Can the chloride ion concentration in water after treatment by a reverse osmosis system be reduced to below 0.1 ppm?
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I would like to ask everyone: can the chloride content in water after treatment by a reverse osmosis system be reduced to below 0.1 ppm?
Two-stage reverse osmosis should be able to achieve it.
It should still be achievable with a two-stage approach
But after checking some information, the requirements for the water entering the reverse osmosis membrane are: residual chlorine
It’s hard to say; some raw water doesn’t contain chlorine at all. Moreover, 0.1 mg/L is equivalent to 0.1 ppm, right?
Was it asking about chloride ions upstairs? Is it residual chlorine? The two are not the same thing! RO composite membranes are not resistant to residual chlorine; residual chlorine will oxidize the membrane material, causing irreversible damage. Therefore, the maximum allowable level of residual chlorine in the feed water is 0.1 mg/l. As for chloride ions, the removal efficiency of RO membranes is generally high; a single-stage treatment can achieve a removal rate of over 90 percent. However, it is not possible for RO membranes to reduce the chloride ion concentration in the output water to 0.1 mg/l. EDI or mixed-bed systems might work
This depends on the chloride content in the incoming water; by calculating the membrane desalination rate, it can be determined whether the target is achieved. For example, if the chlorine ion concentration in the feed water is 400 ppm, the concentration of chlorine ions in the water after primary RO treatment, assuming a desalination efficiency of 97%, is 12 ppm; after secondary RO treatment, with a desalination efficiency of 98%, the concentration is 0.24 ppm. If a concentration lower than 0.1 ppm is required, then an mixed-bed system or EDI is necessary. Residual chlorine refers to oxidizing chlorine; since the materials used in reverse osmosis membranes are mainly acetate fiber, polyamide, and polysulfone, which do not have high oxidation resistance, it is necessary to control the residual chlorine in the incoming water during operation. Depending on the membrane manufacturer, the ORP is generally kept within a range of plus or minus 100 or plus or minus 200.