As plans for Coquina Coast desal plant go forward, lessons come from Tampa Bay

An interview with Tampa Bay Water Operations Manager Chuck Carden

By Pat Hatfield
BEACON STAFF WRITER

posted Mar 4, 2010 - 5:23:24pm

The most ambitious desalination project in the U.S. is in the works on the Flagler County coastline.

The plant, called Coquina Coast, is part of a push to find alternative water sources, to protect the aquifer where this area of the state now gets most of its water.

If it is eventually built, Coquina Coast won't be Florida's first desalination plant.

The largest sea-water reverse-osmosis plant in the country is at Tampa Bay, next to the Big Bend power station on the south shore at Apollo Beach, 18 miles south of Tampa. It's owned by Tampa Bay Water, a public utility.

The Tampa plant produces 25 millions of gallon of water per day (mgd), the initial amount Coquina Coast is projected to produce. By 2050, Coquina Coast is expected to produce 80 mgd.

The Tampa Bay plant has had a turbulent history. Three companies went bankrupt. A fight over ownership and control went to court.

The plant opened in 2008, five years later than scheduled. Problems continued to beset the plant, which uses the same technology planned for use at Coquina Coast.

Tampa Bay Water Director of Operations and Facilities Chuck Carden believes the turbulent waters have calmed.

"We're happy at this point, but it hasn't been easy," he said.

He said the main lesson learned from early technical problems was that pretreatment is a major issue.

"We learned a good lesson – it has to be robust," Carden said.

The process must remove pretty much everything but the salt from the water before it is forced, under very high pressure, through membranes to remove the salt.

Otherwise, the membranes clog up. That was a major problem early on.

The membranes should be cleaned periodically, but not too often, because the down time reduces production, and too-frequent cleaning shortens the life of the membranes.

"That's like washing your favorite shirt every day," Carden said.

Though there's an occasional glitch, things are running pretty well now in Tampa, he said.

Another important lesson learned by the early disasters was control.

Tampa Bay originally planned to let a private company own and operate the plant. The public utility would simply buy water from the private entity.

That didn't turn out as expected. The company that promised water at the cheapest rate got the contract to own and operate the plant. The public utility had no control in correcting problems, and no say in daily operations.

There were bankruptcies and other court actions. Finally, Tampa Bay Water took over the plant.

Now, the utility hires out operations under its supervision. Tampa Bay Water is in charge.

The desalination plant has been averaging a production of 20 mgd for the past 24 months. Since October, it has been averaging a little more than 25 mgd, Carden said.

The plant just completed a series of milestones to get a full $85 million in grants, plus another $10 million in interest from the Southwest Florida Water Management District.

The plant cost a total of $158 million to build. That was $48 million over the original estimate.

A solution to water wars

The stimulus for the Tampa Bay plant was the water wars of the 1990s. Three counties — Hillsborough, Pasco and Pinellas — and three cities — Tampa, St. Petersburg and Newport Richey — each faced mandatory reductions in groundwater use. There were legal fights over the aquifer, wells and wetlands.

The Southwest Florida Water Management District told the utility companies pumping from the Upper Floridan aquifer was lowering water levels in lakes and wetlands, reducing river flows and increasing saltwater intrusion in the aquifer along the coast. Those are the same problems East Central Florida is facing now.

The Southwest Florida Water Management District told its constituents to reduce pumping and look for alternative water sources — just as the St. Johns Water Management District is telling its constituents.

The Southwest Florida Water Management District pledged a total of $183 million for alternative water supplies. Out of that came the $85 million for the desalination plant.

A regional supplier — Tampa Bay Water — also was created. It relies on three sources of water: the aquifer, the desalination plant, and surface water from the the Alafia and Hillsborough rivers.

"We are a wholesaler," Carden said.

The three counties and three cities all buy water from Tampa Bay Water, and pay the same rate, $2.39 per thousand gallons.

How the system works

It's a balance, Carden said.

The desalination plant doesn't run at full capacity all the time.

When it's rainy and the rivers are high, a 15-billion-gallon reservoir is filled with river water for use later. It's sort of a "reservoir savings account," Carden said.

A plant that filters the river water averages 99 mgd, and produces up to 120 mgd in rainy summer months. Groundwater is used also.

