The application of membrane technology in municipal water supply field

In essence, membrane separation technology is a physical form of phase separation, which mainly uses the selective separation characteristics of membrane to filter out impurities in water. According to the arrangement of membrane pore size from large to small, membrane filtration can be generally divided into microfiltration, ultrafiltration, nano filtration and reverse osmosis.

Microfiltration and ultrafiltration have common advantages, such as no by-products in the treatment process, easy automatic control, wide range of pH application, effective removal of viruses, bacteria, parasites and reducing the amount of disinfectant, etc. It have been widely concerned and applied in the municipal water supply field. And also It is suitable for the purification of micro polluted water source, and the effluent quality is excellent. In addition, after microfiltration, especially ultrafiltration membrane treatment, the microbial safety of drinking water is greatly improved.

In addition to the disinfection of the by-products, the ultrafiltration technology has the advantages of reducing the disinfection by-products. Compared with microfiltration and ultrafiltration, nano filtration has a certain ability to remove BDOC in raw water, which can further improve the chemical safety of drinking water. However, the water production rate of nano filtration membrane is relatively low, and the working pressure is larger than that of microfiltration and ultrafiltration, so the application of nano filtration membrane in municipal water supply field will be constrained by economic rationality.

Because of the finer pore size of reverse osmosis membrane, many substances (including ions) in water can not pass through the reverse osmosis membrane, so nearly pure water can be prepared. However, reverse osmosis membrane is generally suitable for desalination and hardness reduction of seawater and brackish water, treatment of water source polluted by heavy metals and nuclides, and industrial water treatment with special water quality requirements. It lacks of economy of general application in municipal water supply field.

Therefore, combined with the actual characteristics of municipal water supply field, considering the treatment capacity, engineering cost and operation economic rationality and other factors, it is generally considered that microfiltration membrane and ultrafiltration membrane are more suitable for municipal water supply field.