Sterilize Water for Free with Something You Probably Throw Away

It’s often said that the best disinfectant is sunlight, and in terms of water purification that’s absolutely true. Ultraviolet rays are used in industrial settings to sterilize everything from titanium medical implants to contact lenses – including drinking water. But you don’t need fancy bulbs and fixtures to sterilize drinking water – you just need some sunlight and an ordinary pop bottle.Screenshot 2015-10-11 10.11.16Select a clear, clean plastic soda bottle. Most pop bottles in the United States are made from polyethylene terephthalate: better known as PET plastic. Specifically, you’ll want PET Type 1 – you’ll find a logo somewhere on the bottom or the packaging that indicates the type of plastic for recycling purposes. If the water you’re sterilizing is relatively clear, you can use up to a two liter bottle – otherwise use a single liter or smaller bottle: the sun’s UV rays are better able to penetrate more deeply.
Screenshot 2015-10-11 10.15.17 Filter out any particulates with a bandana or other piece of cloth and fill the bottle about three-quarters, cap it and give it a good shake. Fill it the rest of the way – then just lay it in the sun! On a bright, sunny day about ten hours of sunlight will eliminate common bacteria, virii and parasites – including e. coli, salmonella, campylobacteria, rotovirus, cryptosporidium and giardia. The sun’s ultraviolet light destroys the structures of bacterial cells and reacts with oxygen (shaken into the water) to produce very small amounts of pathogen-destroying hydrogen peroxide. And the plain-old heating of the water speeds the process.Screenshot 2015-10-11 10.18.12The pop bottle method has been used extensively in developing countries to combat bacterial-borne diseases and save lives. Researchers indicate that while trace quantities of chemicals, including adipates, phthalates and the heavy metal antimony, leach from the plastic into the bottle, even after 17 hours the amounts remain well below the safety thresholds established by the World Health Organization. The method is also ineffective at removing toxic chemicals or heavy metals, so use more aggressive filtration if you find yourself downstream from a chemical plant.

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