Threads from the Asian green mussels are clogging the filters and frustrating the builder.
By CRAIG PITTMAN
Published September 24, 2003
[Times photo: Bill Serne]
Biologist Dan C. Marelli holds up one of the green mussels that is causing problems for the plant.
An exotic invader has so badly gummed up Tampa Bay's $110-million desalination plant that its builder is now seeking help from former competitors to finally finish the project.
Asian green mussels are contaminating the water going into the plant and fouling its works, said a spokeswoman for Covanta, the New Jersey company building the plant in Apollo Beach.
"They're clogging the filters," said Covanta spokeswoman Beth Leytham. And so far, she said, the company has been unable to figure out how to deal with the problem.
Covanta, whose parent company went bankrupt last year, has been struggling to complete the nation's largest desal plant for its client, Tampa Bay Water. The company missed its initial deadline in January, then failed a crucial test in May and appears headed for a default on its contract on Sept. 30.
Frustrated Tampa Bay Water officials already have begun talking to companies that could replace Covanta if it falters. Now Covanta itself is negotiating with former competitors, including giant U.S. Filter, to get more money and staffing.
As of Tuesday evening the plant was on track to produce 18-million gallons of water a day, and was slowly ramping up production, said Tampa Bay Water general manager Jerry Maxwell, who defended the utility's decision to stick with Covanta last year when bankruptcy threatened the project. It is supposed to produce 25-million gallons a day.
Even if Covanta gets help with its mussel problem, it will still need more time to finish the plant than its contract allows. Maxwell said the company wants a 17-week extension, which could require a special Tampa Bay Water meeting this week to approve it.
Otherwise Covanta could be in default and would face $465,000 in fines as well as handing over 306-million gallons of free water. A default gives Covanta just 48 days to fix everything before Tampa Bay Water can go after the $23-million performance bond, and use that to finish the plant.
Begun with great fanfare two years ago, the plant is supposed to take 40-million gallons of seawater everyday and force it through 10,000 tightly woven membranes to produce 25-million gallons of potable water and 15-million gallons of brine.
The water comes from Tampa Electric Co.'s Big Bend plant, one of the first places the Asian green mussels were discovered in the United States.
To cool its generator, the plant pumps in millions of gallons of bay water through intake pipes covered with mesh screens. In 1999, Tampa Electric discovered the mollusks covering the screens, forcing the pumps to work harder than usual. Divers cleaned the screens, but the mollusks returned worse than before.
The Asian green mussel is native to the Indian and Pacific oceans. Ten years ago green mussels cropped up in Caribbean waters in Trinidad. Scientists think they traveled there in the ballast water of a bulk cargo ship, and they suspect that's how they arrived in Tampa Bay. Since then they have rapidly spread through the state's coastal waters.
Green mussels can grow to 3 or 4 inches long. They have shown up on pilings, docks, seawalls, boat hulls and navigational markers - anything hard enough for them to attach themselves to using tiny hairs called "byssal threads."
Those threads are a problem for the desal plant, said Leytham. The mussels are screened out, but the hairs collect on the plant's 10,000 membranes, dirtying them faster than expected.
The clogs caused by the byssal hairs have required far more and stronger cleaning solution than expected, Leytham said. The used cleaning solution can't be dumped into Tampa Bay. Instead, Covanta is putting it into the sewer system.
But the company did not get permission until Aug. 25, and the Hillsborough County permit limits the amount that can be put into the sewer.
For a while, 80 tankers were parked around the desal plant containing more than 1-million gallons of used cleaning solution waiting to be dumped into the sewer. Covanta had to get rid of that backlog before it could clean enough filters for a full-fledged test of the new chemicals.
