Peel off the bark of your nearest pine tree, fasten it to a source of dirty water, and wait for the clean water to come out the other side.
Providing a simple, cheap, and sustainable method for filtering dirty water is that simple, according to a new study published this week in PLoS ONE. The study demonstrates that a 2 cm long piece of branch with a 1 cm diameter can filter 99.9% of the E. coli out of a water sample and that each segment could be effective for a few liters a day. Not surprisingly, it needs to be fresh branch wood, not dried.
Providing a simple, cheap, and sustainable method for filtering dirty water is that simple, according to a new study published this week in PLoS ONE. The study demonstrates that a 2 cm long piece of branch with a 1 cm diameter can filter 99.9% of the E. coli out of a water sample and that each segment could be effective for a few liters a day. Not surprisingly, it needs to be fresh branch wood, not dried.
The plant's xylem, and more specifically the torus-margo pit membrane, is responsible for all of the action. Xylem is the series of tubes that water travels through in a branch --- torus-margo pits are tiny closable valves between tubes. The interesting thing about the torus-margo pits is that they have the appearance of a spiderweb, with a pancake in the middle (the best description I can come up with...), and that spiderweb is where all of the E. coli is captured. Torus-margo pits serve a vital function in the plants, when there is not enough water the spiderweb flexes so that the pancake presses against the connection between the two tubes, effectively isolating one (empty) tube from another (full tube). It's very cool to consider another possible function, albeit totally unintended, for this anatomical feature.
| It's clear that this paper is a proof of concept and that a lot of work remains to be done. The authors, all mechanical engineers at MIT, did an admirable job of teaching themselves about xylem...I wonder how these efforts could be advanced more rapidly with some help from the plant ecophysiologists among us. Nevertheless, my understanding is that cheap and efficient water filters are something of a holy grail...nearly 1 billion people still do not have access to clean water. Imagine the possibilities this could inspire... | Torus-margo pit. The torus is the valve (pancake) in the center and the margo is the membrane (spiderweb). From Choat et al. (2008). |
Boutilier et al. 2014. Water filtration using plant xylem. PLoS ONE 9(2): e89934.
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