The raw water in the hollow fiber ultrafiltration membrane flows under pressure outside or in the cavity of the hollow fiber, and constitutes an external pressure type and an internal pressure type respectively. Ultrafiltration is a dynamic filtration process in which the captured material can be removed with concentrated water without blocking the membrane surface, and it can run continuously for a long time. Hollow fiber ultrafiltration membrane is one of the earlier developed polymer separation membranes. Now let us understand how to clean the hollow fiber ultrafiltration membrane?
In the continuous normal operation of the hollow fiber ultrafiltration membrane, various cleaning methods must be carried out on a regular basis. At present, the commonly used cleaning methods mainly include the following: Back pressure backwashing method: rinse with clean water from the ultrafiltrate side to the front. Since the pressure resistance of the membrane is different in the front and rear directions, usually only low pressure can be used for backwashing, and the backwashing strength is not strong and the effect is not great. The membrane with higher compressive strength must be selected, and the backwash effect of higher pressure and larger flow is better. The rinse time is 30-60 seconds.
Isobaric hydraulic flushing method: Close the ultrafiltration outlet valve and fully open the concentrated water outlet valve to increase the flow rate of the hollow fiber ultrafiltration membrane surface, which is more effective for removing loose materials attached to the surface.
Chemical cleaning method: According to the types of contaminants on the membrane surface, select appropriate chemical substances for dissolution, oxidation or other chemical reactions to achieve the purpose of removal.
The choice of commonly used chemicals must be based on the properties of the hollow fiber ultrafiltration membrane materials, such as acids, alkalis, oxidants, bactericides, surfactants and enzyme-added detergents. The method is the same as the normal ultrafiltration process.
The cleaning liquid enters from the original liquid inlet, and the concentrated liquid and ultrafiltrate are all returned to the cleaning liquid container, discharged after circulation, and then cleaned with clean water.
Ultrafiltration membrane technology is a high and new technology that is widely used in water purification, solution separation, concentration, and extraction of useful substances from wastewater, and wastewater purification and reuse. It is characterized by simple use process, no heating, energy saving, low pressure operation, and small area of equipment.
