Thames Water tests find PFOS levels 13 times above the limit
Tests of Thames Water’s water reuse project in southwest London found that the level of perfluorooctane sulfonate (PFOS) reached up to 13 times the limit set in the United Kingdom for surface waters. The Guardian reports, citing the company’s technical documents.
Test results
PFOS belongs to the group of per- and polyfluoroalkyl substances (PFAS), known as “forever chemicals” because they do not break down in the environment. In the first test, the PFOS concentration was 6.3 nanograms per litre, while in the second it was 8.7 nanograms per litre. The UK standard for surface waters is 0.65 nanograms per litre.
The documents state that PFOS quickly exceeded the permitted threshold in less than a month of the plant’s operation. The company said that meeting the standard would be operationally challenging: it would require frequent regeneration, reactivation and replacement of carbon filters, as well as significant additional costs. The tests also showed high iron content in the treated water, which the documents described as having a significant adverse impact on the river.
Scheme for periods of drought
The Teddington Direct River Abstraction project provides that when water levels in the Thames are low, the company will take up to 75 million litres of water per day in the Teddington area and replace this volume with treated effluent from the Mogden wastewater treatment plant through a new tunnel. Thames Water plans to use the system to address water shortages linked to population growth and forecast droughts.
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Thames Water has applied for permission to implement the project and previously said that it would not harm the river and its habitats or pose a threat to people. A company representative stressed that the project could not operate without an environmental permit from the Environment Agency. According to him, the pilot plant tested different technologies to refine the final design of the polishing treatment system, and its data do not reflect the indicators of water that would be discharged into the Thames after the facility is launched.
Cost and regulator’s position
Thames Water has publicly estimated the project’s cost at at least £350 million. At the same time, according to the newspaper’s sources, the initial estimate of £350 million could rise to more than £500 million due to the need to install additional mechanical pumps in a nature reserve near Teddington. The Environment Agency received the results of two tests. In 2019, it rejected an earlier version of the scheme because of the unacceptable environmental impact of discharging millions of litres of treated effluent.
The regulator said that the Teddington site would continue to undergo thorough environmental assessments before any construction work begins. The project is also criticised by the local council, local members of parliament and the community group Solar, which believes it could cause irreversible environmental damage to the river.
