3 Mar 2026

Overview of PFAS in Aquatic Environments

Abstract: PFAS are highly stable fluorinated compounds with unique properties and are used in a broad array of industrial processes and commercial products. PFAS are extremely recalcitrant and are widespread in the environment, with measurable concentrations in soils, sediments, groundwater, surface water, and rainwater, even at sites far removed from known sources or releases. Select PFAS (especially longer-chain perfluorinated carboxylic and sulfonic acids) are known to bioaccumulate in aquatic food webs, presenting potential risk to higher trophic species, including hu-mans. Evidence suggests sediment serves as a repository and potential ongoing source for many of these long-chain PFAS. The global presence and persistence of PFAS pose a fundamental challenge to addressing potential effects on environmental quality and health. The public and policymakers are increasingly concerned about the potential presence and effects of PFAS in water and sediments. This concern includes knowledge gaps for dredged material management, posing challenges to execution of the US Army Corps of Engineers Civil Works navigation program. This document provides a comprehensive review of PFAS in the aquatic environment based on published studies and includes overviews of chemical classifications, regulatory considerations, historical uses and sources, environmental distribution, fate and transport pathways, and uptake and effects in aquatic organisms.

20 Feb 2026

Demonstration Validation of Industrial Supercritical Water Oxidation (iSCWO) PFAS Destruction Technology: Aqueous Film-Forming Foam Treatment by General Atomics (GA) iSCWO System

Abstract: The Department of Defense (DoD) is confronted with a pressing environmental challenge concerning legacy aqueous film-forming foam (AFFF) concentrate, historically used in firefighting activities. Legacy AFFF contains PFAS, which are identified as persistent environmental contaminants associated with adverse health effects. Considering increasing environmental regulations and concerns regarding human health impacts, the DoD needs to properly destroy legacy AFFF. The US Army Engineer Research and Development Center (ERDC) led a project focused on the demonstration and validation of technologies for the destruction of PFAS in AFFF. Results are presented for the treatment of 100 gal. of AFFF using the General Atomics industrial Supercritical Water Oxidation system. The demonstration showed destruction removal efficiencies (DREs) for total PFAS analyzed via total oxidizable precursor (TOP) assay (S24 PFAS), ranging from 98.5% to 99.9991%. No volatile fluorinated compounds were detected in the stack emissions as analyzed via Other Test Method 50; however, up to 6,000 ppt S51 PFAS as analyzed via TOP assay was detected in demister effluent. The energy consumed per cubic meter of AFFF and order of magnitude S24 PFAS destroyed ranged from 2 to 24 MWh, while the energy consumed per gram of S24 PFAS destroyed ranged from 0.046 to 48 MWh.

29 Aug 2025

Adaptive Management Framework for Microseira wollei in Lake St. Clair, Michigan

Abstract: Microseira wollei has grown to problematic densities within Lake St. Clair, located between Lake Erie and Lake Huron. Though stakeholders have issued a call-to-action for the management of M. wollei, no substantive plan exists, which was the impetus for this adaptive management framework. Field surveys, emerging technologies, laboratory evaluations, and a literature review were integrated to develop this site-specific frame-work. Adaptive management consists of a series of iterative steps to define and characterize the issue; identify goals, plan, and prioritize; determine a plan; implement management; measure the outcomes; and adapt and re-fine the plan. M. wollei is widely distributed within the study area and across large sections of the lake bed. Due to its large spatial extent, long-term management should focus on regaining and maintaining uses within Lake St. Clair that have been affected by shoreline accumulations. Mechanical removal is anticipated to be the most effective tool; however, the potential addition of algaecides or nutrient sequestration products could be explored for increased effectiveness. The planning and execution of a substantive management plan for M. wollei in Lake St. Clair are outlined and described, but effective management will require a concerted effort on a scale that matches the scope of the problem.

