Municipal wastewater treatment
Every day, millions of cubic metres (m3) of wastewater are discharged from homes, businesses, institutions, and industries into city sewer systems. Municipal wastewater is one of the largest sources of pollution to surface water in Canada. Before being released to the environment, wastewater needs to be treated. A higher level of wastewater treatment leads to cleaner effluent (liquid waste) and a smaller impact on the environment. The indicators show the level of wastewater treatment provided to the Canadian population and present the proportion of wastewater systems meeting the effluent quality national standards.
Population served
Population served in Canada
Population served by municipal wastewater systems
Key results
- Over the 2013 to 2023 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%, 43% and 13% for tertiary, secondary and primary treatments, respectively
- In 2023,
- 0.8% of the population was served by systems discharging untreated wastewater
- 14.1% of the population was not served by municipal wastewater systemsFootnote 1
Proportion of population served by municipal wastewater systems, Canada, 2013 to 2023
Data table for the long description
| Year | Total population estimated | No treatment (percentage) |
Primary treatment (percentage) |
Secondary treatment (percentage) |
Tertiary treatment (percentage) |
Total (percentage) |
|---|---|---|---|---|---|---|
| 2013 | 34,146,704 | 1.8 | 13.9 | 43.0 | 27.3 | 86.0 |
| 2014 | 34,481,712 | 1.8 | 13.7 | 43.1 | 27.5 | 86.2 |
| 2015 | 34,816,720 | 1.8 | 13.7 | 43.0 | 27.6 | 86.1 |
| 2016 | 35,151,728 | 1.8 | 13.7 | 42.8 | 27.7 | 86.0 |
| 2017 | 35,519,779 | 1.8 | 13.6 | 42.8 | 27.8 | 86.0 |
| 2018 | 35,887,829 | 1.9 | 13.5 | 42.8 | 27.9 | 86.1 |
| 2019 | 36,255,880 | 1.8 | 13.6 | 42.6 | 28.0 | 85.9 |
| 2020 | 36,623,930 | 1.8 | 13.5 | 42.5 | 28.0 | 85.9 |
| 2021 | 36,991,981 | 0.9 | 13.5 | 42.4 | 29.2 | 85.9 |
| 2022 | 37,360,032 | 0.8 | 12.9 | 43.0 | 29.2 | 85.9 |
| 2023 | 37,728,082 | 0.8 | 12.9 | 42.9 | 29.3 | 85.9 |
Note: Totals may not add up due to rounding.
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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 (2025) 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 in Figure 1 are sequential and 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. The efficiency of these treatment systems can be similar to larger municipal wastewater systems. In this indicator, populations they serve would be considered as "not covered by this indicator".
Population served by province and territory
Population served by municipal wastewater systems by province and territory
Key results
In 2023,
- the proportion of population served by municipal wastewater systems varied from 51.9% in Prince Edward Island to 89.5% in QuebecFootnote 3
- Alberta had the highest proportion of population (75.6%) served by tertiary-level wastewater treatment
- Yukon had the highest proportion of population (72.7%) served by secondary-level wastewater treatment
- Nova Scotia had the highest proportion of population (37.4%) served by primary-level wastewater treatment
- A significant proportion of the Newfoundland and Labrador population (33.4%) 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, 2023
Data table for the long description
| Year | Total population estimated | No treatment (percentage) |
Primary treatment (percentage) |
Secondary treatment (percentage) |
Tertiary treatment (percentage) |
Total (percentage) |
|---|---|---|---|---|---|---|
| Newfoundland and Labrador | 506,884 | 33.4% | 29.8% | 13.1% | 1.3% | 77.6% |
| Prince Edward Island | 158,901 | 0.0% | 0.0% | 42.7% | 9.2% | 51.9% |
| Nova Scotia | 987,697 | 4.3% | 37.4% | 19.4% | 8.0% | 69.1% |
| New Brunswick | 787,014 | 0.0% | 0.0% | 60.5% | 0.2% | 60.7% |
| Quebec | 8,636,822 | 0.8% | 33.0% | 47.1% | 8.6% | 89.5% |
| Ontario | 14,534,121 | 0.0% | 0.0% | 49.7% | 38.0% | 87.7% |
| Manitoba | 1,367,668 | 0.0% | 0.0% | 66.7% | 13.5% | 80.1% |
| Saskatchewan | 1,146,166 | 0.0% | 0.0% | 40.2% | 31.0% | 71.2% |
| Alberta | 4,340,819 | 0.0% | 0.0% | 13.6% | 75.6% | 89.1% |
| British Columbia | 5,142,009 | 0.5% | 29.1% | 40.9% | 16.9% | 87.4% |
| Yukon | 41,975 | 0.0% | 0.0% | 72.7% | 0.0% | 72.7% |
Note: Totals may not add up due to rounding.
