Author(s): Giuditta Trinci; Geraldene Wharton; Kate Heppell; Thomas Kelly

Linked Author(s): Giuditta Trinci

Keywords: Chalk streams; Soluble reactive phosphorus; Sewage treatment; Bed sediment; Monitoring

Abstract: This study evaluates the effects of phosphorus stripping at Chesham Sewage Treatment Works (CSTW) on water quality and habitat recovery in the River Chess, a globally rare UK chalk stream. Chalk streams support ecologically distinctive habitats sustained by clear, mineral-rich groundwater and aquatic macrophyte communities, but they are highly vulnerable to nutrient enrichment and urban pressures. High-frequency monitoring data from the Chess Watch citizen science programme, together with Modular River Surveys (https://docs.modularriversurvey.org/) and laboratory analyses of water and sediment quality, are providing a framework for assessing changes in physicochemical characteristics and soluble reactive phosphorus (SRP) concentrations. Preliminary results show that SRP concentrations downstream of CSTW declined by 74.6% following phosphorus stripping, with partial improvement in Water Framework Directive (EC, 2000) compliance. However, compliance remained below target, and sediment analyses identified elevated legacy phosphorus stores downstream, likely constraining recovery. Findings suggest that phosphorus stripping alone may be insufficient for rapid ecological restoration, highlighting the need for sustained integrated catchment management and long-term monitoring of both sediment -bound and dissolved phosphorus.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.353

Year: 2026