The U.S. Is facing a water CRISIS: Could desalination be a solution?

by KATHERINE SYPHER | August 2, 2021

Editor’s note: This article is part of a collaboration between APM Research Lab and the Ten Across initiative, housed at Arizona State University.

The United States—like the rest of the world—has a water problem.

Water in the Colorado River is running low, Lake Mead recently reached record low levels, groundwater in Arizona and California is in jeopardy and the federal government is expected to declare a water shortage sometime this summer. An increased demand for water coupled with diminishing supplies leaves big questions: Where will our water come from? How will we ensure we have enough?

In the face of pressing water scarcity, some places in the U.S. in recent decades have looked to a specific type of technology to supply their drinking water: desalination.

Desalination—the process by which salty water is transformed into fresh water—can be a solution, especially in places where steady supplies of fresh water are scarce. This can be done by heating up salt water and collecting the pure water vapor, or by pumping salt water through a special membrane in a process called reverse osmosis.

Desalination has many uses. In addition to being a source of clean drinking water, the technology is also employed by industries that produce oil and gas and in power stations.

While more reliable than other water sources, desalination does have its drawbacks. The facilities needed to complete the process on a large scale can be expensive to build and operate and use a lot of energy. Plus, these plants can generate waste that can be difficult to dispose of and harmful to the environment.

There are nearly 17,000 operational desalination facilities worldwide, many of the largest of which are located overseas. Countries where water is scarce like Saudi Arabia, the United Arab Emirates and Israel employ desalination technology on large scales to generate reliable fresh water.

In the U.S., over 400 municipal desalination plants have been opened since 1971 and an estimated 200 or more are currently in operation, though the precise number is not known for certain. Most are in California, Florida and Texas.

Seawater Desalination

Sea water is abundant on Earth—the oceans, unlike other water sources, are always full. To be useful as a water source, it first must be transformed into fresh water.

Typically, of the water extracted from the ocean, only about half is converted to fresh water in the desalination process. This means that for every two gallons of sea water extracted, only one gallon of fresh water is created. Left over is a byproduct called brine, a concentrated salty mixture that needs to be disposed of. 

The biggest seawater desalter in the western hemisphere is the Claude “Bud” Lewis Carlsbad Desalination Plant in San Diego County, California. Completed in 2015, the plant can produce up to 60 million gallons of desalted water in one day. In a region plagued with heat and drought, it’s the only water supply in the county that is not dependent on snow or rainfall.

In 2016, California passed an amendment in support of using ocean water to supplement its traditional water supplies like river and groundwater. Called the “Desalination Amendment,” the move provided a consistent method for permitting desalination plants statewide, prioritized protecting marine life, and required tighter regulations for how water is taken from the ocean and the brine is put back in.

Not everyone is convinced that desalinating ocean water is a smart investment. Critics of California’s efforts say that expanding the state’s use of the technology will only make it more challenging and expensive to reach the state’s climate goals. In a 2016 issue brief from the National Resources Defense Council, the authors recommended that the state “proceed with caution.”

“Given the significant energy, climate, and financial costs of desalination, California should prioritize water conservation, water use efficiency, stormwater capture, wastewater recycling, and renewably-powered groundwater desalination,” they wrote. Only after these cheaper, lower impact alternatives have been pursued, the authors said, should seawater desalination be considered.

One of the major downsides of desalination is its price tag. Though the cost of running a desalination facility has dropped over time, the cost is still high, especially when compared to other water sources. The Carlsbad plant cost nearly $1 billion to build, and the water it generates is more expensive than water imported from other sources, costing between $2,125 to $2,368 per acre foot in 2017 (an acre foot is the amount of water needed to cover an acre one foot deep).

Removing salt from sea water also requires a lot of energy—more than any other source of water—which contributes to its cost. According to the authors of the 2016 National Resources Defense Council issue brief, seawater desalination in California requires about twice the amount of energy required by water imported from the Colorado River, and about 50% more energy than desalinated brackish (less salty) water and water imported from the California State Water Project require.

