Modelling of different measures for improving removal in a stormwater pond

Abstract

The effect of retrofitting an existing pond on removal efficiency and hydraulic performance was modelled using the commercial software Mike21 and compartmental modelling. The Mike21 model had previously been calibrated on the studied pond. Installation of baffles, the addition of culverts under a causeway and removal of an existing island were all studied as possible improvement measures in the pond. The subsequent effect on hydraulic performance and removal of suspended solids was then evaluated. Copper, cadmium, BOD, nitrogen and phosphorus removal were also investigated for that specific improvement measure showing the best results. Outcomes of this study reveal that all measures increase the removal efficiency of suspended solids. The hydraulic efficiency is improved for all cases, except for the case where the island is removed. Compartmental modelling was also used to evaluate hydraulic performance and facilitated a better understanding of the way each of the different measures affected the flow pattern and performance. It was concluded that the installation of baffles is the best of the studied measures resulting in a reduction in the annual load on the receiving lake by approximately 8,000 kg of suspended solids (25% reduction of the annual load), 2 kg of copper (10% reduction of the annual load) and 600 kg of BOD (10% reduction of the annual load).

Computational fluid dynamics modelling of residence times in vegetated stormwater ponds

“…These observations are consistent with several previous studies (e.g. German et al, 2005;Khan et al, 2013). However, while previous researchers did not attempt to model stem-scale mixing processes occurring within the vegetation, these effects were represented in the current work.…”

“…Tsavdaris et al (2014) showed similar recirculation zones in non-vegetated ponds. German et al (2005) modelled a nonvegetated stormwater pond with an island and showed a recirculation zone similar to the one visible in Figure 4(c) formed around their island. Interestingly, removing their island did not alter the RTD.…”

Hydraulic and Design Parameters in Full-Scale Constructed Wetlands and Treatment Units: Six Case Studies

“…The hydraulic efficiency, λ, lies within the wider context of hydraulic performance, and is a measure expressing the combined effects of the distribution of incoming water in the system and of the amount of mixing in the system (Persson et al, 1999). Several studies have investigated factors that influence hydraulic performance of CWs and ponds, and have tried to optimise the systems and to provide general design guidelines (Aguwamba, 2006;Bodin et al, 2012;Diaz et al, 2012;German et al, 2005;Holland et al, 2004;Jadhav & Buchberger 1995;Koskiaho, 2003;Persson et al, 1999;Persson, 2000;Somes et al, 1999;Su et al, 2009;Wörman & Kronnäs, 2005). Nevertheless, the majority of those studies was either conducted via simulations (which overlooks the field effects), or has neglected vegetation (which affects the hydrodynamics).…”

Can we close the long-term mass balance equation for pollutants in highway ponds?

“…Optimizing of pond geometry for higher removal rates has been investigated in various studies e.g. [18], [12], [20], [7] and [8]. It is generally agreed that the removal efficiency varies from one facility to another [18] and from one event to another, even including negative efficiencies due to short circuiting flow, resuspension, release of pollutants due to changes e.g.…”