Gas analysis specialist Servomex has used its oxygen analyser technology to help support an initiative to restore depleted oxygen levels in the Thames River, London.

Oxygen levels have been monitored by vessels - the Thames Bubbler and Vitality - equipped with the SERVOTOUGH Oxy 1800 (Oxy 1800). The 50m long vessels are capable of each injecting 30 tonnes of oxygen into the river every day and cost around £250,000 per year to run. 

Oxygen levels in the river are susceptible to depletion following periods of heavy rainfall, which cause storm overflows resulting in millions of tonnes of diluted sewage entering the river. 

Known as an acute oxygen ‘sag’, the polluting load can cause oxygen levels to fall to near zero. In 2004, the Thames received around 600,000 tonnes of untreated sewage and urban following torrential storms, causing the deaths of thousands of fish in a single day.

The Oxy 1800 helps monitor dissolved oxygen levels allowing the vessels to prioritise oxygen supplementation in the areas that need it most. Although oxygen content in water can fluctuate according to natural cycles, anthropogenic causes can severely impact the numbers of fish within the Tidal Thames, in addition to affecting predator-prey relationships. 

With anything less than 45% of dissolved oxygen potentially resulting in depleting fish numbers, parts of the river had been declared ‘biologically dead’ in 1957 by scientists at the Natural History Museum due to heightened levels of pollution within the estuary. 

A recent report by the Zoological Society of London (ZSL) has revealed that the boats and the oxygen technology have played a key role in returning the river to one now abundant in life. 

The tidal Thames is now home to various mammals and birds including the grey seal, harbour seal and the avocet and redshank. 

Considered an important spawning area for the European smelt, the river also contains over 120 species of fish. 

Commenting on the biodiversity of the river, Graeme Watson, Field Service engineer, Servomex, said, “From witnessing the biodiversity it is clear to see that the river is in great condition and the Environment Agency are doing a spectacular job of allowing that life to thrive.” 

“We are proud to be able to support this all-important ongoing project with our application.” 

Equipped with the ability to measure up to 100% oxygen in many industrial applications, the analyser is regarded as an indispensable part of rejuvenating aquatic life. 

“Being able to measure how much oxygen is in the river water quickly and accurately is essential to be able to position the oxygenation vessels in the correct position,” stated Neil Dunlop, Water Quality Technical Specialist, Environment Agency.