Double Duty

A 1,650-acre wetland gives the City of Orlando an effective resource for nutrient removal — and a popular attraction for nature observers.
Double Duty
Cormorants perch on flooded trees in the mixed marsh.

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The Iron Bridge Wastewater Reclamation Facility can claim several firsts. It was one of the world’s largest treatment plants to use rotating biological contactors (RBCs) for BOD removal and first in the United States to use RBCs for denitrification. But its best-known feature is the world’s first large-scale tertiary treatment constructed wetland — which doubles as a hugely popular recreation stop.

Built in 1987 on the site of a former dairy farm, the 1,650-acre wetland helped the City of Orlando, Fla., meet a mandate to lower nutrient discharges at a time when population was increasing and the 24 mgd capacity of the Iron Bridge plant was maxed out. Reclaimed water from the plant travels 17 miles in a 4-foot-diameter buried pipe to a structure that distributes it among three separate but integrated wetland cells, each with its own ecological character.

Part of the process

“The wetlands are part of our permitted treatment process,” says Bob Rang, plant manager at Iron Bridge (which no longer uses RBCs). “They have expanded its role into some public uses, but water that’s out there is nonpublic access reuse water.”

The public-use portion is the wildly successful Orlando Wetlands Park, which the city created a couple of years after the wetlands proved successful in nutrient removal. As recalled by Mark Sees, a colleague of Rang, the mayor at the time commented during a visit: “Wow! This place is gorgeous — let’s make it into a park.”

Since then the Wetlands Park, which Sees manages, has developed into a nature complex with 18 miles of earthen-berm roads that compartmentalize the wetlands into 17 treatment cells. Six more miles of hiking, biking and horseback-riding trails meander through various habitats past rest areas with benches, observation decks and four picnic pavilions.

Trailside information kiosks with brochures and maps complement an education center that explains the treatment functions of the plant and wetlands. A 50-car parking lot serves the park’s more than 15,000 annual visitors — locals as well as tourists. The park is open to the public from February through mid-November.

Festive time

Environmental organizations sponsor events at the park, such as the North American Butterfly Association’s annual butterfly count, which has recorded more than 60 species. Native-plant hikes and bird-watching tours are common. Boy Scouts have placed birdhouses and bat boxes throughout the park, and they hand-planted 2,000 seedling trees.

But the biggest event is the annual Wetlands Festival in mid-February. “This year’s festival was awesome,” says Sees. “More than 4,000 people attended, and we unveiled our incredible wastewater display.” The 22-foot-long display includes an operating scale model version of a lift station, bar screens, aerator, clarifier and disinfection, along with miniature wetlands and rapid infiltration basins. The display was created by Athena Parslow, the city’s wastewater compliance program manager, and her team. The festival included many other attractions:

  • An American Indian youth organization performed a tribal dance demonstration.
  • The Florida Trail Association led wilderness hikes.
  • The Florida Native Plant Society conducted native plant identification tours.
  • A local radio station personality hosted a lawn and garden show.

Other activities included photo hikes led by professional wildlife and nature photographers, bird-banding and butterfly netting demonstrations, hay rides and guided bus tours. Music from a live band added to the festivities.

A long journey

Park visitors can view the 17 cells that make up three wetlands systems, separated by earthen berms and designed to process a total of 35 mgd of reclaimed water. Flow begins at the distribution structure with a deep marsh habitat of cattails and giant bulrush. Next come mixed marsh and wet prairie cells of pickerelweed, duck potato and aquatic shrubs. The water’s final holdover before discharge to the St. Johns River is a hardwood swamp populated with cypress, ash, hickory and tupelo trees.

Altogether, more than 2 million aquatic plants provide habitat for wildlife like foxes, squirrels, raccoons, bears, alligators and turtles. Wading and migratory birds, such as brown pelicans, sandhill cranes, great blue herons, least terns, bald eagles, hawks and vultures, also find refuge in the wetlands.

Sees and his wetlands staff routinely sample the water at designated points. Flow takes a 15-foot drop in elevation from the inlet to the outfall during its 30- to 40-day trip through the wetlands. “Operators from the Iron Bridge Facility sample at the outfall each day,” Sees notes. “They also help us out with mechanical and electrical maintenance when we need it.”

To maintain the wetlands’ nutrient collection capacity, the cells — from 15 to 150 acres each — are periodically drained and about 18 inches of sediment mucked out. Heavy equipment is used to dig wind-ditches around the cell, and hydraulic pumps dewater the muck before bulldozers and excavators move it to windrows for drying. After a few months, the dried muck is trucked to on-site storage piles. Restoration and replanting completes the 15- to 30-year cycle.

After about a year in storage, the dried material becomes a nutrient-rich topsoil the city ultimately intends to sell. A nearly completed agreement with a fertilizer contractor will ensure future reuse, according to Sees.

He concludes, “The combination of wetlands treatment and advanced wastewater treatment has proven that strict water-quality goals can be achieved while providing an amenity for wildlife and the public.”



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