Green Bay MSD Combined Wastewater Treatment Plant, Wisconsin

Green Bay MSD Combined is a major wastewater treatment facility serving the city of Green Bay and surrounding areas in Brown County, Wisconsin. With a population served of about 229,000, it is classified as a large agglomeration under U. S. EPA guidelines. The plant is operated by the Green Bay Metropolitan Sewerage District (MSD) and plays a critical role in managing municipal and industrial wastewater for the region. As a large-scale facility, Green Bay MSD Combined is expected to provide at least secondary treatment under the Clean Water Act, with possible advanced treatment to meet nutrient removal requirements for the Great Lakes basin. The plant's designed capacity is 1.00 million gallons per day, though actual flow may vary. The facility operates under a National Pollutant Discharge Elimination System (NPDES) permit issued by the Wisconsin Department of Natural Resources, which sets effluent limits to protect water quality. The plant's treated effluent is discharged into the Fox River, which flows northward into Green Bay, an arm of Lake Michigan. Lake Michigan is part of the Great Lakes system, the largest group of freshwater lakes on Earth by surface area. The discharge contributes to the nutrient load in the bay, which has experienced algal blooms and hypoxia in recent decades, making nutrient management a key environmental concern for the region.

The plant discharges into the Fox River, which flows into Green Bay, a shallow bay of Lake Michigan. The Fox River watershed drains agricultural and urban areas, contributing nutrients and sediments. Green Bay's southern end is ecologically sensitive, supporting diverse aquatic life including fish and migratory birds. The bay is part of the Lake Michigan basin, which holds 20% of the world's surface freshwater and requires careful management to prevent eutrophication.