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Written question asked by Sarah Olney (Liberal Democrat) on Wednesday, 8 July 2026, in the House of Commons. It was due for an answer on Tuesday, 14 July 2026 (named day). It was answered by Emma Hardy (Labour) on Tuesday, 14 July 2026 on behalf of the Department for Environment, Food and Rural Affairs.

River Thames: Water Treatment

Question

To ask the Secretary of State for Environment, Food and Rural Affairs, what assessment she has made of the efficacy of an indirect potable reuse scheme which would take treated sewage from Mogden Sewage Treatment Works, process it using an advanced water recycling plant using reverse osmosis to remove PFAS, and discharge the treated water into the Queen Mary Reservoir for subsequent treatment to potable water by a water treatment works.

Answer

Water companies explore a wide range of options, and variants of those options, through the Water Resources Management Planning process. Many of these are not taken forward due to technical, practical, or cost considerations. Any new water recycling schemes for water supply must be included by water companies in their preferred Water Resources Management Plans and developed by the company. Schemes taken forward must secure environmental permits from the Environment Agency, including water quality permits that include conditions to manage impacts from any discharge to the environment.

The Drinking Water Inspectorate carried out a research project published last year outlining that ‘reverse osmosis (RO) and nano filtration (NF) provide a near absolute barrier for passage of PFAS compounds when operated correctly’.

Secondary information

Type
Written question
Reference
16968
Session
2026-27
Subjects
River Thames Water treatment
Link
View this Written question on www.parliament.uk