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. Urban stormwater in water-stressed cities could provide a local water source to augment existing water supplies and expand the urban water portfolio. Unfortunately, existing stormwater management practices primarily designed to reduce surface runoff volume and promote recharge are not suited for contaminant removal. Low-cost engineered materials can be applied to stormwater infiltration developments to treat stormwater during groundwater recharge. We have developed and characterized functionalized polymer-clay composite as a potential media for urban stormwater treatment. 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. A suite of representative trace organic compounds and metals were employed to assess the polymer-clay composite performance against biochar, a carbonaceous biomass adsorbent that has been examined for stormwater treatment. Both batch and column filtration studies were conducted in a simulated stormwater matrix and in the presence and absence of dissolved organic matter (DOM) to gauge media reactivity and longevity under more realistic conditions. 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. Oxyanion removal was greatest for PDADMAC-clay composites (particularly Cr[VI]), while PVPcoS-clay composites displayed over 95% removal of Ni, Cd, and Cu. DOM decreased all organic compound removal, yet increased trace metal removal on clay composites due to sorption of complexed metals. 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 to 30 years before replacement is required.<br/> <br/>

Low-cost polymer-functionalized clay composites for trace organic compound and metal removal during urban stormwater treatment

2019 Fall National Meeting

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