Best-Laid Plans

Despite new systems, Tampa Bay Water still facing supply challenges

By Scott Judy

EDITOR’S NOTE: Due to new developments – and some help from Mother Nature – this story has been updated from the version that appeared in the print version of the magazine with the latest information.

Tampa Bay Water is continuing to experience the challenges of overcoming the power and whims of Mother Nature at a time when some of the authority’s new systems must continue to overcome other hurdles in order to deliver the water the region needs.

The agency is heading into 2008 with a few lingering clouds over two of its newest components, with acceptance testing still under way at its much-ballyhooed seawater desalination plant and the possibility of drought-induced limitations on its recently built, 15-billion-plus-gallon, aboveground reservoir.

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And 2008 is a critical date in Tampa Bay Water’s master plan because that’s when the agency is scheduled to reduce its wellfield pumping from 121 MGD to 99 MGD.

For example, the 15-billion-gallon reservoir, which came online in 2006, dipped down to just over 7 billion gallons in September due to drought conditions experienced through most of 2007. However, by late October, significant rains had helped bring the reservoir’s level back up to an estimated 11 billion gallons.

Meanwhile, the agency’s 25-MGD seawater desalination plant – which, after years of delay, had been advertised by a major media event in April as nearly ready for full capacity – was still experiencing technical issues in September and was delivering only 8 MGD of treated water. Here, too, conditions improved by the end of October, though, when the agency and its contractor was able to produce at the 25 MGD rate for 16 consecutive days during the month and was again cleared for acceptance testing.

Because Tampa Bay Water was able to significantly tap the reservoir this year, Ken Herd, director of operations for Tampa Bay Water says, “We’re not in dire need of the water right now.”

“Next year is when we’re going to need the full capability of this (desal) plant at our disposal,” Herd says. “We need this plant producing significant amounts of drinking water next year in order to meet the permit requirements.”

More Desal Trouble

Despite the project’s history, Herd says he is optimistic that the contractor, a joint venture of American Water and Pridesa, can finally get the desalination plant up to speed by the end of the year.

The 25-million-gallon-per-day facility, located in Apollo Beach, is the nation’s largest reverse-osmosis seawater desalination plant and has long been seen nationally as a bellwether for the viability of future similar projects.

The plant became operational on April 4 upon certification by the Florida Department of Environmental Protection. However, in early May, the plant was still only producing between 10-15 mgd and before October had reached a rate of 20 MGD on only a limited basis.

This most recent schedule extension is merely the latest. Construction of the facility started in 1999 under a $110 million contract with a group led by Stone & Webster of Boston. After that firm went bankrupt just a year later and technical difficulties followed, the agency hired another contractor, Covanta, which then also filed for bankruptcy shortly after experiencing its own set of performance problems.

In 2004, Tampa Bay Water signed a $31.6 million contract with American Water and Pridesa America Corp. to remediate the troubled plant, whose initial filter systems were clogging much more frequently than expected. The American Water-Pridesa team reworked much of the existing facility and added other processes to enhance pretreatment and provide greater operational flexibility and automation. The installation of 18 precoat diatomaceous earth filters was a highlight of the remediation, as was a major retooling of the existing sand filter process and notable enhancements to the cartridge filtration and reverse osmosis processes.

As of September, however, filters were still clogging too quickly and another fix was in the works.

“What we have seen is that these sand filters have not produced the quality filtrate that was originally anticipated,” Herd said in September. “So the diatomaceous earth system is having to work a little harder than (planned).”

As a result, American Water-Pridesa is implementing a body-feed modification to the diatomaceous earth filtration system. This job involves regularly adding more DE to the filter cartridges, which are already precoated with DE, in an effort to keep the filters from clogging so frequently.

That should extend the filter cycles, before the cartridges have to be backwashed and DE reapplied. The enhancement has helped on small-scale basis.

