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Using Flocculation for Drinking Water

  1. Jul 8, 2010 #1
    Is it possible to take dirty river water (or any other water for that matter) and use flocculation to turn it into clean and safe water in a short amount of time?

    I know that you would need a flocculant, something to disinfect the water and I've read that I need a buffer but I'm not sure about what that is, and some clay for better flocculation.

    For the flocculant you could use aluminium or iron sulfate
    For the disinfectant you could use calcium hypochlorite
    Not sure about what clay to use
    And all I know of buffers is that they are used to keep PH constant (would calcium carbonate work in this case?)

    Is there anything else that is needed?
    Also what would be the ratio for all the ingredients (say if you needed 20 litres of clean water)?

    I'm curious to know if this method can be used to drink seawater?
  2. jcsd
  3. Jul 9, 2010 #2


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    Well yes and no. Flocculants will help you get rid of suspended particles, so it'll look clean, but that's about it. I'm not so sure about how good they are at removing bacteria.
    You seem aware water processing plants use flocculants to get rid of suspended particles. They also use filtration/sedimentation, balance the pH, remove salts through ion exchange, and finally disinfect the water.
    But as any "survival guide" will tell you, the main issue is just the bacteria. So if you had to choose one step, that'd be it, rather than flocculation. Disinfection followed by filtration is really good enough in most cases.

    Flocculation definitely can't be used to remove salts, so no seawater.
  4. Jul 10, 2010 #3
    There used to be a product years ago called PUR, it was a sachet filled with powder which would clean water and was meant to be used in third world countries.

    I found this from the cdc website:

    The benefits of flocculant/disinfectant powders are:

    Proven reduction of bacteria, viruses, and protozoa in water;
    Removal of heavy metals and pesticides;
    Residual protection against contamination;
    Proven health impact;
    Acceptable to users because of visual improvement in the water;

    The sachets have been used all around the world so am I right in thinking that even though the water will look clean the bacteria and other micro-organisms will be there (but dead due to the calcium hypochlorite?

    Also if you were to go about having a simple way to make 10 litres of water a day, every day for a year and if the price had to be something like $2 could you do it?
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