I think we can all agree that having access to potable water is a critical component of our disaster planning. Using the SODIS (SOlar water DISinfection) method of purifying water is just one more tool in our toolbox.
For this method, you need to start with reasonably clean water. By that, I mean it should have sediment and debris filtered from it and it should be free of heavy metals and chemicals. Thus, this won’t work on water you get from your swimming pool or hot tub but will work great on lake and river water.
Next, you need a PET bottle. PET stands for polyethylene terephthalate. Yeah, say that three times fast. The plastic bottles should be clear and if you look at the bottom, you should see the familiar three arrow triangle informing you the bottle is recyclable. Inside the triangle, if you see a number 1, that means it is a PET bottle and you’re good to go.
Remove all labels and stickers from the bottle. You want them as clear as possible. Obviously the bottles themselves should be clean inside and out as well. Oh, and make sure you have caps for the bottles.
A great way to reduce the amount of foreign bodies in the water is to pour it into your plastic bottles using a coffee filter and funnel. This will capture all but the very smallest debris.
For the process to work properly, you’ll need about six hours of sunlight. Yeah, this method won’t work well on rainy days. Fill your bottles to the top with water and screw the caps on tight. Then, lay them on their sides in the sun. Ideally, you will be able to place them on a hard, dark surface like a darkly stained table. The idea is that the surface of the table will obviously get hot as the day goes on and this heat will transfer to the water in the bottle. If you can get the temperature of the water to reach 122 degrees F or greater, the time the process takes is reduced considerably to about two-three hours.
What happens is the UV rays from the sun kill off the pathogens. Again, it won’t do anything for chemicals that may be present in the water so keep that in mind. This only works on bacteria and other harmful organisms.