PFAS

In the USA, the US Environmental Protection Agency (USEPA) has set a maximum contaminant level of 0.004 micrograms per litre for just two PFAS compounds – PFOS and PFOA. Beyond this, there is significant variation in the regulation of PFAS compounds in drinking water across the USA because of differences in regulations and standards at state-level.

The EU limits levels of 20 individual PFAS to 0.1 micrograms per litre and total PFAS in drinking water is limited to 0.5 micrograms per litre. Several countries have chosen to enact stricter measures for the sum of four PFAS compounds; Denmark (0.002 micrograms per litre), Sweden (0.004 micrograms per litre), and Germany (0.02 micrograms per litre by 2028).

In the UK, our guideline value of 0.1 micrograms per litre is applicable to 48 individual PFAS compounds and, additionally, the sum of all 48 compounds must also be below 0.1 microgram per litre providing much broader protection to consumers than other countries.

We have an in-depth understanding of PFAS across our supply area based on long-term data and monitoring at levels that aren’t replicated across the industry.

Our awareness of PFAS increased significantly following the Buncefield fire in 2005, which needed the use of tonnes of PFAS containing fire-fighting foams to put out. Our response led us to look at the impacts of the incident on our water sources, ground and river water. We quickly developed a monitoring programme in the immediate area, which we then expanded allowing us to gain better understanding as to the level of PFAS (initially two compounds) within our catchments.

Following the Buncefield fire in 2005 and resultant fire-fighting effort, the risk of contamination from PFAS-containing foam reaching the wider environment (including the groundwater aquifer used for public water supplies) was recognised and managed as part of the wider incident response. The outcome of this risk mitigation strategy was that there was no impact on the quality of drinking water supplies and therefore we didn’t need to communicate any precautionary advice to consumers in the area.

One consequence of the Buncefield fire was that it highlighted the potential widespread presence of PFAS compounds in the natural environment (from a variety of sources, not just fire-fighting activities). We initiated collection and analysis of samples for two of the most common compounds (PFOS and PFOA) in our raw water sources and have a comparatively large dataset spanning more than 10 years.

Our laboratory has continued to develop in-house analytical methods for a growing range of PFAS. In February 2022, it successfully completed the work on increasing the number of compounds detected in our PFAS analysis to include all the 47 compounds in the Environment Agency (EA) list. The laboratory team completed the validation process for the 20 PFAS compounds used in the EU “Sum of PFAS” calculation in 2022. They then extended this work to include the validation process for the other 27 PFAS compounds used in the DWI “Sum of PFAS” calculation in 2024.

The DWI introduced an interim safe PFAS level, five-six months following Buncefield fire. Treatment was initially limited to blending water sources to reduce concentrations of PFAS overall.

In 2018 the DWI issued a list of 47 compounds and reduced acceptable levels substantially.

Throughout our PFAS journey our teams have worked collaboratively with regulators, sharing data and knowledge. This approach has allowed our treatment processes to evolve, most recently to include an ion exchange trial at one of our treatment works.

Our knowledge of PFAS enabled us to work with HS2, putting in place a comprehensive monitoring and testing plan including the 47 PFAS compounds. Our extensive historic data means we can analysis comparison data pre and post construction and identify changing conditions to better protect our sources and wider catchment. To date, we have found no changes in pre- and post-construction samples.