Annandale Water MSA STW - Secondary Wastewater Treatment in Johnstonebridge, Scotland

Annandale Water MSA STW is a wastewater treatment plant located near Johnstonebridge in Dumfries and Galloway, Scotland. The facility serves a small population of around 2,000 people and is situated inland, approximately 50 km from the coast. It operates under the regulatory framework of the United Kingdom, which implements the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this scale. The plant provides secondary treatment, a standard level required under the directive for inland freshwater discharges. With a designed capacity of 2,000 m³/day and a discharge volume of 445.27 m³/day, the facility operates well below its capacity. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids. The treated effluent is discharged into local watercourses that drain into the Solway Firth, an important estuary on the west coast of Scotland. The Solway Firth supports diverse aquatic life and is a key migratory corridor for salmon and sea trout. The plant's location inland helps protect the sensitive coastal and marine environment of the firth from nutrient pollution.

The plant discharges into local rivers that flow into the Solway Firth, a large estuary on the Irish Sea. The firth is ecologically sensitive, supporting diverse bird populations and marine species. As an inland facility, the plant's secondary treatment helps reduce nutrient loads that could otherwise contribute to eutrophication in the coastal waters.