Municipal wastewater treatment

Since 1983, Canadian municipalities have continued to upgrade their level of wastewater treatment. The percentage of Canadians on municipal sewers with secondary treatment or better has improved from 40% in 1983 to 69% in 2009, leaving approximately 18% with primary treatment or less and another 13% of Canadians using household septic systems to treat their sewage.

Wastewater treatment levels, Canada, 1983 to 2009

Bar chart
Long description

The bar chart shows the percentage of the Canadian population with different levels of municipal wastewater treatment between 1983 and 2009. There are five treatment categories: no treatment, primary treatment, secondary treatment, tertiary treatment and septic systems or haulage. The percentage of Canadians on municipal sewers with secondary treatment or better has improved from 40% in 1983 to 69% in 2009, leaving approximately 18% with primary treatment or less and another 13% of Canadians using household septic systems to treat their sewage. No data is available for 2001 as there were not enough respondents to produce meaningful results.

Data for this chart
Wastewater treatment levels, Canada, 1983 to 2009
Year Percentage of Canadian population with no treatment Percentage of Canadian population with primary treatment Percentage of Canadian population with secondary treatment Percentage of Canadian population with tertiary treatment Percentage of Canadian population with septic system or haulage
1983 20 11 20 20 28
1986 20 11 19 22 28
1989 14 14 20 23 29
1991 11 15 21 27 27
1994 5 17 22 28 27
1996 4 17 23 31 26
1999 3 14 28 30 26
2001 N/A N/A N/A N/A N/A
2004 3 20 48 19 10
2006 3 15 43 27 12
2009 3 16 53 15 13

Download data file (Excel/CSV; 757 B)

How this indicator was calculated

Note: In 2006 and earlier, the definition of tertiary treatment included any advanced treatment. The definition was narrowed in 2009 to refer to tertiary treatment processes only.
*Data from the 2001 survey were not included, as there were not enough respondents to produce meaningful results.
Source: Municipal Water Use and Pricing Survey 1983-1999. Municipal Water and Wastewater Survey 2004-2009. Environment Canada.

Every day, millions of cubic metres of sanitary sewage are flushed from homes, businesses, institutions and industries through sink drains and toilets into city sewer systems. Municipal wastewater contains sanitary sewage and is sometimes combined with stormwater from rain or melting snow draining off rooftops, lawns, parking lots and roads. The sewer system either takes the wastewater to a municipal wastewater treatment plant or releases it directly into a lake, river or ocean.

Municipal wastewater is one of the largest sources of pollution, by volume, to surface water in Canada. Municipal wastewater normally receives treatment before being released into the environment. The higher the level of treatment provided by a wastewater treatment plant, the cleaner the effluent and the smaller the impact on the environment. Despite treatment, 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 in drugs and in personal care products like  shampoo and cosmetics.

Much of the Canadian population is served by wastewater collection and treatment systems; however, the level of treatment applied to wastewater prior to discharge varies widely. In primary treatment, wastewater is pumped into a large tank where the heavy solids are allowed to settle. In the secondary treatment process, bacteria and oxygen are added to primary-treated wastewater to further remove biological waste. Tertiary treatment removes specific substances of concern after secondary treatment using a number of physical, chemical or biological processes. Septic systems consist of a buried tank that holds wastewater long enough to separate solid waste from liquid waste. While bacteria continue to decompose solids in the septic tank, the wastewater exits the tank and enters the drain field where the soil further treats it. Haulage refers to systems where wastewater is pumped from a collection tank and taken to a disposal site. While wastewater treatment levels in communities vary a lot some patterns are evident. Inland cities, for example, tend to have higher treatment levels than those on the coast, because there is less surface water to dilute the pollution in the wastewater.

Report a problem or mistake on this page
Please select all that apply:

Privacy statement

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: