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Biochar for Stormwater Treatment: Technology Overview and Case Study

Myles Gray
Geosyntec Consultants
Presentation file: 
PDF icon 4.2.3 Gray, Myles.pdf1.06 MB

Biochar-based filtration is an emerging stormwater BMP and has generated interest among stormwater professionals, particularly for removal of certain contaminants.  Biochar is a granular, highly porous by-product of bioenergy production and can be considered a lower cost, “green” alternative to activated carbon.  Its physical and chemical properties, including surface area of up to 400 m2/g, make it suitable for a range of environmental applications.  In addition to research, pilot and full-scale projects have been installed, with several projects in the Pacific Northwest.  These have included media filters, engineered aboveground biofiltration systems, and in-ground biofiltration systems.  Due to the early stage of this technology, successful projects must be carefully designed to account for several biochar-specific design considerations including: 1) Variability between different biochars, 2) Media blends with other components, and 3) Biochar post-processing and other methods to ensure suitable media flow rates.  To broaden the appeal of biochar for use in stormwater management, a product research and development project was completed at Oregon State University to create biochar-based media blends specifically for the removal of copper and zinc from stormwater runoff.  Results from this project have shown that high flow rate biochar-based filtration mixtures are capable of removing more than 95% of dissolved and total copper and zinc over long timescales using a range of influent stormwater samples.  Secondary components were selected to enhance contaminant removal but also to encourage beneficial biological activity, buffer effluent pH, and improve hydraulic performance.  Post-processing methods were incorporated to ensure suitable material flow rates and enhance contaminant removal properties.   This presentation will include: 1) A brief introduction to biochar science and its value in stormwater filtration; 2) An overview of biochar-based stormwater installations in the PNW, 3) Critical biochar-specific design considerations for successful installations; and 4) Results and data from an OSU R&D project.

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