Algae Farm – A New Birding Site! – Egret Marsh Stormwater Park – Thanks to Keith McCully

The President’s Hoot
by Richard H. Baker, Ph.D.
September 2010

Our county now has another innovative project by Keith McCully who was one of the main inventors of the stormwater filter screens next to the County’s Administration Complex of 26th St., which removes trash from the Main Canal before it gets to the Indian River Lagoon.

Mid-August, Keith McCully, Indian River County Stormwater Engineer and Allen Stewart, Vice President of HydroMentia, Inc. invited me to see his newly completed Egret Marsh Stormwater Park off of 4th St. and 73rd Ave. in Indian River County.  I had seen the site for the proposed project two years ago, but now completed, I was impressed with the presence of so many birds feeding at the facility. 

Photo by Richard H. Baker.

While it is a great site for birds, its major purpose is to improve water quality by expecting to remove 80 to 90 percent of the dissolved nitrogen and phosphorus in the Lateral D canal.  The park uses a relatively inexpensive system called the Algal Turf Scrubber that Allen adapted from Dr. Walter Adey, Director of the Marine Lab at the Smithsonian Institute.  It is really a large algae farm that grows algae raised on a gently sloped surface over which is placed a plastic membrane covered by an “algal turf” geotextile grid that grows when the nutrient-rich waters from the canal are pumped onto the surface, about 1-1/2 inch deep. The water is pulsed over the mat in waves and is collected in a trough at the bottom of the sloped surface.  The algae using the nutrients to grow, remove large amounts of nitrogen, phosphorus, color, and other pollutants from the water. Essentially it’s the excess fertilizers from our lawns’ and agriculture’s runoffs that contribute these polluting nitrogen and phosphorous nutrients. Many wading birds are drawn to the Algal Turf Scrubber surface where they eat small organisms that are found in the algal mass. 

The “cleaner” water then moves into a series of three large polishing ponds to remove any algal material escaping the Algal Turf Scrubber and the residual nutrients by allowing the remaining solids to settle.  Each pond littoral zones (shore area) are planted with a variety of native plants.  The ponds contain populations of fish- including 60 lb tarpon, amphibians, reptiles, insects, and other animals.  Sorry, no fishing is allowed.  The water then flows back into the canal.

Small tractors scrape the algae off the algal grid in a rotation every two weeks, which is pushed and washed into a collection trough where it is removed by an automatic rake at a centralized harvesting station.  Keith says it will be composted and used as a soil supplement.  Perhaps with further research it might also be used to generate methane gas.

Egret Marsh is estimated to remove 14,400 pounds per year of total nitrogen and 3,300 pounds per year of total phosphorus before it gets to the Indian River Lagoon. The County and HydroMentia have just begun to monitor the system under an EPA/FDEP grant.  The Storm water Division will construct at least two more regional nutrient removal systems similar to the Egret Marsh.  One will serve the North Relief Canal and the other, the South Relief Canal.

Indian River County is ahead of other counties who are spending their money on attorney fees to fight Total Maximum Daily Load (TMDL) regulations.  TMDL is a calculation of the maximum amount of a pollutant that a water body (e.g. IR Lagoon) can receive and still safely meet water quality standards. Instead of fighting the issue, Indian River County is working to meet the intent of TMDL and with Keith McCully’s leadership, has pro-actively sought a better and healthier solution for us all.  (Under section 303(d) of the Clean Water Act, states are required to develop lists of impaired waters. These are waters that are too polluted or otherwise degraded to meet the water quality standards set by states.  The law requires that states and thereby counties, establish priority rankings for waters on the lists and develop TMDLs for these waters.)

What’s even better, the polishing ponds will be managed to provide a habitat for birds in a safe, clean, and well-stocked wetland system that will assist in the survival of wetland birds.  In my brief visit I saw a dozen black-necked stilts, 20 Florida mottled ducks, 3 pairs of black-bellied whistling ducks, semipalmated plovers, tricolors, great blue and little blue herons, snowy and great egrets, anhinga, osprey, and other wading birds.  While for now the Park is still generally closed to the public, but Keith hopes to open it to students, birders, and educators in the near future.  We will be leading tours there this year.  If you are interested in being a tour guide leader there or at other birding areas, please call our office or visit out website for more information.

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