“We’ve run it full-scale on a temporary basis in manual mode, and that has gotten us back to the 24-hour cycles, which should enable us to reach 25 MGD,” Herd says.

Despite the ongoing problems, people in the water-supply business are still following the Tampa project’s progress.

“Tampa is an important project,” says Bob Yamada, water resources manager with the San Diego County Water Authority and past president of the American Membrane Technology Association industry group. “It needs to be successful because it’s really leading the way for other projects, such as in California, Texas and Florida.”

He adds that the San Diego region, for example, is “counting on” desalinated seawater to become an element of the area’s water supply over the next 10-15 years.

Yamada has followed the project since its inception and says the plant’s delays were related mostly to project delivery. “The technology was not the problem,” he says. “It was the execution that was the problem.”

Closer to home, the problems at Tampa’s seawater desal plant definitely have delayed the development of similar systems in South Florida, says Ashie Akpoji, lead engineer with the South Florida Water Management District’s Implementation Division, Water Supply Department.

“It’s been a huge setback to desal in South Florida and around the country,” Akpoji says. “The Tampa Bay plant was a pilot (test) project to us. We’ve been watching to see what happened there before we do desal in South Florida, and its problems have set us back.”

Even so, Akpoji says, “I don’t think of Tampa Bay as a negative, just as a learning curve.”

For example, he says, “Desal is site specific. The quality of the water is very important. There was a problem with red tide, a type of algae that upset the system. You need to check water quality when starting and it takes one to two years to understand the quality. Intense monitoring is needed to come up with a reliable system that won’t fail.”

Reservoir Issues

Performance has not been an issue with the reservoir, which has served the agency’s needs well during a mostly dry 2007.

“The reservoir was extraordinary this year,” Herd says. “It performed just as expected and provided us with surface water while we were experiencing a lack of rainfall.”

In fact, Tampa Bay Water leaned pretty heavily on the reservoir, dropping its volume to just slightly more than 2 billion gallons at one point.

“The reservoir was huge in terms of continuing to allow us to use alternative water supplies even during the times of a drought,” Herd adds.

The potential problem doesn’t come until next year, when water levels at the reservoir may be below what they were this year.

“A reservoir can sustain us through a period of drought, but when you get into multiple periods of droughts, there is only so much storage that we have,” Herd says. “We can only quench a drought for so long.

“Our reservoir is at the lowest level it has ever been at the end of any wet season,” he said in September. “If we don’t receive significant rainfall next year, then that could present another challenge in our ability to meet these permanent (wellfield pumping) cutbacks because if it doesn’t rain then we don’t have surface water.

“If we haven’t been able to store surface water and the river system flows drop, we can’t take any water from those systems. We have to honor the permits that have a required minimum flow in the river that have to be maintained.”

Despite the doubts for next year, the reservoir has been so successful to date that the agency is currently considering the possibility of building another one.

Surface Water Treatment

Meanwhile, Veolia Water North America-South of Houston is overseeing a roughly $158.4 million contract that will nearly double the capacity of Tampa Bay Water’s regional surface water treatment plant in Brandon.

Veolia is delivering that project under a design-build-operate contract, with the project’s scope increasing the existing plant’s capacity from 70 MGD to approximately 120 MGD.

The plant will blend and treat source water from the Alafia River, the Tampa Bypass Canal, the Hillsborough River and the reservoir for ultimate final use by Tampa Bay Water’s member governments.

The plant expansion is scheduled for final completion and acceptance by the end of 2010. Herd says that once this treatment plant is expanded, it will enable the agency to draw more surface water from these sources.

Tampa Bay Water obtained a water-use permit from the water management district to increase its withdrawals from the Hillsborough River and the Tampa bypass canal, Herd says.

“So we’re going to have access to more water during the high-flow periods,” he adds. “It’ll provide us with a much greater ability to withdraw water from the surface water system, greater treatment capacity and more operating flexibility in terms of treating surface water.”

The rest will be up to Mother Nature.