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Desalination of water and its effect on the human body

  1. Jun 2, 2017 #1
    I have been thinking, looking for an answer.
    It is known to me that drinking pure H2O is bad for the body, reason is it saps all of the minerals from the body since it does not contain any.

    I have been thinking, if I take salt water from a certain sea, put it in a container and boil the water to the point where the H2O(gas) which is lighter than air climbs to the upper container and the unhealthy substances stays in the lower boiled container, if I now seal both containers from each other and take the H2O container and cool it down, and drink the pure water, wouldn't it eventually kill me? If so how then does desalination of water works, it has to have minerals.
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  3. Jun 2, 2017 #2
    I think we may assume that, by its surviving for tens of years, the human body has control systems able to regulate its loss and gain of nutrients, including water itself, as necessary.
  4. Jun 2, 2017 #3
    Then why pure water is considered dangerous.
  5. Jun 2, 2017 #4

    jim mcnamara

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    @Ishay I assume you are referring to ultrapure water, which is extremely expensive to generate from "normal" water. You are correct: drinking ultrpure water is a bad idea.

    Your distillation process does not create ultrapure water, not in any way. Normal distillation methods do not create ultrapure water.

    Ultrapure water sitting in an open glass or your apparatus for a few minutes contaminates the water with bacteria and dust particles, possibly impurities in the glass itself - or detergent residue.

    See: https://blogs.scientificamerican.com/guest-blog/the-purest-of-them-all/
    Extensive discussion of ASTM standards for ultrapure generation, handling, etc.:
  6. Jun 2, 2017 #5
  7. Jun 2, 2017 #6

    jim mcnamara

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    I'm defining dangerous as immediately harmful or fatal.

    Missing minerals in drinking water does not equal dangerous. Sub-optimal for long periods, definitely. Micronutrients exist in foods as well. Where you get more serious issues longer term is the case where micronutrients are missing in both soils and drinking water, too. WHO is great for covering all of the bases.
  8. Jun 3, 2017 #7

    jim hardy

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    Have you ever tasted ultra pure demineralized water ? I just had to try a swig from our boiler sample line. You can feel it permeate the membranes in your mouth, much like pure grain alcohol but without the sting.

    I read someplace when you consume enough demineralized water that it's become a significant fraction of you body weight you are at serious risk of death.
    Mice died at around 50% of their weight in heavy water, i don't know whether from the deuterium or the ultra purity..
    MSDS for the little vial of D2O that i bought said biggest risk was 'drowning in large volumes of it.'

    World Health Organization report here. They say you should re-mineralize desalinated water.

  9. Jun 3, 2017 #8


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    When I was running fish facilities for research labs, we would make (usually R) water), to remove whatever impurities might have gotten into it. We would than add specific minerals back to make it OK for the fish (ions and buffers).
    Most fish would not do well in pure water. Carbonates are important for them because they are a major pH buffer, but they are also used by bacteria in biological filters which change highly toxic ammonia compounds to much less toxic nitrites and nitrates.

    I would guess that drinking pure water in of itself would not be too bad, but if you did it for a long time and did not have the right minerals in your diet you might end up washing out (through your kidneys) some important components like @jim mcnamara mentioned above, which could be sub-optimal.
  10. Jun 3, 2017 #9
    Most naturally occurring water is very far from pure, so this isn't really an issue.
    Water which is contaminated with dangerous substances are usually isolated from public water supplies, as would be expected.
  11. Jun 6, 2017 #10
    Is 0 tds considered to be "ultra pure". I make RODI water all the time for my reef tank. I've drank it (albeit not long term) and so far I'm good.:cool:

    I've heard that "ultra pure" water can supposedly strip your body of electrolytes. I'm unsure though, and have seen a lot of conflicting information.
    1. Water should not be a main source of minerals
    2. I would not think that it would cause enough of an unbalance to be an issue.
  12. Jun 6, 2017 #11


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    Ultra pure water usually measures at 5.5 × 10−6 S/m (18 MΩ cm in the reciprocal terms of electrical resistivity) and is due only to H+ and OH− ions produced in the water dissociation equilibrium (from wikipedia). All other ions are removed. A TDS reading of 0 in aquarium instrumentation is a much less sensitive measurement.

    Ultra pure water is much more pure than the water a home RODI unit would make for fish tanks.
    Fish tanks don't require ultra pure and it would be expensive to get the machinery and it supplies to do it.
    Less pure water is fine for the fish. The less pure water will protect your fish from impurities in the tap water and provide a standardized kind of water to which you can add chemicals to get a pretty reproducible final mix.

    It is my impression that ultra pure is not like a poison, but if it were your only source of water and did not have other sources of minerals you would run out of the minerals eventually.
    A good reason to not drink ultra pure lab water is that there is always a chance that it or lab receptacles you might use could be contaminated with something nasty from the lab.
    You are not supposed to eat or drink in labs for that reason.
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