ARLINGTON E DIST STP 4 Wastewater Treatment Plant, Jacksonville, Florida

ARLINGTON E DIST STP 4 is a municipal wastewater treatment plant located in Jacksonville, Duval County, Florida. Serving an estimated population of 90,000, it is a medium-to-large facility within the region's wastewater infrastructure. As a US-based plant, it operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Florida Department of Environmental Protection. For plants serving this population tier, secondary treatment is typically required, with possible additional nutrient removal standards in sensitive watersheds. The plant discharges into the St. Johns River watershed, which flows north through Jacksonville to the Atlantic Ocean. The river supports diverse aquatic life and is an important ecological corridor in northeastern Florida.

The plant discharges into the St. Johns River basin, which flows northward through Jacksonville and empties into the Atlantic Ocean at Mayport. The river is a blackwater system with slow flow, supporting diverse fish and bird populations. Downstream areas include estuarine habitats important for juvenile marine species.