A low-tech water filter system made from a branch of a tree can filter up to four liters of water per day, removing up to 99% of E. coli bacteria and producing fresh, uncontaminated, drinking water.

A team at MIT used a small piece of sapwood, which contains xylem tissue that transports sap inside the tree, to build an effective water filter that could make a big difference in places where contaminated water is the norm. By using this type of filter, rural communities may be able to solve some of their water issues in a low-cost and efficient manner.

“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.” – Rohit Karnik, associate professor of mechanical engineering at MIT

The team used white pine branches, with the outer bark stripped off, and secured the pieces in a piece of plastic tubing to create the water filter. Sapwood, which is made up of porous tissue called xylem, moves sap from the trees’ roots to their crowns with a system of tiny pores and vessels, and lends itself naturally to the task of filtering water of contaminants measuring as small as 70 nanometers.

While the team used white pine for their initial study, they will also be looking at the potential of using other types of sapwood as a filter, including flowering trees, which have smaller pores and could be used to filter out additional contaminants.

“There’s huge variation between plants. 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.” – Karnik

The team’s research was published in PLoS One, and could lead to cheaper, more effective water filtration devices.

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