Jeff Gamlin

At potential source areas of per‐ and polyfluoroalkyl substances (PFAS), a current priority is to delineate and control the risk of exposure of groundwater aquifers to PFAS. However, with the combination of mobility and persistence of some PFAS, the stormwater migration pathway may also pose risks to potential receptors. This study (1) analyzes the environmental criteria that may drive stormwater remediation, (2) models the stormwater hydrologic response of hypothetical aqueous film‐forming foam (AFFF) sites, (3) compiles perfluorooctane sulfonic acid (PFOS) concentration data in stormwater, and (4) compares the potential PFOS mass discharge in stormwater versus groundwater. Results indicate that typical stormwater mass discharge of PFOS was relatively smaller than groundwater contributions at AFFF sites. However, given the faster impact timescale of stormwater movement and the variability in receiving water types and uses, many AFFF sites may require some form of stormwater management. As PFAS in stormwater represents a relatively new environmental challenge, regulatory approaches and management strategies are expected to evolve over time, adapting to new research findings and site‐specific conditions. This paper presents a series of potential regulatory approaches for PFAS‐impacted stormwater, including expansion of existing regulatory programs, use of best management practices (BMPs), individual site mass discharge limits, and watershed‐scale PFAS mass balance approaches.

This article addresses the urgent need for cost‐effective and sustainable methods to mitigate per‐ and polyfluoroalkyl substances (PFAS) contamination in surface water and stormwater. Although the majority of PFAS research and development to date has focused on groundwater and soil treatment technologies, in some cases there may be a greater risk posed by the high mobility and potential for direct contact with PFAS in surface water and stormwater. Based on the evolving regulatory landscape and the elevated PFAS concentrations observed in available stormwater data near some fire training facilities, additional attention to this topic is needed to support the development of effective and practical treatment technologies for PFAS in surface water and stormwater. We propose addressing the need to bridge the current technology gap between (1) expensive mechanical and/or construction‐intensive technologies and (2) the development of cost‐effective and sustainable surface water and stormwater PFAS treatment options. We envision a future where nature‐based approaches could be employed for stand‐alone PFAS treatment. Alternatively, nature‐based approaches could be used for initial PFAS mass removal as a pretreatment step within a treatment train followed by engineered adsorbents or other technologies, if needed to achieve low concentration cleanup thresholds. We provide an example of a potential nature‐based treatment train that would rely on the natural propensity of PFAS to accumulate in surface water foams using foam‐enhancing weirs and flumes (FWFs), combined with the demonstrated treatment potential of constructed floating wetlands (CFWs). Additional research into the validation, optimization, and site‐specific design factors of nature‐based treatment trains, such as the FWF+CFW approach, warrants future research and development.

Much attention is placed on organohalide-respiring bacteria (OHRB), such as Dehalococcoides, during the design and performance monitoring of chlorinated solvent bioremediation systems. However, many OHRB cannot function effectively without the support of a diverse group of other microbial community members (MCMs), who play key roles fermenting organic matter into more readily useable electron donors, producing corrinoids such as vitamin B12, or facilitating other important metabolic processes or biochemical reactions. While it is known that certain MCMs support dechlorination, a metric considering their contribution to bioremediation performance has yet to be proposed. Advances in molecular biology tools offer an opportunity to better understand the presence and activity of specific microbes, and their relation to bioremediation performance. In this paper, we test the hypothesis that a specific microbial consortium identified within 16S ribosomal ribonucleic acid (rRNA) gene next generation sequencing (NGS) data can be predictive of contaminant degradation rates. Field-based data from multiple contaminated sites indicate that increasing relative abundance of specific MCMs correlates with increasing first-order degradation rates. Based on these results, we present a framework for computing a simplified metric using NGS data, the Microbial Community Structure Index, to evaluate the adequacy of the microbial ecosystem during assessment of bioremediation performance. Graphical Abstract

Contaminated sites with per‐ and polyfluoroalkyl substances (PFASs) are the cause of environmental, health, and financial concerns. Understanding and addressing PFASs at their source areas is important for effective characterization, risk assessment, and remediation. This paper introduces a framework that relies on commonly available PFAS data to assist in identifying PFAS source areas and assess PFAS fate and transport considerations along flowpaths. Currently accepted PFAS physical and chemical behaviors have been incorporated into metrics that can be evaluated geospatially, and/or over time, to build a weight‐of‐evidence approach to refine conceptual site models (CSMs). Graphical representation of data according to a PFAS “family tree” is also proposed for more consistent interpretation and pattern recognition. Combined, these tools create a PFAS data evaluation framework (PFAS Framework) that consists of a tiered analysis approach based on data availability and site complexity. Case studies from real sites are presented to demonstrate the capabilities of the PFAS Framework in identifying source areas.