Increasing releases from point sources and diffuse sources are leading to the accumulation of trace organic contaminants (TOrCs) in surface and groundwater bodies. To address non-point source pollution, low-impact development (LID) systems, particularly those focused on infiltration, have gained traction among practitioners. Though often considered “black box” passive treatment systems, knowledge of the dominant treatment processes impacting system performance can ultimately inform design improvements and the maintenance and lifetime of such systems. The overall objective of this study was to assess the fate of selected Neonicotinoids and the herbicide Atrazine in biochar-amended biotic sand filtration, and to better understand the complex interplay between sorption and biodegradation. Both aspects are affected by the change of media properties as a function of time, such as exhaustion of sorption sites or aging of carbonaceous sorbents. While previous research suggested that sorption to the biochar surface can substantially reduce the bioavailability of TOrCs, newer findings suggest that the degradation of TOrCs can occur outside of the dissolved phase. To investigate the impact of microbial biofilms on TOrCs attenuation in biochar-amended sand filtration systems, a long-term lab-scale column study (120 days) was conducted. Besides the treatment condition (sand + 0.5 wt% biochar with biofilm), a range of experimental control conditions (inhibited, and sand only) were employed to allow for data comparison and process insights. Over the course of 92 days, TOrCs were continuously spiked to the column influent. A novel LC-HRMS method was developed to simultaneously conduct targeted and non-target analysis. The latter was specifically used to identify degradation products. Analysis of column effluents showed that TOrCs retention was greater in biotic biochar-sand columns compared to the controls, and effluents did not reach full breakthrough (BT) (Ceff = C0) in the case of Atrazine. Of the studied TOrCs, Clothianidin reached full breakthrough first, followed by Imidacloprid. Consistent with the literature on biological activated carbon filtration for water treatment, these findings suggest that processes other than sorption impact overall retention and that biosorption and/or biodegradation plays a key role. This is further supported by the observation that the inhibited biochar-sand columns reached full BT much earlier than the biotic columns.

Biochar-based bioinfiltration for enhanced and prolonged removal of pesticides from stormwater

2019 Fall National Meeting

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