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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 (2025) 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 in selected countries
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 19 countries from the Organisation for Economic Co-operation and Development (OECD) for which data were available for the year 2023.
Key results
In 2023,
- In terms of the proportion of the population served by municipal wastewater systems, Canada ranked 12th among the 20 countries for which data were consideredFootnote 4
- Among the 20 selected countries, Canada was the second lowest proportion of population served by tertiary treatment (29.3%), ahead of only the Slovak Republic (2.2%)
Proportion of population served by municipal wastewater systems, selected countries, 2023
Data table for the long description
| Country | No treament (percentage) |
Unspecified treatment (percentage) |
Primary treatment (percentage) |
Secondary treatment (percentage) |
Tertiary treatment (percentage) |
Total (percentage) |
|---|---|---|---|---|---|---|
| Israel | 2.3% | 1.4% | 2.0% | 31.2% | 63.2% | 100.0% |
| Luxembourg | 0.5% | 0.0% | 0.6% | 11.5% | 87.4% | 100.0% |
| Netherlands | 0.0% | 0.0% | 0.0% | 0.0% | 99.7% | 99.7% |
| Switzerland | 0.3% | 0.0% | 0.0% | 8.0% | 90.0% | 98.3% |
| Austria | 0.0% | 0.0% | 0.0% | 1.2% | 95.1% | 96.2% |
| Korea | 0.4% | 0.0% | 0.0% | 0.7% | 94.2% | 95.4% |
| Australia | 0.0% | 0.0% | 16.5% | 26.6% | 49.7% | 92.9% |
| Denmark | 0.0% | 0.0% | 0.1% | 1.0% | 91.2% | 92.3% |
| Norway | 1.5% | 0.0% | 23.6% | 9.1% | 54.4% | 88.5% |
| Belgium | 3.5% | 0.0% | 0.0% | 5.4% | 79.0% | 88.0% |
| Czechia | 2.2% | 0.0% | 0.1% | 7.3% | 77.1% | 86.7% |
| Canada | 0.8% | 0.0% | 12.9% | 42.9% | 29.3% | 85.9% |
| Finland | 0.0% | 0.0% | 0.0% | 0.0% | 85.0% | 85.0% |
| Hungary | 2.9% | 0.0% | 0.1% | 6.8% | 73.8% | 83.6% |
| Estonia | 0.0% | 0.0% | 0.0% | 2.0% | 81.0% | 83.0% |
| Lithuania | 0.0% | 0.0% | 0.1% | 7.1% | 70.9% | 78.1% |
| Latvia | 0.0% | 0.0% | 0.5% | 21.9% | 55.1% | 77.5% |
| Poland | 0.3% | 0.0% | 0.0% | 14.4% | 61.5% | 76.2% |
| Slovak Republic | 0.3% | 0.0% | 0.1% | 68.9% | 2.2% | 71.5% |
| Slovenia | 0.0% | 0.0% | 0.0% | 25.2% | 44.4% | 69.6% |
Note: Totals may not add up due to rounding.
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How is this indicator calculated
Note: The graph shows the proportion of population served by public sewerage systems in 2023 for the 19 reporting OECD member countries for which data were considered. Similar data for Canada, obtained through Statistics Canada, is also included in the graph. 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 (2025) Connection rates to wastewater treatment database. Statistics Canada (2025) Population served by municipal wastewater systems by treatment category.
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 infrastructure. Canada’s population density, combined with the fact that only the population served by municipal wastewater systems with a daily flow of 100 m3 or more are considered could lead to Canada’s total population served being underestimated.
