The Treatment Process

Treatment Plants
The City of Toronto has four water treatment facilities which provide potable water to all of Toronto including the North York Region. The R.C Harris Plant, F.J Horgan Plant, R.L Clark Plant and Island Plant all draw water from Lake Ontario to treat and distribute to the city (City of Toronto, n.d).

Treatment Process
Water from Lake Ontario is pumped to the plant through intake pipes and, upon entering the plant, travel through screens to remove large debris. Chlorine and alum are then added to remove microorganisms and clump small particles together respectively. The clumps (called 'floc') drop to the bottom of a settling basin for collection and the clean water undergoes filtration through layers of carbon, gravel and fine sand which remove finer bits of floc and taste/ordour-producing chemicals ('How is Lake Water Turned Into Drinking Water?', n.d)

After filtration the purified water is stored in basins which release chlorine, to kill microorganisms, and sulphur dioxide to remove excess chlorine. Just before distribution ammonia is also added to stablize the cholrine for safe distribution ('How is Lake Water Turned Into Drinking Water?', n.d). The visual on the side demonstrates the entire process.