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An investigation has been launched after a foamy discharge was found originating from a sewage treatment plant in Chesham.
It was spotted flowing into the River Chess from Chesham Sewage Treatment Works and has sparked an investigation by Thames Water.
The water company said the discharge is not caused by sewage, and the plant is working as intended.
Initial investigations suggest the foam has been caused by a substance that has entered the sewage network upstream of the treatment works, and which the treatment process isn’t designed to remove.