This paper presents an estimation of the service life of three filters composed of sand and three alternative adsorbents for stormwater treatment according to Norwegian water quality standards for receiving surface waters. The study conducted pilot scale column tests on three adsorbent amended filters for treatment of highway runoff in cold climates under high hydraulic loads. The objectives were to evaluate the effect of high hydraulic loads and the application of deicing salts on the performance of these filters. From previous theoretical and laboratory analysis granulated activated charcoal, pine bark, and granulated olivine were chosen as alternative adsorbent materials for the present test. Adsorption performance of the filters was evaluated vis-à-vis four commonly found hazardous metals (Cu, Pb, Ni and Zn) in stormwater. The results showed that the filters were able to pass water at high inflow rates while achieving high removal. Among the filters, the filters amended with olivine or pine bark provided the best performance both in short and long-term tests. The addition of NaCl (1 g/L) did not show any adverse impact on the desorption of already adsorbed metals, except for Ni removal by the charcoal amended filter, which was negatively impacted by the salt addition. The service life of the filters was found to be limited by zinc and copper, due to high concentrations observed in local urban runoff, combined with moderate affinity with the adsorbents. It was concluded that both the olivine and the pine bark amended filter should be tested in full-scale conditions.

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This paper studies the hydraulic performance of two swales composed of filters for stormwater management (filtering swales) in a large-scale experimental study and compares them to the performance of a swale composed of traditional bioretention soil (bioswale). Using experimental data, dimensionless formulations are derived to reflect the influence of swale design parameters on hydraulic performance. The developed formulas can be used to design swales accounting for practical factors for decision makers such as local rainfall patterns, volume capture requirements, and drainage area. The experimental data show that while the bioswale is characterized by large overland flows, the tested filtering swales manage, in the majority of cases, the complete inflow volume without overland flow. The longitudinal slope of the swales does not affect the infiltration capacity of the filtering swales for the tested experimental boundary conditions, only the inflow rate and media water content are found to be statistically significant. As an example, filtering swales tested in this study captured 90% of the runoff generated by a 12.2 mm/h storm (approximately a 5-year return period 1-h duration storm event in the city of Trondheim) on a road 40 times larger than the swale. This highlights the capacity of such swales for handling infrequent events.

Coastal cold climates experience frequent intermittent melting and freezing periods over the cold period. This intermittent freezing in stormwater systems affects the infiltration capacity and hence the performance. This paper investigates the infiltration capacity of engineered filter media (composed of sand mixed with charcoal, pine bark, or olivine) under freezing temperatures in a column-based laboratory setup. Infiltration into partially frozen filter media was replicated using a climate room. The filter media in the columns were brought to −2.5 • C, and water at +2 • C was percolated through the columns with a constant head of 5 cm. Infiltration performance was assessed by observing the time until breakthrough, and the infiltration rate 24 h after breakthrough. The results were compared to the observed hydraulic conductivity for the unfrozen filter media. A novel approach combining the unfrozen water content curves with X-ray tomographic (XRT) images of the materials was adopted to better understand the thermal and infiltration processes. Breakthrough was observed between ca. 21 and 56 h in all columns. The column with homogeneously mixed filter media with sand yielded the quickest breakthrough. The infiltration rates were higher than recommendations for infiltration-based systems in cold climates, making them a suitable option in cold climates.