Climate change means some coastal groundwater may soon be too salty to drink. What can cities do?

Desalination is a solution for cities on the coast that are running out of freshwater sources—but the process can turn out to be more than cities bargained for.

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The front of brick building that says Cape May Water Works and 1926.

Cape May's desalination is inside an almost-century-old building, and is due for an upgrade. (Alan Yu/WHYY)

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Cape May, New Jersey has a long history as a resort town with seafood, ballrooms, and Victorian-era mansions, dating back to the 18th century. The idyllic, seaside town is surrounded by ocean on three sides.

But in the 1950s, the city started to have a problem with its water supply, which comes from groundwater. Saltwater was seeping into wells, making the water undrinkable. The city had to abandon its old wells and drill new ones, over and over again.

This kept them going until 1995.

The U.S. Geological Survey and New Jersey Department of Environmental Protection told then-mayor Ed Mahaney the water supply would only last another three years. Tens of thousands of people in Cape May and the surrounding area count on the water supply in Cape May. Mahaney said the future of Cape May was at stake.

“We wouldn’t have tourism; tourism is 70 percent of our economy.”

The only feasible solution was desalination, a process to take the salt out of salt water, which no town in New Jersey had done before. City officials applied for state and federal grants and built a plant for 5 million dollars.

Water and Sewer Superintendent Rob Cummiskey said the plant today is a “living testament that you can make good choices and still provide a high quality and … affordable source of water to people.”

The plant takes salty water from a well — 800 feet deep — into a historic waterworks building. A few powerful pumps push the water through white pipes with membranes to filter out the salt. The workers add either carbon dioxide or lime if the water is too acidic or alkaline by drinking water standards. And then, it’s ready to go to taps, or one of several water towers, depending on how much water people need at the time.

Several vertical white pipes surround a grey pump in the center of a room inside the Cape May Water Works building.
A pump pushes water through pipes and filters that removes salt, making the water good for humans to drink. (Alan Yu/WHYY)
This model shows a cut open cross section of a membrane, through which the desalination plant pumps water to remove the salt.
A model shows the cross section of the membranes that filter out salt from water. (Alan Yu/WHYY)

Plant operator Joe Mendo says 70 percent of the water that goes in comes out as fresh water. The other 30 percent is concentrated salt water that goes into a nearby creek, which, he said, is not harmful because it is far less salty than actual salt water. But they still do regular checks of what comes out.

When the city first built the plant, researchers tested local plants and animals to make sure the discharge would not harm anything living in the creek.

Now, the plant is due for an upgrade.

The near century-old building is not quite holding up to the strain of millions of gallons of water going through. Mendo said the moisture is attacking the pipes and electrical systems, and a new plant would have electrical components in an environmentally protected room.

“We’re looking to really step it up …[with] the next plant … that’ll be sustainable for … the next 50 plus years,” Mendo said.

Six Cape May Water and Sewer Department employees stand in front of pumps, pipes, and water filters at the Cape May Water Works building.
Photo courtesy of the Cape May Water and Sewer Department

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Shifting salt line

Salt in the drinking water supply is going to become more common in cities, especially on the coasts, said Allison Lassiter, assistant professor of city planning at the University of Pennsylvania.

“Most towns historically located in places that weren’t going to experience saline water, this is starting to change,” Lassiter said. “The salt line is shifting inland already.”

Picture the ocean shore, but underground, there’s a line where the freshwater and the seawater meet, called the salt line.

This salt line moves with the tides. But rising sea levels and an increase of people living by the shore tapping into freshwater underground can also pull more saltwater from the ocean toward the land.

She said places all around the U.S. and the world are now starting to study this problem. This is such a big problem in Jakarta, Indonesia, that it’s part of an ongoing conversation to relocate the entire capital.

‘No’ to desalination

Cape May solved its problem with desalination. Could the rest of the world follow suit?

Former Cape May mayor Ed Mahaney thinks there is a lot of potential.

“[In] 1995, desalination would have been the last alternative because of its lack of familiarity to the general public and to governing bodies, and also its expense. Today, I think it has a tremendous uptick.”

So does Joaquin Esquivel, chair of the Water Resources Control Board in California.

“Removing those salts … is a really important strategy that California has been utilizing and will have to utilize more to … make every drop count here in a state that’s increasingly obviously stressed by climate change and aridification.”

California is going through drought conditions. Aridification refers to the climate getting drier in the long term, not just in seasonal drought cycles.

California recently considered a desalination plant in Huntington Beach, southeast of Los Angeles. The plant would have provided 50 million gallons of fresh water from seawater. The governor weighed in to support the plant. But after a nine-hour-long meeting, the California Coastal Commission voted unanimously “no”.

So why would California turn down a drought-proof supply of water?

This gets to some of the problems with desalination.

The proposal for the plant in Huntington Beach is not quite the same as what Cape May did.

First, the Huntington Beach plant would use seawater, not groundwater that is a little too salty. There is a lot more salt to be filtered out, and the leftover water that has to be dumped is a lot saltier than seawater. It would also come out so fast that it would kill aquatic life, which the commissioners in California objected to.

Second, desalination of any kind is expensive. It takes a lot of power to run those big pumps to push water through the filters. A widely cited 2019 report from researchers at the University of California Los Angeles found that this Huntington Beach plant would make water much more expensive, which the commissioners could not accept. The power needed for desalination creates an additional problem if much of it comes from burning fossil fuels, which makes climate change worse.

Also, no local towns had agreed to buy this water. Lassiter, the researcher studying saltwater intrusion, said this could have been a problem later on. She pointed to the case of Brockton, Massachusetts, which pushed through in 2008 to build a desalination plant after a drought.

“After the contract was signed, they ran a conservation campaign, and people were able to reduce their water use so much that they didn’t actually need the desalination facility any longer and yet they were locked into an expensive contract afterwards,” she said. “Desalination is typically the most expensive option relative to all other options, so it’s best to exhaust all other types of options.”

The future of desalination  

One important alternative that Allison and various other researchers said cities should try first is wastewater recycling — make better use of the water that right now we flush down a drain. Southern California is already a leader in this type of technology.

This isn’t to say desalination is not part of the future.

Meagan Mauter, an associate professor of civil and environmental engineering at Stanford University, leads a research group that focuses on desalination. She points out two other smaller desalination plants in California did not face the kind of resistance the failed Huntington Beach plant did, so the vote against that plant is not a vote against desalination overall.

“What I expect to see are a combination of things: I think that we are going to use desalination technologies that were originally designed for seawater desalination to desalinate a whole host of nontraditional waters.”

One example of desalinating nontraditional water would be to treat groundwater that’s too salty, like what Cape May did.

The technology behind desalination could also improve. Mauter said the research now focuses on making plants smaller, pairing them with renewable energy, and figuring out better ways to get rid of the extra salty water that remains.

Joaquin Esquivel, chair of the Water Resources Control Board in California, said that with climate change, his state is facing an unprecedented challenge when it comes to water access.

At the same time, the potential for better technology makes him hopeful for the future. He recently attended the opening of a small desalination plant in Menifee, California, not far from Los Angeles.

“It’s exciting to see, because the needs … from the pressures of drought, climate change are driving the innovation that is going to fuel this next generation of projects in the state.”

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