In many arid and dry regions of the world, such as the Middle East, Western Australia, and North Africa, desalination plants provide a large percentage of drinkable water for the areas they serve.
However, the process that takes place during desalination produces more than just drinkable water. It also produces brine (water with higher salt content), filtered back into the ocean.
Recent studies show that the amount of brine produced is much higher than originally thought. The figure is around 1.5 liters of brine for every 1 liter of water.
Many ecologists are concerned that pumping this amount of brine back into the ocean – particularly in regions like the Gulf, where the water is only 100 meters deep at most – could have very negative effects on the flora and fauna that dwell in those waters.
However, results haven’t proved all bad, as NUAE reports:
In the report, published in Science of the Total Environment, the authors point out that the higher density of briny water can reduce dissolved oxygen levels, affecting marine life.
Following the publication of the study, however, researchers have argued that while there is cause for concern, there is also evidence suggesting that the adaptability of organisms may have been under-estimated.
Instead of creating kill zones, the regions of saltier water around discharge outlets have been found to encourage life-forms.
One thing that all the scientists agree on is that the brine could be disposed of in a safer way.
Practically, though, this is harder to manage than it seems as if the brine is not put back into the ocean, it can make its way into the groundwater and affect the ecosystem all the same that way.
National Geographic reports on how alternatives to desalination should be sought for various reasons – not just the ever-fretted about brine.
Arguably best known is the copious amount of fossil fuels that are often used to power the plants, resulting in a significant amount of emissions. Most desalination plants work by reverse osmosis, meaning energy is needed to push water past a membrane at high pressure in order to separate the salt (learn more how it works). A typical plant takes an average of 10 to 13 kilowatt-hours of energy per every thousand gallons processed. That energy use adds to the cost of the process. A recent desalination plant in California cost a billion dollars, and now provides about ten percent of the drinking water of the county of San Diego. The cost, and environmental impacts, of this overall industry, have spurred researchers to look for alternatives, including developing more efficient separation membranes and desalination units that can be powered by solar energy.
The question ultimately is not really about desalination. The question is how to provide drinking water to a world population of close to 8 billion people when natural sources are subject to environmental change and human pollution?
Long-term planning for drinking water resources is a key component of water network future demand analysis.
PHOTO CREDIT: Inset photo of a reverse osmosis desalination plant in Barcelona, Spain by James Grellier – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11038652