As a deep filtration means, the surface of reverse osmosis membrane element will inevitably remain colloids, microorganisms, impurity particles and insoluble salts on its surface. Therefore, once put into use, the reverse osmosis devices used in many fields will eventually need to be cleaned, but the length of cleaning cycle is different. However, as a means of reverse osmosis system cleaning and maintenance, impact sterilization and regular protection, on-line cleaning is powerless in the face of severe pollution of reverse osmosis membrane elements. At this time, it is necessary to clean the reverse osmosis membrane elements off-line.
Although there will be a certain degree of margin in the design of reverse osmosis system to ensure that there will be no threat to safe production due to insufficient water supply due to the decrease of water production or desalination rate of reverse osmosis system and the increase of differential pressure of reverse osmosis system in case of emergency, But in fact, it is because of the existence of these margins that sometimes hidden faults can not be displayed in time, which may eventually evolve into severe pollution of reverse osmosis membrane components.
The concept of severe pollution of reverse osmosis membrane elements refers to the surface adhesion and Deposition Pollution of RO membrane caused by suspended solids, colloids, organics, microorganisms and other particles contained in the influent of reverse osmosis system, or the formation of chemical scale after the ion product is greater than the solubility product due to concentration polarization and other factors on the membrane surface. Severe pollution refers to the situation that the single section pressure difference after pollution is more than 2 times of the single section pressure difference at the initial stage of system operation, the water production of reverse osmosis system decreases by more than 30 percent , or the weight of single reverse osmosis membrane element exceeds the normal value by more than 3kg.
Severe pollution is often the superposition of severe physical pollution and severe chemical pollution. In some cases, they are accompanied at the same time.
