Enhancement of surface runoff quality using modified sorbents

The objective of this study was to develop and test nanoparticle-and polymer-based bioactive amended sorbents to enhance stormwater runoff treatment in best management practices (BMPs). Red cedar wood and expanded shale were the sorbents tested. Red cedar wood chips (RC) were modified with 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) and silver nanoparticles (AgNPs) at different mass loadings (0.36 mg/g, 0.67 mg/g, and 0.93 mg/g for TPA and 0.33 mg/g and 0.68 mg/g for AgNPs) to simultaneously improve the sorption of organic and inorganic contaminants and pathogenic deactivation in BMPs treating stormwater runoff. Unmodified expanded shale is often used as a filter material for stormwater treatment and was used as a base comparison. The results showed that TPA and AgNPs loading onto red cedar increased the Langmuir maximum sorption coefficient (Q) for polycyclic aromatic hydrocarbons, up to 35 fold and 29 fold, respectively, compared to unmodified red cedar. In the case of heavy metals, Q for lead increased with increased loading of TPA and AgNPs, whereas no significant change in the Q value for cadmium was observed, while zinc and nickel sorption slightly decreased. The Langmuir maximum sorption coefficient of copper was higher for modified red cedar; however, no correlation was observed with TPA or AgNP loadings. The log reduction value (LRV) for Escherichia coli using unmodified red cedar was \u3c1 log, while modified red cedar exhibited LRV up to 2.90 ± 0.50 log for 0.67 mg/g TPA-RC and up to 2.10 ± 0.90 log for 0.68 mg/g AgNP-RC. Although AgNP-modified red cedar shows a comparable performance to TPA-RC, the high cost of production may limit the use of AgNP-amended materials. While TPA-modified red cedar has advantages of lower cost and lower toxicity, the fate, transport, and environmental implications of TPA in natural environments has not been fully evaluated. The findings from this study show that if BMPs were to incorporate the modified red cedar, stormwater treatment of PAH and E. coli could be enhanced, and the quality of the treated water will improve. © 2014 American Chemical Society