Constructed Wetlands for Water Quality Improvement in Surface Water Discharges to the Everglades: Stormwater Treatment Areas

Everglades Stormwater Treatment Areas (STAs) are constructed freshwater wetlands designed for reducing phosphorus concentration and load from drainage waters that flow into the Everglades. Currently, six stormwater treatment areas with a total effective treatment area of 16,098 ha are under operation. Operation of the STAs started in 1994 with a 1,544 ha prototype constructed wetland, the Everglades Nutrient Removal Project, and additional STAs were constructed over the following years. For the period of operation of the STAs, the average total phosphorus (TP) concentration was 140 ppb in the inflow and 43 ppb in the outflow. The average phosphorus load reduction was about 70 percent. Hydraulic loading rate, TP loading rate and hydraulic retention time are recognized as factors that affect TP removal efficiency. Since the start of operation of the Everglades Nutrient Removal Project and the subsequently constructed additional stormwater treatment areas, about 826,540 ha-m of water has been treated and 810.3 mt of total phosphorus have been removed. An additional expansion of the STA treatment system by another 2,389 ha is currently in progress.