Ultrafiltration membrane filtration methods: internal pressure and external pressure

Release Date:

2024-05-15

Source:

Ultrafiltration membrane filtration methods: internal pressure and external pressureUltrafiltration membrane is a widely used membrane separation technology, and its filtration methods mainly include internal pressure and external pressure. These two methods have significant differences in characteristics, application scenarios, advantages and disadvantages.

First, let's look at the internal pressure ultrafiltration membrane. Internal pressure ultrafiltration membrane refers to the flow of raw water from the inside of the membrane assembly to the outside, that is, the water enters the inner cavity of the tube, capillary or hollow fiber membrane, the filtered water enters the outer membrane through the membrane, and the particles larger than the membrane aperture are trapped on the inner surface of the membrane. The main advantages of this method are simple structure, easy operation, and because the direction of water flow is perpendicular to the membrane surface, the pollutants on the surface of the membrane are easy to be washed away, thus extending the service life of the membrane. However, the internal pressure ultrafiltration membrane also has some shortcomings, such as in high concentration of suspended solids or high viscosity fluids, it is easy to clog, affecting the filtration effect. In addition, for high-flow processing, internal pressure ultrafiltration membranes require a larger membrane area, which increases the cost of equipment.

Ultrafiltration membrane filtration methods: internal pressure and external pressure

Next, we discuss external pressure ultrafiltration membranes. The external pressure type ultrafiltration membrane is that the raw water flows from the outside of the membrane component to the inside, that is, the water enters from the outside of the membrane, the filtered water enters the inside of the membrane through the membrane, and the particles larger than the membrane aperture are trapped on the outer surface of the membrane. The main advantages of this approach are that the flow direction is parallel to the membrane surface, which makes the filtration efficiency higher, and the processing capacity for high concentration of suspended solids or high viscosity fluids is greater. In addition, the external pressure ultrafiltration membrane in the processing of large flow, because the membrane area is relatively small, so the equipment cost is low. However, the disadvantage of external pressure ultrafiltration membrane is that the pollutants on the surface of the membrane are not easy to be washed away, which is easy to cause blockage and pollution of the membrane, and it needs to be cleaned and replaced regularly.

In terms of application scenarios, internal pressure ultrafiltration membranes are more suitable for the treatment of low concentration suspended solids and low viscosity fluids, such as drinking water and surface water. The external pressure ultrafiltration membrane is more suitable for the treatment of high concentration suspended matter, high viscosity fluid and large flow rate, such as industrial wastewater, oilfield reinjection water and so on.

In summary, internal pressure and external pressure ultrafiltration membranes have their own characteristics and application scenarios. When choosing which method to use, it is necessary to comprehensively consider factors such as actual water quality, treatment volume and operating costs. At the same time, no matter which method is used, it is necessary to regularly clean and replace the membrane to ensure the filtration effect and the stable operation of the equipment.

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