16 Jun 2025

Estuarine Dams and Weirs: Global Analysis and Synthesis

Abstract: Estuarine dams and weirs are constructed in estuaries for blocking the salt intrusion, securing freshwater, and stabilizing upstream water levels. While they can provide many social benefits, they also alter physical and sedimentary processes. To address this, we perform and extensive remote sensing and literature analysis. Remote sensing was conducted based on a global river database of 1531 rivers representing the largest rivers cumulatively draining 85 % of the landmass discharging into the global ocean. It was found that 9.7 % of global estuaries and deltas are currently affected by estuarine dams or weirs acting as the upstream limit of salt, tide, or storm surge intrusion. Most estuarine dams and weirs are located at x = 0–100 km inland from the mouth and their discharge intervals can be continuous. They are found most in river mouths which are wave-dominated followed by tide-dominated and then river-dominated. They can cause significant changes to the quantity and timing of freshwater discharge, tides, stratification, turbidity, sedimentation, oxygen conditions, phytoplankton blooms, and fish migration. We propose a conceptual model for physical and geomorphological change in mixed wave- and river-dominated and tide-dominated estuaries with estuarine dams.

20 May 2025

Guidance for Managers of USACE Waterbodies: Deploying the ERDC CyanoSTUN™ for Suppression of Cyanobacterial Harmful Algal Blooms

Purpose: The purpose of this document is to guide US Army Corps of Engineers (USACE) district personnel in using the US Army Engineer Research and Development Center’s (ERDC) CyanoSTUN™ (Cyanobacterial Suppression Through Ultraviolet-Light-C Neutralization) vessel for suppression of cyanobacterial harmful algal blooms (cyanoHABs). This document describes CyanoSTUN’s capabilities and components, intended operating conditions, and instructions for safe and effective operation of the vessel.

2 Apr 2025

Bacterial Remediation of Microsystin-HAB Toxins Utilizing Microcystinase (MlrA)

Abstract: Microcystins are a class of hepatotoxins produced by some harmful algal bloom–associated cyanobacteria and are the most reported tox-ins in freshwaters. Their cyclic structure makes them resistant to conventional methods used in water treatment operations (boiling, chlorination, and UV treatment). Some bacteria can naturally degrade microcystins via the mlrABCD cluster, a pathway initiated by the primary enzyme microcystinase (MlrA). MlrA linearizes the cyclic microcystin, greatly reducing its toxicity. Protein fusion was employed to produce a recombinant MlrA enzyme fused to maltose-binding protein ([MBP] MBP-MlrA) and to evaluate long-term enzymatic stabilization and reconstitution for future applications. MBP-MlrA degraded cyclic microcystin in vitro and demonstrated stability across a range of biological pHs. At a concentration of 0.61 ng/µl in buffer, MBP-MlrA achieved and maintained an average degradation rate of approximately 101.95 µM/h/ng of protein across fifteen freeze/thaw cycles. Stability assays demonstrated that enzyme activity was preserved over 5 months at −20°C. Results also demonstrated the effectiveness of MBP-MlrA to linearize microcystin upwards of 55.59 µM/h/ng of protein at the bench scale in both buffer and various freshwater matrices. The presence of the linear metabolite is of concern regarding intermediate toxicity, and future studies to incorporate the MlrB peptidase are discussed.

17 Oct 2024

Literature Review of Microseira wollei Distribution, Environmental Drivers, and Risks: Lake St. Clair, Michigan, Case Study

Abstract: Microseira wollei (formerly Lyngbya wollei) has grown to noxious densities within Lake St. Clair, located between Lake Erie and Lake Huron. De-spite the limited data on this cyanobacterium within Lake St. Clair, data exists for M. wollei within the Great Lakes region and in the southeastern United States, where water resource managers have been managing growths for decades. These data provide pertinent insights into the environmental distribution, environmental drivers, risks, and management of M. wollei, which is mainly distributed within eastern states and provinces in North America, from Canada to Florida. Environmental drivers may be site-specific and specific to the M. wollei population; therefore, the environmental drivers identified in this literature review are a starting point to inform further investigations. M. wollei within Lake St. Clair may pose risks to humans. Risks may originate from toxins, disinfection by-products, and, potentially, fecal indicator bacteria. M. wollei has the potential to produce a range of toxins; however, the most prevalent toxins are saxitoxins, a group of neurotoxins. This literature review will help the US Army Corps of Engineers Detroit District; Macomb County, Michigan; and other interested parties understand potential triggers for growth, communicate risks, and help develop an adaptive management framework.

