Introduction: The degradation and dissolution of reverse osmosis element membrane are mainly due to the irreversible changes in the microstructure or molecular structure caused by physical or chemical effects, which leads to the decline of membrane characteristics.
1. Reverse osmosis element membrane has deteriorated in physics.
An obvious example of known physical degradation is water hammer during startup, causing membrane damage, exceeding the allowable working pressure, and operating above the limit temperature. Membrane degradation causes a drop in water flux.
a. Telescope phenomenon.
The reason for the telescope phenomenon is that the pressure difference between the seepage and the concentrated water is too large. The 5.5-inch element is prone to this phenomenon due to the large total membrane cross-sectional area. It is necessary to ensure that the anti-earth stress ring is installed in the membrane high-pressure container. , In order to support the outer covering of the 5.5-inch ro membrane element, the smaller diameter components are suitable for the production of water pipes and anti-earth stress devices to avoid the outer covering from rolling. After the telescope phenomenon occurs, replace the damaged ro membrane element with a new element, and remove the damaged membrane element.
b. The surface of the membrane is worn.
Sometimes it is not some parts that have this common failure, but the front-end components are often the most susceptible to damage by crystallization in raw water or suspended solids of metallic materials with sharp edges. The water should be checked for the above-mentioned chemical substances, such as welding scars, etc. The damage can be detected by a high-power microscope on the membrane surface. Once this common failure occurs, there is no remedy. The only way is to improve the pretreatment and ensure that the membrane There are no similar particles falling from the front high-pressure pipe, and then all the damaged membrane in ro plant are disassembled.
c. Water back pressure.
At any time, if the production water pressure is higher than 0.3 bar of seepage or concentrated water, the composite membrane is likely to cause separation of the composite solid layer. This damage can be determined according to the water production detection method.
2. Chemical deterioration of reverse osmosis element membrane.
Chemical deterioration means that reverse osmosis element membrane is affected by oxidants such as residual chlorine, potassium permanganate, persulfate, and hexavalent chromium, and the polymer chain of aromatic polyamide is cut; or it is cleaned by excessive acid, alkali and other drugs. The attenuation coefficient of the characteristics of membrane separation technology.