In the Pacific Northwest, elevated soluble zinc and copper concentrations originating from urban stormwater runoff pose a significant threat to native salmon and steelhead populations. In response to urbanization, existing stormwater infrastructure needs to be upgraded to treat non-point source pollution, including soluble metals, before they enter receiving waters. Media filtration best management practices provide the flexibility and small treatment footprint needed to retrofit areas where space is limited, such as ferry terminal staging areas, and dry plant matter has shown promise as an available and effective filtration medium. A previous study evaluated its use in raw form, thermally treated (torrefied), and carbonized. Laboratory column tests indicated that the most efficient adsorption for both copper and zinc is non-torrefied wood, followed in order by pea gravel, torrefied wood, and charcoal. The goal of this project is to provide a mechanistic understanding of the interactions of raw (non-torrefied) wood pieces with copper and zinc. The study will also make recommendations about the longevity of the filter media when they are used at ferry terminals.
Principal Investigators:
Indranil Chowdhury, Civil and Environmental Engineering, WSU
Michael Wolcott, Civil and Environmental Engineering, WSU
Sponsor: WSDOT
WSDOT Technical Monitor: Tom Bertucci
WSDOT Project Manager: Lu Saechao
Scheduled completion: June 2017