PATHOGENIC MICROBES FACT SHEET
Some of the particles found in high levels in prairie waters are microorganisms, such as viruses, bacteria and parasites. The parasites include previously mentioned Cryptosporidium, as well as the Beaver fever parasite (Giardia). Some people believe that all that is required to produce safe water is to have a chlorine residual in the water. This, unfortunately, is not correct. The presence of particles will, in fact, shield pathogenic microbes from being killed by chlorine or other disinfectants. This can be seen in the drawing below, which shows that within aggregates of particles (these can be inorganic or organic debris) it is quite possible to have viruses, bacteria and parasites that will not have any contact with the chlorine in the surrounding water. It is, therefore, important to remember that only good quality water can be safely disinfected. Even correct use of disinfection is not enough to kill the previously mentioned parasites. Additional treatment is required for them.
If a water has a large level of particles in it (like most rural water supplies) then applying chlorination is not effective as the particles shield pathogenic microorganisms. The drawing shows how these microorganisms will not come in contact with the chlorine, as the chlorine cannot penetrate the clump of particles.