Water Purification Methods for Survival

Humans can go weeks on end without food, but water is a different story. According to Randall K. Packer, a professor of biology at George Washington University, humans could last up to a week or so without water. But that's a best-case scenario in comfortable conditions; if you're forced to walk significant distances in hot or dry conditions, you could become dehydrated more quickly -- even within a matter of hours. No matter how clean water looks and no matter how thirsty you are, you'll want to make sure the water is pure before drinking.

  1. Filtration

    • Part of effective wilderness survival is preparation. Even on shorter, less imposing hikes, you should consider bringing along a survival kit that provides for water purification. The first piece of gear that you'll want to have is a filter. A filter will remove contaminants like sand, debris and larger organisms. Depending upon the size of the filter, which will be denoted in micron-based 'pore size', smaller organisms, particularly viruses can pass through the filter.

      Types of filters include gravity filters and pump filters. In a pinch, you could pour water through a cloth or shirt to filter out larger particles.

    Purification

    • Filters are effective for larger contaminants but are often too large for the smallest ones, particularly viruses. To effectively kill all smaller organisms, you'll want to purify the water. Purification does not remove larger particles like sand, but removes small, microscopic organisms including protozoa, bacteria and viruses. Purification comes in a number of forms including UV devices, which use ultraviolet light to clean out contaminants, and chlorine dioxide tablets, which are a chemical treatment.

    Boiling

    • The most versatile method for cleaning water when you're not prepared with purifying equipment is boiling. Boiling water is simple and universal and so long as you have fire-starting equipment and something to hold the water in, you'll have access to this method. It is also 100 percent effective at killing protozoan cysts, bacteria and viruses. Bring the water to full boil and let it boil for at least one minute (or three minutes at elevations above 6,500 feet) before cooling and drinking.

    Shortcomings

    • The above methods work for filtering out the average natural sediment and organisms that exist in much water. However, these methods will not make chemically tainted water safe. For instance, if the water source is a river that has been polluted with industrial waste, you will not be able to purify it based on the above methods and should look for a cleaner water source. Avoid sources that are downstream from active or former industrial, agricultural or mining operations.

      Water that is filled with particularly large or concentrated sediment can clog your filter; use the cleanest, clearest water that you can find.