A study published from the University of Singapore has found a way to use a vinyl tube, hose clamp and peel pine branch to effectively filter out bacteria and viruses from drinking water. Also of note is that the study is published to be read freely by all. Most of my readers know by now my hatred of scientific journals that publish studies funded by taxpayer money, but require payment to view the results.
Trees transport water in the xylem (aka sapwood) from the roots to the rest of the tree. By tightening a vinyl tube using a hose clamp around a section of branch with the bark removed, a watertight seal is made while the porous sapwood filter the water. After all, plants have had millions of years to learn how to remove bubbles in order to transport the water using pressure differentials through the entirely of the organism. The reason softwoods are recommended is that the pores in the xylem are smaller. Surprisingly, this simple filter even captured 20 nm gold particles from the water indicating that viruses are expected to be trapped by the filter. So it should not be a surprise that the filter is effective to 200 nm, the size required to remove bacteria and protozoa.
This is amazing stuff, especially considering the impacts of treating water and distributing it through municipalities. Chlorine treatment is expensive and the piping to distribute chlorinated water corrodes making it both expensive to build as well as maintain. Boiling, distilling and subjecting water to reverse osmosis has a large fuel cost. Membrain systems are prone to clogging, are expensive and require a pump/fuel to force the water through the filter.
Xylem filtration might be a key development in small scale water filtration!