Environmental Trends 2002

Mitigation of Impact

Percentage of Population Served by Secondary or Tertiary Wastewater Treatment in British Columbia

SOURCE: Environment Canada, Municipal Water Use (MUD) data, 2001. Ministry of Water, Land and Air Protection. Summary of Municipal Treatment Facilities, 2001. NOTES: Secondary treatment includes waste stabilization ponds. These data refer to the proportion of the municipal population in British Columbia that is served by a municipal wastewater system. Approximately 17% of British Columbians have on-site sewer systems under the Ministry of Health, which are excluded from this analysis.

Status and trends in wastewater treatment

• The purpose of wastewater treatment is to protect human health and to reduce stress on the receiving environment.

• Preliminary treatment removes solid material using screens. Primary treatment removes material through settling chambers. After primary, secondary treatment removes suspended material and organic matter, while tertiary goes beyond this to remove target substances such as nutrients.

• In 1999, 7% of British Columbians with municipal wastewater treatment were served by preliminary treatment, 29% were served by primary, and 63% were served by secondary treatment or better.

• The increase from primary to secondary treatment between 1996 and 1999 is a result of the Annacis Island and Lulu Island wastewater treatment plants. Together these plants serve a million people before discharging into the Fraser River.

Why is it important?

• Wastewater not only consists of human waste, which can carry disease-causing pathogens; it also contains other substances such as motor oil, heavy metals, paint thinner, pesticide residues, pharmaceuticals and solvents, which can threaten human and ecological health.

• Substances found in sewage effluent are capable of affecting the endocrine systems of biological organisms. This could result in reproductive and immune system dysfunction, neurological, behavioural and developmental disorders, and possibly certain forms of cancer.

• In Canada, 80% of marine pollution comes from terrestrial activities including industrial and agricultural runoff.

What is being done?

• The Federation of Canadian Municipalities best practices guide encourages the development of sustainable municipal infrastructure.

• Federal and Provincial agencies are developing strategies for consistent and improved wastewater management, which include two municipal investment funds to support the upgrade of municipal infrastructure.

For detailed information, including graph data, see In-Depth report [pdf].