Municipal wastewater is a complex mixture of human waste, suspended solids, debris, nutrients, pathogens, toxics, and a variety of chemicals that are washed down the drains and toilets of residences, businesses and industry. Municipal wastewater is also a source of endocrine disrupting substances, pharmaceutical, personal care products, and other contaminants. 

Wastewater is of serious concern as it contains numerous harmful pollutants and is produced in a large volume.  Environment Canada reported that municipal wastewater represents one of the single largest effluent discharges in Canada. 

Across Canada, a high proportion of the population is served by municipal wastewater collection and treatment systems. The level of treatment to remove pollutants can range from no treatment at all to very extensive multi process treatment. As a result, the quality of effluent that is discharged to the receiving waters varies according to the level of treatment.

Adapted from Environment Canada's National Water Research Institute: Municipal Wastewater