Urban stormwater runoff can be a significant source of pollutants, including nutrients, metals, and organic compounds. A persistent organic contaminant of emerging concern is benzotriazole. Commonly used as an anticorrosive and UV-inhibiting agent, as well as in deicing processes, benzotriazole has many pathways into urban stormwater runoff with the potential to accumulate in aquifers and surface water. Urban stormwater is increasingly treated using decentralized bioretention stormwater best management practices (BMPs). While many studies have documented the removal of nutrients and metals from stormwater using biofilters simulating bioretention BMPs, very little research has focused on the removal and biotransformation of trace organic contaminants of emerging concern, particularly in non-carbon amended systems. This study aims to understand the mechanisms of removal for benzotriazole in traditional biofilters planted with Carex praegracilis, a drought and flood tolerant sedge native to California. Bench-scale experiments show that the main removal mechanisms of benzotriazole is through sorption to compost and uptake and biotransformation by C. praegracilis. Biofilters planted with C. praegracilis reduced the effluent benzotriazole concentration in simulated stormwater to a value half that of the non-vegetated biofilters. Further, the decrease in the amount of benzotriazole sorbed to the compost over time after the simulated storm events for the vegetated biofilters relative to the non-vegetated biofilters was statistically significant, suggesting that benzotriazole continued to be biotransformed in the vegetated biofilters. The most significant biotransformation product is glycosylated benzotriazole, which was found in C. praegracilis biomass as well as in the pore water and sorbed to the soil.

Benzotriazole removal mechanisms in biofilters planted with Carex praegracilis

256th National Meeting (2018)

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