From Yale Environment 360 (Jim Robbins):
After decades of slow progress, desalination is increasingly being used to provide drinking water around the globe. Costs for processing salt water for drinking water have dropped, but it remains an expensive option and one that creates environmental problems that must be addressed.
It’s been a long time coming for desalination — de-sal for short. For decades, we have been told it would one day turn oceans of salt water into fresh and quench the world’s thirst. But progress has been slow.
That is now changing, as desalination is coming into play in many places around the world. Several factors are converging to bring new plants on line. Population has boomed in many water-stressed places, including parts of China, India, South Africa and the United States, especially in Arizona and California. In addition, drought — some of it driven by a changing climate – is occurring in many regions that not that long ago thought their supplies were ample.
San Diego is one of those places. With just 12 inches of rain a year in the Mediterranean climate of Southern California and no groundwater, the region gets half of its water from the distant Colorado River. The amount of snow that falls in the Rocky Mountains and keeps that mighty river flowing, however, has greatly diminished over the last two decades and according to some researchers may be part of a permanent aridification of the West. Climate change is a very real phenomenon for water managers throughout the Southwest and elsewhere.
Meanwhile, the cost of desalinated water has been coming down as the technology evolves and the cost of other sources increases. In the last three decades, the cost of desalination has dropped by more than half.
A boom in de-sal, though, doesn’t mean that everywhere with access to the sea has found a new source of fresh water. Circumstances play a large role. “As populations increase and existing surface water supplies are being tapped out or groundwater is depleted or polluted, then the problems are acute and there are choices to be made” about de-sal, said Michael Kiparsky of the Wheeler Water Institute at the University of California, Berkeley School of Law. “There are places around the world where de-sal makes economic sense, where there is high pressure on the water resources plus a lot of available energy resources,” such as the Middle East.
De-sal proponents acknowledge the industry must confront and solve some serious environmental issues if it is to continue to grow. Desalination requires vast amounts of energy, which in some places is currently provided by fossil fuels. Kiparsky warns of a feedback loop where more de-sal is needed as the planet warms, which leads to more greenhouse gas emissions. In addition, there are serious concerns about the damage to marine life from the plant’s intake systems and extra-salty wastewater.