Reasons for the Oxidation of Reverse Osmosis Membranes and How to Prevent It?

Reverse osmosis membranes have been widely used in the field of water treatment. Many users encounter a problem where reverse osmosis is easily oxidized by oxidants, resulting in a decrease in the performance of membrane components.

So, what are the reasons for the oxidation of reverse osmosis membranes? And how to prevent it?

Figure 1 Oxidation in RO membrane

Several Common Oxidation Phenomena and Their Reasons

Chlorine attack: Chlorine-containing disinfectants are added to the system’s inlet water. After pretreatment, they are not completely consumed and enter the reverse osmosis system.

Trace residual chlorine and heavy metal ions such as Cu2+, Fe2+, and Al3+ in the incoming water undergo catalytic oxidation reactions in the polyamide desalination layer.

Oxidizing bactericides other than residual chlorine are used in the water treatment process, such as chlorine dioxide, potassium permanganate, ozone, hydrogen peroxide, etc. The residual oxidants enter the reverse osmosis system, causing oxidative damage to the membrane.

How to Prevent Oxidation?

1. Ensure that the reverse osmosis inlet water does not contain residual chlorine.

  • Install an online ORP (oxidation-reduction potential) meter or residual chlorine detection meter in the reverse osmosis inlet water pipeline and use reducing agents such as sodium bisulfite to ensure that residual chlorine is not present in the inlet water in real time.
  • For water sources such as treated wastewater or systems that use ultrafiltration as pretreatment, chlorine is generally added to control ultrafiltration microbial contamination. In this operating condition, a combination of online instruments and periodic offline testing should be used to detect residual chlorine and ORP.

2. The reverse osmosis cleaning system should be separated from the ultrafiltration cleaning to avoid residual chlorine from leaking from the ultrafiltration system into the reverse osmosis system.

3. The sterilization process of the reverse osmosis system should use non-oxidizing bactericides such as isothiazolinones or DBNPA.

It is mainly important to pay attention to regular maintenance and cleaning in daily life and prevent oxidation over time. If oxidation occurs, the above measures can be taken to solve it.

Figure 2 NEWater RO membranes

NEWater provides reverse osmosis (RO) membranes, seawater desalination membranes, nanofiltration (NF) membranes, ultrafiltration (UF) membranes, and MBR flat membranes. We are committed to providing customers with more cost-effective products, higher quality, and comprehensive services.

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