Brine from Desalination Can Be Put to Use

Currently, the world produces more than 100 billion liters (about 27 billion gallons) a day of water from desalination, which leaves a similar volume of concentrated brine. Much of the brine is pumped back out to sea, and current regulations require costly outfall systems to ensure adequate dilution of the salts to prevent damage to marine ecosystems.

A new MIT study shows that through a fairly simple process the waste material can be converted into useful chemicals — including ones that can make the desalination process itself more efficient.

The approach can be used to produce sodium hydroxide, among other products. Otherwise known as caustic soda, sodium hydroxide can be used to pretreat seawater going into the desalination plant. This changes the acidity of the water, which helps to prevent fouling of the membranes used to filter out the salty water — a major cause of interruptions and failures in typical reverse osmosis desalination plants.

Another important chemical used by desalination plants and many other industrial processes is hydrochloric acid, which can also easily be made on site from the waste brine using established chemical processing methods. The chemical can be used for cleaning parts of the desalination plant, but is also widely used in chemical production and as a source of hydrogen.

Converting the brine can thus be both economically and ecologically beneficial, especially as desalination continues to grow rapidly around the world. Environmentally safe discharge of brine is manageable with current technology, but it’s much better to recover resources from the brine and reduce the amount of brine released.

Adapted from MIT News.