What are the differences between dry and wet reverse osmosis membrane elements?

Differences in the use of reverse osmosis membranes: The manufacturing processes of conventional aromatic polyamide reverse osmosis composite membranes are similar. A polyester non-woven fabric is used as the structural support layer. A highly permeable microporous polysulfone layer is pre-coated on the non-woven fabric as a support layer. Then, an ultra-thin film separation functional layer is formed through interfacial polymerization, generally as a wet membrane. If a dry membrane is required, the wet membrane must be passed through a drying unit. Therefore, the difference between a dry membrane and a wet membrane is that a dry membrane is made by drying a wet membrane.

Differences in the reverse osmosis membrane element winding process: Wet membrane elements use wet membranes, and dry membrane elements use dry membranes. There is no significant difference in the winding process flow of the two.

Advantages of wet reverse osmosis membrane elements:

1. Each wet reverse osmosis membrane element generally undergoes performance testing before leaving the factory, ensuring that the performance of each element meets the standard, eliminating defective products.

2. Wet reverse osmosis membrane elements have superior initial performance. After simple rinsing upon on-site installation, the best performance of the membrane element can be achieved, saving start-up time and rinsing water.

3. The basic reverse osmosis performance of wet membrane elements is generally superior to that of dry membrane elements, i.e., the salt rejection rate and water production are slightly better.

Disadvantages of wet reverse osmosis membrane elements:

1. Wet membrane elements require protective liquid or other protective measures, and the membrane elements must always be kept moist and free from microbial contamination.

2. Because the membrane elements are wet, transportation below freezing point in winter should preferably use insulated vehicles, or they should be stored in a place above freezing point upon arrival.

Advantages of dry reverse osmosis membrane elements:

1. The manufacturing technology and equipment of dry membrane elements are relatively more complex, but dry membrane elements do not require protective liquid or other special protective measures. They are lighter, have relatively lower transportation costs, and have a longer storage time.

2. Because dry membrane elements are not wet, special vehicles are not required for transportation below freezing point in winter, making transportation convenient. The requirements for storage conditions are also lower.

Disadvantages of dry reverse osmosis membrane elements:

1. Random sampling is used before the membrane elements leave the factory, which cannot guarantee that the performance of each element meets the standard, and there is a possibility of defects in the elements leaving the factory.

2. The initial performance of the membrane elements is lower after installation in the system, requiring prolonged soaking and rinsing before the membrane element performance gradually reaches its optimal state, wasting time and rinsing water.

3. The basic reverse osmosis performance of the membrane elements, i.e., water production and salt rejection rate, is generally slightly lower than that of wet membrane elements.