Evaluation of Stormwater Treatment Vault with Coanda-Effect Screen for Removal of Solids and Phosphorus in Urban Runoff

Abstract

Catch basins commonly are used by cities as part of a stormwater management plan to remove sediment and associated contaminants from stormwater, keeping them in compliance with regulations. Recently, the city of Madison, Wisconsin modified traditional catch basins by incorporating a fine-mesh (1-mm) Coanda-effect screen into the design with the goal of increasing removal of sediment and organic matter from stormwater. The US Geological Survey (USGS), in cooperation with the City of Madison, installed a water-quality monitoring station at such a catch basin to quantify reductions in total suspended solids (TSS), volatile suspended solids (VSS), suspended sediment concentration (SSC), total phosphorus (TP), and dissolved phosphorus (DP) from urban stormwater before entering Lake Monona. A comparison of the cumulative load from 33 samples collected during the summers of 2016 and 2017 showed 23% and 45% reductions in TSS and SSC, respectively. A smaller reduction was observed for TP, 16%, whereas DP remained unchanged. Reported traditional catch basin sediment removal varies greatly, although typical removal rates are similar. Results from this study will help regulated municipalities determine whether the use of screened catch basins can help meet water-quality goals.

Quantifying Stormwater Pollutants and Porous Surface Infiltration on a Midwestern University Campus

“…The TSS concentrations observed here were well below the international average [25] and nearly half of those from similar catchments around Madison, Wisconsin [34,35]. These differences may be explained from the lower proportion of impervious surfaces that characterize the university grounds sampled in this study compared to the city of Madison [34,35].…”

“…The TSS concentrations observed here were well below the international average [25] and nearly half of those from similar catchments around Madison, Wisconsin [34,35]. These differences may be explained from the lower proportion of impervious surfaces that characterize the university grounds sampled in this study compared to the city of Madison [34,35]. It was demonstrated with the use of geotextiles that urban areas with greater extent of pervious ground showed reductions in TSS concentrations specifically when that pervious ground is managed to prevent erosion [36].…”

“…Second, WinSLAMM modeled an average TSS concentrations over five years using parametrized precipitation values from a rainfile spanning 1980-1985, which likely varies from the two-month sampling average used in this study. Third, the overestimations of the WinSLAMM modeled TSS concentrations may be due to the model's lack of appropriate parameters to represent an increasingly complex landscape that integrates stormwater management infrastructures [34,49]. For example, a study reviewing the role of particle size distribution in stormwater modeling found that particle size distribution can have a significant effect on modeled outputs of loading [49][50][51], a physical aspect of the soil influenced by stormwater mitigation and not quantified in our study.…”