Ultrafiltration membrane technology is a membrane separation technology based on screening and filtration, with pressure difference as the main driving force. Its main principle is to create a small pressure difference on both sides of the filtration membrane, so as to provide power for the water molecules to get through the small pores of filtration membrane, and block the impurities on the other side of the filtration membrane, which ensures that the water quality after treatment meets the relevant standards.
Generally, ultrafiltration membrane can be divided into internal pressure ultrafiltration membrane and external pressure ultrafiltration membrane according to different ways of water inlet. The internal pressure ultrafiltration membrane technology firstly injects sewage into the hollow fiber, and then pushes the pressure difference to make the water molecules penetrate out of the membrane and the impurities remain in the hollow fiber membrane. The external pressure ultrafiltration membrane technology is the opposite of the internal pressure, after a pressure push, water molecules infiltrate into the hollow fiber membrane and other impurities are blocked outside.
Ultrafiltration membrane plays an important role in the application of ultrafiltration membrane technology. Ultrafiltration membrane is mainly made of polyacrylonitrile, polyvinylidene fluoride, polyvinyl chloride, polysulfone and other materials, the properties of these materials determine the characteristics of ultrafiltration membrane. In the actual application process, relevant operators need to fully consider the temperature, operating pressure, water yield, water purification effect and other factors to maximize the effect of ultrafiltration membrane technology, so as to realize the saving and recycling of water resources.
At present, there are usually two filtration methods in the application of ultrafiltration membrane technology: dead end filtration and cross-flow filtration.
Dead end filtering is also called full filtering. When the suspended matter, turbidity, colloid content in raw water is low, such as tap water, groundwater, surface water, etc., or there is a strict design of the pre-treatment system before ultrafiltration, ultrafiltration can use the full filtration mode operation. During full filtration, all the water passes through the membrane surface to become water production, and all the pollutants are intercepted on the membrane surface. It needs to be discharged from the membrane components through regular air scrubbing, water backwashing and forward flushing, and regular chemical cleaning.
In addition to dead-end filtration, cross-flow filtration is also a relatively common filtration method. When the suspended matter and turbidity in raw water are high, such as in reclaimed water reuse projects, cross-flow filtration mode is usually used. During cross-flow filtration, part of the inlet water passes through the membrane surface to become water production, and the other part is discharged as concentrated water, or is re-pressurized and then returned to the membrane inside the circulation mode. Cross-flow filtration makes the water circulate continuously on the membrane surface. The high velocity of water prevents the accumulation of particles on the membrane surface, reduces the influence of concentration polarization, and alleviates the rapid fouling of the membrane.
Although ultrafiltration membrane technology has incomparable advantages in the process of use, it does not mean that only ultrafiltration membrane technology can be used alone to purify polluted water in the process of polluted water resources treatment. In fact, when facing the problem of polluted water resources treatment, relevant personnel can try to flexibly combine various treatment technologies. To effectively improve the treatment efficiency of polluted water resources, so that the quality of water resources after treatment can be effectively guaranteed.
Due to different causes of water pollution, not all polluted water resources are suitable for the same pollution treatment. The staff should improve the rationality of the combination of ultrafiltration membrane technology, and choose the most suitable treatment method for water purification. Only in this way, on the premise of ensuring the efficiency of water pollution treatment, can the water quality of the polluted water be further improved after purification.