Reverse Osmosis System Residual Chlorine Removal Process

Chlorine gas is a very common oxidizing agent in the reverse osmosis process, and the chlorination process for sterilization and disinfection is usually used to remove bacteria, algae, viruses, and other impurities from the water. The amount of chlorine remaining after the chlorine gas has been consumed by interaction with bacteria, microorganisms, algae, etc. in the water is called residual chlorine, and is generally hypochlorous acid and hypochlorite. Residual chlorine oxidizes and destroys the reverse osmosis membrane, resulting in lower salt rejection. In order to prevent the membrane from being oxidized and degraded, dechlorination should be carried out before entering the RO membrane.

Removing residual chlorine from water can be done by filtering and removing impurities through granular activated carbon filters, or by adding chemicals to the water.

Removal of residual chlorine with activated carbon filters

Removal of residual chlorine with activated carbon involves its chemical reduction rather than the use of carbon adsorption. Chlorine gas decomposes in water as HClO, HClO meets the activated carbon will take place in a reduction-oxidation reaction, the activated carbon is oxidized to CO₂, with strong oxidizing properties of the HClO is reduced to H⁺ and Cl^-, which can be followed by the RO membrane to be filtered out, the whole reaction equation is:

Activated carbon FPR tanks can remove residual chlorine.

Removal of residual chlorine with chemicals

Common chemicals used to remove residual chlorine are sodium bisulfite (SBS) or sodium metabisulfite (SMBS). Sodium bisulfite (SBS) is generally generated by dissolving sodium metabisulfite (SMBS) in water, and the resulting SBS is used to reduce hypochlorite to remove residual chlorine, with the specific reaction equation:

NaHSO₃ chemical can remove residual chlorine.