Principle and prevention of water treatment ultrafiltration membrane pollution

In the process of using, ultrafiltration membrane will be polluted continuously. This is not only related to membrane material, pore size and distribution, membrane performance, but also closely related to the characteristics of raw water. The surface of the membrane and the soluble substances in the solution interact with each other, which largely determines the extent of membrane pollution. The molecular size, molecular weight and shape of the solution are closely related to the membrane pollution. At the same time, the situation of membrane pollution and the nature of pollutants interact, which affects the process of membrane pollution.

I. overview of pollution mechanism of ultrafiltration membrane technology

The fouling mechanism of ultrafiltration membrane in water treatment is that the interaction between particles and membrane materials is the main factor affecting membrane fouling. It is generally believed that membrane fouling is mainly caused by concentration polarization, formation and compression of filter cake layer, adsorption and pore plugging. In ultrafiltration process, membrane adsorption is considered to be the key to membrane fouling, which is related to the interaction of membrane, solvent and solute. Due to the different chemical properties and structures of membrane components, the mechanism of adsorption is also different, which can be generally divided into van der Waals force, electrostatic action, hydrophobicity, hydrogen bond, etc.

II. Pollution prevention and control of water treatment ultrafiltration membrane

By improving the properties of membrane and the characteristics of raw water, the process of membrane pollution can be delayed as much as possible, and the degree of membrane pollution can be reduced. The research on prevention and control of concentration polarization and membrane pollution mainly focuses on improving the properties of membrane, changing the characteristics of raw water and optimizing the separation operation conditions.

III. common cleaning methods of ultrafiltration membrane

Common cleaning methods: after the ultrafiltration membrane is used, the separation substances and other impurities will gradually accumulate on the membrane surface, causing pollution and blockage to the membrane. The effective cleaning of the membrane is an important means to extend the service life of the membrane. Common cleaning methods include chemical cleaning and physical cleaning.

Equal pressure cleaning method: close the ultrafiltration water valve, open the concentrated water outlet valve, and wash the membrane surface by increasing the flow rate. This method is effective for removing a large number of soft impurities on the membrane surface.

High purity water cleaning method: due to the increase of water purity, the dissolving capacity is enhanced. During cleaning, the loose dirt on the membrane surface can be washed away with ultrafiltration water first, and then it can be cleaned by pure water circulation.

Reverse cleaning method: that is to say, the cleaning water enters from the ultrafiltration port of the membrane and passes through the membrane and rushes to one side of the concentration port. The reverse washing method can effectively remove the coverage, but special attention shall be paid to prevent overpressure and avoid breaking the membrane or damaging the sealing bonding surface.