Biochar and fungi as bioretention amendments for bacteria and PAH removal from stormwater.

Bioretention has been widely used to mitigate hydrologic impacts of stormwater runoff and is increasingly being relied upon to treat chemical and biological pollutants transported by stormwater. Despite this reliance, we still lack an understanding of treatment performance for certain organic and biological contaminants which may interact with biotic and abiotic components of bioretention systems. We evaluated the treatment of fecal indicator bacteria (FIB) and polycyclic aromatic hydrocarbons (PAHs) in stormwater runoff by bioretention. We compared treatment performance by Washington's standard bioretention mix of 60% sand: 40% compost (by volume), and by three other mixtures amended with biochar, fungi (Stropharia rugosoannulata), or both. All bioretention columns were conditioned with clean water and then dosed with collected roadway runoff at a rate equivalent to a 6 month, 24 h storm in this region during 8 events over a 14-month period. Effluents for each column were analyzed for 23 PAHs, Escherichia coli, fecal coliform, dissolved organic carbon (DOC), and total suspended solids (TSS). The fate and transport of PAHs within the bioretention columns was tracked by measuring soil PAHs in media cores taken from the columns. ΣPAH were almost completely removed by all treatments across all storms, with removal rates ranging from 97 to 100% for 94 out of 96 samples. Compost appeared to be a source of PAHs in bioretention media, as biochar-amended media initially contained half the ΣPAHs as treatments with the standard 60:40 sand:compost mixture. We observed a net loss of ΣPAHs (19-73%) in bioretention media across the study, which could not be explained by PAHs in the effluent, suggesting that bioremediation by microbes and/or plants attenuated media PAHs. E. coli and fecal coliform were exported in the first dosing event, but all columns achieved some treatment in subsequent dosing events. Overall, these findings suggest that PAHs in stormwater can be remediated with bioretention, are unlikely to accumulate in bioretention media, and that biochar amendments can improve the treatment of E. coli.

Urban stormwater characterization, control, and treatment.

This review summarizes over 280 studies published in 2019 related to the characterization, control, and management of urban stormwater runoff. A summary of quantity and quality concerns is provided in the first section of the review, serving as the foundation for the following sections which focus on the control and treatment of stormwater runoff. Finally, the impact of stormwater control devices at the watershed scale is discussed. Each section provides a self-contained overview of the 2019 literature, common themes, and future work. Several themes emerged from the 2019 literature including exploration of substrate amendments for improved water quality effluent from stormwater controls, the continued study of the role of vegetation in green infrastructure practices, and a call to action for the development of new models which generate reliable, computationally efficient results under the physical, chemical, biological, and social complexity of stormwater management. PRACTITIONER POINTS: Over 280 studies were published in 2019 related to the characterization, control, and treatment of urban stormwater. Studies on bioretention and general stormwater characteristics represented the two most common subtopics in 2019. Trends in 2019 included novel substrate amendments, studies on the role of vegetation, and advancements in computational models.

Urban stormwater characterization, control, and treatment.

This review summarizes over 250 studies published in 2018 related to the characterization, control, and management of urban stormwater runoff. The review covers three broad themes: (a) quantity and quality characterization of stormwater, (b) control and treatment of stormwater runoff, and (c) implementation and assessment of watershed-scale green stormwater infrastructure (GSI). Each section provides an overview of the 2018 literature, common themes, and future work. Several themes emerged from the 2018 literature including exploration of contaminants of emerging concern within stormwater systems, characterization and incorporation of vegetation-driven dynamics in stormwater control measures, and the need for interdisciplinary perspectives on the implementation and assessment of GSI. PRACTITIONER POINTS: Over 250 studies were published in 2018 related to the characterization, control, and treatment of stormwater. Studies cover general stormwater characteristics, control and treatment systems, and watershed-scale assessments. Trends in 2018 include treatment trains, vegetation dynamics, and interdisciplinary perspectives.