Water Supply and Treatment 

Where does our drinking water come from?
The Ann Arbor water supply is comprised of both surface and groundwater sources. Approximately 85% of the water comes from the Huron River. The remaining 15% comes from multiple wells located south of Ann Arbor.  

Treatment Plant
Facility
The Water Treatment Plant is actually two separate water plants.  Plant one was built in 1938 and 1949 and can process 22 million gallons of water per day (MGD).  Plant two, built in 1966 and 1975, can process 28 MGD.  The plants are upgraded continually to keep up with regulations, increase reliability and to improve water quality. 

© Aerial Photo by Dale Fisher. All rights reserved  

Staff
Making high quality drinking water takes a team of licensed, educated, caring personnel: operators, lab analysts, mechanics, engineers, scientists, administrative assistances and administrators.

Treatment Process
   
Water from both sources (the Huron River water and groundwater from local wells) is blended at the Water Treatment Plant and then moved through a rigorous treatment process. Because Ann Arbor uses surface water as a source for drinking water, we practice complete treatment which consists of:
(1) Rapid Mixing: for quick dispersion of the chemicals being added
(2) Flocculation (slow mixing): gives the chemical reaction the time it needs to go to completion
(3) Settling: the removal of solids from the water by gravity
(4) Filtration: to clean the water of physical, chemical and biological impurities 

In addition, Ann Arbor softens it’s water; lime softening uses calcium hydroxide to remove calcium, magnesium and iron.  Lowering water hardness reduces build up and scaling on pipes, a factor that could extend the life of home hot water heaters, household pipes and other water-using appliances.  Lower water hardness also reduces the amount of soap needed for effective cleaning and the potential for less spots remaining on utensils, glassware and dishware.