Protozoan Drinking Water Contaminants

Protozoa represent another type of drinking water contamination. These creatures live in soil, water, and in the intestines of humans and other mammals and contaminate water when it comes into contact with sewage and animal waste. Protozoa are neither bacteria nor viruses and have fairly complex life cycles compared to other waterborne pathogens. Although the cycles of different protozoa vary somewhat, the basic cycle consists of these stages:

This is a very simplified example of the protozoan life cycle, but even a small sample of feces from an infected host may contain millions of protozoan cysts.

The Main Protozoan Culprits

These three protozoans are the most common threats to drinking water safety as they are somewhat resistant to normal levels of the chlorine used to control waterborne pathogens.


Because protozoa tend to be more resistant to standard chemical filtration like chlorination, a multi-step approach seems to be the best way to filter these critters out of our drinking water. A whole house filtration system consisting of activated carbon, ultraviolet light, reverse-osmosis, and other filtration methods seems to be the most effective way to eliminate these pathogens.

If you�re camping or looking for a quick method for removing protozoans from smaller amounts of drinking water, bringing water to a boil for a couple of minutes is a very reliable way to kill them and prevent contamination. If you get your drinking water from a private well and are concerned about protozoan contamination in your water, you can call your county water commission for a list of reputable laboratories nearby that can perform a comprehensive test of contaminants for a reasonable fee.