Overview
LLANLLYFNI C STW is a secondary wastewater treatment plant in Clynnog, Gwynedd, Wales, serving approximately 4,068 people. It discharges treated effluent into the local catchment, which ultimately drains into the Irish Sea.
LLANLLYFNI C STW is a municipal wastewater treatment plant located in the village of Llanllyfni, near Clynnog in Gwynedd, Wales. The plant serves a population of around 4,068, placing it in the small-to-medium agglomeration category under UK and EU regulatory frameworks. Its location in the scenic region of Snowdonia National Park underscores the importance of effective treatment to protect local water quality. The plant provides secondary treatment, which is the standard required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for inland discharges from agglomerations of this size. The plant has a designed capacity of 4,231 cubic meters per day and a reported discharge volume of 905.68 cubic meters per day, indicating it operates well below its design capacity. As a facility in the United Kingdom, it is regulated by Natural Resources Wales (NRW) under the Water Resources Act 1991 and related environmental permitting regimes. The treated effluent from LLANLLYFNI C STW is discharged into a local watercourse that flows into the Afon Llyfni, a river that runs through the Nantlle Valley and eventually reaches the Menai Strait and the Irish Sea. This coastal discharge point is within 10 km of the coast, making the plant's performance critical for protecting the marine environment of the Menai Strait, a region known for its diverse marine life and important fisheries.
Environmental context
The plant discharges into the Afon Llyfni, which flows through the Nantlle Valley and enters the Menai Strait, a narrow tidal channel separating Anglesey from mainland Wales. The Menai Strait is an ecologically sensitive area supporting diverse marine habitats, including seagrass beds and important bird populations. The ultimate receiving water is the Irish Sea, a key fishing ground and migratory route for species such as Atlantic salmon and sea trout. The plant's secondary treatment helps reduce nutrient and organic loads, protecting these downstream ecosystems from eutrophication and oxygen depletion.
Frequently asked questions
LLANLLYFNI C STW is located in Llanllyfni, near the village of Clynnog in Gwynedd, Wales, United Kingdom. Its postcode is LL54 6PB.
The plant serves approximately 4,068 people, classifying it as a small-to-medium agglomeration under EU and UK wastewater treatment regulations.
The plant discharges treated effluent into a local watercourse that feeds into the Afon Llyfni, which flows through the Nantlle Valley and into the Menai Strait, ultimately reaching the Irish Sea.
The plant provides secondary treatment, which is the standard required by the EU Urban Waste Water Treatment Directive for inland discharges from agglomerations of this size.
As a UK plant in Wales, it is regulated by Natural Resources Wales under the Water Resources Act 1991 and environmental permitting regulations. It also complies with the EU Urban Waste Water Treatment Directive (91/271/EEC) standards.
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