Abstract The Everglades Stormwater Treatment Areas (STAs) are large-scale freshwater wetlands constructed to reduce total phosphorus (TP) concentrations in runoff to support restoration of the Everglades. TP reduction and retention in STAs occurs through settling, plant growth and accumulation of dead plant material in a layer of peat. This study evaluated the performance of six treatment flow-ways in STA − 2 and STA-3/4, two of the best performing Everglades STAs, through water and TP budget analyses based on over a decade of hydrological, meteorological, and water quality data. STA performance was evaluated by comparing annual and long-term average annual flow-way and treatment cell TP flow-weighted mean outflow (FWMC) concentrations, TP load retention percentage, and TP FWMC reduction percentage. The effects of annual hydraulic loading rate, annual phosphorus loading rate, annual average hydraulic residence time, inflow TP FWMC and annual average water depth on annual flow-way TP FWMC were evaluated. For the six flow-ways studied, a higher frequency of low-level outflow TP annual FWMC was achieved when the annual hydraulic residence time was longer than 14 d, annual hydraulic loading rate was less than or equal to 3.5 cm day−1, the annual water depth was shallower than or equal to 0.65 m, the annual phosphorus loading rate was smaller than or equal to 1.2 g m2 yr−1, or the annual inflow TP FWMC was less than or equal to 100 μg L−1. This study demonstrated that TP settling rate alone is not adequate to evaluate STA treatment performance especially when hydraulic loading rates differ. This study also helped improve understanding of the factors that affected the treatment performance of large-scale constructed wetland flow-ways which consistently retained TP and reduced TP concentrations over a long-term operational period.

中文翻译：

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大规模人工湿地除磷，一种有效的面源污染治理技术

摘要 大沼泽地雨水处理区 (STA) 是大型淡水湿地，旨在降低径流中的总磷 (TP) 浓度，以支持大沼泽地的恢复。STA 中 TP 的减少和保留是通过沉积、植物生长和死植物材料在泥炭层中的积累而发生的。本研究通过基于十多年水文、气象和水质数据的水和 TP 预算分析，评估了 STA − 2 和 STA-3/4 这两个性能最佳的大沼泽地 STA 中六个处理流道的性能. 通过比较年度和长期平均年度流量和处理单元 TP 流量加权平均流出 (FWMC) 浓度、TP 负载保留百分比和 TP FWMC 减少百分比来评估 STA 性能。年水力负荷率的影响，评价了年磷负荷率、年平均水力停留时间、流入TP FWMC和年流道TP FWMC的年平均水深。对于研究的 6 个流道，当年水力停留时间大于 14 d，年水力加载速率小于或等于 3.5 cm day−1 时，实现了较高的低位流出 TP 年 FWMC，年水深≤0.65 m，年磷负荷率≤1.2 g m2 yr−1，或年流入TP FWMC≤100 μg L−1。该研究表明，单独的 TP 沉降速率不足以评估 STA 处理性能，尤其是当水力加载速率不同时。