Phosphorus removal performance of a large-scale constructed treatment wetland receiving eutrophic lake water

• Published in: Ecological engineering Vol. 79; pp. 132 - 142
• Main Authors: Dunne, Ed J., Coveney, Michael F., Hoge, Victoria R., Conrow, Roxanne, Naleway, Robert, Lowe, Edgar F., Battoe, Lawrence E., Wang, Yaping
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2015
• Subjects: Benefits; Constructed wetland; Construction costs; Costs; Economic costs; Freshwater; Lakes; Management; Marshes; Phosphorus; Phosphorus removal; Receiving; Wetlands; ASW, USA, Florida; USA, Florida, Apopka L; Phosphorus; Economic costs; Benefits; Performance; Constructed wetland
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2015.02.003

Eutrophication continues to impact watersheds and their receiving water bodies. One approach to mitigate this problem is to use constructed treatment wetlands. Our objectives were to determine long-term phosphorus (P) removal by a large-scale constructed treatment wetland (the marsh flow-way at Lake Apopka, Florida, USA) that treats lake water and to quantify the monetary costs for performance. The marsh flow-way treated substantial amounts of lake water (30myr−1, which is about 30% of the lake’s volume on an annual basis). Associated with this, P was removed at an average rate of 0.85gm−2yr−1 (2.6 metric tons yr−1). The marsh flow-way removed mostly particulate P, while it released dissolved P fractions (mostly during the first few years of operation; thereafter, release was negligible). The long-term first-order removal rate constant (k) for P averaged 27myr−1. Phosphorus removal performance varied seasonally, with greater removal during cool periods (September–May) and poor removal during warm periods (June–August). Incurred annual operation and maintenance (O&M) costs averaged $455,000 (2012$), which was equivalent to $1,648hayr−1 or $177 per kilogram of P removed. We also calculated costs for a 25-year project life cycle, and compared the incurred and the 25-year costs to other systems that illustrated the marsh flow-way was cost competitive. Both P removal and costs were useful metrics in helping us determine operational and management changes. This resulted in a seasonal management strategy that contributed to increased P removal and a reduction in O&M, thereby increasing cost effectiveness. In addition to costs, treatment wetlands provide benefits that include a range of ecosystem services. We challenge ourselves and other treatment wetland managers to adopt both a cost and benefit approach to assessing system performance.