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The City of Bozeman was facing three major drivers to upgrade its wastewater treatment plant. As the plant had reached its design hydraulic capacity, the loadings exceeded the design by approximately 10 to 20 percent to the point that violation of discharge limits was eminent. In addition, Bozeman was experiencing rapid population growth which was pushing the influent flows and loads even higher in a short period of time. In addition, the city’s new discharge permit included more stringent nutrient discharge limits and future permits were likely to contain extremely low nutrient limits.

The Montana Department of Environmental Quality (DEQ) developed the Total Maximum Daily Load (TMDL) for nitrogen and phosphorus, among other pollutants, for the East Gallatin River. This process determined the in-stream nutrient limits. Because the East Gallatin River experiences very low flows in the summer and elevated background nutrient concentrations, the permitted discharge limits for the Bozeman Water Reclamation Facility were extremely stringent. Since the plant effluent accounts for approximately 33 percent of the total summer flow to the river, the most environmentally sound use is to continue returning it to the river.