Volume
Volume discharged by treatment category
Municipal wastewater volume discharged by treatment category
Key results
- Over the 2013 to 2023 period, 94.9% to 96.4% of the municipal wastewater collected underwent a treatment (primary, secondary, or tertiary) before being discharged
- In 2023, 3.6% of the volume of municipal wastewater discharged was untreatedFootnote 6
Proportion of municipal wastewater volume discharged by treatment category, CanadaFootnote 7 , 2013 to 2023
Data table for the long description
| Province/Territory | Volume of municipal wastewater discharged (million of cubic metres) |
Combined sewer overflow (percentage) |
No treatment (percentage) |
Primary treatment (percentage) |
Secondary treatment (percentage) |
Tertiary treatment (percentage) |
|---|---|---|---|---|---|---|
| 2013 | 5,980 | 2.4 | 1.9 | 25.5 | 45.8 | 24.4 |
| 2014 | 6,064 | 2.9 | 1.9 | 25.2 | 46.1 | 24.0 |
| 2015 | 5,716 | 3.0 | 1.8 | 24.9 | 46.0 | 24.3 |
| 2016 | 5,834 | 2.3 | 1.8 | 25.6 | 46.3 | 24.0 |
| 2017 | 6,115 | 2.9 | 1.9 | 25.1 | 46.5 | 23.6 |
| 2018 | 5,950 | 3.2 | 1.8 | 25.3 | 45.3 | 24.3 |
| 2019 | 6,162 | 2.2 | 1.8 | 24.4 | 47.1 | 24.5 |
| 2020 | 5,910 | 2.0 | 1.7 | 24.5 | 47.0 | 24.8 |
| 2021 | 5,478 | 2.4 | 1.4 | 24.0 | 46.2 | 26.1 |
| 2022 | 5,795 | 2.4 | 1.4 | 23.4 | 47.3 | 25.5 |
| 2023 | 6,031 | 2.2 | 1.4 | 23.7 | 47.2 | 25.5 |
Note: Percentages may not add up to 100 due to rounding.
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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 (2025) 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 2023, the volume of municipal wastewater discharged remained relatively stable, ranging from 5,478 million m3 to 6,162 million m3.
In 2023, the volume of municipal wastewater discharged with no treatment was 215 million m3, corresponding to 3.6% of the total volume discharged. This includes 134 million m3 from combined sewer overflows. Comparatively, in 2022 the volume of untreated wastewater discharged amounted to approximately 221.9 million m3 (including 140 million m3 from combined sewer overflows), or 3.8% of the total volume conveyed by municipal wastewater systems in Canada. Note that these statistics exclude Quebec, for which combined sewer overflow volumes have not been available since 2017. From 2013 to 2017, Quebec accounted for 24% to 30% of all combined sewer overflow volumes in Canada. Since 2018, even though volumes are no longer available, Quebec represents the vast majority of combined sewer overflow release points (about 90%). This situation suggests that the volume of combined sewer overflows may be significantly underestimated and the proportion of untreated wastewater being released is likely higher than estimated.
Volume discharged by province and territory
Municipal wastewater volume discharged by treatment category by province and territory
Key results
In 2023:
- Quebec and Ontario accounted for the majority of wastewater discharged nationally, with respective volumes of 2,170 and 2,065 million m3
- Municipal wastewater was almost entirely treated at secondary or tertiary levels in Alberta, Saskatchewan, Ontario, Yukon, Manitoba and Prince Edward Island
- Municipal wastewater that was treated in Newfoundland and Labrador and Nova Scotia, was mostly treated at a primary level or untreated
- Combined sewer overflow contributed a significant amount to the discharged wastewater in Nova Scotia (25.6%) and New Brunswick (13.4%), and to a smaller degree in British Columbia (4.9%) and Manitoba (3.6%).
- Combined sewer overflow volumes of 0 were reported for Prince Edward Island and Saskatchewan. No combined sewer overflow volume was available for Quebec.
