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The regenerative role of biofilm in the removal of pesticides from stormwater in biochar-amended biofiltersLow-impact, green infrastructure systems such as biofilters, particularly when amended with biochar, can help address chemical pollution conveyed via stormwater that is increasingly posing a threat to aquatic ecosystems and groundwater quality. Although removal of organic contaminants including pesticides by biochar-amended systems has been studied, the role of a biofouling layer on contaminant removal, biotransformation, and filter lifetime remains poorly understood. This study evaluated the removal of the pesticides atrazine, imidacloprid, and clothianidin in biologically active biochar-amended columns through complete exhaustion of contaminant removal capacity. The resultant data indicate that biological processes accounted for 20–36% of overall removal in the biochar-amended sand columns. In addition, a combined target and suspect screening approach using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) was employed to evaluate the potential transformation of these three pesticides and release of the transformation products (TPs). All TPs detected in the effluent remained below 2.5% of their respective parent influent concentrations for the duration of the experiment. Furthermore, at a biochar application rate of 0.5 wt%, the presence of an active biofilm prolonged the filter lifetime by 1.8–2.3 times compared to a fouled but inactive filter, where removal was presumably dominated by adsorption only. Scenario modelling estimates showedmore »Free, publicly-accessible full text available May 5, 2023
Co-Design of Engineered Hyporheic Zones to Improve In-Stream Stormwater Treatment and Facilitate Regulatory ApprovalGreen infrastructure is an increasingly popular approach to mitigate widespread degradation of urban waters from stormwater pollution. However, many stormwater best management practices (BMPs) have inconsistent water quality performance and are limited to on-site, land-based deployments. To address basin-wide pollutant loads still reaching urban streams, hyporheic zone engineering has been proposed as an in-stream treatment strategy. Recognizing that regulator and practitioner perspectives are essential for innovation in the water sector, we interviewed U.S. water management professionals about the perceived risks, opportunities, and knowledge gaps related to in-stream stormwater treatment. We used engineered hyporheic zones as a case study to understand interviewee perspectives on an emerging class of in-stream treatment technologies. Interviews revealed that many considerations for in-stream stormwater treatment are common to land-based BMPs, but in-stream BMPs have additional unique design and siting requirements. Here, we synthesize practitioner goals, their recommendations on in-stream BMP design, and open research questions related to in-stream BMPs. Many interviewees suggested pairing engineered hyporheic zones with other BMPs in a treatment train to improve in-stream treatment, while simultaneously reducing risk and cost. We discuss how treatment trains and other strategies might also help overcome regulatory hurdles for innovative stormwater treatment.