Gizmos & Gadgets: Clean Freshwater Gets Help from Plant Xylem Filter

March 30, 2014 – The engineers and scientists at Massachusetts Institute of Technology (MIT) always come up with some interesting ideas. Why not mimic the way plants transport water from root to leaf eliminating contaminants like bacteria along the way?

Xylem is the porous tissue that conducts fluids throughout plants. You see it when you peel back bark on a healthy tree, that somewhat spongy wood that lies just inside the bark. It is called sapwood because when deciduous trees emerge from hibernation each winter, the sap travels from the roots to the budding leaves by this route. And although conifers don’t lose their needles during the winter, much of the sap within them is channeled to the roots for storage.

In an experiment the scientists at MIT chose xylem from white pine trees to create an effective water filter.They took sapwood from trees and stuffed it into a tube. They sealed all gaps with epoxy. Then they added water and pressure equivalent to that which trees experience from gravity. The fluid filtered through the 1 centimeter square filter at a flow rate of approximately 4 liters per day, enough drinking water to sustain one person. The water that came through filtered out particles and bacteria including E-coli.

When they examined the filters they found out that a 3 millimeter length was all that was needed to effectively remove suspended particles of a size 100 nanometers or greater. So viruses can get through but when you consider the worst waterborne infectious diseases are largely of bacterial origin, this easy to manufacture filter that is cheap to produce and biodegradable, could clean up 99% of the contaminants in water that make us sick. This includes salmonella, cholera, giardia and E-coli.

Related articles across the web

• Stick filters out ’99 per cent’ of bacteria from water
• Xylem tissue in sapwood can filter bacteria from contaminated water
• MIT researchers make a water filter from the sapwood in tree branches