Wastewater Treatment in Canada
A Brief History
1800s – Awareness & Response
The modern history of wastewater treatment begins in 1854 when Dr. John Snow of London, England, established a clear linkage between contamination in the water supply and the outbreak of cholera and typhoid epidemics. Prior to that time, some cities had built primitive sewer systems as an alternative to having human and animal wastes collected in cesspools or dumped directly into the streets. In some places, while sewage solids were collected for use as an agricultural fertilizer or for making saltpeter (an essential ingredient in the manufacture of gunpowder) the health implications of untreated sewage were not understood. However, following Snow’s discoveries, the authorities in London and other large cities began the construction of more elaborate sewer systems designed to collect municipal wastewater and move it to locations where it could be discharged without contaminating the sources of drinking water. Treatment of wastewater remained very basic, mainly with sedimentation facilities that facilitated some separation of solids from the liquid stream.
1900s – Technology & Regulation
More sophisticated treatment technologies were developed in the early 20th Century, including secondary treatment (biological digestion) and chemical treatments to disinfect the plant discharges.
In Canada, most cities are located on large bodies of water or fast-flowing rivers, so that for the early parts of the 20th Century, direct discharge from sewers into nearby lakes, rivers and oceans was the most common approach. Towns developed sewer systems, but wastewater treatment took a back seat to the development of clean water supplies. For example, the City of Lethbridge, Alberta, which is in a relatively arid region, had a basic sewer system by 1904, then commissioned a wastewater treatment plant in 1912. Toronto’s Ashbridges Bay wastewater treatment plan came into operations in 1910 – prior to that, the City’s sewage flowed directly into Lake Ontario. Much of Montreal’s wastewater was discharged directly into the St. Lawrence River until 1987. In Victoria BC, the provincial capital, current plans call for a wastewater treatment plan to come on stream in 2020.
A significant expansion and upgrade of wastewater treatment facilities took place in the years following World War II, driven by the rapid growth of cities and increasing industrialization. In the City of Calgary, for example, a wastewater facility built in the 1920’s had its capacity tripled in 1958, then more than almost tripled again by 1994. Government agencies, such as the Ontario Water Resources Commission (which evolved into the Ministry of the Environment), were established and empowered by new legislation. By 1983, 40% of Canadians were served by wastewater management system that featured secondary or tertiary treatment, 11% by systems with primary treatment alone and 20% by systems that discharged untreated sewages directly into a lake, ocean or river. 28% relied on septic tanks or haulage (where wastes are trucked to a treatment facility). By 2009, the numbers served by systems with direct discharge was down to 3% of the population, while 85% of Canadians were served by a system that incorporated primary or secondary treatment.
21st Century – Challenges & Opportunities
There are a number of global trends that are expected to have significant impact on wastewater treatment practices. The world’s population is growing and becoming increasingly urbanized. It is projected that by 2030, 60% of the world’s population will live in coastal regions. With this pressure, the current practice of withdrawing water from inland areas, transporting it to urban population centers, treating it, using it once, and discharging it into coastal waters will be increasingly unsustainable. Water supply and wastewater management will also be challenged by climate change, which will cause higher sea levels and more violent storm events.
Rising to these challenges will require a paradigm shift in the way that we view water. As well as developing alternative collection systems, we will need to embrace the recycling of wastewater into potable water. By integrating wastewater management with food waste management, we can develop strategies for energy and nutrient recovery.
The future contains both challenges and exciting opportunities. And, it’s coming at us quickly.