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TRENDS | SCIENCE WATCH / LEE DYE

This Time, It's the Smell of Success in the Air

May 12, 1997|LEE DYE

In these days of high-tech breakthroughs, sometimes it's the folks with the low-tech expertise who save the day.

The city of Davie, near Fort Lauderdale, Fla., found itself faced with spending up to $500,000 to tear down an outdated sewage treatment plant. But after huddling with oceanographers and marine biologists at Nova Southeastern University, the community came up with a bold plan.

For less than half the cost of tearing down the plant, it was converted into a fish farm and is expected to pay for itself within about three years. The private university will run the facility, known as the Davie Aquaculture Research Center, but the profits from the sale of the fish will go to the city.

The university will use the center to conduct research, train students and carry out experiments aimed at increasing production of marketable fish.

"Everybody wins," according to marine biologist Bart Baca, director of the center.

Baca says the Davie facility is believed to be the country's first abandoned sewage plant converted into a fish farm, but he predicts that others will follow. Representatives of several communities with outdated sewage plants have visited the center, but so far none has decided to follow the same course.

"They want to see how successful this one is first," Baca says. "You can do all the spreadsheets and analyses you want, but the proof is in the production."

Like many communities throughout the country, Davie outgrew its sewage plant, leaving city officials with a real challenge. What do you do with reinforced concrete tanks with walls about a foot thick, once used to dispose of hazardous waste products?

"They are stuck with something that is very tough to get rid of," Baca says. Baca believed the plant in Davie was too valuable to tear down. With an extensive pumping and water purification system, he thought the eight abandoned tanks were ideally suited for growing fish.

"A processing facility that is built to handle a lot of water, and filter and treat it and keep it clean, is ideal for aquaculture," Baca says. "It just needs to be cleaned up, squeaky-clean."

The tanks were sandblasted and the walls were coated with resin. Water pumped into the tanks remained so pure "you could drink it," Baca says.

In February, the center got its first fish and started a test run. Baca chose tilapia, a white fish that is native to Africa but widely grown in farms from the Middle East to Central America. Tilapia is a fast-growing, fast-breeding fish, and it adapted quickly to its new environment, Baca says.

The test run eased Baca's fears that the fish might not reproduce in the tanks, which are 13 feet deep--four times deeper than most commercial fish ponds. For the test run, the water in the tank was lowered to a depth of 3 feet, but when the fish started reproducing it was raised to 13 feet and the fish continued to reproduce, Baca says.

He wants to keep the water as deep as possible because more water means higher production rates.

Later this summer, Baca expects to have 15,000 fingerlings in each of four 76,000-gallon tanks. All eight tanks are expected to be functioning within two years, with a goal of producing 400,000 pounds of fish each year. And he expects his first commercial harvest in about six months.

Mia Tegner, a marine biologist at Scripps Institution of Oceanography in La Jolla, thinks Baca may be on to something. The extensive plumbing and water transport systems used in a sewage treatment plant could lend themselves well to growing fish, she says.

"The uses sound very different, but the basic plumbing is pretty much the same," she says. "It sounds like they are making excellent use of an infrastructure that is not used any more."

She also agrees with Baca that there are many communities, mostly small to medium-sized cities, that could adapt their outdated sewage facilities to commercial fish farms.

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Lee Dye can be reached via e-mail at leedye@compuserve.com

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