For decades, rapid desertification and erratic rainfall had made guaranteeing water security nearly impossible in Israel. Sullied lakes and plummeting water tables led to one agricultural collapse after another and, having tapped most freshwater resources dry, people were growing desperate. The country had tinkered with desalination in its very early stages, but the technology had not been developed enough to support Israel’s substantial water needs. Then, in 1997, the first reverse osmosis desalination plant was installed. This groundbreaking technology motivated the government to approve the construction of large seawater desalination plants along the Mediterranean coast in 2002. Today, the country purifies so much water, it’s providing the excess to surrounding countries.
More than 7,000 miles west of Israel, areas within the United States are facing increasing pressure on their water systems as well: the 2014 California drought was said to be the worst the state had seen in 1,200 years and prompted emergency measures including expensive federal aid. Disaster interventions due to water shortages cost the United States billions of dollars, threaten the livelihoods of millions, and are likely to be exacerbated by climate change. So why hasn’t large scale desalination taken off in the States?
Desalination in the United States
While desalination in the United States is not as widespread as it is in the Middle East, technological breakthroughs have led to its recent expansion. More than 300 municipal-level seawater and brackish water desalination plants with the ability to produce at least 25,000 gallons of potable water per day exist in the United States, with countless projects in the pipeline.
Florida takes the lead for municipal desalination by volume, with 282 million gallons of potable water produced per day from both ocean and brackish water treatment, according to the South Florida Water Management District. Ranking second in the country is California: the state’s Department of Water Resources reported that 140,189 acre-feet per year—or 125 million gallons per day—were treated in 2013. The Claude “Bud” Lewis Carlsbad Desalination Plant, the largest in the United States, was completed in 2015 and can produce up to 50 million gallons of fresh water a day. Municipal desalination plants in Texas can produce about 142 million gallons per day, according to the Texas Water Board, all from brackish groundwater and surface water treatment (there are, as of yet, no municipal seawater desalination plants in Texas).
The Evolution of Desalination Technology
Desalination, or the process of removing salt and other minerals from water, had its first modern, large-scale applications in the late sixties through multi-stage flash distillation (also known as thermal desalination) and reverse osmosis (RO) technologies. Thermal desalination is perhaps the oldest form of desalination in the world: this method uses heat to evaporate water, leaving the salt behind, then re-condenses the clean water. Following the invention of the first synthetic reverse osmosis membrane in 1960, RO was used as a water filtration system: hydraulic pressure forces salt through a membrane, producing potable water. Reverse osmosis is the most widely used method for municipal desalination in the United States.
Both desalination methods require a lot of energy to pump and purify water, making energy costs one of the main barriers to the widespread adoption of desalination technology. Dramatically cheaper solar panels are poised to become a game changer in this respect, and are already helping to make desalination much more affordable. Indeed, places that lack rainwater tend to have sunlight in abundance. Today, many small-scale desalination facilities have adopted solar power and industry leaders are currently working on plans for municipal-scale solar-powered treatment plants, the first of which is planned for operation in Saudi Arabia by 2021. Desalination by solar evaporation array (SEA) panels is one of the latest developments in solar technology. SEA panels are self-contained water purification devices that can be set up in minutes and are cheaper than traditional desalination methods for small-scale applications.
Other forms of renewable energy also hold promise. In Australia, a wind-powered desalination plant has been providing the town of Perth with nearly 40 million gallons of drinking water every day for twelve years. This plant and others are connected via a grid to local wind farms, lowering overall energy costs while reducing carbon emissions.
Scientists have also started experimenting with algae as a desalination agent. According to the U.S. Environmental Protection Agency, certain species of salt-tolerant algae (called halophytic algae) can absorb significant amounts of salt from ocean and brackish water, and the spent algae can be used as a base for biofuels. Researchers are experimenting with new types of halophytic algae, and while complete desalination of ocean and brackish water cannot be achieved by algae absorption alone, they have found that a combination of algae treatment and reverse osmosis results in considerable energy savings.
Part of the reason why municipal desalination has never gained the same footing in the United States as it has in other countries is because of the high, energy-related costs associated with treatment techniques. However, the recent innovations discussed above show that increased energy-efficiency and a decreased dependence on fossil fuels in the desalination process is achievable.