Sapwood Capable of Filtering E. Coli From Water

A team of MIT researchers have discovered a small piece of sapwood can filter out approximately 99 percent of the bacteria E. coli from water, according to a PLOS ONE press release.

Researchers were looking into studying low-cost options for filtering dirty water, a huge cause of human mortality all over the world.

Sapwood of pine trees contains xylem, a tissue that moves sap from the tree's roots to its top by using a system of pores and vessels, according to the press release.

Researchers collected white pine branches, removed the outer bark, and then cut them into small sections, approximately an inch-long, in order to study the sapwood.

Then they put each into plastic tubing, "sealed and secured, and filtered water through" that had E. coli bacteria or small particles, according to the news release.

The researchers determined that sapwood filtered out particles larger than 70 nanometers wide, but was not able to separate out 20-nanometer particles.

The filtration system produced approximately four liters of clean drinking water a day, which is usually enough for one person, according to the news release.

The authors have confirmed however that just hydrated sapwood, not dried-out wood, can be used as a filter.

"There's huge variation between plants," says Rohit Karnik, senior author on the paper, according to the news release. "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."

Research was published in a recent edition of PLOS ONE by Michael Boutilier and Jongho Lee, along with fellow colleagues from MIT.