Florida Wetlands Filter City Waste
| ORLANDO, FLA.
ON a walk through the Orlando Wilderness Park, a visitor finds eye and ear drawing skyward. A profusion of bird life - great blue heron, white ibis, northern bobwhite, Savannah sparrow - roost in the tops of trees, dart amid the giant bulrushes, or spear fish in the wetlands.
Marsh water stands everywhere. It drains imperceptibly eastward through a 1,200-acre wetlands on its way to the nearby St. Johns River, which meanders northeast another 150 miles, dropping a mere three feet before emptying into the Atlantic. It is winter - no mosquitoes.
Five years ago, this was a cow pasture. Today, it is one of the largest and most successful waste-treatment wetlands in the United States.
The marsh was designed as a means of reducing nitrates and phosphates from city waste water before its discharge into ecologically sensitive surface waters. The marsh's nutrient-rich water is catalyst in a food chain that supports the abundant bird life.
The Orlando Easterly Wetlands Reclamation Project takes in 13 million gallons per day of treated effluent. Thirty days later and after passage through three distinct wetland habitats, the water exits the park's boundaries into the St. Johns River, a "rotating biological filtration plant," says Elizabeth Skene, assistant Wastewater Bureau chief for the city of Orlando.
Water quality has met or exceeded all expectations since the pilot project started in 1987, says G. Ronnie Best, director of the Wetlands and Water Resources Research Center at the University of Florida in Gainesville.
A considerable amount of data support the extended premise of the project, he says, that wetlands not only enhance water quality and discharge, something that has become relatively common, "but also create additional wetland functions, especially habitat for wildlife."
When Orlando was looking for a waste-treatment site, Dr. Best identified the reclaimed cow pasture as a former wetlands that had been drained for cattle ranching in the late 1800s.
But the significance of this wetlands extends far beyond Orlando's boundaries. The extensive research done on this reclamation project has led Florida state officials and environmentalists to designate the concept as one of the principal means to reverse the decline in water quality entering the Everglades National Park, says James Hulbert of the Florida Department of Environmental Regulation.
From 1961 to 1971, thousands of acres of wetlands north of the Everglades were drained to make acreage for cattle ranches and sugar-cane farms. The change in terrain plus the runoff from the ranches and farms altered the natural drainage patterns, increasing the flow of damaging nutrients, especially phosphorous, into Lake Okeechobee.
The critical step in the restoration of the Everglades National Park is to cleanse the water flowing out of Lake Okeechobee and the farmland south of the lake of harmful nutrients in exactly the same manner as the city of Orlando cleans its waste water, says Best.
"We will apply what Orlando did but on a much larger area - 35,000 acres," says Garth Redfield, director of Research, Appraisal, and Publication for the South Florida Water Management District. The big challenge in the south Florida situation, he says, is that the level of nutrients found in water that leaves the Orlando project is not acceptable in the Everglades National Park. "We have to reduce primarily the phosphorous, but also nitrates, by at least half of what is done in Orlando," Mr. Redfield say s.
Original estimates for the cost of the Everglades Park project totaled $150 million last March, but since then estimated costs have doubled.
The goal is to cut in half the phosphorous in the water flowing into the Loxahatchee National Wildlife Refuge and the Everglades National Park over the next five years. Farmers have already committed $40 million of trade association money to planting filtration marshes.
The water-management district for the area will convert 35,000 acres of sugar fields into marshes planted with cattails, bulrushes, and other plants that absorb phosphorous. Since the level of pollution in the waste water coming into the Orlando site is on the magnitude of five to seven times that of the nutrients in the agricultural runoff affecting the Everglades, the chances for success are extremely high, says Best.
At the outset, Orlando planted 2.1 million plants and 120,000 trees in the waste-water wetlands. The waste water is piped 14 miles east of the city before discharge into the wetlands where the first stage of the filtration process begins.
Cattails and bulrushes in the deep marsh start the nutrient removal process. A second stage, deeper into the wetlands and a mixed marsh area, further "polishes" the nutrients. A 400-acre hardwood swamp at the eastern boundary of the park serves as both a final filter and sink for any remaining nutrients.
Besides the size of the acreage, the key difference between the Orlando waste-water removal and the south Florida Everglades Park cleanup is the volume of inflow, says Redfield. The city of Orlando has a pipe bringing 13 million gallons per day. South Florida is talking on the order of an entire river emptying into the ecosystem.