Need To Filter Your Water? Use Tree Bark!

The fact that trees are vital to our well-being is no secret. They provide us with food, wood and most importantly, oxygen. Now there is one more thing you can add to this already lengthy list - filtering out harmful bacteria from water.

The discovery was made by a team that comprised of scientists from the Massachusetts Institute of Technology (MIT), as well as, students from Fletcher-Maynard Academy and Jericho High School, who were seeking a natural water filter - one that would help communities in developing countries that do not have access to state-of-the-art filtration systems.

The researchers, led by Rohit Karnik, an Associate Professor of Mechanical Engineering at MIT, decided to turn to trees for help because of their capability to allow sap to flow through, while blocking out air bubbles. A water filter requires the same attributes - Something that will let water flow through while blocking out microbes.

They began by cutting 1.5-inch-wide sections of external tree bark from the branches of a white pine tree (the same that pose as Christmas trees), and mounting each in a plastic tubing that was sealed with epoxy and fastened with clamps. The researchers then tested the wood's filtering capability by pouring water containing red dye particles of different sizes (from 500 to 70 nanometers wide), through. To their astonishment, they found that it was effective at trapping the entire range. Encouraged, the team conducted another experiment, this time with water that was contaminated with E.coli bacteria. Sure enough, the sapwood held back 99% of the bacteria, allowing only a measly 1%, to flow through.

Mr. Karnik, who published the results of the study in the February 26th edition of the scientific journal Plos One, says that the bark was able to filter water containing particles as small as 20 nanometers. This means that they can be used to get rid of a majority of bacteria, since most are at least 10 times as wide. What tree barks are not useful for however, is filtering out viruses, which tend to be much smaller.

Also, while the pine sapwood is effective, there is a caveat - it only works when moist. This means that before this natural filter can be put to practical use, the researchers will have to figure out how to keep the wood damp, or find a way to retain the bark's superb filtering capability even when it's dry!

But the team is not done yet. They plan on evaluating other types of sapwood, including those from flowering trees which have smaller pores. They speculate that these may be more effective in trapping smaller particles and hence viruses - So stay tuned!

newsoffice.mit.edu