Compton Bassett STW - Secondary Wastewater Treatment Plant in Calne, England

Compton Bassett STW is a wastewater treatment facility located near Calne in Wiltshire, England. The plant serves a population of approximately 2,554 people and 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. As a secondary treatment plant, it provides biological treatment to reduce organic matter and suspended solids before discharge. The plant's designed capacity is 3,081 m³/day, with a current discharge volume of 568.61 m³/day, indicating operational headroom. Under UK regulations, secondary treatment is the minimum standard for inland freshwater discharges, ensuring compliance with environmental quality standards. The facility is part of the national wastewater infrastructure managed by water companies under permits issued by the Environment Agency. The treated effluent is discharged into a local watercourse that ultimately drains into the River Avon (Bristol) and then to the Severn Estuary. This catchment supports diverse aquatic life and is important for regional biodiversity. The plant plays a key role in protecting water quality in the Wiltshire countryside and downstream ecosystems.

The plant discharges into a tributary of the River Avon (Bristol), which flows through Wiltshire and into the Severn Estuary. The Avon catchment supports a variety of fish species, including salmon and brown trout, and is designated as a Site of Special Scientific Interest in parts. The estuary is a major migratory corridor for birds and supports internationally important wetland habitats. The plant's secondary treatment helps reduce nutrient and organic pollution, safeguarding these sensitive environments.