7 Aug 2024

A Broadscale Assessment of Sentinel-2 Imagery and the Google Earth Engine for the Nationwide Mapping of Chlorophyll a

Abstract: Harmful algal blooms degrade water quality and can adversely impact human and wildlife health. Monitoring these at scale is difficult due to the lack of coincident data. Additionally, traditional field collection methods are labor- and cost-prohibitive, resulting in disparate data collection in capable of capturing the physical and biological variations within waterbodies or regions. This research attempts to alleviate this by leveraging large, public, water quality databases and open-access Google Earth Engine-derived Sentinel-2 imagery to evaluate the practical usability of four common chlorophyll a algorithms as a proxy for detecting and mapping algal blooms nationwide. Chlorophyll a data were aggregated from spatially diverse sites across the continental US between 2019 and 2022. The 2BDA and the NDCI algorithms were the most viable for broadscale mapping of chlorophyll a, which performed moderately well, encompassing highly diverse spatial, temporal, and physical conditions. The most compatible field data acquisition method was the chlorophyll a, water, trichromatic method, uncorrected. Resulting data indicate the feasibility of utilizing band ratio algorithms for broadscale detection and mapping of chlorophyll a as a proxy for HABs, which is valuable when coincident data are unavailable or limited.

12 Jul 2024

Qualitative Habitat Evaluation Index for Louisville Streams (QHEILS)

Purpose: Urban stream restoration typically involves multiple objectives addressing different aspects of ecosystem integrity, such as habitat provision, geomorphic condition, watershed connectivity, water quality, and land-use change. Multiple stream assessment tools and models have been developed and applied to inform restoration prioritization, planning, and design. Here, we present the Qualitative Habitat Evaluation Index for Louisville Streams (QHEILS, pronounced “quails”), which was designed as an interdisciplinary assessment method for urban streams in the Louisville, Kentucky, metropolitan region. The model adapts a regional habitat assessment procedure, the Qualitative Habitat Evaluation Index (QHEI), by incorporating additional processes related to geomorphic change and watershed connectivity. The QHEILS was developed in the context of the Beargrass Creek Ecosystem Restoration Feasibility Study, and it provides a rapid procedure for assessing multiobjective benefits associated with proposed restoration actions. This technical note summarizes the model and provides example applications within the Beargrass Creek watershed.

31 May 2024

pH Pivoting for Algae Coagulation: Bench-Scale Experimentation

Abstract: Harmful algal blooms (HABs) threaten recreational waters and public supplies across the US, causing detrimental economic and environmental effects to communities. HABs can be mitigated with dissolved air flotation (DAF) treatment, which requires addition of pH-sensitive charged chemicals to neutralize algae, allowing them to attach to microbubbles and float to the surface. During HAB events and photosynthesis, algae raise the pH to levels that are not ideal for DAF. Traditionally, pH is reduced with a strong acid; however, this adds operational cost and permanently adjusts the water’s pH. This study assessed an approach that might allow for infusing CO₂ from diesel-powered electricity generators into the water prior to DAF treatment. It was hypothesized that formation of carbonic acid could temporarily reduce the pH. Results showed that 2.5%–5.0% CO₂ mixed within compressed air can achieve pH levels between 6–7 in algal water with an initial pH of 9–11 and alkalinity of 150 mg/L as CaCO₃. Further, dosing CO₂ before chemical addition yielded a 31% improvement in water clarification. Returning the pH back to natural levels was not achieved using ambient air microbubbles; however, coarse bubble air spargers should be tested to provide more volumetric capacity for CO₂ absorption.