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Managed treatment wetlands technology is now used around the world to treat wastewater and stormwater by removing nutrients and other contaminants to obtain a desired water quality. In this paper we present a brief review of a large-scale application of the nature-based technology known as stormwater treatment areas (STAs). These STAs were constructed to treat agricultural and urban runoff to reduce outflow total phosphorus (TP) concentrations to <20 μg P L−1, which is required to protect downstream water quality and preserve the remaining Everglades ecosystem. Five STAs with a total area of approximately 25,000 ha were built at strategic locations to reduce TP loads to the Everglades Protection Area. For the past three decades, these Everglades STAs have done remarkable job by 70 to 85% TP load reduction, with an average outflow TP concentrations of 15-40 μg P L−1. In this Everglades STAs special issue, we present research findings on the influence of both external and internal drivers influencing STA performance and potential adaptive management strategies to enhance treatment efficiency to further reduce outflow TP concentrations. • Introduction of the Everglades STAs – largest constructed treatment wetland network in the world. • Everglades STAs serve as 'kidneys' of the Everglades ecosystem by reducing phosphorus loads to downstream waterbodies. • Phosphorus loading is one of the key drivers regulating treatment efficiency STAs. [ABSTRACT FROM AUTHOR]

This paper describes the ecology and management of two flow-through created wetlands that, in turn, defined 30 years of research by Bill Mitsch, 20 years in Columbus, Ohio (1992–2012) and 10 years in Naples, Florida (2012−2022). The Olentangy River Wetland Research Park was built in several stages from 1993 through 2010. The first stage was the creation of dual 1-ha kidney-shaped wetlands primarily fed by pumped Olentangy River water. A pattern of inflow that depended on river stage was maintained for 17 years. The two experimental wetlands were established by planting one of the wetlands with a variety of wetland macrophytes and leaving the second wetland unplanted to ultimately determine whether human introduction of wetland plants matter in the long run. In addition to maintaining data collection for hydrology, water quality, and other functions, these wetlands and several others constructed on the 20-ha floodplain site were heavily used as was the mesocosm compound, mostly for short-term (2 to 3 year) experiments by graduate students. Another 20-ha created wetland complex, called Freedom Park Wetlands, was constructed in 2007–2008 in Naples, Florida, at an abandoned citrus grove, to seasonally treat urban stormwater runoff. During that wet season, the design calls for an average water detention time of 18 days. The wetland system included a 1.9-ha deepwater pond for temporary storage of the urban stormwater pulses from what is mostly an urban watershed, followed by 2.7 ha of shallower vegetated wetland ponds designed to sequentially improve water quality. Within each wetland, there are three deep-water cells and two shallow-water cells. The water eventually exits the treatment wetlands via a rectangular and travels diffusely through a restored bottomland forest to the Gordon River and ultimately toward Naples Bay and the Gulf of Mexico. During our tenure at Florida Gulf Coast University's (FGCU) Everglades Wetland Research Park, Freedom Park was a venue with active mesocosm experiments in a constructed mesocosm compound. Several of these mesocosm experiments were the subjects of master's theses from FGCU and doctoral dissertations from our partner, University of South Florida. Our students also contributed to the local environmental communities by giving tours of the Freedom Park wetlands and our mesocosm research. • This paper describes the ecology and management of two created wetlands. • The Olentangy River Wetland Research Park in Ohio, USA has provided data since 1994. • The Freedom Park wetlands in Florida, USA were constructed in 2007–2008. • Both wetlands offer ecosystem services (i.e. nutrient reduction and flood protection). • These wetlands provide the framework for thirty years of wetlands research. [ABSTRACT FROM AUTHOR]

