Nitrogen and Sediment Capture of a Floating Treatment Wetland on an Urban Stormwater Retention Pond—The Case of the Rain Project

Abstract

Abstract:Nitrogen is widely recognized as a chronic urban stormwater pollutant. In the United States, wet retention ponds have become widely used to treat urban runoff for quantity and quality. While wet ponds typically function well for the removal of sediments, nitrogen removal, performance can be inconsistent due to poor design and/or lack of maintenance. Retrofitting ponds to improve their nitrogen capture performance, however, is often expensive. By hydroponically growing macrophytes on wet ponds, floating treatment wetlands (FTW) may provide a cheap, sustainable means of improving nitrogen removal efficiency of aging stormwater ponds. Few studies have been performed on the effectiveness real-world stormwater systems, however. In this study, we investigated the nitrogen and sediment capture performance of a 50 m 2 floating treatment wetland deployed for 137 days on a stormwater wet pond located within an urban university campus near Washington, D.C. A total of 2684 g of biomass was produced, 3100 g of sediment captured, and 191 g of nitrogen removed from the pond. Although biomass production was relatively low (53 g/m 2 ), we found that nitrogen uptake by the plants (0.009 g/m 2 /day) was comparable to contemporary FTW studies.

Nitrate Removal by Floating Treatment Wetlands Amended with Spent Coffee: A Mesocosm-Scale Evaluation

“…While FTWs have had great success in nutrient removal, nutrient reductions have been highly variable among studies. Those differences are attributed to the variability of plant type, maturity, study length, FTW placement, hydraulic retention time (HRT), surface coverage, and loading concentration (Borne et al, 2013;Lane et al, 2016;McAndrew et al, 2016;Nichols et al, 2016;White and Cousins, 2013). Therefore, improved understanding of the NO 3 -N removal processes in FTWs is critical for improving the design and efficiency of this BMP.…”

Designing Wetlands as an Essential Infrastructural Element for Urban Development in the era of Climate Change

“…Stormwater best management practices (BMPs) including rain gardens, bioswales, and the ubiquitous retention ponds can provide decentralized street-to landscape-scale methods serving stormwater purposes that include the attenuation of stormwater flow into natural waterways as an effort to reduce stream bank erosion and the risk of flooding downstream. While these "micro-scale" features can be installed with redundancy across a watershed to efficiently reduce runoff at the source [14], urban created wetlands provide a unique opportunity to couple such stormwater functions of flow control, infiltration, detention, and/or retention with landscape-scale ecosystem conservation and/or restoration [15][16][17]. Wetlands can be integrated into the existing urban fabric through creative problem-solving on the part of urban planners and stormwater managers-for example, floating treatment wetlands (FTWs) which retrofit wet retention ponds by providing a growing medium for wetland vegetation [18].…”

“…Figure 1 summarizes the knowledge produced through our decade-long research on the three design elements and their relations to two major ecosystem services regarding water and habitat quality in created urban wetlands. The outcome of the research [4][5][6][7][8]16,17,[21][22][23][24][25][26][27][28][29][30][31][32][33] reveals how the design elements interact or are interrelated and how they influence key variables of wetland hydrology, soils, and plant community which drive and control the two ecosystem services ( Figure 1). Planners, designers, and wetland construction specialists may determine if their watershed development goals are best served through a specific combination of these design elements.…”

“…Removal of nutrients from the stormwater was provided by the large surface area of hanging roots of wetland plants that trapped and filtered sediments and by bacterial communities living in the roots. By the end of our project, a total of 2684 g of plant biomass was produced, 3100 g of sediment was captured, and 191 g of nitrogen was removed from the pond by the small floating wetland we implemented during the three summer months [16,17]. The wetland also became a beautiful habitat for a variety of birds, turtles, and macroinvertebrates and a point of conversation for urban sustainability among different members of the campus community, especially at a time when the campus is facing extreme infrastructure development and renovation.…”

Evaluating a Controlled-Release Fertilizer for Plant Establishment in Floating Elements for Bioretention Ponds

“…Stormwater retention ponds are widely used in the best management practices in North America, Australia, and Europe to sustainably manage stormwater runoff [1][2][3][4][5][6]. They are part of the Natural Water Retention Measures (NWRM), which were recently launched by the European Commission to protect and manage water resources using natural means and processes, particularly reducing their vulnerability to the negative effects of floods and droughts [7][8][9].…”