Thanks to Jim Robbins at Yale e360:
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.
Some 30 miles north of San Diego, along the Pacific Coast, sits the Claude “Bud” Lewis Carlsbad Desalination Plant, the largest effort to turn salt water into fresh water in North America.
Each day 100 million gallons of seawater are pushed through semi-permeable membranes to create 50 million gallons of water that is piped to municipal users. Carlsbad, which became fully operational in 2015, creates about 10 percent of the fresh water the 3.1 million people in the region use, at about twice the cost of the other main source of water.
Expensive, yes, but vital for the fact that it is local and reliable. “Drought is a recurring condition here in California,” said Jeremy Crutchfield, water resources manager at the San Diego County Water Authority. “We just came out of a five-year drought in 2017. The plant has reduced our reliance on imported supplies, which is challenging at times here in California. So it’s a component for reliability.”
A second plant, similar to Carlsbad, is being built in Huntington, California with the same 50-million-gallon-a-day capability. Currently there are 11 desalination plants in California, and 10 more are proposed.
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…
Read the whole story here.