Occurrence and Removal of Emerging Contaminants in Urban Stormwater Runoff

Rising populations, exacerbated urbanization, and climate change pose uncertainties on our traditional urban drinking water supplies. Stormwater harvesting schemes could replenish over-drafted groundwater resources, augmenting urban water supplies. However, urban stormwater runoff carries a myriad of dissolved contaminants (e.g., organics, metals, nutrients), which impair receiving water bodies. Moreover, some organic contaminants of urban origin —particularly persistent contaminants of emerging concern (known as CECs), like pesticides, plasticizers, flame retardants, etc.— may not be adequately removed by conventional infiltration treatments.Thus, it is important to fully understand their fate, transport, and effect in the built environment, while designing novel ‒or upgrading conventional‒ treatment systems. First, we have conducted field sampling campaigns to investigate contaminant presence, transport, and source apportionment, during storm events. Preliminary results have confirmed presence of pharmaceuticals (and their corresponding metabolites), pesticides and flame retardants in urban rainwater. Regarding potential treatments prior discharge to both surface and groundwater bodies, we have investigated several passive treatments. To enhance the treatment performance of conventional media, herein we propose sustainable, low-cost and low-energy reactive geomedia. For instance, pyrogenic carbonaceous materials (e.g., biochar) can adsorb trace organic and metal contaminants. We have conducted preliminary laboratory-scale batch experiments to investigate their removal capacities. Our results showed that biochar displayed faster sorption kinetics (<24h) and capacity compared to the other studied materials. Sand, commonly used in infiltration schemes, showed almost no reactivity, highlighting the need to study alternative materials to retain organic and inorganic contaminants from stormwater runoff.