Ultrafiltration membrane elements are often used as pretreatment for other membrane processes. After using the ultrafiltration membrane for a period of time, harmful substances such as bacteria, rust, colloids, suspended solids, and large organic molecules which are intercepted by the membrane will adhere to the inner surface of the ultrafiltration membrane, causing a gradual decrease in water production, especially when tap water is heavily contaminated, it is more likely to cause clogging of the ultrafiltration membrane. Regular flushing of the ultrafiltration membrane can effectively restore the membrane's water production. The factors affecting the water production of the ultrafiltration membrane elements are as follows:
The Effect of Temperature on Water Production: With the increase of temperature, the activity of water molecules increases, its viscosity decreases, and thus the water production increases. Conversely, water production decreases. Therefore, even in the same ultrafiltration system, there is a significant difference in water production between winter and summer.
The Effect of Operating Pressure on Water Production: When the pressure is low, the water production is proportional to the pressure, that is, the water production increases with the increase of pressure. However, when the pressure exceeds 0.3MPa, even if the pressure increases, the water production increases only slightly, mainly because under high pressure, the ultrafiltration membranebecomes more compact and increases water resistance.
The Effect of Inlet Turbidity on Water Production: The larger the inlet turbidity, the less water production of the ultrafiltration membrane, and the inlet turbidity is more likely to cause clogging of the ultrafiltration membrane.
The Effect of Flow Rate on Water Production: The change of flow rate has a less apparent effect on water production than temperature and pressure. A slow flow rate can easily lead to clogging of the ultrafiltration membrane, while a fast flow rate affects water production.
In industrial purification, concentration, and separation processes, the ultrafiltration membrane separation technology can be used as a pretreatment for the process or as a deep processing process in ultrafiltration water treatment equipment.
The ultrafiltration membrane is very common in the water treatment industry and is widely used in the industrial, processing, electronics, chemical and other industries. The ultrafiltration membrane can intercept bacteria, but it cannot kill bacteria. No matter how good the interception rate of the ultrafiltration membraneis, it cannot guarantee cleanliness and prevent bacteria growth for a long time.
For example, fungal clusters of semi-transparent threads or white flocculent appear in some bottled mineral water products, mainly caused by fungal contamination of the system. Therefore, it is necessary to regularly sterilize the circulation environment and filtration system. The sterilization cycle is determined by the quality of the supplied raw water. For ordinary tap water in cities, the sterilization cycle is 7-10 days in summer, 30-40 days in winter, and 20-30 days in spring and autumn. When surface water is used as the water source, the sterilization cycle is even shorter. The sterilization agent can use 500-1000mg/L sodium hypochlorite or 1% hydrogen peroxide water solution circulating or soaking for about half an hour.