|"We'll never know the worth of water till the well go dry."|
|18th Century Scottish Proverb|
|"The lesson we learned is that it's never too early to start planning for new water supply sources."|
Southwest Florida Water Management District
Coastal communities around the country are beginning to know the worth of drinking water as booming populations strain groundwater supplies, and droughts dry up reservoirs and rivers. With the abundance of ocean water lapping at their shores, many coastal communities long to drink from the sea. What has kept the ocean out of these communities' cups is the high cost of desalting seawater and the potential for environmental damage.
This is why the eyes of coastal resource managers around the country—and even the world—are on Tampa Bay, Florida, where a new $110 million plant promises to convert seawater into fresh drinking water, safely and at a reasonable cost. As a result, Tampa Bay is now the first region in the country to get a substantial portion of its drinking water from the sea.
It will take at least a year, experts say, to determine if the plant's lower cost and environmentally friendly promises are true. In the meantime, Tampa Bay water managers are already planning a second plant, and California and Texas, as well as Singapore and Australia, are examining the feasibility of constructing similar facilities.
While desalting seawater may appear to be the antidote for coastal area drinking water woes, Florida officials advise that communities look at a number of factors, including undertaking significant environmental analysis and monitoring, along with conservation efforts and tapping into other alternative supplies, before jumping on the desalination bandwagon.
Water, Water Everywhere
With one of the largest underground aquifers in the world, 50,000 miles of rivers and streams, 7,700 lakes, 3 million acres of wetlands, and about 600 springs, the abundance of Florida's water has always been taken for granted. But after decades of explosive growth and development, there is no longer enough pure groundwater to meet all the state's needs. Estimates are that by 2020 the state will suck up 9.3 billion gallons of water a day—30 percent more than is used today.
Tampa Bay is one of the fastest growing areas of the state. Over the past 50 years, the area has seen a fivefold population increase. The close to 2 million people who were using water from the area's underground aquifers to drink, bathe, and water their yards proved too much for the resources.
While the impacts of excessive groundwater usage are debated, in Tampa Bay it was most likely a contributing cause of hundreds of acres of wetlands drying up and falling lake levels. There were fears that saltwater from the sea would seep in and contaminate the groundwater, says Dick Eckenrod, executive director of the Tampa Bay Estuary Program.
Much of the damage began decades ago, before state rules prohibited impacts to wetlands within any of the region's 11 groundwater well sites, says John Emery, chief environmental scientist with Southwest Florida Water Management District, which issues renewable water use permits to the region's utility.
When the permits for the region's water wholesaler expired in 1992, the new rules brought the issue to a head. After a lengthy and difficult review process, the permit request went before an administrative judge in 1996. An agreement reached between the utility and water district called for a significant reduction in the amount of groundwater pumped over a number of years, and finding alternative water sources. Conservation rules also were implemented.
The Southwest Florida Water Management District was legislatively mandated to use $183 million in tax money to help pay for creating new water resources.
Looking to the Sea
The utility that would become Tampa Bay Water in 1998 explored a number of alternative water options to create its Master Water Plan, which addresses how to meet the future water needs of the region. "The goal," says Tampa Bay Water Spokesperson Michelle Robinson, "was to diversify the water mix."
"Reliance on one source for your public water supply is a very dangerous thing," advises Emery. "The lesson we learned is that it's never too early to start planning for new water supply sources... Don't wait until you see adverse impacts before you do something."
Two proposals that received a lot of attention were tapping into underground aquifers in other parts of the state, which Emery says was tossed because "we didn't want to perpetuate the problem by moving the impacts someplace else," and the reuse of treated wastewater.
While reusing the water that normally goes down the drain is cited by environmentalists as one of the best ways to address water shortages, Tampa Bay rejected it "because of the public concern over the toilet to tap concept," explains Eckenrod.
In the end, desalination "emerged as one of the most cost-effective sources," Eckenrod says. One of the primary benefits of desalination over other water projects is that seawater is plentiful even in drought.
When running at full capacity, which is expected to be in April, the Tampa Bay desalination plant will supply about 25 million gallons of water a day—about 10 percent of the region's freshwater needs, Robinson says. Water from other newly developed sources, which include river and canal water and a new reservoir, will account for about 25 percent of the region's needs. The rest will come from the permitted supply of groundwater.
One of the challenges with desalination plants, says Emery, is that "you just can't locate them anywhere. Ideally there needs to be a ready made water supply...and some type of energy source to go along with it."
To solve these problems, the Tampa Bay plant was sited next to Tampa Electric Company's Apollo Beach coal-fired power plant, explains Don Lindeman, professional engineer for Tampa Bay Water.
The power plant uses 1.4 billion gallons of water a day in its cooling system. The desalination plant then takes 44 million gallons of this water and uses high-pressure reverse osmosis membranes to remove salt and other minerals to produce freshwater. The clean water travels through 14-and-a-half miles of pipeline to a new regional facility where it is blended with treated surface and groundwater.
What remains is 19 million gallons of highly concentrated seawater, which is then blended back into the power plant's remaining cooling water before it is released into the bay. This 70 to 1 dilution rate, Lindeman says, decreases the salinity of the concentrate to about 0.5 percent above the original background salinity of the bay.
