RO reverse osmosis membrane is one of the key components for water treatment inside the laboratory ultra pure water machine. After pre-treatment and reverse osmosis treatment, the raw water will be transformed into pure water for experimental use. RO reverse osmosis membranes can retain impurities in the raw water in one direction, but long-term use can accumulate debris and require regular cleaning. The cleaning of RO reverse osmosis membranes requires mastering certain methods, otherwise it may cause damage to the membrane. Below, we will briefly introduce the infiltration source.

Cleaning method for RO reverse osmosis membrane of ultrapure water machine

Before cleaning the RO reverse osmosis membrane, we need to understand the pollutants that cause membrane fouling. Common RO reverse osmosis membrane pollutants include calcium carbonate, calcium sulfate, metal oxides, silicides, inorganic or organic precipitates, natural organic matter, synthetic substances (cationic polyelectrolytes), and microorganisms (algae, fungi, fungi). Knowing the types of pollutants, we can "prescribe the right medicine".

RO reverse osmosis membrane cleaning methods can be divided into two categories: physical cleaning and chemical cleaning.

Physical cleaning

Physical cleaning is the use of mechanical flushing to remove pollutants from membrane components and restore their performance. For example, physical methods such as turbulence, vibration, water gas mixing, and ultrasound can be used to flush out pollutants adsorbed on membrane components.

chemical cleaning

Chemical cleaning is a cleaning method that uses corresponding chemical agents to react with pollutants, dissolve them in water, and then discharge them from the membrane element to restore its performance.

The selection of cleaning agents for RO membrane chemical cleaning is very strict. Firstly, there should be no related reactions with the RO membrane components to be cleaned. Secondly, the selected agents should be easy to handle and should not pollute the environment. The commonly used cleaning agents for RO reverse osmosis membranes are acidic cleaning agents (such as phosphoric acid, oxalic acid, citric acid, etc.) and alkaline cleaning agents (sodium hydroxide solution).

It is recommended to conduct experimental analysis on the membrane components before cleaning the RO reverse osmosis membrane, and then select the corresponding chemical agents based on the pollution reasons. At the same time of cleaning, it is necessary to use equal water pressure flushing or reverse flushing methods to effectively remove pollutants on the membrane surface.

Advantages, disadvantages, and precautions of various cleaning methods for RO reverse osmosis membranes

Advantages of physical cleaning method

For pollutants with weak adsorption capacity caused by reverse osmosis membrane fouling, physical cleaning methods are very effective and do not change the properties of the pollutants.

Disadvantages of physical cleaning method

1. Long term and high-frequency use can affect the performance of the membrane to a certain extent;

2. Easy to cause a decrease in water production;

3. Improper operation can easily cause membrane damage;

4. Unable to eliminate contamination from microorganisms, bacteria, and organic matter.

Precautions for Physical Cleaning Method

1. Flushing flow rate. The flushing flow rate should be higher than the flow rate during normal operation of the system to remove pollutants.

2. Flushing pressure. The normal operating pressure of the reverse osmosis system causes pollutants to accumulate on the membrane surface. Therefore, choosing a higher pressure during flushing will make it easier for pollutants to adhere to the membrane surface under high pressure. Therefore, during flushing, a low-pressure and high flow rate cleaning method should be chosen to increase the flushing force in the horizontal direction of the membrane surface, so as to flush pollutants out of the membrane components. The usual flushing pressure is below 0.3MPa. If it is difficult to achieve a certain flow rate below 0.3MPa pressure, the inlet water pressure should be controlled as much as possible, with no or less water production as the standard. Generally speaking, the inlet pressure cannot exceed 0.4MPa.

3. Flushing frequency. If conditions permit, the RO membrane should be rinsed frequently, increasing the number of rinses is more effective than performing a chemical cleaning. Users can control the flushing frequency according to specific usage conditions.

Advantages of chemical cleaning method

Chemical cleaning can effectively prevent contamination by microorganisms, bacteria, and organic matter, resulting in more thorough cleaning and less physical damage to the membrane.

Disadvantages of chemical cleaning method

1. Excessive cleaning frequency can easily affect membrane performance;

2. Improper use of cleaning agents can easily cause membrane damage.

Precautions for chemical cleaning method

1. Choose specialized membrane cleaning agents that not only effectively clean the membrane, but also minimize damage to the membrane as much as possible;

2. Chemical analysis of membrane pollutants before cleaning;

3. Record the water supply conditions and cleaning agent dosage for each cleaning, providing a basis and guarantee for finding a good cleaning method.

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