At present, the deteriorating water quality of water sources puts forward higher requirements for the upgrading and upgrading of water plants. Water plants must not only solve biological safety problems, but also solve chemical and organic pollution problems, so advanced treatment is indispensable. Membrane separation technology is a high-tech in the field of water treatment. At different stages of treatment, different membrane separation technologies are adopted. Nanofiltration and reverse osmosis are mainly used for advanced treatment. Ultrafiltration can be used for precision filtration due to limited retention of molecules. China Water Net interviewed Wang Zhansheng, a professor at the School of Environment of Tsinghua University, and He Shouping, the consultant editor-in-chief of China Water Net, on the question of "Why ultrafiltration technology is not an advanced treatment process in water plants".

Ultrafiltration has limited molecular weight cut-off and can be used for precision filtration

Wang Zhansheng said that due to the limited molecular weight that ultrafiltration can intercept, the molecular weight is usually 10-30 million. Ultrafiltration membranes are inferior to activated carbon treatment technology in removing small molecular organic pollutants. If the odor-producing substances are generally small molecules, which cannot be removed by ultrafiltration, the use of ultrafiltration cannot achieve the effect of advanced treatment. However, ultrafiltration can replace filtration and can remove particles of 0.001-0.01 microns, while traditional sand filtration generally only removes particles above 50 microns, so ultrafiltration can be used as precision filtration.

Wang Zhansheng also pointed out that ultrafiltration equipment saves space, and submerged ultrafiltration can double the water flow compared to conventional filters. Under the situation of tight urban land resources, ultrafiltration will have a broad scope during the reconstruction and expansion of water plants. Application space.

Ultrafiltration mainly solves the problem of water biological safety

He Shouping pointed out that in the domestic and international water quality standards, biological safety is the top priority. Ultrafiltration is the main means to solve the biological safety of water quality, which can remove bacteria and viruses. The biological safety is guaranteed, and the amount of disinfectant used in the water treatment process will be reduced, thereby reducing the problem of disinfection by-products. Wang Zhansheng also said that ultrafiltration does not add chemical pollutants during the treatment process, which can ensure that the turbidity is below 0.1 degrees and ensure the safety of microorganisms.

Related reading: Nanofiltration and reverse osmosis effective means of advanced treatment

Reverse osmosis is the highest-end single treatment technology in the field of water treatment. It can block all soluble salts and organics with a molecular weight greater than 100, and can remove dissolved salts, metal ions and other small molecules. Generally, the effluent quality of reverse osmosis treatment is better. Nanofiltration can cut off the molecular weight between reverse osmosis and ultrafiltration, 200-2000, and has a certain rejection rate for inorganic salts. Nanofiltration and reverse osmosis are effective means of advanced treatment, which can solve the problems of chemical pollution and organic pollution.