PFAS Catchment Investigations

Severn Trent are looking to understand sources of PFAS in 2 surface waters feeding 2 Water Treatment Works (WTW) with a view to understand risk at our WTW now and in the future.

We are also keen to explore what is controlling variation and concentrations, and what mitigation actions may help to reduce PFAS levels in these catchments and their potential effectiveness. This information will be used to plan the necessary level of PFAS removal required at water treatment works in these catchments now and for the future, and work towards less reliance on energy intensive removal / destruction techniques. The work also aims to further develop our stakeholder engagement activity, fulfilling commitments in DWI guidance as well as working with stakeholders to reduce sources in catchment.

The objectives of the work are to:

To understand where PFAS of concern are originating from considering both current and historic activities in our catchments

To understand how PFAS levels may change in the future

To understand what is controlling PFAS concentrations

To review what mitigation options are available to reduce PFAS levels and how feasible / effective they could be in our catchments and at what cost including attempting to reduce the use of carbon and intensive energy systems such as GAC.

Fulfilling our stakeholder engagement commitments in the DWI guidance as well as working with stakeholders to reduce sources in catchment with education

Support ST's stakeholder engagement activity

Scope

This work will be focused on the surface water catchments upstream of 2 WTW's. It should include review of water quality data available from 2022 to 2025 plus outputs from our catchment risk assessment, stakeholder engagement (where shareable) and our AMP7 investigations. For 1 catchment it is expected that the recommendations from the AMP7 investigation are reviewed and where considered appropriate, acted upon. This includes sampling further upstream in the catchment, close to potential PFAS sources identified aspart of the AMP7 investigation, sampling sediments and obtaining flow data from the catchment.

Key tasks likely to be delivered as part of this work include:

WQ monitoring throughout the catchments

Flow monitoring in the catchments, building on data availability from EA flow monitoring

Sampling of effluent and influents of large wastewater treatment work

Sampling up / downstream of possible PFAS discharges into rivers

Desktop analysis and integration of WQ data, flow data and spatial data (linked to possible PFAS sources in the catchments) from monitoring above and existing data

Forensic analysis of data (including compound breakdown analysis) and comparison with potential sources

Mass balance and simple modelling of possible sources

Recommendations around stakeholder engagement activities

Review of options to address likely sources of PFAS in catchments including contributing wastewater works.