The Stormwater Treatment Areas (STAs) are constructed wetlands used to reduce the total phosphorus (TP) level in water discharged to the environmentally sensitive areas of the Everglades Protection Area. Analysis of high temporal frequency TP data reveals that TP concentrations discharged from selected STA flow-ways exhibit diel and seasonal cyclic patterns and are most affected by discharge rate and water depth. The objective of this paper is to describe the diel TP pattern and evaluate the possibility of using it to reduce TP in STA discharge. The amplitude of diel TP pattern ranged from 0.7 to 1.5 μg L−1 (3–6% deviation from daily mean) at three flow-ways, peaking in the early afternoon and reaching lowest concentrations between midnight and 4 am. To assess the possibility of further reducing TP concentration discharged from the STAs by increasing the proportion of daily flow discharged at night when diel TP is at a minimum, a General Additive Model (GAM) was created with discharge rate, water depth, year, location, day-of-year, and time-of-day as covariates. While time-of-day was a statistically significant factor in the model (p < 0.001), its average marginal effect was smaller than all other significant model covariates: discharge rate, season, and water depth. Modeling suggests that within specific ranges of discharge rate and water depth, the opportunity exists to provide additional TP reduction in STA outflow by discharging a greater proportion of the daily flow at night when TP concentrations are lower. Further research is needed to quantify the effect of increasing nighttime flow on annual flow weighted mean TP. Additionally, an evaluation of the practicality and logistical cost required to redistribute flow is needed before attempting to take advantage of this natural cyclic pattern to improve STA TP retention. • A diel pattern in totla phosphorus (TP) was found in south Florida wetlands. • Peak diel TP occured between noon and 3 pm, a minimum concentration between midnight and 4 am. • Amplitude of diel pattern ranged between 0.7 and 1.5 μg L-1 TP or 3–6% from daily mean TP. • Under certain hydrologic conditions increasing the proportion of overnight flow could reduce TP in wetland discharge. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the development of a two-dimensional, spatially distributed model to simulate coupled hydrologic and phosphorus (P) biogeochemical processes in a 147-ha cell of a 1544-ha stormwater treatment wetland designed to help protect the greater Everglades, FL, USA. The model was used to assess the effects of a suite of feasible management alternatives on the long-term ability of the wetland to sustain total P (TP) removal. The spatial and temporal dynamics of TP retention were simulated under historical (1995–2000) conditions, and under assumptions of removal of short-circuiting channels and ditches, changes in external hydraulic and TP loading, and long-term (>20 years) impacts on soil and water column TP dynamics under current and reduced load conditions. Internal hydrology and transport processes were calibrated against measured tracer concentrations, and subsequently validated against outflow discharge and spatial chloride concentration data. Cycling of P was simulated as first-order uptake and release, with different uptake coefficients for open water/sparse submerged aquatic vegetation (SAV) areas (0.2day−1) and dense SAV areas (0.4day−1), and a much lower, uniform release coefficient (1.97×10−4 day−1). The calibration and validation of the P model showed good agreement with field measurements of water column TP concentrations measured at the wetland outlet (calibration RMSE=10.5μgL−1; validation RMSE=15.6μgL−1). Under simulated conditions of preferential channels eliminated, average annual TP treatment effectiveness increased by 25%. When inflow TP loads were assumed to be eliminated after 6 years of loading, the release of accumulated soil P sustained predicted annual average outlet concentrations above 6.7μgL−1 for 18 years, decreasing at a rate of 0.16μgL−1 yr−1. Sensitivity analyses indicate that the most critical model input factors include flow resistance parameters, initial soil TP content, and P cycling parameters compared to initial water level, initial TP concentration in water column, ET and transport parameters. [Copyright &y& Elsevier]

Abstract: The biotic integrity of the Florida Everglades is threatened due to degradation of water quality and hydrologic changes associated with agricultural and urban development in the region. Restoration strategies being implemented by State and Federal governments include building approximately 18,000ha of treatment wetlands to reduce nutrient loads in runoff before this water enters the Everglades. The South Florida Water Management District (District) built and operated a 1544ha prototype wetland, the Everglades Nutrient Removal Project (ENRP), to gain the operational experience and design data needed to maximize long-term nutrient removal performance in the larger wetlands. The District conducted extensive research and monitoring in the ENRP from 1994 to 1999. This paper presents a brief history and description of the project and serves as an introduction to this special issue of Ecological Engineering devoted to the ENRP. [Copyright &y& Elsevier]