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Wastewater effluents are the largest source of pollution by volume to surface water in Canada. Wastewater effluents may contain many pollutants and substances of concern including grit, debris, suspended solids, disease-causing pathogens, decaying organic wastes, nutrients and hundreds of chemicals.
Wastewater is a term typically used to describe liquid wastes from two types of sources. The first source, sanitary sewage, is generated from homes, businesses, institutions and industries. The second source, stormwater, is generated from rain or melting snow that drains off rooftops, lawns, parking lots, roads and other urban surfaces. Wastewater is collected by sewer systems and in most cases is treated before being released to the environment.
There are two types of wastewater collection systems;
- a combined sewer, and
- a separate sewer system.
Combined sewer systems combine both the sanitary sewage and stormwater collection. During periods of heavy precipitation, overflows caused by overloading the combined sewer collection system may result in a direct discharge of raw sewage into surface waters. On the other hand, separate sewers have isolated the sanitary sewage collection from that of stormwater collection.
Below is a simplified schematic showing how pollutants enter the wastewater collection and treatment system from various sources to their eventual release to the environment.
Click the image to enlarge.
In Canada, most wastewater systems are owned and operated by municipalities. Much of the Canadian population is served by wastewater collection and treatment systems; however, wastewater receives various levels of treatment to remove pollutants prior to discharge, ranging from no treatment to very sophisticated, thorough treatment. As a result, wastewater quality and the amount of pollutants released to the environment vary across Canada.
In Canada, all levels of government share the responsibility for managing the collection, treatment and release of wastewater effluent. The Government of Canada is responsible for managing the risks posed by substances listed under the Canadian Environmental Protection Act, 1999 (CEPA 1999).
The Wastewater Systems Effluent Regulations are now in force. The Government of Canada worked with the provinces, territories and engaged municipalities, Aboriginal communities and organizations and other interested parties to establish the country’s first national standards for wastewater treatment. The Regulations are established under the Fisheries Act and include mandatory minimum effluent quality standards that can be achieved through secondary wastewater treatment.
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