How to Purify Water

Most of us in the West don’t think about drinking water. We just turn on the tap and it’s there: clean, pure and reasonably tasty.

But it’s a different story in developing countries or in the wilderness areas in our own backyards. And as we’ve seen with the recent cholera outbreak in Haiti, disaster areas and makeshift camps with poor sanitation are especially susceptible to the spread of water-borne diseases.

Whether you’re headed overseas as part of a relief effort, or simply planning a wilderness camping trip, you’ll need to learn how to purify water.

Water purification removes or kills harmful bacteria, amoebas, viruses and other microscopic bugs that can make you sick. In the United States and Europe, the primary concerns are Giardia and Cryptosporidium. Elsewhere, you may have to worry about cholera and dysentery. If you plan to be in less-developed areas, more serious pathogens may be lurking around.

Start clean

Before we get into the different ways of purifying water, it’s important to select a the best water source available from which to start. Running water is always the best option if you can find it. Avoid standing water, water with an oily sheen to the surface, water that smells bad or has excessive debris in it, or water near latrines or sewers.

Can’t find anything but some disturbingly dirty water? Filter it first by running it through a clean sock or t-shirt to remove the large debris, then let it sit so solids can settle at the bottom. Finally, use one of the purification methods below.

Boiling

The original way to purify your water, boiling is still one of the cheapest options so long as you have reliable access to a camp stove or fire. Just make sure to boil your water for at least one minute at a rolling boil, as recommended by the CDC.

Solar Water Disinfection

A very low-tech way to purify water is to simply leave it in the sun. Try this if you don’t have the supplies necessary to perform the above methods. It’s a method recommended by the World Health Organization, who gave it the snappy name SODIS.

Take a transparent plastic water bottle (don’t use dirty or scratched-up bottles), fill it two-thirds of the way up with water and shake the bottle for 20 to 30 seconds. This improves the oxygen saturation of the water. Now, fill the bottle to the brim with water, tighten the cap and lay it on a black surface (or corrugated steel roof) for six hours in full sun. If there’s more than 50 percent cloud cover, leave the bottle for two full days. The combination of heat and the sun’s ultraviolet rays kills any pathogenic germs. The bottles should be full to the brim — air can deflect the sun’s ultraviolet rays and prevent them from killing bacteria in the water.

Filters

Photo by Jacob Drabik/Flickr/CC

Water filters come in a variety of shapes and sizes, but the basic principle is the same — pushing water through very finely grained filters can eliminate bacteria and other contaminants. When buying a filter, look for one that’s rated to 0.2 microns or smaller.

Even with such very fine filters, most water filter pumps will not remove viruses. For that task, you’ll need additional liquid drops (often sold with the filtration system). If you’re hiking or camping in the United States and Europe, water filters will suffice. Just be sure to follow manufacturer’s instructions for use and cleaning.

While they are effective, filters are often bulky and heavy, and if you’re headed to the developing areas of the world, you’ll want to combine them with another method to kill viruses. Read on for other options.

Ultraviolet light

The new kid on the block, ultraviolet filters purify water by zapping the microorganisms with radiation, destroying their DNA and making them unable to reproduce or cause illness. Portable ultraviolet filters are small, lightweight and kill everything: microbes, viruses and bacteria.

The disadvantage to ultraviolet is that you need a power source, generally a few AA batteries. And, of course, there’s no filtration, so if your water is full of sand or other sediment, your “clean” water may not taste so great.

Purification tablets

The preferred method of purifying water is by use of NaDCC tablets — that’s short for sodium dichloroisocyanurate, a chlorine alternative that’s widely used in emergencies and relief efforts. These NaDCC tablets are available in camping stores and on the web under various brand names. Make sure you pack plenty for yourself, and extra packets to hand out to others.

Just follow the directions on the packaging, drop in the recommended number of tablets and wait (generally around ten minutes).

Alternatively, you can get iodine and bleach tablets made especially for hiking and camping. They are also cheap and lightweight. In the case of bleach tablets, hydrogen peroxide is often used to neutralize the bleach after it has done its job.

The disadvantage with tablet purification is, of course, taste. Your fresh mountain stream water will taste a bit like iodine, chlorine or bleach, but you won’t get sick. If the taste bothers you, just mix in a little bit of powdered lemonade mix or sports drink mix. It will cover up the funky taste, and you’ll add some minerals or vitamins as well.

One note of warning: Iodine tablets can be dangerous for people with thyroid conditions. Consult your doctor.

Source: Wired

Although chemicals such as iodine and chlorine may kill microorganisms, these chemicals are also harmful to the human body, especially over the long term.  However, in survival situations it would probably be better to ensure the water is safe from bacteria and parasites than to worry too much about the chemicals going into your body.  In all other situations, further filtration should be employed to remove the chemicals rendering pure water.

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