Ann Arbor Michigan Uses Ozone for Primary Disinfection

Ann Arbor’s Drinking Water Treatment Plant’s primary source of water comes from the Huron River. Ann Arbor is one of only seven facilities using an inland river as a drinking water source in Michigan. About 85 percent of the water comes from the river, while 15 percent comes from wells located at the city’s airport. The plant pumps on average more than 15 million gallons of water per day to some 125,000 city water customers.

Because the city uses surface water as it primary source, the water goes through a complete treatment process that consists of rapid mixing for quick dispersion of chemicals being added, flocculation to give the chemical reaction time it needs, settling to allow the removal of solids by gravity, and filtration.

The city also softens the water using lime, removing calcium and magnesium. Ozone is used as the primary disinfectant and chloramines as a secondary disinfectant. Fluoride is added to the water for dental protection, and phosphate is added to stabilize the water.

City officials are evaluating replacing portions of the plant that date back to the 1930s, and which could cost tens of millions of dollars.

Spartan periodically posts information about water plants around the world that use ozone. Most people, and even some water professionals, are not aware of the widespread use of ozone in drinking water treatment as well as other applications.


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