Stormwater bioinfiltration basins are a promising means of preventing contamination of urban surface waters by micropollutants, and have the added potential benefit of augmenting urban water storage via increased aquifer recharge. While these treatment systems have been shown to obtain poor removal of some polar micropollutants, amendment of these systems with black carbons (BCs) such as biochar or activated carbon can increase the retention of these compounds. The fate of micropollutant transformation products in these systems has not yet been assessed, though in some cases these compounds have been detected in urban stormwater and are of greater toxicity to aquatic organisms (<i>e.g.</i>, fipronil and its products). More insight into the generation and mobility of transformation products in stormwater bioinfiltration basins will be necessary to inform future efforts to design these systems for removal of micropollutants.<br/><br/>The objective of this work is to assess the mobility of polar micropollutants and their transformation products in BC-amended bioinfiltration systems. A previously validated forward-prediction transport model enables the prediction and comparison of the transport of these compounds based solely on parameters obtained from batch experiments. Furthermore, aqueous analysis by liquid chromatography high-resolution tandem mass spectrometry using an ABSciex triple TOF 5600 system enables the simultaneous quantification of targeted analytes and identification of potentially unknown transformation products. The approach of this study is threefold: (1) identification of major transformation products and quantification of sorption parameters in microcosms and abiotic batch experiments, (2) prediction of transport behavior in stormwater biofilters using a forward-prediction model, and (3) comparison of model predictions with results from saturated biotic column experiments. Results from preliminary batch tests suggest that fipronil can be converted to the reduction product fipronil sulfide on a time scale shorter than predicted contaminant retention times, even in partially aerated systems. As this compound is more toxic than its parent, and there are other harmful transformation products that could potentially be generated, it is essential that bioinfiltration basins are designed to attenuate micropollutants as well as their transformation products.

Fate of urban micropollutants and their transformation products in black carbon amended stormwater bioinfiltration systems

249th National Meeting (2015)

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