An additional cost of seawater desalination is environmental. After the fresh water is removed from the sea water, concentrated brine is left over and deposited back into the ocean. The extra salty mixture doesn’t mix well with the ocean water, so it can sink to the sea floor, lower oxygen levels and harm sea organisms if not managed properly. Not only is the brine salty, but it can also contain some of the chemicals used in the water treatment process.

The potential for negative environmental impacts has led some to oppose construction of the plants in the U.S. After plans for the Carlsbad plant were approved in 2006, the builders faced at least 14 legal challenges from environmental groups opposed to the project.

Despite the drawbacks, enthusiasm for seawater desalination hasn’t completely waned. As of 2019, California has 12 seawater desalination plants, including the one in Carlsbad, and has proposals to build six more.

One of the newly proposed projects is in Huntington Beach. Once complete, the plant will produce 50 million gallons of fresh water a day, becoming one of the largest facilities in the country.

Brackish Water Desalination

Desalination doesn’t just refer to de-salting sea water—it can also be used to transform water that’s not as salty as the ocean, but still too salty to drink, into fresh water.

Known as “brackish water,” this water contains less salt in parts per million (or ppm) compared to sea water, which contains about 35,000 ppm of salt. Fresh water has less than 1,000 ppm of salt, and brackish water falls somewhere in between the two.

Brackish water appears in sources on the surface, like lakes and rivers, as well as in underground aquifers. According to research studies done in 2010, over 95% of the desalination facilities in the U.S. are located inland, away from the ocean, and most are designed to treat brackish groundwater.

In Texas, 27 of the state’s 31 aquifers contain brackish groundwater. The state is also home to the largest inland desalination plant in the country. Located in El Paso, far from any ocean, the Kay Bailey Hutchison Desalination Plant transforms previously unusable groundwater into fresh water, and it’s capable of making up to 27.5 million gallons of fresh water a day. To meet the growing demand for water, the plant plans to expand so it can produce up to 42 million gallons in a day.

Brackish water desalination poses a different set of challenges compared to seawater desalination. While there are fewer dissolved particles to remove from brackish water, it can be harder to dispose of the leftover waste. And though less energy is required to pump the brackish water through filters than sea water, more energy is sometimes required to pump it from its source.

Is desalination a viable water solution in the U.S.?

In the face of water scarcity and the aridification of the U.S. the question remains: Is desalination a viable water solution?

“Desalination is not a panacea,” Michael Kiparsky, director of the Wheeler Water Institute at the University of California Berkeley, told WIRED in an interview. The process is energy-intensive, he told the publication, speaking specifically about seawater desalination, and it will never be cheap.

But researchers are tackling these challenges and more now, making reverse osmosis membranes more efficient, turning the salty brine byproduct into useful chemicals and figuring out how to reliably power desalination facilities with renewable energy.

States like California, Texas and Florida continue to invest in desalination technology. In Texas, regional groups in charge of water planning recommend desalination to meet at least part of their future water needs. If implemented, desalination in Texas could produce an extra 230,000 acre feet of water per year by 2070. And in coastal states, desalination could be used to help counteract the effects of seawater intrusion into fresh water.

In California, those in favor of desalination say the facilities act as a kind of insurance policy.

“The whole purpose of the desal plant is to diversify the water supply portfolio to reduce the need to import water from Northern California into Southern California,” said Scott Maloni, vice president of project development at Poseidon Water, speaking to Yes! Magazine about the proposed Huntington Beach project. Poseidon Water has built several large desalination facilities around the world, including the one in Carlsbad.

While there is a consensus that diverse water supplies are needed, environmental advocates argue that desalination is not as good an option as increasing water conservation, efficiency and recycling through efforts like capturing stormwater.  

“Desal should be the option of last resort,” Newsha Ajami told Yes! Magazine in an interview. Ajami works with Stanford University’s Water in the West program, where she is the director of urban water policy. “There are so many other inefficiencies in the system that can be fixed to potentially harness more water.”

Even so, the tides appear to be moving such that desalination will be part of the country’s water future. In 2018, the U.S. Department of Energy launched the Water Security Grand Challenge, an initiative designed to foster and fund innovation and new technologies to meet the global demand for water. Its first stated goal: To develop desalination technologies that generate clean water at more competitive prices by 2030.

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