Does anyone have a good reference discussing the nitrite levels in reverse osmosis water? It seems RO will reduce nitrite levels, but can a reasonable assumption be made? This paper (https://pubs.acs.org/doi/10.1021/acs.oprd.0c00224) makes some estimates, but I wonder how valid this is to use for general estimates of nitrite levels when not data is available.
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Long story, but I worked for a company in the water purification space for a short minute. Between pressure regulation and the membrane itself, you cannot just say that you’re using RO & have perfect water. Without data, including conductivity or resistivity after the membrane, all you can say is that the water coming out should be better than the water that went in. You cannot say that it is fit for purpose.
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Thanks for your response! I should have mentioned that the post-RO water meets USP <1231> and the final conductivity is ≤1.3 μS/cm at 25°C. However, nitrates and nitrites are not tested. I’m wondering if some worst-case scenario calculations be performed to determine possible nitrite levels.
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RO does not guarantee nitrosamine free water-there is evidence published regarding NDMA azeotrope so distillation is not a guarantee and there is a publication about RO and nitrosamines showing a different efficiency of removal but for simple nitrosamines the efficiency is low
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RO will reduce the nitrite concentration from incoming feedwater, like it does all other ions. But the degree of removal, call the rejection efficiency, does vary from ion to ion. A typical, well-maintained RO system will reject 95-ish% of the ions, sometimes more, sometimes less. The most knowledgeable folks I know are those that build and design water systems, like a Veolia, BWT, Evoqua, etc… as well as RO manufacturers and many other companies. They have the models to predict rejection efficiency for individual ions, and it is backed by their own in-house data. It does exist for the most common ions, Na+, chloride, sulfate, bicarbonate… maybe they have for nitrite too?
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My point was about it removing nitrosamines not nitrite. If you have a water source containing NDMA then from what I can see RO is likely to have little or no effect in removing it. In fact most WFI systems seem to leave a gap regarding NDMA.
Hello,
There are RO systems that are effective at removing low molecular-weight nitrosamines, although their effectiveness will depend on the specific system and the concentration of nitrosamines present in the tap water. My advice is that you carry out analysis, as this is the only way to draw conclusions. You can test the tap water before it enters your system and then test the purified water produced by your RO system using the lowest LOD you can achieve, to verify the system’s effectiveness. These analyses should be repeated throughout the year, considering seasonal variations, the rainy season, droughts, etc. In addition, you can also screen SMNAs in any of your products made with purified water that do not have a risk of containing SMNAs from other sources, thus indirectly rule out the presence of nitrosamines in your purified water.
However, in any case, given that the requirements for purified water are increasing, my recommendation would be to test both the products and the purified water itself.
I started a discussion a few months ago regarding the need to conduct a risk assessment for nitrosamines in purified water.
Nitrosamines risk from Water for Pharmaceutical Purpose according to USP - Guidance, Documents, Resources - Nitrosamines ExchangeRegards,
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Completely agree with you. The point I was making is exactly what you also say-A WFI system is not fit for purpose when considering nitrosamines and monitoring is essential
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