Key facts
- Toxic blue-green algae have been detected at the new official bathing site on the River Thames in south-west London.
- The algae bloom is linked to heat, low river flow, and sewage pollution.
- Thames Water plans to pump 75m litres of treated sewage daily into the river near the site.
- The Environment Agency has warned swimmers not to enter the water.
- Thames Water has postponed essential upgrades to its Hogsmill sewage treatment works.
Swimmers have been warned to avoid the River Thames' first official bathing site in Ham, south-west London, due to a toxic blue-green algae bloom. The unusual occurrence in moving water is attributed to high temperatures, low river flow, and nutrient pollution from sewage. Thames Water's Hogsmill sewage treatment plant is located upstream of the site.
The discovery intensifies opposition to Thames Water's proposed £250m water recycling scheme, which involves abstracting 75m litres of river water daily during low flow periods and replacing it with treated sewage. This project, designated a strategic infrastructure project, has faced objections from local MP Munira Wilson, the council, and river users, despite previous Environment Agency rejection due to concerns about water temperature and biodiversity impacts.
Marlene Lawrence of the Teddington Bluetits swimming group described the algae bloom as unusual for the area and linked it to climate change and the river's current stressed state. Thames Water has also been criticized for postponing essential upgrades to its Hogsmill works, a failure being investigated by regulator Ofwat. The company has a history of breaching permit conditions, discharging raw sewage illegally.
A Thames Water spokesperson assured that the proposed recycling project would meet strict environmental standards and that the treated water outfall would be downstream of the bathing site. However, campaigners argue the scheme will exacerbate the river's environmental pressure, especially given the company's significant daily water leaks.