Municipal wastewater treatment

Population served by municipal wastewater systems

Key results

• Over the 2013 to 2020 period, the proportion of the population served by municipal wastewater systems remained stable at about 86%
• Since 2013, the proportion of population served by each treatment category remained stable with around 28.1%, 42.7% and 13.6% for tertiary, secondary and primary treatments, respectively
• About 1.8% of the population was served by systems discharging untreated wastewater
• In 2020, 13.8% of the population was not served by municipal wastewater systems^{Footnote 1}

Proportion of population served by municipal wastewater systems, Canada, 2013 to 2020

How this indicator was calculated

Note: Only the population served by municipal wastewater systems with a daily flow of 100 m³ or more was considered. Data were unavailable for the populations located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador.
Source: Statistics Canada (2023) Table 38-10-0125-01 Population served by municipal wastewater systems by treatment category.

Municipal wastewater refers to used water from homes, businesses, industries, and institutions that drain into sewers. It contains sanitary sewage and is sometimes combined with stormwater from rain or melting snow draining off rooftops, lawns, parking lots and roads. Municipal wastewater can contain human and other organic waste, nutrients, pathogens, microorganisms, suspended solids and household and industrial chemicals. Treating wastewater before it is released into lakes and rivers reduces the risks posed to human health and the environment.^{Footnote 2}

The treatment processes presented can be summarized as follows:

• No treatment: No treatment process or only screening and/or grit removal
• Primary treatment: Removing a portion of suspended solids and organic matter by physical and/or chemical processes
• Secondary treatment: Removing organic matter and suspended solids using biological treatment processes and secondary settlement
• Tertiary treatment: Removing specific substances of concern (solids, nutrients and/or contaminants) after secondary treatment using a number of physical, chemical or biological processes

A variety of factors, including Canada's physical geography and population density influence the proportion of population served by municipal sewers. For example, communities where population is spread over a large geographical area are challenged when it comes to providing centralized infrastructures to collect and treat wastewater. Those communities tend to rely on independent systems, such as septic systems, or small-scale collective systems. In this indicator, their populations would be considered as "not covered by this indicator". The efficiency of those treatment systems can be similar to larger municipal wastewater systems.

Population served by municipal wastewater systems by province and territory

Key results

In 2020,

• The proportion of population served by municipal wastewater systems varied from 54.3% in Prince Edward Island to 91.4% in British Columbia^{Footnote 3} 
• Alberta had the highest proportion of population (73.6%) served by tertiary-level wastewater treatment
• Nova Scotia had the highest proportion of population (38.2%) served by primary-level wastewater treatment
• A significant proportion of the Newfoundland and Labrador population (32.6%) was served by municipal systems that discharge wastewater to the environment with no prior treatment

Proportion of population served by municipal wastewater systems by province and territory, Canada, 2020

How this indicator was calculated

Note: Only the population served by municipal wastewater systems with a daily flow of 100 m³ or more was considered. Data were unavailable for the populations located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador.
Source: Statistics Canada (2023) Table 38-10-0125-01 Population served by municipal wastewater systems by treatment category.

Much of the Canadian population is served by wastewater collection and treatment systems; however, the proportion of population served, and the level of treatment applied to wastewater varies widely by province and territory. The majority of systems that discharge untreated wastewater are located in coastal communities. Inland provinces tend to have higher levels of treatment in order to protect freshwater resources.

Population served by municipal wastewater systems in selected countries

This indicator compares the proportion of the population served by municipal wastewater systems in Canada with the 24 countries from the Organisation for Economic Co-operation and Development for which data were available for the year 2020.

Key results

In 2020:

• Canada ranked 14th out of 24 countries for proportion of population served by municipal wastewater systems at about 86%^{Footnote 4}   
• Luxembourg reported that 100% of their population was served by a municipal wastewater system
• 38.5% to 99.4% of the population from the selected countries were served by a public wastewater system using a tertiary treatment, which is more than in Canada (28.1%)

Proportion of population served by municipal wastewater systems, selected countries, 2020

How is this indicator calculated

Note: The graph shows the 14 member countries from the Organisation for Economic Co-operation and Development with the highest proportion of population served by public sewerage systems in 2020. The year 2020 was the most recent year for which data were available for Canada. For Canada, only the population served by municipal wastewater systems with a daily flow of 100 m³ or more was considered.
Source: Organisation for Economic Co-operation and Development (2023) Connection rates to wastewater treatment database. Statistics Canada (2023) Population served by municipal wastewater systems by treatment category.

The countries with the highest proportion of population connected by treatment category were:

• Norway for the primary treatment with 25.6%
• Israel for the secondary treatment with 35.6%
• the Netherlands for the tertiary treatment with 99.4%

After Australia, Canada has the lowest population density among the selected countries. ^{Footnote 5} This factor could have an influence on the development of centralized wastewater treatment infrastructures.

Municipal wastewater volume discharged by treatment category

Key results

• Over the 2013 to 2020 period, 95.7% to 96.3% of the municipal wastewater collected underwent a treatment (primary, secondary, or tertiary) before being discharged.
• In 2020, 3.7% of the volume of municipal wastewater discharged was untreated^{Footnote 6} 

Proportion of municipal wastewater volume discharged by treatment category, Canada^{Footnote 7} , 2013 to 2020

How is this indicator calculated

Note: Combined sewer overflows correspond to the stormwater and wastewater conveyed into a combined sewer that are discharged directly into receiving waters because they exceed the capacity of the sewer system or treatment plant. Data were unavailable for the sewer systems located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador.
Source: Statistics Canada (2023) Table 38-10-0124-01 Wastewater volumes discharged from municipal sewage systems by treatment category (x 1,000,000) and Table 38-10-0100-01 Combined sewer overflow discharge volumes (x 1,000,000).

