I came across this the other day on Ranger Rick’s Survival Outdoor Skills website. I’ll confess I’ve not tried it yet myself but the logic appears sound.
While this method of water filtration is time consuming, it is passive. Meaning, you can just set it up and let it go while you’re busy with other things. What you’ll need are two containers and some cotton cloth.
Fill the first container with the dirty water and set it up so it sits a little higher than the second, empty, container.
Rest one end of your cotton cloth in the dirty water and drape the other end into the clean container. It helps if the ends are roughly cut, so as to expose as many cotton fibers as possible.
Slowly, water is drawn up those fibers and eventually will drip down into the empty container. As the water moves through the cloth, the particulates are filtered out.
Now, this method will NOT remove harmful bacteria so you’ll still need to purify it through boiling or chemical means. But, if you’ve run out of coffee filters or just have no other means of getting dirt and such out of the water, this should work well.