In dry season, when the aquifer and the rivers are low, the reservoir is tapped, and the desalination plant runs at full capacity.

Water from the three sources is blended and delivered. A huge pipeline — between 6 and 7 feet wide and 200 miles long — connects the six customers at 21 different points.

"We meter the water from their connections," Carden said.

The pipeline runs north to Pasco County, then turns and runs back south to Pinellas County, delivering water to points in between on the way.

How the desalination plant works

Carden said great benefits were realized by locating Tampa Bay's desalination plant next to Tampa Electric's existing power plant.

The Big Bend Power Station, built in 1971, already drew up to 1.4 billion gallons of sea water a day to cool the plant's condensers.

The desalination plant buys power from the plant, and at full capacity, takes 44 mgd of that warm saltwater for free, hooking onto the power plant's line.

The water is first screened, to remove large particles, then is run through the membrane screens to remove salt.

The membranes operate most efficiently when the water is 95-99 degrees, and not having to heat that water saves money.

The highly pressurized water goes into the membranes at 1,000 pounds per square inch.

Out of that 44 mgd, 25 mgd becomes drinking water. The remaining 19 mgd is a briny discharge, which is returned to the power plant. On its way there, the salty water turns an energy recovery turbine, which helps generate power for the desalination plant.

At the power plant, the discharge is diluted with water from the plant's condensers and returned to the bay. The dilution process decreases the water's salinity from 6 percent to 3 percent — the same as the bay's.

"The salinity change is almost undetectable," Carden said. "There are not only cost savings, but environmental benefits."

The annual operating budget for the power plant is $20 million a year. Half goes to buy electricity. The costs would be a good bit higher if the desalination plant hadn't been located next to the power plant.

It costs Tampa Bay Water around $3.50 per 1,000 gallons for water from the desalination plant. River water from the surface-treatment plant costs around $2 per 1,000 gallons, and ground water costs around $1 per 1,000 gallons.

Blending the water from different sources produces the rate of $2.40 per 1,000 gallons.

The $3.50 cost for desalinated water was a pleasant surprise.

"We had expected around $5 per thousand," Carden said.

The projected cost for Coquina Coast's desalinated water is $4.50 per 1,000 gallons, plus another 70 cents for transmission, for a total of $5.20 per 1,000 gallons.

Advice on establishing an East Coast desal plant

Carden's advice is, "There's a place for desal in our water future."

It is only once source of water, but an important one.

Tampa Bay Water runs the groundwater and pipeline systems in-house.

He suggested going to the private sector for the highly technical tasks. The trend now is to hire a team to do the design and building, then hire qualified engineers to run the plant.

That's what's been done so far for the Coquina Coast Saltwater Desalination Project. The team of Malcolm-Pirnie Inc. is leading the project. Two contractors, Sinclair Knight Merz and Veolia Water, may be involved in the building the plant.

Who will own the plant will be determined in Phase 2, which is just beginning.

The Coquina Coast draft paper on the St. Johns River Water Management District Web site suggests ownership should be organized with "the primary goal of maximizing funding from external sources." A governance council will likely be established to figure those things out.

Coquina Coast is a joint project of of the St. Johns River Water Management District, working with Volusia, Flagler and Lake county utility operators and customers, including the City of DeLand.

The St. Johns River Water Management District is paying $2.2 million in cost-share funding and administrative services for the detailed plan for a sea-water desalination facility.

The Water Management District will foot the bill for up to $14 million of construction costs. The initial 25 mgd facility is expected to cost $539 million, more than three times the cost of Tampa Bay's plant. Building the completed facility to produce 80 mgd is expected to cost around $1.35 billion.

***

Why the need for more water in the future?

The most recent population projections show Volusia County growing from 510,300 in 2010 to 535,500 in 2015.

In 1995, the population was 403,353, or 25 percent less than was expected in 2015.

To prepare for the growth, the St. Johns River Water Management District is focusing water suppliers on new sources of water, including the ocean and the St. Johns River, where a study of the effects of reducing flows and levels is under way. The possibility of a rainwater reservoir in the center of the county is also being discussed.

Read reporter Pat Hatfield's blog, Life in Interesting Times.

— pat@beacononlinenewscom

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