Scientists Use Sapwood To Filter Water
Somewhere in the near future, we may no longer need to use expensive carbon-based filters to purify our glass of drinking water. A piece of sapwood would do just fine. According to a paper published in PLOS ONE Wednesday, a small piece of freshly cut sapwood can filter out more than 99 percent of the bacteria E. coli from water.
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With the Earth's ever-growing population, providing clean and safe drinking water to billions of thirsty people is a huge challenge to administrators worldwide. Providing low-cost and easy-to-make options for filtering dirty water is of great priority in developing and under-developed nations, where unsafe drinking water is a major cause of human mortality. So, exploring natural resources like sapwood presents a very viable solution.
According to a press release Wednesday, he sapwood of pine trees contains xylem, a porous tissue that moves sap from a tree's roots to its top through a system of vessels and pores. To prove sapwood's water-filtering potential, researchers collected white pine branches, stripped the outer bark, and cut them into sections, one inch long. Each of these sections was secured and sealed by mounting it in a plastic tubing and water, which contained either small particles of dirt or E.coli bacteria was passed through it.
The researchers found that sapwood filtered out particles greater than 70 nanometers wide. Particles less than 20 nanometers wide could not be separated indicating that the coniferous sapwood could only filter up to a particular size. But the sapwood filtered out more than 99 percent of E.coli (the cause of a large number of water-borne diseases) from the water which mostly accumulated in the first few millimeters of the wood in what are known as pit membranes. The researchers have established that only hydrated sapwood should be used in this sort of filtration system, since dried-out wood cannot filter out contaminants. This small-branch water filtration system produced up to 4 liters of pure drinking water a day, which is generally sufficient for a person.
"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 (currently) on the market today," said Rohit Karnik, a senior author on the paper.
Source: Boutilier MSH, Lee J, Chambers V, Venkatesh V, Karnik R. Water Filtration Using Plant Xylem. PLoS ONE. 2014.
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