Impact of Wind on Stormwater Pond Particulate Removal

• Published in: Journal of Environmental Engineering
• Main Author: Andradóttir, Hrund
• Other Authors: Umhverfis- og byggingarverkfræðideild (HÍ), Faculty of Civil and Environmental Engineering (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society of Civil Engineers (ASCE) 2017
• Subjects: Particle size; Resuspension; Settling; Short-circuiting; Stormwater pond; Treatment efficiency; Wash loads; Wind mixing; Tjarnir; Umhverfisverkfræði; Vindar; Esther; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/581; https://doi.org/10.1061/(ASCE)EE.1943-7870.0001221

Stormwater ponds provide cost and space-efficient treatment of urban runoff via gravitational settling. The goal of this paper was to quantify different mechanisms by which wind can affect the particle removal efficiency of a shallow retention pond. An analytical bulk model was developed and validated numerically against total suspended solids (TSS) measurements in a small (0.3 ha), optimally designed oval pond during four runoff events with 7–11 m/s winds. Simulations highlighted wind as an effective mixing mechanism, lowering the removal of medium silt particles by 10–20% from ideal plug flow, and severely constraining the removal of small clay and silt particles (<6 μm). Initial background concentrations of <12 mg/L TSS were positively correlated with wind speed 5 h prior to the event, indicative of localized wind resuspension. A widespread remobilization of bed sediments was found unlikely in a 1.7-m deep, 112-m fetch pond. A stirred reactor with 60% effective volume is proposed as a first order tool to assess the treatment performance of ideally structured ponds in areas with strong, unobstructed winds. This work was funded by the University of Iceland Research Fund. The Icelandic Meteorological Office is thanked for data and equipment for PSD assessment. Gudbjörg Esther Vollertsen is thanked for field data collection. Professor Lars Bengtsson at Lund Technical University is thanked for his comments on the manuscript. Peer Reviewed