Research Uncovers Desalted Water's Fingerprint

A new study by Avner Vengosh, associate professor of earth and ocean sciences at Duke University's Nicholas School of the Environment, and colleagues in France and Israel provides tools to identify and trace manmade water as it mixes with natural water supplies and, over time, replaces natural waters in areas entirely dependent on desalination.

Manmade water is created by removing salt from seawater and brackish groundwater through reverse osmosis desalination.

"Water that's been desalted through reverse osmosis contains a unique composition which will induce changes in the chemistry and ecology of aquifers and natural water systems it enters," says Vengosh.

The study, published in June in the peer-reviewed journal Environmental Science & Technology, details for the first time the isotope geochemistry – or chemical fingerprints – of the elements boron, lithium, strontium, oxygen, and hydrogen found in reverse osmosis-desalted seawater and brackish groundwater.

Identifying these unique geochemical and isotopic fingerprints gives scientists and water quality managers a new array of tools for tracing the presence and distribution of manmade fresh water in a region's soils, surface waters, and groundwater, Vengosh says.

Being able to trace water back to a desalinated source through its isotopic and geochemical fingerprints will allow local governments and water utilities to zero in on the problem of valuable water loss and correct it more quickly and efficiently. Moreover, because desalted wastewater can be recycled through the environment and reused as a drinking water source – a process already being used in southern California – the new tools would enable water authorities to trace the relative contribution of desalted water in their system and to test the effectiveness of their water treatment processes.

Vengosh co-authored the new study with Wolfram Kloppmann, Catherine Guerrot, and Romain Millot of the Bureau de Recherches Geologiques et Minieres of France, and Irena Pankratov of the National Water Commission of Israel.

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