The Main Indicators for Measuring the Performance of Reverse Osmosis Membranes Are Desalination Rate and Salt Permeability

Desalination rate – The percentage of soluble impurities removed from the feed water through the reverse osmosis membrane.

Salt permeation rate – The percentage of soluble impurities in the feed water that permeate through the membrane.

Desalination rate = (1 - Permeate salinity/Feed water salinity) × 100%

Salt permeation rate = 100% - Desalination rate

The desalination rate of the membrane element is determined during its manufacturing process. The desalination rate depends on the density of the ultra-thin desalination layer on the membrane element's surface; the denser the desalination layer, the higher the desalination rate, but the lower the permeate flow. The removal rate of different substances by reverse osmosis is mainly determined by the structure and molecular weight of the substance. The removal rate for high-valence ions and complex monovalent ions can exceed 99%. The removal rate for monovalent ions such as sodium, potassium, and chloride ions is slightly lower, but still exceeds 98%. The removal rate for organic matter with a molecular weight greater than 100 can also reach 98%, but the removal rate for organic matter with a molecular weight less than 100 is lower.