From Wood to Water

From carbon to sand to ceramics and more, there are a vast multitude of materials that can be used to filter water. Earlier this month, NPR reported on a new one to add to the list – the xylem of plants.

According to a report on NPR’s website (and featured on its “All Things Considered” segment), Massachusetts Institute of Technology engineer Rohit Karnik developed a method of removing bacteria from water using the xylem of a pine tree. The results of his experiment, which involved placing the xylem in a tube and then running water through it, were published in the journal PLOS ONE.

Karnik estimates that the method removed 99.9% of bacteria from the water. Although his experiment was run only on a small scale in his laboratory, he believes that it would be worthwhile to determine how to scale it up, because wood is a resource that is both inexpensive and plentiful.

NPR reported that not everyone is sold on the idea of using xylem as a filtration medium, however. One skeptic, Robert Jackson of Stanford University, noted in an e-mail that the method may not remove enough bacteria to make it completely reliable – and that while it could be useful in a “survival situation,” it may not be suited for long-term use.

Whether Karnik’s xylem filtration method becomes widely used or turns out to be inefficient, it does show us one thing: The next new development in filtration could already be right under our noses.


Kate Cline is editor-in-chief of WQP. Cline can be reached at [email protected] or 847.391.1007.

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