Winchester N Kingsworthy Harestock STW - Wastewater Treatment Plant in Winchester, England

Winchester N Kingsworthy Harestock STW is a wastewater treatment plant located near Winchester, Hampshire, England, serving a population of around 15,667. The facility is situated along the Winchester Bypass in the Headbourne Worthy area, contributing to the region's sanitation infrastructure. As a plant serving a medium-sized agglomeration, it is subject to the UK's transposition of the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for inland discharges. The plant discharges treated effluent into local watercourses that drain into the River Itchen, a chalk stream of high ecological importance. The River Itchen flows south to Southampton Water and eventually the English Channel, supporting diverse aquatic life and designated as a Site of Special Scientific Interest.

The plant's treated effluent enters the River Itchen catchment, a classic chalk stream known for its clear, nutrient-poor waters and rich biodiversity. The River Itchen flows through Hampshire to Southampton Water, a major estuary that connects to the Solent and the English Channel. The river supports species such as Atlantic salmon, brown trout, and water crowfoot, making it a sensitive ecosystem requiring careful nutrient management.