Stormwater runoff is a major component of the urban water cycle and acts as a large nonpoint source pollution due to elevated concentrations of trace contaminants. In water-stressed cities, urban stormwater could provide a local water source to augment existing water supplies. Unfortunately, existing stormwater management practices are not suited for contaminant removal. Low-cost engineered materials applied to low-impact infiltration developments can greatly reduce contaminant loads to receiving waters. We have developed and characterized polymer-clay composites as a potential urban stormwater treatment media. Montmorillonite clays, which are highly effective trace metal adsorbents, were functionalized with either polydiallyldimethylammonium chloride (PDADMAC) or poly(4-vinylpyridine-co-styrene) (PVPcoS) to enhance organic compound sorption using a simple, scalable synthesis method. Seven representative trace organics and six trace metals were employed to assess polymer-clay composite performance against biochar, a carbonaceous adsorbent previously examined for stormwater treatment. Batch and column filtration studies were conducted in a simulated stormwater matrix in the presence and absence of Suwannee River natural organic matter (NOM) to gauge media reactivity and longevity under realistic conditions, and the effect of NOM on contaminant removal. In batch studies, polymer-clay composites exhibited similar removal of perfluoroalkyl substances to biochar, but exhibited low affinity for polar pesticides and tris(2-chloroethyl) phosphate. Cr[VI] removal was greatest for PDADMAC-clay composites, while PVPcoS-clay composites displayed over 95% removal of Ni, Cd, and Cu. NOM decreased all organic compound removal, yet increased trace metal removal on clay composites due to sorption of complexed metals. This finding was contradictory to previous studies reporting enhanced organic compound sorption via Aldrich humic acid complexes. Polymer-clay composite-amended columns displayed greater or equal trace metal removal to biochar, while biochar-amended columns exhibited superior removal for all trace organics. Polymer-clay composites did however exhibit significantly higher saturated hydraulic conductivity relative to biochar which is advantageous to prevent clogging or when rapid infiltration is needed. We estimate that under typical urban stormwater conditions, the clay composites will remove contaminants for at least 20 years before replacement is required.

Effect of natural organic matter on urban stormwater trace organic compound and metal removal by polymer-clay composites

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.