Abstract
Stormwater runoff from roadways often contains a variety of contaminants such as heavy metals, which can adversely impact receiving waters. The filter media in stormwater filtration/infiltration systems play a significant role in the simultaneous removal of multiple pollutants. In this study, the capacity of five filter media—natural quartz sand (QS), sandy soil (SS) and three mineral-based technical filter media (TF-I, TF-II and TF-III)—to adsorb heavy metals (Cu, Pb and Zn) frequently detected in stormwater, as well as remobilization due to de-icing salt (NaCl), were evaluated in column experiments. The column breakthrough data were used to predict lifespan of the filter media. Column experiment operated under high hydraulic load showed that all technical filters and sandy soil achieved >97%, 94% and >80% of Pb, Cu and Zn load removals, respectively, while natural quartz sand (QS) showed very poor performance. Furthermore, treatment of synthetic stormwater by the soil and technical filter media met the requirements of the Austrian regulation regarding maximum effluent concentrations and minimum removal efficiencies for groundwater protection. The results showed that application of NaCl had only a minor impact on the remobilization of heavy metals from the soil and technical filter media, while the largest release of metals was observed from the QS column. Breakthrough analysis indicated that load removal efficiencies at column exhaustion (SS, TF-I, TF-II and TF-III) were >95% for Cu and Pb and 80–97% for Zn. Based on the adsorption capacities, filtration systems could be sized to 0.4 to 1% (TF-I, TF-II and TF-III) and 3.5% (SS) of their impervious catchment area and predicated lifespan of each filter media was at least 35, 36, 41 and 29 years for SS, TF-I, TF-II and TF-III, respectively. The findings of this study demonstrate that soil—based and technical filter media are effective in removing heavy metals and can be utilized in full-stormwater filtration systems.
Highlights
Stormwater runoff from vehicle trafficked areas and roofs contains a heterogeneous mixture of pollutants including solids, heavy metals, organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), and mineral oil hydrocarbons (MOH), nutrients and compounds of de-icing salts, which can cause significant hydrological and ecological impacts on receiving waters [1,2,3]
III) were >95% for Cu and Pb and more that 87% for Zn. These results demonstrate that all filter were >95% for Cu and Pb and more that 87% for Zn. These results demonstrate that all filter media media were effective for the simultaneous removal of heavy metals, except for quartz sand (QS) which had were effective for the simultaneous removal of heavy metals, except for QS which had significantly significantly lower removal efficiency of Cu and Zn
Experimental results with the QS filter column indicated a breakthrough of Cu, Pb and Zn beginning at 50 bed volume (BV) and was nearly complete (Ce/Ci ≈ 1.0) after a total flow though of 1000 BV
Summary
Stormwater runoff from vehicle trafficked areas and roofs contains a heterogeneous mixture of pollutants including solids, heavy metals, organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), and mineral oil hydrocarbons (MOH), nutrients and compounds of de-icing salts, which can cause significant hydrological and ecological impacts on receiving waters [1,2,3]. A diverse range of soil-based stormwater control measures such as filter strips and swales, infiltration systems, storage facilities (e.g., detention basins, retention ponds and wetlands), filtration systems (storm filter) and porous pavement have been widely used to reduce the adverse hydrological and ecological impacts on receiving waters [11,12]. Some of these treatment technologies are not effective for the removal of dissolved pollutants, spatially too limited or usually suffer from early clogging [2,13]. Stormwater infiltration/filtration systems that utilize granular adsorptive filter media enabling high infiltration rates, which can be retrofitted in small compact systems, are receiving increasing interest due to their ability to remove both dissolved and particulate pollutants [13,14,15]
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