Desalination facilities alter oceans

February 2019: Desalination facilities extract fresh water from oceans and release effluents back into the sea. They produce 50% more brine than previously thought, increasing the ocean’s salinity and may cause hypoxia, which poisons marine organisms and creates dead zones. Researchers now suggest ‘mining’ the brine’s metals or using it as a feed supplement in aquaculture.

Information

Technology for industrial scale desalination of potable water has existed since the 1960s, produces 95mil cubic metres of freshwater per day, and is constantly expanding due to climate change induced global water shortages. Almost 16,000 desalination plants extract potable water from oceans and rivers. This process either uses vaporization or special membranes to remove dissolved minerals. This process results in fresh drinking water and extra-salty brine, which is generally released back into the ocean. Researchers estimate that desalination plants discharge approximately 142mil cubic meters of brine per day back into the oceans. More than half of this originates from facilities in Saudi Arabia, UAE, Kuwait, and Qatar. However, studies now show that facilities produce 50% more brine than previously thought.

Implications & Opportunities

Discharge from desalination facilities is extremely salty which makes it denser than seawater and it can also be extremely hot, oxygen-depleted in comparison to colder water, and contain metals or antifouling chemicals. Consequently, the effluent sinks to the bottom of the sea where it can poison benthic organisms – leading adverse ecological impacts throughout the food chain. This process leads to hypoxia, which creates “dead zones” in the oceans.  However, scientists believe that brine containing metals and salts such as uranium, strontium, sodium, and magnesium could potentially be ‘mined’. Other studies show that the effluent could be used as feed supplement in aquaculture, to cultivate the dietary supplement Spirulina or to water forage shrubs and crops in areas where the soil’s sodium content is low.

Limitations

While the problem of managing effluents from desalination plants is challenging, the technology often presents the only solution for countries to meet their growing population’s demand for fresh water. 90% of all plants are situated in wealthy countries that rely heavily on their facilities to ensure a steady supply of drinking water, water for agriculture, and water as coolant in industries The paper does not aim to address high water consumption patterns in these countries or the high-energy demand to run such facilities, but focuses on their environmental impact.  

Sources

Jones, E., Qadir, M., van Vliet, M. T. H., Smakhtin, V., & Kang, S. (2019). The state of desalination and brine production: A global outlook. Science of The Total Environment, 657, 1343–1356. doi:10.1016/j.scitotenv.2018.12.076 

BBC. (2019). Concerns over increase in toxic brine from desalination plants. Retrieved from https://www.bbc.co.uk/news/science-environment-46863146