Back to nature, amidst all of these high-tech water filtration solutions out there, nature offers a low tech / low cost but effective option. Researchers at MIT have found that a branch from a species of sapwood such as pine can filter out 99% of the bacteria E. coli. The xylem tissue in trees that transport sap up the length of the tree yet allow the flow of water. Read the article for a really interesting study.
If you’ve run out of drinking water during a lakeside camping trip, there’s a simple solution: Break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water.