Seawater desalination: Weighing the positives and negatives
Charlotte Sun
June 17, 2008
By NEIL HUGHES
Staff Writer
The way Ron Parker sees it, every coastal community in Florida needs to consider seawater desalination.
As senior operations manager of the Tampa Bay Seawater Desalination Plant, the largest of its kind in the United States, few aside from Parker would better know the costs and benefits of such a system.
“If you’re along the coastline, you have to evaluate seawater desalination,” Parker said at his office adjacent to the plant located in Gibsonton. “It’s really the only drought-proof supply that we have in this area.”
Seawater desalination can provide a seemingly endless supply of drinking water, and sea levels aren’t dependent on rain flows. In that sense, it’s a perfect fit for the region, which has seen numerous 100-year droughts in the last decade.
But it’s also a costly option that requires a significant investment in fledgling technology that is regularly improving and becoming less expensive. Which begs the question: When, if ever, is the right time to buy into desalination?
Weighing the costs
Though it’s now fully operational and successful, the Tampa Bay Seawater Desalination Plant went through years of trial and error that drew a great deal of criticism.
Most of that concern centered around the $158 million price tag.
Initially their plant cost $110 million, but periodic changes over the years to make the project work tacked on another $48 million to the bill. To keep the system from breaking down, officials added additional water purification steps in the form of pre-treatment, particle settlement and sand filters.
The bad publicity was so ubiquitous that Ron Parker, senior operations manager, said the plant’s successes haven’t gained a lot of attention.
“We’ve had a lot of problems,” he said. “There are a lot of folks who probably don’t even realize it’s running right now.”
In addition to the total $158 million cost, the Tampa Bay Seawater Desalination Plant carries a heavy operating bill.
How expensive? Try a daily electric bill of more than $300,000 to provide only 25 million gallons per day — less than onetenth of the total water provided to the Tampa Bay area.
And the facility also produces 10 to 12 tons per day of waste, or junk pulled from the seawater, such as salt, iron and other nondrinkable particles.
“Where would you site one for intake and then disposal of the brine? Those become big questions down here,” said Pat Lehman, executive director of the Peace River/Manasota Regional Water Supply Authority, of which Sarasota, DeSoto, Charlotte and Manatee counties are members.
All of the costs and troubles are reason enough for Sarasota County Commissioner Shannon Staub, chair of the water authority, to be hesitant to commit to seawater desalination.
“The technology has not been perfected,” Staub said. “It gets better each year, but certainly with the issue that Tampa Bay Water faced, they are just now getting their desal plant working appropriately.”
The plants, for now, are best when co-located with a power plant, which can provide warm water that tends to cause fewer breakdowns in desalination plants.
Lehman noted yet another complication. He said the Southwest Florida Water Management District has looked at potential locations for a seawater desalination plant in Venice and Manatee.
Highlighting the benefits
But in the end, Tampa Bay Water’s desalination plant has become a success. For the first time this year, it has met its maximum daily capacity of 25 million gallons per day consistently.
And the technology associated with removing salt from water to make it drinkable improves every day, perhaps someday leading to an inevitable series of plants in all of coastal Florida.
As droughts in Florida linger and seem to break new records every year, where better to look for an alternative than the most abundant resource on Earth?
“It’s by all means a reliable source no matter what the weather is,” said Lehman.
The core technology behind seawater desalination plants, known as reverse osmosis, is already employed by the water authority to make brackish water drinkable. The main difference between a regular reverse-osmosis plant for brackish water and a desalination plant for seawater is energy use.
In the Tampa Bay area, the plant’s 25 million gallons per day are a welcome relief during the high-use summer. Conveniently, the plant just recently reached full capacity to serve the region.
“It’s really good timing for us,” said Parker, senior operations manager. “We’re in the higher demand period.”
And as demand continues to rise in Southwest Florida, some, like Charlotte County Commissioner Adam Cummings, think seawater desalination should be included in serious discussions.
“Desal should be given much more consideration,” he said. “It should be given the kind of consideration it had been given by the water alliance in the past.”
Risks and rewards to review
For those looking more seriously at desalination, such as Lee County Utilities and the South Florida Water Management District, Tampa Bay Water’s seawater desalination plant has become a good example for both what to do and what mistakes to avoid.
With knowledge in hand, the South Florida Water Management District, which serves Lee County, hopes to see the ball rolling on a desalination plant soon after the year 2020.
“We’re excited about it,” district spokesperson Susan Sanders said.
As water wars in the past in Tampa and in the present in Georgia have shown, relying solely on Mother Nature to provide nourishment for everyone is a definite risk.
Seawater desalination, as Tampa Bay Water’s Parker pointed out, addresses that risk. But as with all solutions, it carries pros and cons.
“That water is always going to be there,” Parker said, “but it will cost a little bit more.”