Experts investigate water desalination

LUBBOCK - Even in drought, more than two-thirds of the Earth's surface is covered by water.

But how much of it is safe to drink?

Potentially almost all of it, thanks to procedures that remove salt and other impurities.

Desalination is the removal of those foreign matters, and - as some suggest - a way to ensure Texas a virtually unlimited water supply. Sources could include any of the world's oceans, or water deep underground that is less pure than surface water.

"People are looking into producing some of these saltier waters and treating them for local use," said Ken Rainwater, a professor of civil and environmental engineering at Texas Tech University.

Few would claim that Texas' water supply is large enough to indefinitely meet the needs of its growing population. While concerns of a water shortage have led some political and environmental leaders to suggest restrictions on well use, other talk centers around new technology.

But could removing salt from ocean water really be that simple, leaving consumers with virtually unlimited drinking water?

Supporters say yes.

"It's a drought-proof supply of water - we have an endless supply from the Gulf of Mexico," said Sanjeev Kalaswad, a research scientist for Texas Water Development Board's Innovative Water Technologies.

Kalaswad said no Texas cities have yet begun to use salt-removed seawater to meet municipal needs - as other locales such as Tampa Bay, Fla., have - but research suggests some probably could.

"There is interest, and it is growing," he said.

J.O. Dawdy farms near Floydada and represents Protect Water Rights Coalition. He and other coalition members support exploring new water supply technologies as an alternative to limiting how much water landowners can use.

"Technology has given us a lot of advances, and I think it will continue to give us advantages to stretch our water supply," he said. "We would like to see seawater desalination maybe as an option for irrigation at some point."

The water development board had success with ocean desalination studies it funded in 2003 in Brownsville, Freeport and Corpus Christi, Kalaswad said. Those and other coastal cities could someday implement that technology into their water treatment plants if they choose to do so, he said.

"We found in all three places seawater desalination is feasible," he said. "The next step is for the entity to pursue what is best for them."

Texas cities have been known to contract with each other for water use. That means if Galveston or Corpus Christi were to adopt that form of water treatment, Lubbock or Amarillo could hypothetically purchase their desalinated seawater and build pipelines to bring it here.

"We would never be able to afford it because we'd have to pump it hundreds of miles uphill," Rainwater said.

Because of the outrageous scope of such a project, neither the water development board nor the Texas Commission on Environmental Quality has specific cost estimates. Determining one isn't easy either, with no

apples-to-apples comparison on pipeline projects.

"It really depends on how much water's being transported and how big the pipeline is," said Andrea Morrow, a TCEQ spokeswoman. "There's no real average because you would have to hire an engineer to develop a cost estimate based on the unique design of the system."

But as one example for pipeline costs, a $250 million proposal from the Canadian River Municipal Water Authority involves 70 miles of pipeline 6 feet in diameter.

If you multiply that $3.57 million per mile average by the 532 miles from Lubbock to Corpus Christi, you're looking at nearly $2 billion. That's a fairly conservative estimate because it doesn't count the extra costs for lift stations as elevation rises farther from the coast.

"The initial construction would be astronomical, but annual operating expenses to have to lift that much water 3,000 feet would be really expensive, too," said Kent Satterwhite, the authority's general manager.

Jason Coleman suggests saltwater alternatives closer to home.

The High Plains Underground Water Conservation District he manages is exploring options for desalination of what's known as brackish water. Generally, the deeper underground a water supply can be found, the less likely it is to meet drinking standards without treatment.

In rainier times, it would likely stay underground. As drought lingers, though, a brackish water treatment plant could make an appearance in the Lubbock area.

"What was considered kind of a far-out option 10 years ago could be a very real option soon," he said.

A 2008 study from the Llano Estacado Water Planning Region estimated $13.2 million for constructing a brackish-groundwater desalination project, including costs for four wells and a reverse-osmosis treatment plant.

Desalination occurs through two main methods - distillation and membrane technology.

The former involves boiling the impure water, then collecting and cooling the water vapor it produces back into a liquid state and discarding the impurities that remain.

Rainwater, the Tech professor, compared distillation to the natural water cycle of evaporated seawater returning to the Earth's surface as pure rainfall.

"Distillation is just replicating what happens naturally," he said.

In the other main way to desalinize, raw saltwater is pushed through membranes that contain microscopic holes through which water molecules can pass but salt is left behind. A common example is reverse osmosis, which uses pressure.

"With membrane technology, we're using it essentially like a strainer to get the salts on one side and the freshwater on the other," Rainwater said.

The city of Wolfforth is in the process of adopting electrodialysis reversal, a desalination method that uses electric currents to move salt ions. Now in the construction phase, a treatment center will be operational by late fall, said Michael Adams, vice president of the city's OJD Engineering.

The plant will use water from the Ogallala Aquifer, the area's main source.

Adams is enthusiastic about the procedure's recovery rate, meaning it's able to return as drinking water more than 90 percent of the raw groundwater it receives. In comparison, reverse osmosis salvages only about 75 percent, he said.

"In this part of the world, every drop of water is valuable," he said. "That's why EDR's higher recovery rates are important."