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ents necessary to perform the SODIS meth- od: reasonably clean water, free of chemi- cals or heavy metals, a PET (polyethylene terephthalate) bottle with cap and sunlight. When the bottle is filled with water and placed in the sun, the sunlight’s UV-rays penetrate the water, destroying any harm- ful pathogens, which may be present. Sun- light does this in three specific ways: The UV-A rays in sunlight directly in-


terfere with the metabolism of bacteria and destroy its cell structures. UV-A rays also react with oxygen dis-


solved in the water to produce oxygen free radicals, highly reactive forms of oxygen, and hydrogen peroxides that are both also believed to damage pathogens. The solar energy absorbed by the water


and radiated from the surface supporting the bottle heats the water and can improve the efficiency of the process. If the wa- ter temperature rises above 122 degrees F (50 degrees C), the disinfection process is three times faster. Higher temperatures can achieve even better results.


SODIS Step By Step To use the SODIS method, you first


need to find an appropriate supply of plas- tic bottles. Specifically, you’ll want clear PET plastic bottles less than two liters in volume. PET bottles are most easily identi- fied by looking at the bottom of the bottle for the recycling symbol (three arrows in a triangular pattern). PET bottles will have a number “1” inside the triangle. Smaller bottles are preferred since they have less depth and allow the sun’s rays to penetrate the water more readily. To work effectively, the bottles must be


clear — not tinted or frosted. You should also remove all labels and stickers, again, to maximize the sun’s ability to penetrate the bottle. Since the bottles are meant to yield clean drinking water, they should be clean and should never have been used to store any substance that could be poten- tially hazardous if consumed. Empty soda or water bottles with their original screw caps washed out with a mild bleach solu- tion are perfect for the SODIS method. Once you have a supply of bottles, you


should collect the water you intend to dis- infect. Obviously, the cleaner the water you start with, the better the results you will achieve. If you are starting with tap wa- ter that is potentially contaminated with pathogens, you have a good head start. If you are drawing water from natural sourc- es, you’ll want to use an intermediate con- tainer — preferably a clear one — to collect the water before pouring it into the SODIS bottles. If your water source has a high de- gree of turbidity (cloudiness), let the water sit for about 30 minutes so any sediment in the water can settle. If possible, you’ll want to add a final fil-


tering step when you pour the water into the SODIS bottles to eliminate any remaining


WWW.AMERICANHANDGUNNER.COM 63


(Below) Start with the cleanest pos- sible water. If it is cloudy or con- tains


sediment,


allow it to settle in another con- tainer for about 30 minutes.


Bottles for the SODIS method should be made of PET plastic, easily identified by a recycling symbol containing the number 1.


An ordinary paper coffee filter used to line a funnel helps remove particulates from the water and makes filling bottles easier.


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