Drinking Water in the NWT

Bacteriological Sampling

Fecal Coliforms

Of all contaminants in drinking water, human and animal feces present the greatest danger to public health. Fecal coliforms, otherwise known as thermotolerant coliforms, are a type of coliform bacteria generally found in the intestines of healthy humans and animals. Coliform bacteria can be found everywhere in the environment, and most coliforms, including most fecal coliforms are relatively harmless, naturally occurring organisms. Fecal coliforms, which include E. coli and a few other species, are an indicator of fecal contamination. Fecal coliform testing has been replaced by E. colitesting in most jurisdictions as more specific tests for E. coli have become routinely available. The maximum acceptable concentration (MAC) of fecal coliforms in drinking water is zero. If fecal coliforms are found in treated drinking water, a boil water advisory is generally issued right away.

Heterotrophic Plate Count

The heterotrophic plate count (HPC), formerly known as the standard plate count (SPC), is an indicator of the general bacteriological content of the water. High HPC levels are not associated with water bourne disease outbreaks. Proper chlorine disinfection can generally reduce HPC levels to less than 10 cfu/mL. HPC levels above 500 cfu/mL should be investigated, but would not normally result in a boil water advisory.

Escherichia coli (E. coli)

Of all contaminants in drinking water, human and animal feces present the greatest danger to public health. E. coli are naturally occurring fecal coliforms found in human and animal intestines. While the strain of E. coli known as E. coli 0157:H7, which contaminated the water in Walkerton, Ontario, is very harmful and potentially deadly, most strains of E. coli are relatively harmless. The reason E.coli is relied on so heavily as a measure is that it is a good indicator of the bacteriological safety of drinking water. It is the only species in the coliform group that is exclusively found in the intestinal tract of humans and other warm-blooded animals and it is excreted in large numbers in feces. If E. coli is found in the water, it means that the water has been contaminated by human or animal feces that can harbour a number of other pathogenic, or disease causing, organisms. The maximum acceptable concentration (MAC) of E. coli in drinking water is zero. If E. coli is detected in drinking water, a boil water advisory is generally issued right away.

Total Coliforms

Coliforms are a type of bacteria found throughout the environment. Most coliforms are relatively harmless and are easily treated with chlorine. Total coliform counts in treated drinking water are an indicator of how well the disinfection process is working. If coliform bacteria is found in treated drinking water, the problem is investigated right away, and the water is re-tested. A boil water advisory will be issued if the problem cannot be corrected.