In the survival world, we sometimes have a tendency to reinvent the wheel. Rather than focusing on learning the tried-and-true survival methods used by primitive survivalists for centuries, we rely on technology to solve our problems. There's nothing wrong with this per se, since technology has a substantial potential to make our lives easier. Rather than rubbing sticks together, we can now spark a fire with a lighter in seconds. However, it's also reassuring to see much of the survival community focusing on getting back to basics.

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A colorized electron microscope image showing green E. coli bacteria trapped on the surface of sapwood. Source: MIT News

One interesting development in this vein came from an unexpected place: Massachusetts Institute of Technology (MIT). This prestigious school has nurtured some of the finest scientific minds of our generation, including numerous Nobel Prize winners. A study performed by a team of MIT researchers has established that the plant xylem found in sapwood can serve as an effective survival water filter, blocking more than 99 percent of E. coli bacteria.

Illustrations from the MIT study. Source:

If you're not too familiar with plant physiology, the implications of this discovery may be unclear at first. In simple terms, this means that the core of a sap-producing tree branch or twig can be used to filter water and prevent illness. Here's how it works:

  1. Find a pine tree, and cut off a small branch.
  2. Peel away the bark and discard it, so only the inner xylem remains.
  3. Plug or cork a water container with this tree branch water filter, and seal to prevent leaks.
  4. Invert and/or pressurize the container, forcing clean water through the wood, and filtering out bacteria.
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A diagram showing the construction of a tree bark water filter. Source:

According to the study, this simple system can produce up to four liters of clean water per day. The scientists used a plastic tube and hose clamp, then applied 5 psi of pressure to the water vessel to increase flow rate. We imagine this could also be done with a plastic water bottle, some duct tape, and a squeezing motion—just be sure no dirty water seeps around the edges of the wood.

Purpose-built water filters from companies like LifeStraw and Sawyer are great to have in a survival setting, but if you don't have access to these modern conveniences, remember this simple tree branch water filter method.

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