Water

Published on February 27th, 2014 | by Derek Markham

16

Water Filter Made from a Tree Branch Removes 99% of E. coli Bacteria

A low-tech water filter system made from a branch of a tree can filter up to four liters of water per day, removing up to 99% of E. coli bacteria and producing fresh, uncontaminated, drinking water.

A team at MIT used a small piece of sapwood, which contains xylem tissue that transports sap inside the tree, to build an effective water filter that could make a big difference in places where contaminated water is the norm. By using this type of filter, rural communities may be able to solve some of their water issues in a low-cost and efficient manner.

“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily. The idea here is that we don’t need to fabricate a membrane, because it’s easily available. You can just take a piece of wood and make a filter out of it.” – Rohit Karnik, associate professor of mechanical engineering at MIT

The team used white pine branches, with the outer bark stripped off, and secured the pieces in a piece of plastic tubing to create the water filter. Sapwood, which is made up of porous tissue called xylem, moves sap from the trees’ roots to their crowns with a system of tiny pores and vessels, and lends itself naturally to the task of filtering water of contaminants measuring as small as 70 nanometers.

While the team used white pine for their initial study, they will also be looking at the potential of using other types of sapwood as a filter, including flowering trees, which have smaller pores and could be used to filter out additional contaminants.

“There’s huge variation between plants. There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away and replace at almost no cost. It’s orders of magnitude cheaper than the high-end membranes on the market today.” – Karnik

The team’s research was published in PLoS One, and could lead to cheaper, more effective water filtration devices.

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About the Author

lives in southwestern New Mexico and digs bicycles, simple living, organic gardening, sustainable lifestyle design, slacklining, bouldering, and permaculture. He loves good food, with fresh roasted chiles at the top of his list of favorites. Catch up with Derek on Twitter, RebelMouse, Google+, or at his natural parenting site, Natural Papa!



  • A

    A Spanish company has been doing something similar for a while: http://www.hidrolution.com/sp/index.php

  • This is some really exciting news, and this is done with a softwood. I would like to see how far their tests and research is going to go on other trees for water filters. I don’t know if they have maple trees around there, but this is a very hard wood that is more dense, and would like to know how well this would fair as a water filter.

  • InklingBooks

    Four liters a day with branch filtering isn’t very fast. It’d be far easier to use those branches in a fire and boil the water. With a one-liter pan, you’ve got a liter in about 15 minutes. Four liters would take about an hour.​

    That said, it’d be interesting to see how well branch filtering works with salt water. There are scenarios where the only water you have is salty or heavily laden with minerals. Boiling doesn’t work because with salt water you need boiling plus condensation. If filtering works, particularly with branches from desert shrubs, this idea might have promise.

    –Michael W. Perry, Across Asia on a Bicycle

    • Dennis

      But making ten filters is super fast, meaning 40 liters every day.

      … And that is still using _much_ less wood than you’d need to boil the four liters, or even just one liter.

    • Aubrey McMaster

      Well, for one thing, it’s only one small piece of a branch and 4 litres per day is enough to sustain two physically active people, secondly, boiling doesn’t remove chemical toxins, thirdly, boiling water containing certain algaes will release trihalomethanes, which are lethal if ingested. Use multiple filter tubes and your volume issue is solved. Likely won’t work for salt water as sodium is soluble and may pass through, though I am unsure of a salt molecule’s diameter. If it is great than 70 nanometres then it’s all good.

      • John Wick

        Obviously they have never boiled something Aubrey haha. Distillation is the only way to go, I would never boil something and then just drink it. potential death soup

    • chris dyrkacz

      but creating a fire and then tending it takes a long time. setting this up, takes almost no time and then you are free to collect firewood or hunt- very nice!

  • John

    How much pressure do you need to push it through?

    • Henry Bowman

      No pressure. It’s a passive filter. Takes a long time. They should make some kind of connector with 10 tubes or something to increase the throughput tenfold.

  • I’ll try it, using brass garden hose connectors!

  • paul tarsuss
  • Anjalee Sharma

    That’s amazing …. Water filter from tree branch. The idea is awesome. But, can I get the pure water from above filter same which I get from my bottled water supplier. I don’t think so.

  • Pat

    Okay, I’m confused. Is this better than a charcoal water filter which is at about 2 microns. I think that 70 nanometers is about .002 microns?

  • Pat

    Sorry, make that 70 nanometers to about .02 microns

  • elda

    I wonder if you could also dip the wood in colloidal silver too.

  • Ring Hotwater

    If you are really good at this process, you can make BINAKBET and hot boiled rice to come out with the fresh water. I highly recommend RING HOT WATER PRODUCTS instead: https://ringhotwater.com.au/!

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