Seawater could help solve Florida water woes
U.S. Water News Online
TAMPA, Fla. – Small plastic bottles with labels proclaiming “a taste of Florida’s future” contain drinking water pumped from the sea.
Filtered and treated at a desalination plant that supplements supplies in the Florida Keys, the bottled water is a crystal-clear marketing gimmick to show that taking the salt out of seawater offers a drought-proof solution to the state’s water woes.
But a few hundred miles from the Keys, Tampa’s troubled desalination plant — built to become the largest of its kind in North America but still struggling to run at full capacity — stands as a monument to how costly and uncertain the investment can be.
During a drought that has led to the toughest water restrictions in South Florida history, water managers have renewed their call to explore using the sea to help meet water needs.
Fort Lauderdale is among the sites where the South Florida Water Management District proposes a pilot program to test tapping into ocean water.
“We are sucking Florida dry right now,” said Arlyn Higley, director of operations for the Florida Keys Aqueduct Authority. “Desalination is the way of the future.”
Desalination is not a new practice — the Keys have relied on it for more than a century.
The first desalination plant in the United States was built in the 1840s in Key West to serve troops at Fort Zachary Taylor.
Today, a desalination plant on nearby Stock Island, which produces the bottled water, and another on Marathon, serve as a backup water supply for the southern Keys in case hurricanes or other emergencies damage the freshwater pipeline from Florida City. Those plants, can produce about 3 million gallons of water a day, compared with the 17 million gallons a day the Keys can pump from freshwater wells.
The earliest desalination involved heating saltwater, collecting the steam, and then condensing the steam for drinking water.
Today’s plants pump water at high pressure through membranes with hair-thin fibers that filter out the salt, producing fresh water that can be used for drinking water.
Fishing boats and barges plow through the water in Safe Harbor Channel beside Stock Island, the same water the Florida Keys Aqueduct Authority taps to supply its desalination plant.
The plant, on a finger of land jutting into the Atlantic Ocean, was rebuilt in 1998 at a cost of $8.3 million. It houses 440 membrane-packed cylinders that filter seawater, pumped through at 1,000 pounds per second by high-powered diesel engines.
Thirty percent of the seawater emerges from the process as usable freshwater, while the salty leftovers get pumped into a 210-foot-deep disposal well.
It costs about $5 per 1,000 gallons to produce the desalinated water, compared with less than $1 per 1,000 gallons to tap into conventional sources, Higley said.
“The energy cost is much more expensive than just pumping it out of the ground,” Higley said. “That’s why we don’t run this plant any more than we absolutely have to.”
The New Water Supply Coalition — made up of water management agencies, including in South Florida and the Keys — is lobbying Congress for legislation to help finance the construction of desalination plants, to follow the lead of countries such as Israel, Australia and Saudi Arabia, which already convert seawater to drinking water.
“We in the United States are behind the curve,” coalition director Hal Furman said. “When you have high growth rates … coupled with droughts, it is natural that you are going to have to look for alternative water supplies.”
The South Florida district in 2001 teamed with Florida Power & Light Co. to explore building desalination plants beside electric power plants, with the hopes of limiting energy costs and using seawater already pumped in to cool the power plants.
A list of 23 possible sites stretching from Fort Pierce to Miami ultimately was trimmed to three & beside FPL’s Lauderdale and Port Everglades power plants, as well as one in Fort Myers.
Eye-popping construction estimates — $276 million for Port Everglades, $148 million for Lauderdale and $91 million for Fort Myers — have kept the plants from being built.
In Fort Lauderdale, the proposals compete with less expensive alternatives such as tapping into the Floridan aquifer, a deeper, more plentiful supply than the more commonly used Biscayne aquifer, and using water from a Palm Beach County reservoir.
The city contends the district should conduct a pilot program at the proposed sites to get a better handle on the costs and how that system would fit with the city’s current water facilities, city spokesman Chaz Adams said.
“It could potentially have regional benefits,” Adams said.
Tampa’s problems with desalination leaves communities leery, said Ken Herd, director of operations and facilities for Tampa Bay Water, which owns the plant.
Tampa opened a plant in 2003 that was supposed to produce 25 million gallons of water a day, but it has been plagued with operational problems.
Pre-treatment of the water drawn from Tampa Bay failed to filter out sediment, algae and other small particles that damaged the salt-filtering membranes.
Switching contractors and fixing deficiencies cost $48 million and pushed the total plant price to $158 million.
The plant now produces about 18 million gallons a day that gets mixed into the drinking water supply. Tampa Bay Water hopes to have the plant at full capacity by the end of the year, Herd said.
“It has huge political risks,” Herd said about policymakers pursing expensive desalinization alternatives.
Along with the cost, desalination plants face environmental concerns. Getting rid of the briny leftovers could threaten fisheries and coral reefs.
Environmental activists are fighting a similar waste product disposal problem for a new Lake Worth water plant that would tap into the Floridan aquifer and dump wastewater a mile off the coast.
“Any waste we produce, we have to be careful where we put it,” said Ed Tichenor, director of Palm Beach County Reef Rescue.
No desalination plants are on the drawing board for South Florida through 2025, said Mark Elsner, water district director for alternative water supplies.
That could change, he said, as South Florida’s population pressures start to outweigh desalinization cost concerns.
In the 1960s, Higley said periodic water “outages” helped persuade the Keys to invest in desalination.
“People don’t like to pay a lot of money for something they think is readily available,” Higley said. “People are going to have to pay a lot more for water.”
Article pulled from: uswaternews.com (2007)
