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How to deal with concentration polarization of reverse osmosis membrane

Reverse osmosis system is an indispensable part of small and medium-sized automatic ultra pure water treatment equipment, but there is also a hidden danger in the reverse osmosis system, that is, the surface of reverse osmosis membrane is easy to form concentration polarization by solute or other retained substances, which will affect the effluent quality of water treatment equipment.

1. Increasing velocity method

First of all, we can adopt the measures commonly used in chemical industry to increase the disturbance. That is, try to increase the linear velocity of the fluid flowing through the membrane surface. The adsorption time of solute can be reduced by reducing the residence time of fluid and increasing the velocity of fluid in small and medium-sized automatic ultra pure water treatment equipment.

2. Packing method

For example, 29 ~ 100um spheres are put into the treated liquid and they flow through the reverse osmosis system together to reduce the thickness of the membrane boundary layer and increase the transmission velocity. The material of the ball can be made of glass or methyl methacrylate. In addition, for tubular reverse osmosis system, micro sponge ball can also be filled into the feed liquid. However, for the plate and frame type membrane modules, the method of adding filler is not suitable, mainly because of the risk of blocking the flow channel.

3. Pulse method

A pulse generator is added in the process of water treatment equipment. The amplitude and frequency of pulse are different. Generally, the greater the amplitude or frequency, the greater the flow velocity. Agitators are widely used in all testing devices. Experience shows that the mass transfer coefficient has a linear relationship with the number of revolutions of the agitator.

4. Installation of turbulence promoter

Turbulence promoters are a variety of obstacles that can enhance the flow pattern. For example, for tubular components, spiral baffles are installed inside. For the plate or roll type membrane module, the mesh and other materials can be lined to promote the turbulence. The effect of the turbulence promoter is very good.

5. Add dispersive scale inhibitor

In order to prevent the reverse osmosis membrane from scaling in water treatment equipment, sulfuric acid or hydrochloric acid is added to adjust the pH value. However, due to the corrosion and leakage of the acid system, the operator is troubled, so the dispersive scale inhibitor is generally added to maintain the normal operation of the water treatment system.

Post time: Aug-31-2020