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How is city water treated?
The City of Toronto produces potable (drinking) water by treating and cleaning raw water taken from Lake Ontario.
- Raw water is taken in from Lake Ontario.
- Large objects are removed by traveling screens.
- Chlorine is added to kill microorganisms.
- Alum is added to trap small particles causing them to clump together and form larger groups of particles called "floc".
- Heavy flocs are collected at the bottom of tank.
- Water is passed through layers of graded gravel and fine sand removing most of the biological impurities while activated carbon removes taste and odor from the water.
- Chlorine is added again to kill any remaining harmful bacteria and fluoride is added to water to help prevent tooth decay.
- Ammonia is added to stabilize the Chlorine during its trip from the plant to where it is used.
- Water is tested for quality.
- Water is distributed to homes, apartments, schools and industries.
Although city water is treated and tested at the municipal plant, it then has to travel through aging infrastructure such as pipes and valves before reaching its destination and picks up impurities along the way.
For more information visit:
City of Toronto - How is lake water turned into drinking water?
DRINKING WATER SYSTEMS Annual Report