Donax STP Wastewater Treatment Plant, Sanibel, Florida

Donax STP is a wastewater treatment facility located in Sanibel, Florida, United States. The plant serves a population of about 6,469 residents, operating as part of the City of Sanibel Utilities. It is situated on Donax Street in Lee County, within the coastal region of southwestern Florida. As a plant serving a small agglomeration, it operates under the U.S. Clean Water Act, which requires National Pollutant Discharge Elimination System (NPDES) permits for all discharges. The designed capacity is 1.00 million gallons per day, indicating a facility sized for the local community. Treatment processes are expected to meet secondary treatment standards as mandated by federal regulations. The plant's treated effluent is discharged into the local watershed, which ultimately drains into the Gulf of Mexico. This coastal environment supports diverse marine life, including seagrass beds and mangrove ecosystems. Proper treatment is essential to protect water quality in the sensitive estuarine and nearshore habitats of the Gulf Coast.

Donax STP discharges into the Sanibel area's surface waters, which flow into the Caloosahatchee River estuary and then into the Gulf of Mexico. This region is ecologically sensitive, supporting seagrass beds, mangroves, and a variety of marine species. The plant's operations are critical to maintaining water quality in these coastal ecosystems, which are important for fisheries and tourism.