Volume and proportion of municipal wastewater discharged by treatment category by province and territory, Canada, 2023
Data table for the long description
| Province/Territory | Volume of municipal wastewater discharged (million of cubic metres) |
Combined sewer overflow (percentage) |
No treatment (percentage) |
Primary treatment (percentage) |
Secondary treatment (percentage) |
Tertiary treatment (percentage) |
|---|---|---|---|---|---|---|
| Newfoundland and Labrador | 112.9 | 0.1% | 42.3% | 44.8% | 12.1% | 0.6% |
| Prince Edward Island | 17.6 | 0.0% | 0.0% | 0.0% | 79.0% | 21.0% |
| Nova Scotia | 226.8 | 25.6% | 7.6% | 36.6% | 20.8% | 9.4% |
| New Brunswick | 142.3 | 13.4% | 0.0% | 0.0% | 86.1% | 0.5% |
| Quebec | 2,170.1 | n/a | 0.6% | 49.4% | 41.9% | 8.1% |
| Ontario | 2,064.6 | 0.6% | 0.0% | 0.0% | 58.1% | 41.3% |
| Manitoba | 149.4 | 3.6% | 0.0% | 0.0% | 80.4% | 16.0% |
| Saskatchewan | 82.9 | 0.0% | 0.0% | 0.0% | 54.2% | 45.8% |
| Alberta | 406.5 | 1.9% | 0.0% | 0.0% | 14.6% | 83.5% |
| British Columbia | 653.0 | 4.9% | 0.5% | 34.4% | 47.6% | 12.6% |
| Yukon | 4.6 | 0.0% | 0.0% | 0.0% | 100.0% | 0.0% |
Note: Percentages may not add up to 100 due to rounding.
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How is this indicator calculated
Note: * Data on Quebec's combined sewer overflow volume are not available. 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. On the left, the volume of wastewater discharged for Yukon (4.6 million m3) is too small to be visible due to the larger volumes discharged by other provinces. 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 (2025) 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 2023, the provinces and territory with the highest proportion of wastewater discharged by treatment category were:
- Newfoundland and Labrador for untreated wastewater with 42.3%
- Quebec for primary treatment, with 49.4%
- Yukon for secondary treatment, with 100%
- Alberta for tertiary treatment, with 83.5%
Quality
Municipal wastewater effluent quality
Following treatment, wastewater is reintroduced in the environment through wastewater systems (wastewater treatment plants). To protect the quality of the receiving waters, the Wastewater Systems Effluent Regulations (the regulations) were developed. These regulations set national effluent quality limits that are achievable through secondary wastewater treatment. They also require effluent monitoring and reporting from the wastewater systems.Footnote 8
Key results
- In 2023, 78.1% of the reporting municipal wastewater systems released effluents that met the regulatory quality standards, corresponding to 71.3% of the effluents volume
- Between 2015 and 2023,
- the proportion of reporting municipal wastewater systems meeting quality regulatory standard effluents decreased slightly from 81.0% to 78.1%
- while the number of systems meeting regulatory standards increased (+331 systems), the greater increase in overall systems reporting (+474 systems) contributed to a decrease in the proportion of systems meeting regulations
- the effluent volume meeting the standards increased slightly from 66.2% (3,302 million m3 out of 4,986 million m3) to 71.3% (4,189 million m3 out of 5,871 million m3)
Percentage of reporting municipal wastewater systems and effluent volume meeting effluent quality regulatory standards, Canada, 2015 to 2023
Data table for long description
| Year | Number of municipal wastewater systems meeting effluent quality regulatory standards |
Proportion of reporting municipal wastewater systems meeting effluent quality regulatory standards (percentage) |
Volume of municipal effluent meeting quality regulatory standards (million of cubic metres) |
Proportion of volume of municipal effluent meeting quality regulatory standards (percentage) |
|---|---|---|---|---|
| 2015 | 1,099 | 81.0 | 3,302 | 66.2 |
| 2016 | 1,122 | 81.1 | 3,537 | 69.6 |
| 2017 | 1,079 | 77.6 | 3,769 | 68.6 |
| 2018 | 1,434 | 75.6 | 3,744 | 68.3 |
| 2019 | 1,441 | 77.9 | 3,747 | 68.8 |
| 2020 | 1,409 | 74.7 | 3,873 | 69.9 |
| 2021 | 1,391 | 76.2 | 3,612 | 70.8 |
| 2022 | 1,370 | 76.5 | 3,895 | 71.4 |
| 2023 | 1,430 | 78.1 | 4,189 | 71.3 |
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How is this indicator calculated
Note: Only the municipal wastewater systems with a daily flow of 100 m3 or more that submitted their monitoring reports were 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: Environment and Climate Change Canada (2025) Wastewater Systems Effluent Regulations Program
The regulations were established in 2012 and came into effect in January 2015. While all new wastewater facilities are required to meet the regulations immediately, some of the existing facilities applied for and were granted extensions until 2020, 2030 or 2040 to plan and finance the upgrade of their infrastructure up to the standards. These provisions were based on criteria set out in the regulations to ensure facilities presenting the highest risks be improved first with the final objective of 100% of wastewater treatment facilities meeting regulatory standards by the end of 2040.
