Treating Drinking Water

Experts estimate that at least 90% of the surface water in the United States, even in the most remote areas, is contaminated with the illness-causing protozoa Cryptosporidium and Giardia lamblia. Bacteria such as Campylobacter, E. coli and Salmonella are also common.


Giardiasis is an intestinal disease caused by Giardia lamblia and related organisms. The giardia organisms are microscopic protozoans and, therefore, invisible to the naked eye. It's important to keep in mind that infected water might look, taste, and smell perfectly safe.

It only takes one giardia organism to cause an infection. Once infected, it may take from a few days to two weeks to become ill. Because of the delay, many people do not immediately expect giardia infection. Symptoms include chronic diarrhea, abdominal cramps, bloating, fatigue, and loss of weight. Giardiasis will not go away on its own! Treatment by a physician is necessary to kill the organisms and produce a cure.

Giardia organisms are carried by humans, wild animals, and some domestic animals. They are spread by improper disposal of human and animal feces. One study completed at Colorado State University found that 90% of all dogs tested were carriers, of giardia organisms.

Bury all feces 8 inches deep and at least 100 feet from water. Also, don't let dogs or other domestic animals defecate in or near water supplies.

The surest way to prevent giardiasis is to take water from public water supplies. Of course, on a long trip this is not an option. Fortunately, there are ways to make the water safe to drink.

The most effective way to kill giardia and other waterborne pathogens is to boil the water for at least one minute.

Filters work, but make sure they filter as small as 1 micron.

Chemical treatment is considered the least effective form of purification. When using chemical treatment in cold water, it may take hours for purification to occur. Even then, there is still a chance that some giardia might survive.