To Clean Drinking Water, All You Need Is A Stick

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Removing all the dangerous bacteria from drinking water would have enormous health benefits for people around the world.

The technologies exist for doing that, but there's a problem: cost.

Now a scientist at the Massachusetts Institute of Technology thinks he's on to a much less expensive way to clean up water.

MIT's Rohit Karnik is a mechanical engineer who works on water technologies. He says it's relatively easy to make membranes that can filter the bacteria out of water. But making membranes cheaply, he says, is not so easy.

One day a few years ago, he was at a meeting on plants and water flow when a light bulb went off in his head. Why not, he thought, use the xylem tissue in plants for water filtration?

Now if you remember your high school biology, you'll know that xylem is the stuff in plants that transports water in the form of sap from the roots to the leaves.

"And the way the water is moved is by evaporation from the leaves," says Karnik.

It's somewhat like what happens when you put a straw into a glass of liquid. Evaporation from the leaves has the same effect as sucking on the straw.

Pulling water up to the leaves this way creates a problem for the plant, but also an opportunity for an inventor.

The plant's problem is something called cavitation, or the growth of air bubbles, which makes it harder for water to reach the leaves. But Karnik says xylem has a way of getting rid of these bubbles.

Written By: Joe Palca
continue to source article at npr.org

11 COMMENTS

  1. “The technologies exist for doing that, but there’s a problem: cost.”

    That pretty much sums up the current political climate of this world. Who cares if millions die of diseases related to polluted water, as long as the rich are allowed to live their lavish luxury lives… Can you imagine this discussion if it was about saving the lives of rich white people in the western world. “Yes, we could of course provide access to clean drinking water… unfortunately it costs to much.” Of course not, if we had no clean drinking water then it would not make any sense to spend money on other things. But, as we all know the lives of people in the third world aren’t worth a dime…

    • In reply to #1 by Nunbeliever:

      That pretty much sums up the current political climate of this world. Who cares if millions die of diseases related to polluted water, as long as the rich are allowed to live their lavish luxury lives…

      You are forgetting opportunity cost. The point is that this technology currently represents bad value for money and we owe it to everyone on the planet not to waste money and resources on stuff that doesn’t (yet) have a future.

      There is plenty of money being spent on clean water projects around the world. But with world population growing so fast, you move two steps forward and one back. Resources are always limited – that has been, so far, one of the facts of life.

      • In reply to #3 by GPWC:

        In reply to #1 by Nunbeliever:

        That pretty much sums up the current political climate of this world. Who cares if millions die of diseases related to polluted water, as long as the rich are allowed to live their lavish luxury lives…

        You are forgetting opportunity cost. The point is that this tec…

        You are of course right. If we can do something more efficiently then it’s of course a good thing. Hopefully this invention will help people in poor countries get clean water. Nonetheless, I’m bothered by the hypocrisy that we take clean water for granted while poor people in the third world can only get it if it’s cheap. It would be one thing if getting clean drinking water was a global problem, but it’s not.

      • In reply to #3 by GPWC:

        “Resources are always limited – that has been, so far, one of the facts of life”. – I disagree. This is not a fact of life per se. We made them limited, or better to say greedy capitalists did. They abduct free energy which is actually “owned” by the Planet and all its inhabitants.

        • In reply to #6 by Modesti:

          In reply to #3 by GPWC:

          “Resources are always limited – that has been, so far, one of the facts of life”. – I disagree. This is not a fact of life per se. We made them limited, or better to say greedy capitalists did. They abduct free energy which is actually “owned” by the Planet and all its inhab…

          Most of the free energy / resources (including water) that you talk of are in an un-useable state and therefore someone has to convert them for human use. This usually means that companies (ie a group of individuals pooling their capital) have to invest. To allow them to do so in confidence, they are granted (again for a price) certain mining/extraction rights. I can’t see the problem with companies making normal profit from such a highly hazardous venture. In the short term, super-normal profits may be available, but these will be eroded away quite quickly through competition – unless there is some form of restrictive practice which is illegal. It is not capitalism that is at fault, though its application may sometimes leave something to be desired. But then what economic system is perfect?

  2. There is already a lowtec method in use. Take a transparent plastic bottle, fill it with water, put it in bright sun and wait a few hours untill the UV-B has killed the bacteria.
    Sadly it´s useless against chemical water pollution though industry, mining and extraction of petroleum

    • In reply to #2 by Gerhardw:

      There is already a lowtec method in use. Take a transparent plastic bottle, fill it with water, put it in bright sun and wait a few hours untill the UV-B has killed the bacteria.

      So, no use here in the UK where UV-B’s available only from metal-halide lamps and solaria.

      • In reply to #9 by Geoff 21:

        In reply to #2 by Gerhardw:

        There is already a lowtec method in use. Take a transparent plastic bottle, fill it with water, put it in bright sun and wait a few hours untill the UV-B has killed the bacteria.

        Its UV-A that does the work in SODIS. UVB doesn’t get through the PET bottles. (PDFs in English here explain all.)

        So, no use here in the UK where UV-B’s available only from metal-halide lamps and solaria.

        • In reply to #10 by phil rimmer:

          In reply to #9 by Geoff 21:

          In reply to #2 by Gerhardw:

          There is already a lowtec method in use. Take a transparent plastic bottle, fill it with water, put it in bright sun and wait a few hours untill the UV-B has killed the bacteria.

          Its UV-A that does the work in SODIS. UVB doesn’t get through…

          Thanks Phil,

          one day when it stops raining for long enough I might find this useful.

          Brilliant for where it’s most needed though.

  3. Sometimes I wonder if capitalist are human beings at all. We are all to blame because we allow them to destroy life,… we agree to be slaves. I would like to see big world revolution of all proletarians, because it is necessary. Egalite, fraternite, liberte !

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