The time extensions to upgrade the infrastructure can impact previously presented compliance rates as some of the facilities have not yet completed the works on their systems to achieve compliance.
About the indicators
What the indicators measure
The municipal wastewater treatment indicators measure the level of wastewater treatment provided to the Canadian population and track the compliance of the treated water discharged with the national effluent quality standards. Higher treatment levels of wastewater reduce the risk of raw wastewater pollutants entering the environment, where they pose risks to human health and the environment.
Why these indicators are important
Wastewater is the largest point source of pollution to surface water in Canada. Even after treatment, some pollutants remain in treated wastewater discharged into surface waters. Treated wastewater may contain grit, debris, biological wastes, disease-causing bacteria, nutrients, and hundreds of chemicals such as those found in drugs and in personal care products like shampoo and cosmetics. The higher the level of treatment provided by a wastewater system, the cleaner the effluent and the lesser the impact on the effluent receiving environment.
Insufficient wastewater treatment could result in environmental, human health and economic impacts, such as oxygen depletion, beach closures and other restrictions on recreational water use, on fish and shellfish harvesting and consumption and on drinking water.
Related initiatives
These indicators support the measurement of progress towards the following Federal Sustainable Development Strategy long-term Goal 6: "Ensure clean and safe water for all Canadians".
In addition, the indicators contribute to the Sustainable Development Goals of the 2030 Agenda for Sustainable Development. They are linked to Goal 6, "Ensure access to water and sanitation for all", and Target 6.3, "By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally".
Related indicators
The Water quality in Canadian rivers indicators provide a measure of the ability of river water across Canada to support plants and animals.
The Releases of harmful substances to water indicator tracks human-related releases to water of 4 toxic substances, namely mercury, lead, cadmium and arsenic, and their compounds. For each substance, data are provided at the national, provincial/territorial and facility level and by source.
Data Sources and Methods
Data sources
Environment and Climate Change Canada uses a combination of reported data under the Wastewater Systems Effluent Regulations (the regulations) as well as data reported annually by Quebec and Yukon governments as a requirement under equivalency agreements in those jurisdictions for all national indicators.
- Statistics Canada's Municipal Wastewater Systems in Canada statistical program used reported data to produce the data on the population served and the wastewater volumes discharged by treatment level
- Environment and Climate Change Canada's Wastewater Program calculated the effluent quality compliance data from reported data
Data for the international comparison of population served by municipal wastewater systems indicator were retrieved from the Organisation for Economic Co-operation and Development's Wastewater treatment database.
More information
Spatial coverage
Reported data under the regulations or equivalency agreements 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. Note that the volume of wastewater discharged by those systems represents less than 3% of the overall volume reported. 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 2023. It is updated every 2 years.
The indicator on the effluent quality compliance to the standards covers the period from 2015 to 2023. 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
Environment and Climate Change Canada’s Effluent Regulatory Reporting Information System (ERRIS) captures more than 1,500 wastewater (sewage) systems with a daily flow of 100 m3 or more. This list is established from owners of wastewater systems that report under the federal Wastewater Systems Effluent Regulations.
Information and data on over 650 wastewater systems in Quebec and Yukon are provided annually to Environment and Climate Change Canada by the provincial/territorial governments as a requirement of the equivalency agreements with those jurisdictions.
Methods
The Municipal Wastewater Systems in Canada data are presented under 5 datasets:
- Population served by municipal wastewater systems
- Population served by municipal wastewater systems by treatment category
- Wastewater volumes processed by municipal sewage systems
- Wastewater volumes discharged from municipal sewage systems by treatment category, and
- Combined sewer overflow discharge volumes
The treatment levels are categorized as none, primary, secondary, secondary with additional phosphorous removal and tertiary treatment.
For the purposes of these indicators, the population not served by municipal wastewater systems corresponds to the population that either were served by other systems with daily flows of less than 100 m3 per day, had their own on-site wastewater system (such as septic systems) or by other facilities outside the scope of the surveys.