"This is a very economical and environmentally sound manner in which to return the seawater back to Tampa Bay," says Ken Herd, Tampa Bay Water engineering and projects manager.
Not everyone, however, agrees that this salty concentrate will do no harm to the bay, and indeed, this is the primary environmental concern with other desalination plants around the world.
A Tampa Bay citizens' group called Save Our Bays, Air, and Canals (SOBAC) mounted an unsuccessful court battle against the plant because its members believe the release of this concentrate will raise salt levels in Tampa Bay, and may harm marine plants and animals.
While this salty concentrate may be a hazard elsewhere, Tampa Bay Water officials say their solution of diluting it with the power plant's cooling water before it is released back into the bay takes care of the problem.
"This is a very important part of the process," says Tony Janicki, president of Janicki Environmental, Inc., and one of the scientists hired by Tampa Bay Water to study the potential impacts of desalination. "This is a very important reason why this project was doable."
He points out that numerous studies, both independent and those commissioned by Tampa Bay Water, found no reasonable risk that salinity in the bay would build over time from the desalination plant, or if all the proposed Master Water Plan projects were implemented simultaneously.
"I felt pretty comfortable after that review," Eckenrod says. "Some of the consultants who played key roles are some of the same ones we have relied upon over the years. I have a lot of confidence in these folks."
The Florida Department of Environmental Protection's (DEP) permitting process also was lengthy and extensive. Over an 18-month period, DEP reviewed scientific research and public comments regarding the desalination plant. Eventually more than 20 environmental and construction permits were required from local, state, and federal agencies.
"We put the applicant through their paces to make sure we were comfortable that it was not going to cause any environmental impacts," says Tim Parker, DEP water facilities administrator.
SOBAC, however, is still not convinced and complains that the desalination plant will prolong the life of an antiquated power plant that is not up to modern-day environmental standards. "That site was selected because they wanted to keep that dinosaur open," says SOBAC President Dominick Gebbia.
Monitoring the Situation
What SOBAC is happy about, says BJ Lower, technical director of the organization, is the extensive monitoring that is being conducted to ensure the predictions of limited environmental impacts are accurate.
Tampa Bay Water is conducting a $1 million a year monitoring program to determine the cumulative effects of its Master Water Plan projects. If impacts are detected, the utility will make immediate adjustments, including shutting down the desalination plant, Spokesperson Robinson says.
SOBAC and many others, including DEP and the Hillsborough County Environmental Protection Commission, have indicated that they will be closely monitoring the desalination plant's discharge.
Eckenrod notes, "We'll need at least a year of operation behind us—operating through a variety of seasons—before we can look at this and say it's reliable."
Time will not only tell the environmental impacts of Tampa Bay's desalination plant, but it will also determine if it's really producing the cheapest desalted seawater in the world. Until now, the cost of desalination has been many times more than that of conventional water sources. Most plants are built in parts of the world where there are no alternatives.
In the U.S., only two cities have invested in full-fledged seawater desalination plants—Key West, Florida, and Santa Barbara, California. Both cities idled operations soon after they began when they found less expensive alternatives.
In the past, the cost of desalinated water averaged $4 to $6 per 1,000 gallons. Despite a three month delay in getting the plant up to full operation, Robinson says that Tampa Bay Water is still on target to provide desalinated water at a 30 year average cost of $2.49 per 1,000 gallons of water—$1.88 per 1,000 gallons if you factor in the Southwest Florida Water Management District's contributions for constructing the facility. The average cost for groundwater in Tampa Bay was $1 for every 1,000 gallons.
There are a number of reasons the Tampa Bay plant, which will have an annual operating cost of about $10 million, is able to produce such cheap desalted water, says Don Lindeman.
One is that the cost of reverse osmosis technology has come down over time, he says. Using the same piping as the power plant also helps reduce costs required to process the bay's water. Another reason is that the bay's water is less salty than ocean water, making it easier to treat.
Watching and Waiting
It is now a matter of waiting to see if the Tampa Bay plant produces as predicted. "We feel like we have the eyes of the world upon us," says Ken Herd. While water officials are confident, there is also recognition that "models are just predictions."
"As a scientist myself, I have to accept the projections, but there is still lingering concern that we could see some changes in the conditions in the bay that the monitoring programs, as extensive as they are, would not be able to detect," Eckenrod admits.
"My take on this," he says, "is there are no options that are free of impacts. Conservation should always be the first option, but even with the best conservation efforts there will always be the demand for new water supplies.
"The challenge is to find the ones that produce the least impact that are consistent with the economic feasibility, and that's always going to be a judgment call. That's the difficult balancing act that public officials have to perform."
For more information on the Tampa Bay desalination plant, point your browser to www.tampabaywater.org. You may also contact Michelle Robinson at (727) 791-2304. For more information on the permitting process, contact John Emery at (813) 985-7481, ext. 2006, or Tim Parker at (813) 744-6100, ext. 407. For more information on SOBAC, go to www.sobac.org.