depends on the pretreatment influent water quality and water requirements. The recovery rate of the membrane system has been determined at the time of design,

Recovery rate = (product water flow/influent flow) × 100%

For large RO systems, the recovery rate is usually limited by the tendency of insoluble salt to foul, that is, by the maximum concentration of concentrated water; for small RO systems, the recovery rate is usually less than 30% to 50%. When the recovery rate is low, the RO device can operate safely without controlling the solubility of insoluble salts. Cost is usually not a priority for small RO systems.

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