Water Treatment

The Milwaukee Water Works treats Lake Michigan water at the Linnwood Water Treatment Plant on the north and the Howard Avenue Water Treatment Plant on the south. The lake water passes through what are called multiple treatment process barriers that destroy and remove illness-causing microorganisms from Milwaukee's drinking water.

The primary form of disinfection is ozone gas. As source water enters the first stage of water treatment, ozone is bubbled into the water from the lake in large contactor tanks. This highly reactive gas destroys illness-causing microorganisms such as Cryptosporidium and Giardia. Ozone also removes taste and odor, and reduces the formation of chlorinated disinfection byproducts. Following inactivation of microorganisms, the processes of coagulation, flocculation, settling, and biologically active filtration remove additional particles. After filtration, chlorine is added as a secondary disinfectant. A regulated amount of fluoride is added to help prevent dental cavities among consumers. A phosphorous compound is added to help control corrosion of pipes. This helps prevent lead and copper from leaching from plumbing into the water. As the water leaves the treatment plants, ammonia is added to change the free chlorine to chloramine. This is a very stable form of chlorine disinfectant that maintains the residual protection in the distribution system. The Wisconsin Department of Natural Resources (DNR) requires water utilities to maintain a detectable level of disinfectant throughout the distribution system to maintain bacteriological protection. All chemicals that are added are certified food grade, safe for human consumption.

View a printable treatment process diagram (Spanish version)