In the arid Middle East, it's been a godsend.

In regions of the United States facing drought, it's the great untapped resource.

But can turning saltwater into drinking water, known as desalination, solve Georgia's water crisis?

Maybe. But it's expensive. It's environmentally unfriendly, unless handled just right. And it presents technical challenges that can't be easily dismissed.

Right now, the state water plan includes desalination as a possible long-term strategy to boost water supplies. Aris Georgakakos, director of the Georgia Water Resources Institute at Georgia Tech and technical adviser to state agencies, said desalination could be viable for coastal Georgia and "take some pressure off Atlanta."

But despite rapid improvements in the technology, desalination remains a costly and challenging option for producing large quantities of fresh water.

For one, it uses more energy than conventional water treatment. That's a major reason it's more expensive and environmentally costly. It also produces a salty sludge that can harm sea life if not disposed of properly.

Two years ago, desalination proponents lobbied the General Assembly to fund a pilot desalination plant on the Georgia coast. Legislators opted for a study committee instead.

A Jonesboro company called Aquasis, ballyhooing desalination's potential, began pursuing a pilot desalination project on the Turtle River near Brunswick, hoping to attract private financing. But the project was recently shelved, said Stuart Jeffcoat with CH2M Hill, the firm involved in the project.

"The technology was there," Jeffcoat said. "But funding became an issue."

In Georgia, the state's seemingly abundant saltwater supplies and coastal hydrology actually make desalination more difficult. The technology is extremely sensitive to sediment, and relatively small amounts of particles can foul the expensive membranes that filter the salt out of the water.

Thanks to continuous deposits from half a dozen major rivers, sediment concentrations in coastal Georgia are 10 times higher than in Florida, said Clark Alexander Jr., a geologist at the Skidaway Institute of Oceano-graphy in Savannah.

"The water doesn't look cloudy, but it is," he said.

The Georgia rivers feeding into the Atlantic Ocean contain brackish water, less expensive to treat than seawater, but also heavily concentrated with sediment.

Twice-daily tidal flows scour the coastal estuaries, kicking up tons of mud and pushing the sediment far upstream. "Think of it as a big blender," said Alexander. Filtering the source water can remove particles and ready it for desalination, but heavy filtering drives up the cost.

Can't do it everywhere

Desalination has been a hard sell in the United States because surface and ground water is generally widely available.

In Georgia, for example, treatment costs run an average of $1.33 per 1,000 gallons for surface water and as little as 50 cents per 1,000 gallons for groundwater, according to Dr. Carol Couch, director of the Georgia Environmental Protection Division. Compare that with $3 per 1,000 gallons for desalination —- under ideal conditions. The Tampa area just opened the nation's largest desalination plant; production costs there have averaged $3.38 per 1,000 gallons.

"Desalination is very site-specific," said John Young, chief operating officer of American Water, the plant's operator. "It may be cost-effective in some communities and not in others."

Young believes, however, that treatment costs for desalination, fresh water and recycled sewage water will converge during the next five years, making desalination competitive.

Sludge special problem

Unlike treating fresh water, the cost of desalination is heavily reliant on the cost of electricity. Energy costs make up as much as 50 percent of the cost to desalinate, and the power needed for purification goes up with the salt content of the source water.

Desalination costs less when the source water is brackish groundwater, which is generally less salty and less turbid than seawater.

Most desalination plants in the United States aren't tapping the ocean; they are pulling salty water from below the ground.

Engineers have developed other tricks to drive down the cost. Among the most promising is locating desalination plants next to power plants. That gives the desalination plant both a ready supply of power —- and water. (See accompanying article, above.)

The power plant also helps with the disposal of the briny sludge extracted from the seawater. The sludge is remixed with the cooling water, diluting the salinity, before returning to the bay.

In Georgia, the handling of saline sludge would be especially problematic because of the delicate ecology of coastal estuaries. Elevating salt levels could affect shrimp and fish, and the livelihoods of those who fish them, according to experts.

"The biggest problem that I would worry about is the brine," said Alexander. "Right now, we are worried about having sustainable flows to keep the ecosystems happy. If you start increasing the salinity, you are changing the environment."

Piping expensive

Even if the technical and environmental issues could be resolved, it's unclear how desalinated water in coastal Georgia would help thirsty residents of metro Atlanta.

The most obvious answer would be to pipe the water here. But that also would be the most costly.

Georgia's coast is at sea level. Atlanta is 1,000 feet higher —- and 250 miles away. Desalinated water would have to be pumped uphill, driving up the cost.

"If you look at the West Coast, they take water out of Yosemite and pump it to San Francisco," said Jim Kundell, professor emeritus at the University of Georgia. "But the difference is that's downhill. It's a lot cheaper when you have gravity working for you."

Water quality also degrades over time and distance, meaning that water treated in Savannah or Brunswick might have to be treated again in Atlanta.

"That's real expensive water," said Kundell.