With the Fukushima nuclear power plant disaster having no end in sight yet, water being contaminated in Japan, it is no surprise if our own waters are polluted with their radiation. Nuclear war survival skills has tips on how to remove the radioactivity in water.
Filtering through earth removes essentially all of the fallout particles and more of the dissolved radioactive material than does boiling-water distillation, a generally impractical purification method that does not eliminate dangerous radioactive iodines. Earth filters are also more effective in removing radioactive iodines than are ordinary ion-exchange water softeners or charcoal filters. In areas of heavy fallout, about 99% of the radioactivity in water could be removed by filtering it through ordinary earth.
Visit http://www.oism.org/nwss/s73p919.htm for the details on how to build this water filter.
On a personal note, I’d rather let nature filter the water. I don’t fancy drinking plain water. In an omnivorous raw paleo diet filled with hydrating raw fat and raw fruit, I don’t need to drink plain water.