Reverse osmosis (RO) is one of the most efficient water filtration systems. It uses the characteristics of a semi-permeable membrane to remove 99% of harmful impurities in water, such as heavy metals, chemical pollutants, and microorganisms. However, RO cleaning is the most easily overlooked issue for many people. Next, you will learn how to clean the reverse osmosis membrane from this article. Proper cleaning of the RO membrane can effectively remove sediment and contaminants on the membrane, thereby ensuring the performance of the RO membrane and the efficient operation of the reverse osmosis water filtration system.
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Why do we need to clean the reverse osmosis membrane?
After a period of use, the reverse osmosis membrane will be polluted on the membrane surface, such as surface scaling and membrane blockage. At the same time, the compaction effect of the membrane causes the membrane's water permeability to decrease. The pollution and blockage of the membrane are mainly caused by membrane surface deposition and the growth of microorganisms. Among them, microorganisms not only block the membrane but also corrode and damage the cellulose acetate membrane. Excessive residual chlorine will cause the membrane performance to deteriorate. If these contaminants on the membrane surface are not removed regularly and on time, the membrane will be irreparably damaged and the normal water production and water quality of the membrane will be affected.
The purpose of reverse osmosis membrane cleaning is to remove pollutants and scaling on the membrane surface and restore the membrane's water permeability and separation efficiency. There are many ways to clean, such as chemical cleaning, physical cleaning, etc.
How often should the RO membrane be cleaned?
The cleaning cycle and method of the reverse osmosis membrane should be determined according to the actual situation. It is generally recommended to clean it once every period to ensure the normal operation and long-term stability of the reverse osmosis membrane. Normally, you need to perform preventive cleaning every 6 to 12 months. If you find that the reverse osmosis is abnormal during use, you need to clean it immediately. Therefore, regular cleaning and maintenance of the RO system can extend the service life of the membrane.
When do you need to clean the RO membrane?
Common contaminants of reverse osmosis membrane elements include suspended solids, colloidal pollutants, organic pollutants, calcium carbonate scale, calcium sulfate scale, metal oxides, silicates, and microorganisms (algae, mold, fungi), etc. If the reverse osmosis membrane element is contaminated, it needs to be cleaned immediately. If it is not cleaned in time, it will cause serious contamination of the reverse osmosis membrane, affecting its performance of the reverse osmosis membrane, thereby affecting the water filtration effect.
Regular maintenance and cleaning of RO membranes is essential. It not only prolongs the life of the water filter element but also provides you with more efficient water filtration performance. Generally speaking, if the following situations occur, the RO membrane needs to be flushed in time.
- The water output is significantly reduced
- The membrane pressure difference is increased
- The water quality index deteriorates
- Scaling or pollution occurs
Steps for cleaning reverse osmosis membranes
Generally speaking, reverse osmosis membranes can be cleaned using physical cleaning and chemical cleaning. Here are the specific detailed steps for the two methods:
Physical cleaning
Physical cleaning mainly uses mechanical brushes to remove contaminants from the reverse osmosis membrane. It can remove loose particles and sediments on the membrane surface. However, physical cleaning is not suitable for long-term use because it may cause a decrease in water permeability and may even cause more damage to the reverse osmosis. The following are simple steps for physical cleaning:
- Shut down the system: Stop the RO system and close the inlet and drain valves.
- Low-pressure flushing: Introduce clean low-pressure water (usually filtered feed water or permeate water) through the reverse osmosis system to flush the membrane components at low pressure (usually 1-2 bar). This removes loose particles and sediments on the membrane surface.
- Backwashing: Some reverse osmosis systems can be backwashed, passing water back through the membrane components to further loosen and remove sediments.
- Rinse: Continue to flush the reverse osmosis system with clean water for a few minutes to ensure that all loose materials on the surface are removed.
Chemical cleaning
It mainly dissolves in water through the reaction of chemicals and pollutants, which can effectively remove inorganic sediments, organic matter, biological fouling, etc. in water. Chemical cleaning is usually carried out after physical cleaning to ensure that the chemical agents can effectively contact and clean the membrane surface. At the same time, improper use of cleaning agents during chemical cleaning can easily cause membrane damage.
- Prepare cleaning solution: Select the appropriate cleaning agent (acidic or alkaline) according to the type of pollutant.
- Circulation cleaning: Circulate the cleaning solution through the membrane assembly.
- Rinse the cleaning solution: After completing the chemical cleaning, rinse the membrane assembly thoroughly with clean water until the discharged water no longer contains any cleaning agent residue.
- Check the pH value: During and after the flushing process, check the pH value of the drainage. After the cleaning is completed, the pH value of the drainage should be restored to the normal pH range of the inlet water.
- Restore the system: Reconnect the inlet and outlet pipes of the RO system to resume normal operation and ensure that the reverse osmosis system is restored to the optimal operating state.
Which chemical is best for RO membrane cleaning?
First, you need to determine whether the RO membrane can withstand it, and second, determine the main contaminants. Then choose the chemicals for cleaning the RO membrane according to the type of contaminants. Generally speaking, there are several common cleaning agents:
- Acidic cleaners: can remove inorganic deposits
- Alkaline cleaners: can remove organic matter, grease, and biological contamination (such as bacteria and algae)
- Oxidant cleaners: can remove biological contaminants and organic matter
First, simply rinse the surface of the RO membrane with water, and then use acidic and alkaline cleaners for cleaning, both acidic and alkaline cleaners can remove residues.
Precautions after cleaning
After cleaning the reverse osmosis membrane, some follow-up inspections and maintenance are required to ensure the long-term and efficient operation of the RO system.
- Check the cleaning effect: record the water output, pressure difference, and water quality indicators before and after cleaning.
- Regular maintenance and inspection: Regular replacement of pre-filters can reduce pollutants and thus extend the service life of the membrane. In addition, regular inspection of the membrane status and the operating parameters of the reverse osmosis system can quickly identify problems and solve them in time.
- Ensure that the water quality meets the standards: Water quality testing should be carried out after cleaning to ensure that the TDS, hardness, and other water quality indicators of the effluent meet the standards for drinking water or industrial water.
FAQ
What is the lifespan of RO membranes?
The service life of RO membrane is 2-5 years. If you clean the reverse osmosis membrane regularly, it will help to extend the service life of the membrane. Therefore, the service life of the RO membrane depends on many factors, such as inlet water quality, operation and maintenance of the reverse osmosis system, and frequency of use. If the RO life is over, the water filter element needs to be replaced immediately.
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What happens when the RO membrane ages?
Symptoms of RO membrane aging include reduced water production, increased salt permeability, membrane component leakage, abnormal noise, increased biological contamination, and unstable water quality.
Can I clean the reverse osmosis membrane myself?
Yes. You can clean the reverse osmosis membrane yourself. However, you need to follow the correct method during the cleaning process to avoid damaging the membrane and the RO system.
