In big American cities with lousy water, a Brita pitcher might feel like as much of a household item as a glass. It’s old tech, though, rapidly being surpassed by other methods, such ultraviolet water-filtering pitchers or insanely fancy ones that can filter 11 liters of water in a sitting. But for developing countries, water filters of any sort are rarely practical or affordable. However, diseases can thrive in the waters of developing nations, to the point that having a water filter can literally be a matter of life or death.
Scientists at MIT might have found a solution to this problem. Researchers have crafted water filters made from the sapwood of white pine trees that can filter out 99 percent of that infamous bacteria E. Coli from contaminated water.
Sapwood is simply the part of a tree where sap flows, and it has millions of tiny pores, which are just big enough to let water pass while trapping bacteria. Sapwood filters out anything that’s 70 nanometers or larger, and most bacteria is larger than 200 nanometers. Viruses tend to be much smaller, but this filtration method is pretty much how today’s water filters work anyhow: as co-author of the study Rohit Karnik explains, "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."
It’s a great step forward, though Karnik says they’ll continue searching for plant material that would also block viruses, which can be much smaller than bacteria. One day, the hope is that people in developing nations could simply chip bark off a tree, filter water through it, and have clean drinking water.