Llangollen STW - Secondary Wastewater Treatment Plant in Llangollen, Wales

Llangollen STW (Sewage Treatment Works) is a municipal wastewater facility located in Llangollen, Denbighshire, Wales, United Kingdom. The plant serves a population of approximately 3,436 people, classifying it as a small agglomeration under UK and EU regulatory frameworks. The facility provides secondary treatment, which is the standard biological treatment required for inland freshwater discharges under the EU Urban Waste Water Treatment Directive (91/271/EEC), transposed into UK law. While specific capacity figures are available, the plant's design capacity aligns with the population served, ensuring adequate treatment for the local community. The treated effluent is discharged into the River Dee catchment, which flows through the Dee Valley and ultimately into the Dee Estuary and the Irish Sea. The River Dee is a designated salmonid fishery and supports diverse aquatic life, making effective wastewater treatment critical for maintaining ecological health in this sensitive watercourse.

Llangollen STW discharges into the River Dee catchment, a major river in North Wales that flows through the Dee Valley and into the Dee Estuary, a site of ecological importance. The river supports salmon, trout, and other freshwater species, and the estuary provides habitat for migratory birds. The plant's secondary treatment helps protect water quality in this sensitive watershed, which ultimately drains into the Irish Sea.