The Ashbridges Bay Wastewater Treatment Plant is the city of Toronto's main sewage treatment facility, and the second largest such plant in Canada after Montreal's Jean-R. Marcotte facility. One of four plants that service the city of Toronto, it treats the wastewater produced by some 1.4 million of the city's residents and has a capacity of 818,000 cubic metres per day. Until 1999 it was officially known as the Main Treatment Plant. The plant has a 185 m (607 ft) high smokestack which is visible from most parts of the city.
The plant opened in 1910. Prior to this, Toronto's sewage flowed directly into Lake Ontario and a layer of thick sludge covered the lake to a distance of several hundred feet from shore. The lake was also the source of the city's drinking water and the pollution contributed to a major typhoid outbreak.
The plant is located on the shore of Lake Ontario at the foot of Leslie Street at Ashbridge's Bay. To the west is the Port Lands area, a once heavily industrial area that is now mostly deserted. To the north is the Leslieville neighbourhood. When the plant was built, it was on the eastern edge of the city, far away from most residents. It is now surrounded by residential areas and strenuous efforts have been made to reduce odours and pollution. Most notable was the shuttering of the plant's incinerators in 1987. An odour control study was completed in 2002 and, beginning in 2002, the area around the plant was also been redesigned into a large landscaped park. In 2005, a contract was awarded to design and construct a new odour control system.
Until recently, all the sludge has been trucked off site. However, summer 2007 saw odour problems, with the Michigan landfill closed and the city removing only 6 of every 10 truckloads of sludge produced, leaving the rest in an aeration slough until autumn when agricultural applications for sludge resumed.