The Treatment Process: Lake Water

Treatment Plants
There are a four water treatment plants in Toronto which provide water to the GTA. The R. C Harris, F.J Horgan, Island, and R.L Clark Treatment Plants all draw water from Lake Ontario to treat and distribute ('Water Treatment', n.d).

Treatment Process
Lake water is pumped to the treatment plant where it first passes through a series of screens to remove large debris. Chlorine and alum are added to kill microorganisms and clump smaller

particles together to form 'floc', which are collected after settling to the bottom of a settling basin ('How is Lake Water Turned Into Drinking Water?', n.d).

The filtration process involves passing water through layers of charcol, graded granite and fine sand to remove fine floc and chemical impurities such as bacteria. The charcol layer removes chemicals that produce odour and taste in the water. The purified water is stored in basins in where more chlorine is added to kill any remaining microorganisms, sulfur dioxide is added to remove an excess chlorine ('How is Lake Water Turned Into Drinking Water?', n.d).

The last step of the process is to add ammonia which stabilizes the chlorine in order to keep the water safe during it's trip from the plant to the home ('How is Lake Water Turned Into Drinking Water?', n.d).