Abstract
Metal roofs are common in urban areas due to their cost-effectiveness and durability, yet stormwater runoff from building roofs is a major contributor of heavy metals to urban waterways. This study investigated the field performance of a downpipe treatment system (DPTS) using waste seashells to remove aluminium, zinc, and copper from roof runoff. First-flush runoff samples were collected before and after treatment during 30 events over 18 months. Results showed that Zn (85–97%) and Cu (59%) in runoff were predominantly dissolved, while Al (71–90%) was mainly particulate. Metal concentrations were largely influenced by the roof material, and weak correlations were observed with climate characteristics. The DPTS effectively removed particulate metals from copper (76 ± 48% Cu, 80 ± 41% Al) and galvanised (75 ± 49% Zn, 74 ± 27% Al) roof runoff. It also removed dissolved metals from Zincalume® (53 ± 32% Zn, 60 ± 30% Al) and Aluminium (96 ± 5% Zn) roof runoff, sustaining performance over 542 days of operation. Metal removal was linked to initial concentrations, partitioning, and metal affinity for the filter media, with precipitation, where metals formed insoluble compounds, and adsorption, where metals bound to the surface of the shells, as potential mechanisms. This study demonstrates that repurposing waste seashells in roof runoff treatment offers a low-cost, scalable and easily retrofittable solution for treating heavy metal pollution at its source, directly supporting Sustainable Development Goals (SDG), particularly Clean Water and Sanitation (SDG 6), Responsible Consumption and Production (SDG 12), and Sustainable Cities and Communities (SDG 11).Graphical
Published Version
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