A tree branch as a water filter? That’s what a new study has found.
MIT scientists discovered that a small piece of freshly cut pine tree sapwood can filter out more than 99 percent of the bacteria E. coli from water.
The scientists published the paper in PLOS ONE on February 26.
Interest in low-cost and easy-to-make options to filter dirty water prompted the study. Getting clean water is a major problem in developing countries around the world.
Researchers collected white pine branches, stripped the outer bark, and cut them into small inch-long sections. They then mounted each in plastic tubing, sealed and secured, and filtered water through that either contained small particles or E. coli bacteria.
While the sapwood filtered out particles greater than 70 nanometers wide, it was unable to separate out 20-nanometer particles.
The small- branch filtration system produced water at rates up to four liters of clean drinking water a day, typically enough for one person.
But only hydrated sapwood (not dry) will work.
“There’s huge variation between plants,” Rohit Karnik, senior author on the paper, said in the study announcement. “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 (currently) on the market today.”