Some believe that desalination could be a savior for areas hit hard by drought or saltwater intrusion from climate change.

But the process of removing salt from seawater or brackish groundwater to make it drinkable is expensive, requiring large amounts of energy. Some environmentalists don't like the concept because it takes away from water conservation efforts.

Now, researchers at the Massachusetts Institute of Technology say they may have found a way to dramatically improve the efficiency of the most widely used desalination systems and their associated costs.

"The material we studied holds tremendous promise," said David Cohen-Tanugi, an energy fellow at MIT and a co-author of the study, appearing in Nano Letters.

Specifically, Cohen-Tanugi and MIT associate professor Jeffrey Grossman ran computer simulations on a material called graphene. They found that the material is 100 times more permeable than other types of membranes used to remove salt from water.

The material has been studied before, but not in a desalination context, the researchers said.

Some 60 percent of the world's roughly 15,000 desalination plants use a technology called reverse osmosis. In that process, water travels through a membrane that traps salt on one side of the filtering membrane. The system requires heavy pressure -- and resulting large amounts of electricity -- to make sure the water does not leak back through to the salt side of the membrane.

"It's a brute force method in a sense," said Cohen-Tanugi.

Ultra-thin material

To improve the efficiency of the process, the MIT team poked simulated holes in the graphene and then modeled how saltwater would pass through those holes, or nanopores.

The reason graphene was so much more permeable is that it is extremely thin, being the size of one atom. In comparison, a reverse osmosis membrane would be about 1,000 times thicker, said Cohen-Tanugi.

That means that with the same amount of pressure used in today's commercial desalination plants, much more water could move through the graphene holes, the researchers said. In essence, water wouldn't have to travel as far to have its salt taken out and wouldn't need as much of a push to stay on one side of a graphene membrane.

In theory, that pressure reduction could dramatically reduce the cost of desalinating water. The desalination of brackish groundwater can be double the cost of regular water treatment, according to some estimates. The treatment of seawater would be even more expensive, doubling the cost again.

Almost 50 percent of the cost of a traditional osmosis system derives from the fuel and electricity necessary to run pumps that generate pressure, said Cohen-Tanugi.

Graphene also is "pretty much the hardiest material known as far as flexibility and stress are concerned," meaning it holds great promise in being able to withstand pressure in real-world solutions, he said.

The key in moving graphene from a computer world to an actual desalination system is perfecting the process of poking holes one-billionth of a meter, said Cohen-Tanugi. The hole has just be the right size -- to make sure water passes through but not salt -- to be an operational idea.

Some promising ideas to create holes that small are to use lasers or chemical methods, but the "poking" process is not yet a commercialized concept, he said.

A boon for Texas and Fla.?

Climate change and extreme weather are bringing desalination into the limelight. With warming temperatures projected to increase drought and raise sea levels, it is an obvious possible solution for new drinking water supplies.

"This is getting a lot of attention from state lawmakers right now," said Amy Hardberger, a water specialist based in Texas for the Environmental Defense Fund.

Texas state Rep. Bill Callegari (R) of Houston, for example, wrote an editorial this spring titled "Desalination could help solve Texas water woes." The state has 325,851 gallons of brackish groundwater that could be desalinated, in addition to an ocean coastline with ample supplies.

Callegari said desalination plants are "risky endeavors" but may be one of the few options to address future water stress. Texas currently has a state water plan calling for 3.4 percent of the state's water to come from desalination by 2060, but Callegari called for new regulations to increase the numbers.

Similarly, officials in southeast Florida say they may have to turn to the technology eventually in water-stressed spots. There, rising sea levels driven by climate change could push salt water into existing drinking-water wells, making desalination a fallback option (ClimateWire, Jan. 10).

But the technology has critics. Last year, the Stockholm Environment Institute released a report on the Southwest's water supply that concluded that deslination is a limited option to address drought, partially because "it has controversial environmental impacts on the nearby ocean environment and it requires scarce oceanfront property."

Hardberger of the Environmental Defense Fund said she had no issues with existing research to reduce the cost of desalination. But she said Texas needs to focus much more on conserving water, considering that many cities in the state do not have extensive programs. There also needs to be greater consideration of the water pipeline network that would have to be constructed to carry desalinated water from salty areas to municipal centers.

"A lot of people are saying this is a silver bullet," she said. "It isn't."