The Ottawa Drinking Water System consists of the Lemieux Island Water Purification Plant and the Britannia Water Purification Plant that supply approximately 850,000 people with drinking water.

Where does the water come from?

Intakes draw water from the Ottawa River and direct it into the water treatment plants.

How is the water treated and distributed?

Raw water from the river is screened to remove debris. A coagulant is then added prior to the water entering the mixing chambers where it follows a spiraling flow pattern to promote gentle mixing (flocculation). The coagulant binds fine particles together forming “floc”. Water then flows into sedimentation basins where floc settles to the bottom. Clear water then flows from the top through filters. Water is then disinfected using chlorine and ammonia, pH is adjusted for corrosion control and fluoride is added before the water enters the distribution system. The City of Ottawa Drinking Water System operators must adhere to the strict requirements for the treatment, testing and distribution of drinking water specified in the Safe Drinking Water Act. The water is consistently in compliance with Ontario Drinking Water Quality Standards.

How is the drinking water source protected?

Ontario’s Clean Water Act was created specifically to protect drinking water at the source rather than simply relying on water treatment to deliver safe, clean water. Because of work completed under the Clean Water Act, Ottawa now has mapped Intake Protection Zones (IPZs) that are protected through policies in the Mississippi-Rideau Source Protection Plan.