Cassington Yarnton Road Cassi STW - West Oxfordshire Wastewater Treatment Plant

Cassington Yarnton Road Cassi STW is a wastewater treatment plant located in Cassington, West Oxfordshire, Oxfordshire, England. The facility serves a population of approximately 15,500 people, classifying it as a medium-sized agglomeration under UK and EU regulations. As a plant operating in the United Kingdom, it falls under the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for discharges to freshwater and estuaries for populations over 2,000. For agglomerations of this scale, the directive mandates at least secondary treatment, with tertiary treatment required if discharging to sensitive areas. The plant's treated effluent is discharged into local watercourses that ultimately drain into the River Thames catchment, which flows through southern England into the North Sea. The Thames basin supports diverse aquatic life and is an important ecological corridor for migratory fish and bird species.

The plant discharges into the River Thames catchment, which flows through Oxfordshire and eventually into the North Sea via the Thames Estuary. The Thames basin is a vital freshwater ecosystem supporting species such as Atlantic salmon, brown trout, and Eurasian otter. Downstream waters are influenced by agricultural runoff and urban development, making effective wastewater treatment crucial for maintaining water quality and biodiversity.