Why should nanofiltration membranes be cleaned regularly?
Because the nanofiltration membrane will be used for a long time in the process of use, the suspended solids and some impurities in the water will block the pore size of the filter membrane surface, causing the membrane to block, and the long-term blockage will cause the water production to decrease, and it will affect the nanofiltration membrane element. Cause irreversible damage.
How long is the cleaning cycle of nanofiltration membranes?
Generally, the cleaning cycle of the nanofiltration membrane is mainly determined according to the use of the membrane element, usually about three months, but when the water production of the membrane element decreases, the nanofiltration membrane must be cleaned in time.
What should I pay attention to when cleaning the nanofiltration membrane?
Use high-quality oxidant water without residual chlorine and other oxidants for flushing
When preparing the cleaning solution, make sure that all cleaning chemicals are well dissolved and mixed before entering the component cycle.
After the cleaning chemicals and membrane elements are circulated, the membrane elements should be rinsed with high-quality water that does not contain residual chlorine and other oxidants (minimum temperature>20℃).
Temperature and PH value
During the cycle of the cleaning solution, the temperature should not exceed 50C at pH 2-10, the temperature should not exceed 35C at pH 1-11, and the temperature should not exceed 30C at pH 1-12.
The flow direction of cleaning fluid
For components with a diameter greater than 6 inches, the flow direction of the cleaning fluid must be the same as the normal running direction to prevent the component from generating the "telescope" phenomenon, because the thrust ring in the pressure vessel is only installed at the concentrated water end of the pressure vessel. It is also recommended to pay attention to this point when cleaning the system of small components.
Thoroughly clean the remaining detergent
When cleaning, pay attention to thoroughly clean the cleaning agent remaining in the membrane. If the cleaning agent is not thoroughly cleaned, it is extremely easy to accumulate dirt in the membrane-forming system, and even shorten the service life of the nanofiltration membrane. Alkaline cleaners have low cleaning power to remove stains.
How to extend the cleaning cycle of nanofiltration membranes?
Increasing the pretreatment process is generally the longest used, and the raw water can be preliminarily treated through processes such as multi-media filters and ultrafiltration membranes to improve water quality, which can effectively reduce the pollution of nanofiltration membrane elements.
The CaCO3 in most surface water and groundwater is almost saturated. Therefore, by adding the H leaf in the acid, the chemical balance can be shifted to the left to keep the calcium carbonate in a dissolved state. The quality of the acid used must be food grade. In most countries and regions, sulfuric acid is easier to use than hydrochloric acid, but on the other hand, the content of sulfate radicals in influent water increases. As far as the sulfate scale is concerned, the problem will be serious.
Scale inhibitors can be used to control carbonate scale, sulfate scale, and calcium fluoride scale. There are usually three types of scale inhibitors: sodium hexametaphosphate (SHMP), organic phosphate, and polyacrylate. It is suitable for preventing the scaling of insoluble aluminum and iron, and the high molecular weight polyacrylate can reduce the formation of SiO2 scaling through the dispersion effect.
Add softening resin
Na+z ion can be used to replace and remove scale cations such as Ca2+, Ba2+, and Sr2+ in water. During this treatment, the pH of the influent water will not change. Therefore, no degassing operation is required.
Post time: Jun-28-2021