University of Wisconsin-Milwaukee
OP-28: Wastewater Management

MMSD (Milwaukee Metropolitan Sewerage District) uses 4 stages to clean wastewater and uses large-scale processes that mimic nature to produce Milorganite. Wastewater enters the Jones Island water reclamation facility where all solid materials such as sand, boards, shop rags, plastic and debris are first removed. Microbes are added to the water—the activation process—and oxygen is bubbled through the water to create the ideal environment for microbes to digest the nutrients in the water. The microbes die after they consume all of the nutrients. Binding agents are added to the water causing the microbes to clump together and settle to the bottom of the undisturbed water in sedimentation tanks. After everything has settled the cleaned water is returned to Lake Michigan and the microbe clumps are sent on for dewatering and drying. Moisture is first squeezed out of the clumps using belt presses resulting in something similar to wet cardboard. The semi-solid material moves on to 12 rotary kiln driers heated to 900–1200⁰F. The extreme heat kills pathogens. Product samples are thoroughly tested 18-20 times every day to ensure Milorganite complies with the Environmental Protection Agency (EPA) standards for protecting human health and the environment. After passing all tests, it’s ready to be packaged and shipped throughout North America.