A Cheap, Promising Way to Filter Water: Through A Twig

Shambling Shaman

Bushcrafter (boy, I've got a lot to say!)
May 1, 2006
In The Wild
Seen this thought it worth sharing.


One way to avoid getting sick while traveling is to only eat fruit that you peel yourself, since plants can filter out bacteria and prevent it from traveling throughout their tissues. Well, why not apply this principle to filtering water directly? A team of scientists have done just that, testing how well pine wood filtered water with its xylem, the tube-like tissue that transports water from plant roots to leaves. The results, published last week in the journal PLOS ONE, were very promising. "Filtration using three different xylem filters showed nearly complete rejection of the bacteria," catching at least 99.9% of them, the authors wrote.

The xylem filters used in the study appeared to catch nearly all particles larger than 100 nanometers in diameter, meaning they would exclude protozoa (like Giardia) as well. Smaller viruses would be expected to pass through, but research suggests that other types of wood with smaller pores could possibly be used to filter out these pathogens as well; pine was used in this experiment since a larger percentage of its cross-section is made up of xylem, making it a more feasible choice for a prototype.

To make a filter, all you need to do is peel the bark off a pine twig and stick it into a tube, sealing holes between twig and tube with epoxy. Then the pressure must be optimized, which is a little bit trickier. But once that's worked out, each twig-filter processed 4 liters of water per day, enough for one person.