Run out of drinking water and don’t have your water filter with you? Here’s a simple solution: Simply break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water.
In fact, a group of MIT researchers has discovered that this low-tech filtration system can produce up to four liters of drinking water a day — enough to quench the thirst of a typical person
In a paper published this week in the journal PLoS ONE, the researchers demonstrate that a small piece of sapwood can filter out more than 99 percent of the bacteria E. coli from water. They say the size of the pores in sapwood — which contains xylem tissue evolved to transport sap up the length of a tree — also allows water through while blocking most types of bacteria.
“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily,” Karnik says. “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.”
To study sapwood’s water-filtering potential, the researchers collected branches of white pine and stripped off the outer bark. They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps.
Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size.
“There’s huge variation between plants,” Karnik says. “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 on the market today.”
Via newsoffice.mit.edu |Image courtesy of the MIT researchers