Bioretention Design Modifications Increase the Simulated Capture of Hydrophobic and Hydrophilic Trace Organic Compounds

Stormwater rapidly moves trace organic contaminants (TrOCs)
from
the built environment to the aquatic environment. Bioretention cells
reduce loadings of some TrOCs, but they struggle with hydrophilic
compounds. Herein, we assessed the potential to enhance TrOC removal
via changes in bioretention system design by simulating the fate of
seven high-priority stormwater TrOCs (e.g., PFOA, 6PPD-quinone, PAHs)
with log KOC values between −1.5
and 6.74 in a bioretention cell. We evaluated eight design and management
interventions for three illustrative use cases representing a highway,
a residential area, and an airport. We suggest two metrics of performance:
mass advected to the sewer network, which poses an acute risk to aquatic
ecosystems, and total mass advected from the system, which poses a
longer-term risk for persistent compounds. The optimized designs for
each use case reduced effluent loadings of all but the most polar
compound (PFOA) to <5% of influent mass. Our results suggest that
having the largest possible system area allowed bioretention systems
to provide benefits during larger events, which improved performance
for all compounds. To improve performance for the most hydrophilic
TrOCs, an amendment like biochar was necessary; field-scale research
is needed to confirm this result. Our results showed that changing
the design of bioretention systems can allow them to effectively capture
TrOCs with a wide range of physicochemical properties, protecting
human health and aquatic species from chemical impacts.