How to prevent the reverse osmosis membrane from being contaminated?

1. Contaminants of reverse osmosis membrane components in pure water equipment:


After a period of normal operation of pure water equipment, the reverse osmosis membrane elements in pure water equipment may be contaminated by suspended matter or insoluble substances that may exist in the feed water. The most common of these pollutants are calcium carbonate scale and calcium sulfate scale. , metal oxide scales, silicon deposits and organic or biological deposits.


The nature of the pollutants and the rate of contamination are related to the water supply conditions. The pollution is slowly developed. If no measures are taken early, the pollution will damage the performance of the membrane components in a relatively short period of time.


Regular inspection of the overall performance of the system is a good way to confirm contamination of the membrane components. Different contaminants can cause varying degrees of damage to the performance of the membrane components.


Second, the removal of pollutants from reverse osmosis membrane components in pure water equipment


Contaminant removal can be achieved by chemical cleaning and physical rinsing, sometimes by changing operating conditions. As a general rule, cleaning should be performed when one of the following conditions occurs.


1. Under normal pressure, if the product water flow drops to 10-15% of the normal value.


2. In order to maintain normal product water flow, the temperature corrected water supply pressure is increased by 10 to 15%.


3. The water quality of the product is reduced by 10-15%. The salt transmission rate is increased by 10 to 15%.


4, the use of pressure increased by 10 to 15%


5. The pressure difference between the RO sections increases significantly (maybe there is no instrument to monitor this indication).


3. Common pollutants of reverse osmosis membrane components in pure water equipment and their removal methods:


1, calcium carbonate scale
When the scale inhibitor addition system fails or the acid addition system appears and the feed water pH rises, then calcium carbonate may deposit, and the precipitation of calcium carbonate scale should be discovered as early as possible to prevent the growth of crystals from occurring on the membrane surface. Damage, such as early detection of calcium carbonate scale, can be removed by reducing the feed water pH to between 3.0 and 5.0 for 1 to 2 hours. For calcium carbonate scales with longer precipitation time, citric acid cleaning solution should be used for circulation cleaning or overnight immersion.


Note: Make sure that the pH of any cleaning solution is not lower than 2.0. The cup may cause damage to the RO membrane components, especially when the temperature is high. The highest pH should not be higher than 11.0.


Check the use of ammonia to increase the pH and sulfuric acid or hydrochloric acid to lower the pH.


2, calcium sulfate scale
The cleaning solution is the best way to remove calcium sulfate scale from the surface of the reverse osmosis membrane.


3, metal oxide scale
The deposited hydroxide (e.g., iron hydroxide) can be easily removed using the method of removing calcium carbonate scale as described above.


4, silicon scale
For silicon scales that are not symbiotic with metallized or organic materials, they can only be removed by professional water treatment. For detailed methods, please contact the water treatment specialists.


5, organic sediments
Organic deposits (such as microbial slime or mildew) can be removed using cleaning solution 3. In order to prevent re-growth, an approved sterilizing solution can be used to circulate and soak in the system, which usually takes a long time to be effective, such as reverse osmosis. Disinfection is preferred when the device is out of service for three days. Consult with a water treatment specialist to determine the appropriate biocide.


6, cleaning fluid
It is recommended to use a special cleaning solution for water treatment when cleaning reverse osmosis membrane elements. It is very important to determine the chemical analysis of the contaminants before cleaning. The detailed analysis and comparison of the analysis results can ensure the selection of the best cleaning agent and cleaning method. The cleaning method and the cleaning effect obtained during each cleaning should be recorded. Under the water supply conditions, find the basis for the best cleaning method.