Between 2013 and 2020, the volume of municipal wastewater discharged remained relatively stable, ranging from 5 690 million m³ to 6 162 million m³.

In 2020, the volume of municipal wastewater discharged with no treatment was 219 million m³, corresponding to 3.7% of the total volume discharged. This includes 116.9 million m³ from combined sewer overflows. In 2019, the volume of untreated wastewater discharged amounted to approximately 243 million m³ (including 135 million m³ from combined sewer overflows), or 4% of the total volume conveyed by municipal wastewater systems in Canada, with exception of Quebec whose combined sewer overflow volumes have not been available since 2017.

Municipal wastewater volume discharged by treatment category by province and territory

Key results

In 2020:

• Quebec and Ontario accounted for the majority of wastewater discharged nationally, with respective volumes of 2 132 and 1 998 million m³
• Municipal wastewater was almost entirely treated at secondary or tertiary levels in Alberta, Saskatchewan Ontario, Prince Edward Island, Yukon, and, to a lesser extent, Manitoba
• Municipal wastewater in Newfoundland and Labrador, Nova Scotia, and Quebec were mostly, at best, treated at a primary level

Volume and proportion of municipal wastewater discharged by treatment category by province and territory, Canada, 2020

How is this indicator calculated

Note: Combined sewer overflows correspond to the stormwater and wastewater conveyed into a combined sewer that are discharged directly into receiving waters because they exceed the capacity of the sewer system or treatment plant. Data were unavailable for the sewer systems located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador. 
Source: Statistics Canada (2023) Table 38-10-0124-01 Wastewater volumes discharged from municipal sewage systems by treatment category (x 1,000,000) and Table 38-10-0100-01 Combined sewer overflow discharge volumes (x 1,000,000).

The level of treatment applied to wastewater varies widely by province and territory. In 2020, the provinces and territory with the highest proportion of wastewater discharged by treatment category were: 

• Newfoundland and Labrador for untreated wastewater with 37.6%
• Newfoundland and Labrador for primary treatment, with 48.8%
• Yukon for secondary treatment, with 100%
• Alberta for tertiary treatment, with 79.9%

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Spatial coverage

The Effluent Regulatory Reporting Information System captures data from all the reporting wastewater systems that collect a daily average volume of 100 m³ or more. Systems that service First Nations reserves, government institutions, commercial and industrial establishments, and provincial parks are not included in this report, however, are covered by the Regulations. The regulations do not apply to wastewater systems located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador.

Temporal coverage

The Municipal Wastewater Systems in Canada statistical program was published for the first time in 2019 and now includes the data for the years 2013 to 2020. It is updated annually.

The indicator on the effluent quality compliance to the standards covers the period from 2015 to 2021. Even though the Wastewater Systems Effluent Regulations came into force 2012, the effluent quality standards did not come into force until January 1, 2015. Therefore, there were no compliance limits for the 2013 and 2014 reporting years. 

Data completeness

The Effluent Regulatory Reporting Information System lists mere than 1 500 wastewater (sewage) systems with a daily flow of 100 m³ or more and does not include data reported through an equivalency agreement with Quebec or the Yukon. This list is established from owners of wastewater systems that report under the federal Wastewater Systems Effluent Regulations.

Wastewater treatment categories

Wastewater treatment levels for this indicator were categorized based on the definitions used in the Municipal Wastewater Systems in Canada.^{Footnote 10} 

The data were derived from administrative records collected by Environment and Climate Change Canada via the Effluent Regulatory Reporting Information System, as required by the Wastewater Systems Effluent Regulations. Those records provide information on each sewage system, including the volume of wastewater discharged and the treatment utilized. The population served by each sewage system was estimated using census population data. The regulations do not apply to any wastewater system located in the Northwest Territories, Nunavut and north of the 54th parallel in the provinces of Quebec and Newfoundland and Labrador; therefore, no data were available for these populations.

Population served by municipal wastewater systems

The percentages of population served by municipal wastewater systems at the national and provincial and territorial levels were calculated using the population served by municipal wastewater systems by treatment category data which was developed based on the 2011 and 2016 census of population. The population for 2020 was extrapolated using the 2016 census data.  of wastewater and were considered as untreated water.

Municipal wastewater volume discharged

The volume of wastewater discharged for each treatment category, as established by the Municipal Wastewater Systems in Canada statistical program, was divided by the total volume of wastewater discharged. For the purposes of these indicators, the volumes corresponding to the combined sewer overflows were added to the total volume of wastewater and were considered as untreated water.

Municipal wastewater effluent quality

Under the regulations, wastewater systems must submit monitoring reports that indicate:

• the number of days when effluent was deposited;
• the volume of effluent deposited;
• the average carbonaceous biochemical oxygen demand and the average concentration of suspended solids.

Depending on the type of wastewater system and the volume of effluent, the reports must present the annual average, the quarterly average, or the monthly average for each of the parameters (carbonaceous biochemical oxygen demand and suspended solids).

A wastewater system is considered compliant with the regulations if it meets the following conditions:

• For wastewater systems reporting monthly averages:
  • average carbonaceous biochemical oxygen demand is <25 mg/L in at least 10 months during a calendar year
  • average concentration of suspended solids is <25 mg/L in at least 10 months during the calendar year
• For wastewater systems reporting quarterly averages:
  • average carbonaceous biochemical oxygen demand is <25 mg/L in all quarters during the calendar year
  • average concentration of suspended solids is <25 mg/L in all quarters during the calendar year
• For wastewater systems reporting annual averages:
  • average carbonaceous biochemical oxygen demand and average concentration of suspended solids is <25 mg/L