There are many reverse osmosis membrane materials, including various organic polymer materials and inorganic materials. At present, the commonly used membranes in industry are mainly cellulose acetate membrane (CA) and aromatic polyamide membrane (PA) and composite membrane.

During the operation of the system, the surface of the reverse osmosis membrane will be polluted by the deposition of heavy metal hydroxide produced by the presence of subfine particles, colloids, organic matter, microorganisms and other pollutants in the raw water and the multiple concentration of heavy metal hydroxide during the operation. When the reverse osmosis membrane is contaminated, the system water production decreases and the desalination rate decreases. Therefore, the system needs to be automatically backwash regularly, and the remaining concentrated water in the membrane element is washed off to remove the pollutants on the surface of the reverse osmosis membrane, prevent the concentrated water from being deposited on the surface of the reverse osmosis membrane and prolong the service life of the membrane; in addition, regular chemical cleaning is needed to restore the excellent properties of the membrane, and sometimes aseptic treatment is needed.

Extension: Softener

ion exchange softening device is the most commonly used equipment in water treatment process. its function is to remove calcium and magnesium ions that form scale in hard water. in many cases, soluble ions (iron ions) can be removed using softened water equipment. Standard soft water equipment has four main parts: resin column, resin, salt adding device, valve controller.

Soft water equipment resin column containing treated ion exchange resin - polystyrene particles. The resin particles initially adsorb sodium ions during regeneration, which has a much greater affinity for multivalent ions such as calcium and magnesium ions. Therefore, when hard water flows through the resin, calcium and magnesium ions will adsorb on the resin, and at the same time desorption ions until the equilibrium state is reached. At this point, the soft water equipment to complete the sodium ion and water calcium magnesium ion exchange.

During regeneration, the NaCl solution flows through the resin and the hard ions are replaced by sodium ions. This affinity between the resin and hard ions is reduced by using high concentration of brine. this regeneration process can be carried out indefinitely without damaging the resin.

The softener is a simple ion exchange process that solves the most common form of water pollution: hardness. regeneration using NaCl is a simple but not expensive process, also enables automatic regeneration without strong chemical reagents.