Metal species infused particulate matter associated with urban rainfall-runoff is a unique and profuse source of pollution. Generated from urban activities, such as traffic activity and vehicular/infrastructure abrasion, contaminated residual material is deposited to roadways during dry weather and transported to surrounding environments and/or best management practice (BMP) treatment facilities during wet-weather events. These particulates range in size from 1 ƒÝm to 10000 ƒÝm and are contaminated with metal species that originate from such sources as vehicular body wear (Cu), tire wear (Zn), and brake dust (Pb). Depending on the efficiencies of the BMP treatment facilities, these containment systems have the potential to be an abundant source of solid and potentially hazardous waste.
Rainfall-runoff residual matter was collected from five urban BMP sites and characterized for granulometric indices. The sites were located in Baton Rouge, LA, Little Rock, AR, North Little Rock, AR, and Cincinnati, OH. The residual matter collected from the five BMP sites was characterized as a function of particle size for particle mass, particle size distribution (PSD), particle density (ƒâs), total surface area (SA), specific surface area (SSA), and metal species contamination. This characterization study showed that the majority of the metal species mass contamination is associated with the coarse to mid-sized range of particles with large amounts of SA, while the predominance of metal species concentration contamination is found in the fine particulates with high SSA.
Cement-based solidification/stabilization (S/S) was applied to residual matter recovered from the BMP facility located in Baton Rouge, LA, using three cement types. Cement-based S/S has been used in the treatment of a wide range of metal contaminated wastes, but there is no record of the technology being applied to rainfall-runoff residuals. Three gradations (total (entire gradation), coarse (> 75 ƒÝm), and fine (< 75 ƒÝm)) of rainfall-runoff residuals were treated using a type I portland cement (PC), a slag cement (SC), and a 1:1 mass ratio of type I portland cement and slag cement (PS). An assessment of the solidification of the treated residuals was made using techniques to analyze the hydration behavior and physical strength and the leaching potential of the untreated and treated residuals was assessed in order to determine the stabilization effectiveness of the S/S application to the rainfall-runoff residuals.