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 <1 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.

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.

Nonpoint source pollution (NPS) such as stormwater runoff may introduce high loads of bacteria, impairing surface water bodies. The existing filter materials in stormwater best management practices (BMP) are typically not designed to inactivate bacteria. Herein, novel filtration media were extensively tested for microbial load reduction in stormwater runoff. Red cedar wood chips (RC) were amended with different loadings of either 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) or silver nanoparticles (AgNP). Under batch conditions at 25 °C, log10 removal values (LRV) up to 3.71 ± 0.38 (mean ± standard error) for TPA-RC and 2.25 ± 1.00 for AgNP-RC were achieved for Escherichia coli (E. coli), whereas unmodified RC achieved less than 0.5 LRV. Similar trends were observed at 17.5 °C, however at low temperature (10 °C) no statistically significant difference in E. coli inactivation between modified and unmodified RC was detected. Inactivation kinetic studies show that TPA-RC has higher inactivation rate constants compared to AgNP-RC. Under dynamic flow conditions a mass balance approach indicates that even after remobilization up to 99.8% of E. coli removal using 9 mg/g TPA-RC compared to 64.8% for unmodified RC. This study demonstrates that RC wood chips amended with antimicrobial compounds show promising applications as filtration material for the reduction of microbiological contamination load in stormwater runoff.

Non-point source pollution of stormwater contributes high contaminant loads into surface water bodies and poses a threat to the ecosystem, public health and economy. Although (pre)treatment standards have not been introduced at the federal level, Rhode Island (RI) has set minimal contaminant reduction standards for stormwater using structural best management practices (BMP). As BMP performance depends highly on geographical location and climate, and the Northeastern United States experiences broad ranges of temperatures throughout the year along with long intermittent periods between precipitation events, stormwater treatment can be challenging. In this field study, two tree filters were evaluated: a conventional unit (CTF) with sand/shale mix as filter media, and a modified tree filter (ITF) with an added layer of red cedar wood chips amended with 3-(trihydroxysilyl)propyldimethyloctadecyl ammonium chloride. Both BMPs were monitored for 346 days primarily for Escherichia coli and polycyclic aromatic hydrocarbons (PAH). Both tree filters met or outperformed RI's standards for bacteria removal (60%) and TSS (85%), making them a good choice for BMP use in this climate. Total suspended solids, E. coli, PAHs, nitrate, and phosphate removal is higher in ITF. A controlled field scale tracer test using E. coli confirmed these results.