Tuesday, March 6, 2012

Water for Survival — What's Your Plan?

A couple days ago, I posted six possible solutions for purifying drinking water, asking readers to ponder the right answer. So now let's examine each of those possibilities.

1. Boiling for 5 minutes at sea level and one additional minute for each 1000 feet of elevation.
  • This is the age-old recommendation that goes back to the era of hobnail boots and chamois shirts, but it is no longer the doctrine. First of all, boiling is intended to kill organic contaminants such as bacteria, virus, cysts, fungus, etc in the water, and it doesn't take 5 minutes at sea level to do the job. One minute is sufficient. However, the theory about adding another minute for each 1000 feet of elevation gain adds a safety margin because water boils at a temperature less than 212ºF as altitude increases. 
2. Filtering with a sub-micron ceramic filter system.
  • This is a good start, but there are better systems available today than the old ceramic block technique.  Sawyer (www.sawyer.com) makes what I consider to be the best water filter systems on the market, and they use a hollow fiber membrane that not only far exceeds the capability of ceramic blocks to filter out small stuff, but can also be back-flushed to reboot their ability to keep on filtering for up to a million gallons (company guarantee).
3. Exposure to a UV light source.
  • UV radiation, at certain frequencies, has the ability to disrupt the RNA of organisms, leaving them unable to reproduce. If a "bug" can't reproduce, it can't harm you, even if you ingest it. That's the concept behind UV water treatment. The problem I see with this, as a personal water treatment system, is two-fold — first, the components are fragile; second, the system requires a power source that may or may not be available when you need it most. 
4. Treatment with chlorine or iodine.
  • Chemical purification of water is another age-old technique with a solid track record, but problems persist. These chemicals are toxic — that's how they kill the bad organisms in the water. But they're also toxic to humans, in some degree. How much of that do you want to ingest? Iodine, in particular, is potentially lethal to sensitive individuals who have allergies to this substance. Not only that, but these chemicals have a shelf life, and they work slowly if the water is cold or turbid, so effectiveness is impaired. 
5. Distillation.
  • There is a myth about distillation that it removes all the bad properties from water, leaving it pristine. Not so. Some contaminants can actually be carried through the system and deposited on the far side. Okay, so that's a technicality. But another problem with distillation is that it requires a lot of heat energy and/or time to accomplish in sufficient quantities to keep you alive. 
6. Other.
  • So what else is there? Well, there's pasteurization. Everybody knows boiling kills organisms, but very few are aware that you can kill them at a temperature far below boiling. At 160ºF, 90% of waterborne pathogens will be killed in one minute. Keep the water at that temperature for 5 minutes and you'll achieve a 99% reduction of pathogens. A solar cooker can easily bring water to that temperature, but only if the weather permits the use of the solar appliance. 
I should mention that, of all these techniques, only filtration removes inorganic contaminants. In fact, boiling actually increases the concentration of the inorganic compounds due to water loss. And, it's not always easy to get a fire started often enough to satisfy your needs for drinkable water in a survival situation — especially if you're on the move.

1 comment:

  1. Good stuff, Rich. As usual! Iodine is toxic - as is chlorine. But the body can benefit from small doses of Iodine to ward off things like goiters or gout(?), which is why they put it in table salt. As for chlorine, or bleach, a few drops per gallon of water makes it drinkable in a survival situation, it is preferable to getting parasits or sick from bacteria. But as you say, there are better ways to keep the drinking water clean. -Peter D.