1. Concentration polarization. In the reverse osmosis desalination system, the selective permeability of the membrane makes water molecules continuously permeate through the membrane from the high pressure side, while solute molecules remain in the original solution, resulting in a concentration difference between the feed liquid on the membrane surface and the imported feed liquid. In severe cases, it will produce a high concentration gradient. This phenomenon is called concentration polarization.
2. Inorganic salt scaling. Salts with small solubility products, such as CaCO3, CaSO4, BaSO4, SrSO4, CaF2 and SiO2, may be separated out during reverse osmosis due to concentration exceeding their solubility products, resulting in deposits staying on the membrane surface or forming scale in the inlet channel.
3. Adsorption pollution. Some well water sources in the brackish water range generally contain low-valent iron ions and manganese ions, which have certain reducibility. The main reason for membrane fouling caused by such water sources is that iron, aluminum, manganese, etc. produce colloidal particles fouling on the membrane surface. When O2 enters the influent water containing Fe2+, high alkalinity water source forms ferric carbonate and ferric silicate, reducing bacteria are mixed in, and iron scale is formed faster and faster, and colloidal iron is caused by the transformation of ferric flocculant.
