As climate change intensifies droughts and extreme weather events, countries across the world are struggling to secure enough clean water for drinking, farming and industry. In response, governments and utilities are increasingly turning to water reuse, desalination and wastewater treatment. But these solutions come with a growing challenge of their own: contaminated brine.
Brine is the highly concentrated wastewater left behind after desalination, sewage treatment and water-intensive industrial processes such as mining and energy production. Globally, brine generation has reached staggering levels. The latest estimates suggest that more than 25 billion gallons of brine are produced every day, a figure that has likely increased further with the rapid expansion of desalination plants worldwide.
Most coastal facilities release brine directly into the ocean, while inland cities rely on evaporation ponds, deep-well injection or blending it with other wastewater streams. Each of these methods carries environmental risks. Highly saline brine discharged into the sea can kill fish or disrupt marine ecosystems, a problem documented off the coast of Bahrain and other regions.
On land, evaporation ponds must be carefully lined to prevent groundwater contamination. When they dry out, the remaining salts can become airborne, contributing to air pollution. This phenomenon is already being observed around shrinking water bodies such as the Great Salt Lake in the United States. Deep-well injection, meanwhile, has been linked to increased seismic activity, including a sharp rise in earthquakes in parts of Oklahoma over the past decade.
Researchers are now rethinking brine not as waste, but as a potential resource. Emerging treatment technologies aim to recover clean water and valuable materials such as lithium, magnesium and sodium from brine streams. Traditional approaches that use heat and pressure to evaporate water are effective but expensive, energy-intensive and difficult to scale.
Alternative methods, including electrodialysis and membrane distillation, offer different advantages but face limitations related to energy use, membrane clogging and operational costs. These trade-offs have slowed large-scale adoption so far.
Newer, decentralised systems could change that equation. At the University of Arizona, researchers are testing a multi-step brine reclamation process designed to recover up to 90 per cent of the water from municipal brine. The system integrates filtration, reverse osmosis and electrochemical treatment to produce water suitable for drinking after final disinfection.
Early studies suggest that the process can also recover industrial chemicals at a fraction of their market cost, while sharply reducing the volume of brine that needs disposal. Pilot projects are now underway to assess whether the technology can be scaled up and used to treat other forms of contaminated brine.
With freshwater supplies under increasing strain, scientists argue that reclaiming water from brine could play a critical role in future water security strategies. If deployed responsibly, such technologies may help cities meet growing demand while reducing the environmental harm caused by conventional brine disposal.