Monday, October 5, 2009

Pure Water

Without clean drinking water, you aren't going to last very long in a survival situation. You can go a long time before starvation will kill you, but dehydration will take you down in just a couple of days — or less, under the right conditions. 

There are five viable ways to clean up drinking water — boiling, distillation, filtering, chemical treatment, and exposing to UV light. Not all of these methods can be considered “purifying” in the strictest sense of the word. Pure water has nothing harmful in it. Water that has been treated to kill or otherwise remove living organisms might still contain harmful substances such as toxic chemicals or minerals. Using only a single method is almost always insufficient to truly purify water, making it necessary to combine methods such as boiling and then filtering, or chemical treatment followed by filtering.


To kill pathogens in water by boiling, bring the water to a rolling boil (lots of strong bubbles) and hold it there for at least one minute at sea level. At higher elevations, increase boiling time to three minutes. Keep in mind that boiling the water doesn’t endow it with a magical immunity against future contamination. If the water in placed in a contaminated vessel, it will be polluted again. The other thing is that boiling does not eliminate non-organic contaminants. In fact, boiling reduces the volume of water through steam loss, so non-organic contaminants (chemicals or other toxins) actually become more concentrated.

Distillation transforms liquid water into a steam that can be collected and condensed on a relatively cool surface. As the steam condenses, droplets of water form, which can be collected in a container. In the process of distillation, nearly everything is left behind (both organic and inorganic substances), and pure water comes out at the far end. However, contaminants that have the same or lower boiling point as water can actually distill along with the water, turn to steam, condense on the cooling surface, and end up in the container along with the water.


This is by far the most popular and convenient method of water treatment. Portable “backpack” filters are easy to carry and easy to use, but they don’t all offer the same degree of protection. For the best treatment of water, a filter should include a prefilter to trap the larger particulates before they can reach the main filter system. Next comes a sub-micron filtering element that traps organic contaminants such as bacteria and cysts. An activated carbon filtering element should be included, to absorb toxic compounds and to improve both taste and odor.

In spite of all that, notice that I didn’t mention the filtering out of virus. Those little buggers are so small that they slip right through most filter elements. The traditional way to handle virus is to either boil the water before filtering (boiling kills all the organic pathogens) or dosing the water with a chemical treatment that will kill virus, and then running the treated water through a filter. Doing it in that order helps eliminate the chemical treatment before you drink the water.

However, there is a portable filter that claims to meet EPA standard for virus removal. It is the First Need XL by General Ecology ( The company actually calls this a “water purifier” which is a standard far above most filters on the market. This system weighs 16 ounces, is compact enough for easy transport, and includes all the necessary features (pre-filter, activated carbon filter, and a “structured matrix” filter system that traps everything including virus). As testament to the effectiveness of this filter system, the company points to a report by Charles P. Gerba, PhD; Jamie E. Naranjo, BS; and Ellen L. Jones, MPH, PhD from the Department of Soil, Water and Environmental Science at the University of Arizona, Tucson. To quote the report, “This study demonstrated that a structured matrix unit is available that can be expected to remove a wide range of viruses with different isoelectric points and hydrophobicity, even in water with a quality that would be expected to present conditions far less than ideal for structured matrices (ie, the presence of organic matter in the worst-case challenges can block adsorption sites to which the virus adheres to on the matrix). This technology offers the advantage of simplicity of use without the need for chemical addition to water and rapid processing of the water.

“Given that the unit in this study was capable of adsorbing a wide variety of types of viruses with a wide range of physical and chemical properties, it should be expected to remove any known viruses capable of transmission by water.” In the heading to the report, was the following: “Results — The removal of all virus types tested exceeded 99.99%.”

Average filter canister life for this unit is 150 gallons, and the pump is field-serviceable. For convenience, the unit comes with a collection of adapters that allow connection directly to a variety of hydration systems and water bottles.

Chemical Treatment

The chemicals used for disinfection of drinking water are chlorine and iodine. Both are toxic, which is why they kill the organisms, and must be used as directed on the product package. Some people are allergic to iodine, so check with your doctor before use. Chlorine is effective against bacteria, but offers only limited protection against some protozoa such as giardia and cryptosporidium.

A more high-tech approach to chemical water treatment was developed for the military and tested by the U.S. Marines and Special Forces in Afghanistan. MIOX, made by Mountain Safety Research, also known as MSR (www.cascadedesigns/, is unlike any other water purifier currently on the consumer market. The way it works is to use a small amount of untreated water, some salt and a small electrical charge to create a chemical solution (a powerful oxidant) that when added to untreated water is toxic to all manner of organic pathogens (virus, bacteria, giardia, Cryptosporidia) but is not toxic to humans in its diluted form.

UV Light

One of my water bottles is the AquaStar made by Meridian Designs ( that comes with a battery-powered UV light inside. 

The SteriPen System Pack UV Water Purifier ( is another high-tech product that operates along the same line. The concept is that UV light wavelengths disrupt the DNA and RNA of organic pathogens (bacteria, cysts, and virus), thus rendering them unable to reproduce and therefore harmless to humans. Even though there is no doubt about the effectiveness of this technology (it is, after all, employed by municipal water treatment plants), some limitations exist for portable units. Batteries wear out. Lights can break or burn out. All the non-organic contaminants are still in the water and must be filtered for removal.

Because you can’t see the bad guys in water with your naked eye, it’s tempting to think of frigid water tumbling down a stream after melting from a glacier high in the mountains with complacency. Don’t do it. The only safe way to think about water is that there is NO source of clean water in the outdoors, other than rain that you catch as it falls from the clouds. Unless you are facing imminent death from dehydration, don’t drink from wild water sources until you purify it. 

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