Monitoring and Testing – Proving Water is Safe

• Verifies the quality of drinking water and allows for quick intervention as required.

Testing occurs at the following intervals:

• E. coli and Total Coliforms: For treated water delivered through a piped system, a minimum of four samples are required each month (additional samples are done for populations over 4000), and they are normally taken weekly. For treated water delivered by truck, at least one sample is required from each truck in use each month, plus samples from public buildings. For all systems, one raw water sample per month is required.
• Chlorine: Treated water samples are taken every day to check chlorine levels in the plant’s storage tank and in delivery trucks. Many plants also have continuous monitoring by inline meters in the treatment system. Raw water samples are not done for chlorine, as it is added during treatment.
• Turbidity: One raw water sample is taken per day. Where practical, plants have continuous monitoring of treated water turbidity by inline meters in the treatment system. Where this is not practical, at least one treated water sample is taken each delivery day, with an additional sample taken for every four hours of plant operation.
• Trihalomethanes (THMs): Treated water samples are taken quarterly, with a minimum of four per year. Raw water samples are not needed.
• Chemical and Physical Parameters: One treated water sample is done every year to check a suite of 28 parameters, which are listed in the left menu.  Raw water samples for the same 28 parameters are taken if the treatment process includes any technologies other than chlorine or UV disinfection; disinfection alone does not alter these parameters, so no raw water sample is required for disinfection-only systems

Environmental Health Officers with the Department of Health and Social Services are responsible for reviewing test data and taking action if any test results exceed the Guidelines for Canadian Drinking Water Quality.

All NWT community water treatment plants were tested for PFAS following the 2023 wildfire season. This enhanced testing was a precautionary step to confirm drinking water remained safe and to support ongoing monitoring because severe wildfires can temporarily affect how water and existing contaminants move through the environment.

• Lets the public know if there is a problem and what actions are required to correct it.
• Holds officials accountable to the public, building confidence in the system, and provides an opportunity for public education.

• Provides annual public account of drinking water status in the NWT.
• Provides an opportunity for highlighting trends and discussion of major issues.

• Helps ensure that Water Treatment Plant infrastructure is in good condition, and is being operated and maintained safely.

• Assuring the public that the water supply is safe and reliable by informing them about tests and testing results, and who is responsible.

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.