Coylton STW - Secondary Wastewater Treatment Plant in Coylton, South Ayrshire, Scotland

Coylton STW (Sewage Treatment Works) is a municipal wastewater facility located on Ayr Road in Coylton, South Ayrshire, Scotland. The plant serves a population of approximately 2,700 residents and operates under the regulatory framework of the UK, which implements the EU Urban Waste Water Treatment Directive (91/271/EEC) through Scottish Water. As a secondary treatment plant, it provides biological treatment to reduce organic matter and suspended solids before discharge. The plant has a designed capacity of 7,000 cubic meters per day, with an average discharge volume of 601 cubic meters per day, indicating significant spare capacity. The treatment process is secondary, which is the standard required for inland freshwater discharges under the Directive for agglomerations of this size. The facility is owned and operated by Scottish Water, the public water authority for Scotland. The treated effluent is discharged into the local watercourse, which flows into the River Ayr and eventually reaches the Firth of Clyde, a major sea inlet on Scotland's west coast. The Firth of Clyde supports diverse marine life, including salmon and sea trout, and is an important area for fishing and tourism. The plant's proximity to the coast (within 10 km) means its discharge can influence coastal water quality, though secondary treatment provides substantial protection.

Coylton STW discharges into a tributary of the River Ayr, which flows westward into the Firth of Clyde. The Firth of Clyde is a large sea inlet that supports a variety of marine habitats, including mudflats, saltmarshes, and seagrass beds, which are important for birdlife and fish species such as Atlantic salmon. The area is also used for recreational activities like sailing and fishing. The plant's secondary treatment helps reduce nutrient and organic pollution, protecting the downstream estuarine and coastal environment.