What’s wrong with our pure water? Experts, please come in!
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Our pure water treatment process: multi-media filter + reverse osmosis + mixed cation-anion ion exchange bed; currently, there is a white powdery substance in the water. But the pH value and conductivity are within the acceptable range; I would appreciate some advice from those with more experience! Thank you first! The above is a pure water sample. It’s the security filter element before the water outlet; the element stopped working after just three days of use
Has the original poster analyzed this white powdery substance? It is likely salts such as calcium and magnesium; it is recommended to conduct an analysis to determine what they are.
It should be residue from a damaged filter element, so it has no effect on either pH or conductivity!
I agree with the opinion from the second floor: conduct laboratory tests first, and then make a judgment. If regeneration is carried out using sulfuric acid, poor control of acidity can result in the formation of white CaSO4 flocculent precipitates. Your manufacturing process is unclear, so it’s hard to draw a conclusion. Personal opinion, for reference only.
If acidity is not well controlled, the pH value of the water quality will be abnormal. Since there is no issue with PH, it shouldn’t be precipitates such as calcium sulfate, and the sulfate ions should also have been completely displaced before the water is released. Check whether resin has been carried out of the fixed bed.
I strongly agree with the opinion from the third floor: it should be residues from damaged filter elements, so it has no impact on either pH or conductivity! "
You can measure the conductivity...
This post was last edited by pzhmotor on 2009-10-22 at 10:17. 5# When jothan uses sulfuric acid for step-by-step regeneration, poor control of acidity can lead to the formation of white CaSO4 precipitates in a short period of time. In such cases, backflow of water from the ejector often occurs, forcing an interruption of the regeneration process (backflow of water is very dangerous). The analysis upstairs is good; usually, the water is replaced thoroughly before it is sent to the bed, to ensure that the output water does not contain any residual regeneration liquid. Explain: CaSO4 is a precipitated salt, and in cases where the water volume is high, it does not have a significant impact on the pH value of the produced water. It is not necessarily possible to completely remove all CaSO4 during displacement (this is especially true when the resin loading is high). We are a two-chamber floating bed, and such situations often occur during the initial operation phase. Since there is no safety filter in the subsequent stage (both the fiber filter and membrane filter are located at the front end), the resin trap is unable to accurately capture white precipitates in the desalinated water. Once, before a shutdown for maintenance, the level of water in the demineralized water tank was quite low; it was time to carry out anti-corrosion treatment on the tank. I went in personally and saw that there were small amounts of white precipitates attached to the walls of the tank within the demineralized water. Sulfuric acid is rarely used for regeneration; using hydrochloric acid to regenerate the cation exchange resin does not lead to such a situation. Judging from LZ’s photos, this doesn’t seem like something that formed as a result of resin degradation and fragmentation (it’s just my opinion; resins are usually not white, oh! ! The white balls in the floating bed are indeed white; they might appear this way after breaking. It’s more likely that they are salts (due to problems with regeneration), and there’s a very small possibility that they result from the peeling off of anti-corrosion materials inside the pipes (this doesn’t apply to pipes lined with rubber or plastic; but what about those with poorly applied anti-corrosion coatings?) I have no experience with it, so I can’t say for sure). It should also be noted that low-potential deionized water places special requirements on online pH detectors; ordinary integrated analyzers may experience salt bridge blockages, resulting in significantly high readings. Even if the selection is correct, regular verification is necessary. Conductivity meters are more reliable. All of the above are based on hands-on experience and are provided for reference only. I hope this can provide some help in ultimately resolving this issue. It is still advisable to conduct laboratory tests on it first.
We use hydrochloric acid for regeneration; the water sample comes from the mixed-bed system. The water quality from the anion and cation beds is better than that from the mixed bed. The problem lies with the mixed bed itself. For the mixed bed, we use both hydrochloric acid and sodium hydroxide for regeneration. If it’s a salt, what kind of salt would it be? How to analyze it?