In 2012, the Wastewater Systems Effluent Regulations were established under the Fisheries Act and included mandatory minimum effluent quality standards that can be achieved through secondary wastewater treatment. The proportion of wastewater systems meeting the effluent quality standards corresponds to the number of reporting wastewater systems achieving compliance divided by the total of reporting wastewater systems. Wastewater systems are deemed compliant when their effluent meet the average carbonaceous biochemical oxygen demand and the average concentration of suspended solids applicable limits.
More information
Wastewater treatment categories
Wastewater treatment levels for this indicator were categorized based on the definitions used in the Municipal Wastewater Systems in Canada.Footnote 9
| Treatment category | Definition |
|---|---|
| No treatment | No treatment processes are applied, or only screening and/or grit removal are applied. |
| Primary treatment | Primary treatment removes a portion of suspended solids and organic matter by physical and/or chemical processes. At least 1 of the following processes is applied:
|
| Secondary treatment | Secondary treatment removes biodegradable organic matter and suspended solids using biological treatment processes and secondary settlement. At least 1 of the following processes is applied:
|
| Tertiary treatment | Tertiary treatment further removes residual suspended solids, nutrients and/or other contaminants using various physical, chemical, or biological processes. At least 1 of the following processes is applied in addition of secondary treatment processes:
|
The data were derived from administrative records collected by Environment and Climate Change Canada as required by the Wastewater Systems Effluent Regulations or equivalency agreements with Quebec and Yukon. 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 were developed based on the 2011, 2016, and 2021 census of population releases. The population for 2023 was extrapolated using the 2021 and 2016 census data.
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 [the oxygen demand of the bacteria present in the water] 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 does not exceed 25 mg/L in at least 10 months during a calendar year
- average concentration of suspended solids does not exceed 25 mg/L in at least 10 months during the calendar year
- For wastewater systems reporting quarterly averages:
- average carbonaceous biochemical oxygen demand does not exceed 25 mg/L in all quarters during the calendar year
- average concentration of suspended solids does not exceed 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 do not exceed 25 mg/L
Caveats and limitations
The Municipal Wastewater Systems in Canada statistical program excludes communities that have their own on-site wastewater system, or that are served by other systems with daily flows of less than 100 m3 per day or by other facilities outside the scope of the survey. The Wastewater Systems Effluent 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 are available for these populations.
Although these indicators assume municipal wastewater treatment plants are functioning at their design level, equipment failure and weather conditions may prevent them from doing so. Severe storms can cause overflows in combined sanitary and stormwater sewer systems. During such events, the everyday treatment level is not applied, and raw sewage is released directly to surface waters.
The Municipal Wastewater Systems in Canada statistical program does not provide information on sewage treated by private septic systems or other independent/private or federal systems. Treatment levels depend on the efficiency and maintenance of the septic system. Similarly, no information is collected on the destination of hauled sewage or its treatment level.
Even though the Wastewater Systems Effluent Regulations were federally registered in 2012, the effluent quality standards did not come into force until January 1, 2015. Therefore, there are no compliance limits for the 2013 and 2014 reporting years.
For more information on the Government of Canada's role in wastewater management, see Environment and Climate Change Canada's Wastewater website. For more information on national efforts to develop a harmonized regulatory framework for municipal wastewater treatment, see the Canadian Council of Ministers of the Environment's Canada-wide Strategy for the management of municipal wastewater effluent (PDF; 175 kB).
Resources
References
Environmental Protection Agency (2025) Learn about small wastewater systems. Retrieved on June 26, 2025.
Organisation for Economic Co-operation and Development (2025) Wastewater treatment database. Retrieved on June 26, 2025.
Statistics Canada (2025) Table 38-10-0100-01 Combined sewer overflow discharge volumes (x 1,000,000). Retrieved on June 26, 2025.
Statistics Canada (2025) Table 38-10-0124-01 Wastewater volumes discharged from municipal sewage systems by treatment category (x 1,000,000). Retrieved on June 26, 2025.
Statistics Canada (2025) Table 38-10-0125-01 Population served by municipal wastewater systems by treatment category. Retrieved on June 26, 2025.
Related information
Canada-wide strategy for the management of municipal wastewater effluent (PDF; 174 kB)
Wastewater Systems Effluent Regulations
Alternative format
Download the alternative format of the Municipal wastewater treatment indicator (PDF; 810 kB).