Spaceship-like machines used to prevent algae

Floating machines which are designed to improve water quality are being tested in Essex and Norfolk in what is a first for the UK.

The yellow devices, which resemble science fiction spaceships, have been used since April at Hanningfield Reservoir in Essex and at Ormesby Broad near Hemsby in Norfolk.

Essex and Suffolk Water, which runs the site near Chelmsford, said they were used in more than 20 countries but it was the first time they had been trialled in the UK for drinking-water reservoirs.

The solar-powered devices are engineered to reduce the growth of algae.

Chris Fulton, the company's head of water supply, said: "We know we won't be able to completely prevent algae, but algae blooms happen when the weather is warm and calm, so it has become something we need to manage going forward."

The machines - called an Equilibrium Modulating Fluids Device - are designed to emit a very low-power signal (less than one watt) that changes how the water behaves at the surface.

This can double the rate of gas transfer between the air and water, helping to moderate the pH. It creates conditions that favour the production of algae-eating zooplankton.

The trial is due to end in the autumn.

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