The Environment Agency (EA) has identified a bloom of potentially toxic blue-green algae at the River Thames' first official bathing water site, located between the Half Mile Tree and the YMCA Hawker Centre near Teddington Weir. The discovery comes just three months after the site was officially designated on May 15 as London's first bathing water spot. High concentrations of blue-green algae can produce toxins harmful to humans, pets and wildlife.
Swimmers advised to avoid the area
Richmond Council has advised visitors not to swim in or around the spot until further notice. The council also urged pet owners to keep dogs out of the water and people to avoid contact with visible algae near the riverbank. The EA will be taking water samples over the next 24 hours to confirm the extent of the algal bloom, which is at greater risk of growing in hot, dry weather. The site has not yet been classified for water quality, as samples are still being taken; classification is due to be issued after the bathing season ends on September 30.
An advice against bathing notice has been activated on the SWIMINFO website, and signage has been placed at the location by the Royal Borough of Kingston Upon Thames. The EA stated that the section of the River Thames between Hampton and Kingston has likely also been impacted, and the public should not enter the river along this stretch.
Campaigners express concern over sewage and algae link
Campaigners from Save Our Lands and River (SOLAR) expressed concern for public health over the findings. Ian McNuff from SOLAR told the Local Democracy Reporting Service (LDRS): "It’s deeply concerning, but sadly not surprising, that London’s new bathing site at Ham and Kingston has been hit by a toxic algae warning just weeks after opening." He added that toxic algae experiences "turbo-charged growth with sewage overflows in warm, sunny conditions – exactly what you’d expect just downstream from the Hogsmill that has failed its recent environment audit."
An EA inspection on May 11 found the nearby Hogsmill Sewage Treatment Works in breach of its environmental permit on four counts, including inadequate storm sewage storage. The bathing spot is also located near Thames Water's target location for the Teddington direct river abstraction project, which proposes replacing up to 75 million litres of water a day with treated wastewater during drought conditions.
Thames Water project and public health concerns
Thames Water's plan aims to ensure London has enough drinking water during prolonged dry weather by taking huge volumes from the Thames above Teddington Weir and transferring them along a new pipeline to an existing underground tunnel. This water would join the Lee Valley reservoirs, ready to become drinking water, and would be replaced with "highly-treated" wastewater from Mogden Sewage Treatment Works via a new tunnel. SOLAR has been campaigning against the scheme since it was announced in 2023 over concerns for public and environmental health.
Ian McNuff raised concerns for the bathing spot if the scheme proceeds, as it would be very close to where the treated wastewater would be pumped into the river. He said: "Families were promised a safe place to swim and enjoy the river, not a public health gamble." A Thames Water spokesperson said: "We would like to reassure river users that our proposed Teddington direct river abstraction project would not deteriorate water quality and would be required to meet strict environmental and water quality standards set by the Environment Agency." The spokesperson added that the new treated water outfall would be located downstream of the proposed bathing water site, meaning recycled water would flow downstream over Teddington Weir into the tidal Thames.
SOLAR is running a petition demanding all new wastewater treatment infrastructure meet stricter standards as demanded in EU countries, effectively adding a fourth stage of treatment to remove micropollutants. The petition has attracted more than 42,850 signatures and needs to hit 100,000 by November 1 to be considered for a debate in Parliament.
