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.
The Claude "Bud" Lewis Carlsbad Desalination Plant, the largest in the United States
(Credit: San Diego County Water Authority)
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.
Reverse osmosis desalination process
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.
Energy costs aside, one of the biggest concerns regarding desalination in the United States is brine waste. After ocean and brackish waters are stripped of salt and minerals to produce freshwater, the resulting byproduct contains very high salinity levels. This leftover brine is either poured into surface waters, pumped back out to sea, or occasionally stored in wells and holding tanks. When brine is poured back into a source without proper mixing, the concentrate could potentially contaminate the surrounding habitat and poison aquatic organisms.
While research on the environmental impacts of desalination is still limited, states such as California are implementing standardized brine disposal regulations which include proper mixing techniques and pipe requirements to minimize marine life disturbance. Scientists are also working on ways to transform brine salt into marketable baking soda and calcium chloride products, which have numerous industry applications.
Expanding Water Security
Earlier this year, Cape Town, South Africa, narrowly escaped a menacing ‘Day Zero’ – the day the city risked running out of water after a devastating three-year water crisis (see "Cape Town’s Water Crisis: How Did It Happen?"). Cape Town is currently building up its water management system with water recycling measures and ocean water desalination. Although a crisis was averted, climate scientists are now predicting extreme drought conditions in similar areas throughout the world in as little as 12 years. Unprepared cities might soon find themselves facing their own ‘Day Zero’ situations.
Stateside, Californians are growing especially concerned about the threat of worsening droughts as water tables begin to, once again, dip below average. The state government recently granted more than $30 million toward eight new desalination projects along the California coast and, although residents remain wary of the technology, state officials are pouring all of their efforts into strengthening water security. Tom Missimer, a geology professor and longtime desalination consultant, has stated, “Under global climate-change scenarios, you’re going to have more extreme droughts . . . if you look at your current situation, if it doesn’t rain very soon you’ve got one whale of a problem. Do you really want to take the chance of having to evacuate Southern California if it doesn’t rain?”
According to the International Desalination Association, more than 300 million people throughout the world get at least some of their freshwater from desalination plants. Continued funding into desalination research will lead to greater efficiency gains within the industry, and attention to safe waste disposal should become a priority for water management agencies. But desalination is not a silver bullet. In order for the United States to remain resilient in the face of climate change, the first measures that citizens and governments should take to build up water security is to reduce overall water consumption and reuse wastewater whenever possible.
Author: Meryl McBroom
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