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Several hundred thousand tests are performed annually to ensure that Ann Arbor drinking water not only meets, but surpasses, water quality standards. The treatment process includes lime softening, which adds calcium hydroxide to the water to reduce hardness and remove iron; ozone disinfection to kill pathogens and improve water taste; sand and activated carbon filtration to clean the water of physical, biological and chemical impurities; and a final disinfection with combined chlorine that protects the water as it travels through the City's piping systems. Phosphate is added for corrosion control, and fluoride is added to the water as a preventative dental measure for children, as suggested by the American Dental Association. Ann Arbor's reliable water system ensures that wells and groundwater aquifers are protected from contamination.
Source: Ann Arbor Water Treatment Services |
Where does our drinking water come from?
Ann Arbor’s drinking water comes from a combination of sources. Eighty-five percent is drawn from the Huron River in Barton Pond. The remainder comes from groundwater wells located on the south side of town. All of the source water is treated, filtered and disinfected with state-of-the-art techniques at the Water Treatment Plant. The plant processes 5 billion gallons of water a year (14 million gallons per day) and services 120,000 permanent residents, not including the highly fluctuating student population. Together, Scio and Ann Arbor Townships buy 1.2 million gallons each year.
How has our water treatment changed over time?
Ann Arbor's Water Treatment Plant (WTP) for drinking water was built in 1938 and has been upgraded continually to keep up with regulations, increase reliability and to improve water quality. In 1996 ozone treatment was added for disinfection and taste and odor control. Ozone is a powerful disinfectant which creates fewer disinfection by-products than chlorine. The city has won the American Water Works Association’s Regional “Water Taste Off” competition six times.
The City's laboratory is located at the WTP. It is certified by the Michigan Department of Environmental Quality (MDEQ) and the U.S. Environmental Protection Agency (EPA) for performing drinking water analyses for compliance with regulations under the Safe Drinking Water Act.
How does the Ann Arbor environment affect our drinking water?
Most Ann Arbor rainfall and irrigation that does not get absorbed into the ground eventually finds its way to the Huron River – our main source of drinking water. As the water passes over paved streets it may pick up chemicals, oils, sediments and organic material. When the water enters a storm drain, all of these pollutants make their way to the river. Therefore, the cleaner we keep our urban environment, the more we reduce the risk of contaminated runoff entering the river and our water supply.
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