Transport and Removal of Stormwater Vehicle-Related Contaminants in Laboratory Columns

Abstract

Stormwater runoff capture can provide means of flood control and augmentation of local water supplies. However, urban stormwater is considered a major transport vector of contaminants, primarily from vehicle-related sources. Unfortunately, conventional green infrastructures fail to consistently remove the contaminant dissolved fraction – in particular persistent, mobile, and toxic (PMT) organic pollutants. We investigated the transport and removal of stormwater vehicle-related trace organic contaminants, such as 1H-benzotriazole, N'N-diphenylguanidine, and hexamethoxymethylmelamine utilizing continuous-flow sand columns amended with granulated activated carbon (GAC) and wheat-straw produced biochar (WSP550). All the pollutants were subjected to nonequilibrium interactions in sand-only (control) and GAC/biochar-amended sand columns, with kinetic effects on transport. The Langmuir sorption kinetics model could well describe the observed breakthrough curves, which assumes the saturation of sorption sites that might occur in infiltration systems with DOM fouling. Furthermore, we found that GAC amendments can attenuate the contaminants significantly better with faster adsorption kinetics and higher sorption capacity than the biochar. Based on the optimized sorption parameters, we concluded that HMMM had the lowest affinity in both carbonaceous adsorbents. These column results corroborated observations from preliminary batch experiments. Based on the case study simulation, the amendments of pyrogenic carbonaceous adsorbents could improve vehicle-related organic contaminant removal and exhibit a service life of more than a decade in a green infrastructure. Overall, our research contributes to improving polar organic pollutant removal technologies in environmental applications.