Darlington STW Wastewater Treatment Plant, Croft-on-Tees, England

Darlington STW is a wastewater treatment plant located in Croft-on-Tees, North Yorkshire, England. It serves a population of approximately 101,553, classifying it as a large agglomeration under UK wastewater regulations. The plant is situated near the River Tees, which flows into the North Sea. As a facility serving over 100,000 people, Darlington STW is required to meet secondary treatment standards under the Urban Waste Water Treatment Directive (91/271/EEC), as transposed into UK law. The plant's designed capacity is reported as 1.00, though the unit is unspecified. The regulatory framework ensures that the plant's effluent meets quality standards to protect the receiving water environment. The treated wastewater from Darlington STW discharges into the River Tees, which flows eastward to the North Sea. The river supports diverse aquatic life and is an important migratory corridor for salmon and sea trout. The plant's operation helps maintain water quality in the Tees estuary and downstream coastal areas.

The River Tees flows from its source in the Pennines through Darlington and into the North Sea at Teesmouth. The estuary supports a range of habitats including mudflats and saltmarshes, which are important for overwintering birds and fish species. The plant's discharge contributes to the overall nutrient and pollutant load in the river, making treatment standards critical for maintaining ecological balance in the downstream environment.