Research
AFFF/PFAS Bioremediation
Poly and perfluoroalkyl substances (PFAS) are key components in aqueous film forming foams (AFFFs), complex chemical mixtures that typically contain fluorinated and hydrocarbon surfactants and one or more glycol ether-based solvents. AFFFs have been widely used since the 1960s by the military and municipalities to extinguish hydrocarbon fuel fires and prevent reignition.
PFAS compounds, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), are environmentally persistent, exhibit toxicity in human and animals, and can bioaccumulate. For these reasons, the use of PFOA, PFOS, and other C8 PFASs has been discontinued. In 2023, the EPA proposed new regulations to officially limit the level of six PFAS species in drinking water.
Repeated AFFF application at training facilities where firefighting exercises were conducted in unlined pits has led to elevated levels of PFAS in groundwater at sites that are often contaminated with chlorinated solvents, such as trichloroethene (TCE), its toxic daughter products, and dioxane, a common stabilizer of chlorinated solvents. Although a number of studies have been conducted to understand the biotransformation and remediation strategies for PFAS present in AFFF, few have evaluated the impact of biotransformation and remediation of PFASs on the remediation of common cocontaminants or the local ecosystem.
Our research seeks 1) to evaluate the interplay of PFASs and common cocontaminants during biotransformation and remediation of these compounds, and 2) to identify effective biological and chemical treatment strategies to address AFFF and common cocontaminants. Our research will provide a holistic, rather than reductionist, approach to evaluate and treat AFFF-contaminated sites.
Nitrogen Removal from Wastewater by Anammox
The Haber-Bosch process has drastically influenced the Earth’s nitrogen cycle by doubling the global rate of nitrogen gas transformation to reactive nitrogen. In aquatic ecosystems, reactive nitrogen is often a limiting nutrient; when released, it can promote proliferation of primary producers, leading to eutrophication, reduction of biodiversity, and production of toxins.
Anaerobic ammonium oxidation (anammox) is the basis for an innovative biological treatment process for the removal of reactive nitrogen from wastewater effluent. Anammox bioreactors are 60% more energy efficient than the more traditional process of sequential nitrification-denitrification, and can be operated at approximately 10% of the cost.
Today, over 100 full-scale anammox bioreactors have been installed worldwide and are in operation for the remediation of ammonium-rich, in-plant municipal wastewater streams. However, these processes are plagued by long start-up times and unstable operation. Further, the bacteria responsible for anammox have very low growth rates, are inhibited by a variety of factors, and have not yet been isolated. Few studies have examined anammox bacterial response to perturbations on a cellular level, or the role of other bacteria within anammox enrichments under fluctuating reactor conditions.
The Alvarez-Cohen lab seeks to fill this gap by identifying the molecular mechanisms for anammox responses to reactor perturbations, and the metabolic roles played by community members within anammox enrichments. Recent advancements in meta-omics based systems biology technologies provide powerful tools for analyzing the metabolism and interactions pertinent to anammox performance at the community level. Coupled with novel applications of stable isotope tracers, the Alvarez-Cohen lab seeks to generate a fundamental, community-based understanding of anammox enrichments, enabling more comprehensive control and widespread adoption of this promising technology.