Copper and Zinc as Roofing Materials—A Review on the Occurrence and Mitigation Measures of Runoff Pollution

Abstract

Stormwater runoff from metal roofs has been a significant subject of discussion, especially when it comes to its treatment and the target concentrations that need to be achieved prior to discharge into the aquatic environment. To raise further awareness on this issue, occurrence, characterization, and also mitigation measures for metal roof runoff were analyzed using the example of copper and zinc roofs. These stormwater runoffs were found to contain metals in significant concentrations, mainly due to the wash-off of corrosion products by precipitation. Factors influencing metal corrosion and runoff concentrations were compiled. As Cu and Zn mainly occur in dissolved and thus bioavailable forms in roof runoff, harmful effects on the environment were detected. Therefore, adequate treatment of the runoff before discharge to groundwater or surface water is necessary to protect the aquatic environment. Vegetated infiltration swales as an sustainable urban drainage system enable a reduction in pollution loads. However, especially in densely built-up urban areas, stormwater quality improvement devices (SQIDs) offer an attractive alternative for pre-treating metal roof runoff, as they are mostly located underground. There is not yet a uniform legal approval system for SQIDs in Germany, but the German state of Bavaria has approved four types of SQIDs according to its own developed test criteria.

Rainwater Quality Analysis for Its Potential Recovery: A Case Study on Its Usage for Swimming Pools in Poland

“…The implemented standard of 0.5 NTU equates to an extremely low level-the scale demonstrating the standard calibration (see Figure 5) only begins at 10 NTU, while the Polish Standard set for turbidity in drinking water is 1 NTU [34]. The concentration of total Zn in this study ranged from 0.025 to 0.55 mg/L, which coincides very well with some results obtained elsewhere for this metal from roof runoff [35,36]. Thus, one of the studies from Christchurch, New Zealand [37] reported that the Zn concentration in the roof runoff ranged from 0.098 to 0.64 mg/L with a pH of 6.87.…”

Review on inorganic pollutants in stormwater runoff of non-metal roofs

“…In contrast, the runoff of untreated wood shingle roofs had maximum concentrations of As and Zn of 1 μg/L each. The median Cu concentration in the runoff of wood shingle roofs treated with chromated copper arsenate is in the range of copper roof runoff concentrations (Galster and Helmreich, 2022). Median Zn concentrations were elevated for treated compared to untreated wood shingle roof runoff and compared to the control slope runoff of frosted glass, but under the GFS value (see Table 1).…”

“…For example, in a field study, Schriewer et al (2008) found a median of 5 600 μg/L (n = 38 rain events) in the runoff of a zinc roof. Therefore, the runoff of an impregnated wood shingle roof must be treated prior to discharge into groundwater, as is the case for Zn roof runoff (Galster & Helmreich, 2022).…”

“…One type of impermeable surface is roofs, which can be constructed using a wide variety of materials. Until now, metal roofs have always been a strong focus as a source of contamination of stormwater runoff and thus also of water bodies (e.g., Gromaire et al, 2002;Hedberg et al, 2014;Galster and Helmreich, 2022). However, non-metal roofing materials are also suspected of releasing pollutants in stormwater runoff (e.g., Förster, 1996;Müller et al, 2020).…”

Evaluation of a sand filter material for road runoff treatment– pilot-scale field trial focused on copper and zinc removal

“…Zinc (Zn) and copper (Cu) are metals generally appearing in the highest concentrations in road runoff. Corrosion of materials, driven mainly by low water pH, causes the release of Zn and Cu to the environment (Galster & Helmreich 2022). In this paper, we decided to choose these two metals in our study of sand as filter medium, because of their occurrence in high concentrations found in a pre-study (Hallberg et al 2021) as well as their harmfulness in the water environment.…”