Collaborative Research: WERF: Determining the role of organic matter quality on PFAS leaching from sewage sludge and biosolids

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Poly- and perfluoroalkyl substances (PFASs) are a class of synthetic compounds that have been widely used in a variety of industrial applications and consumer products for over 50 years. PFASs are a national concern due to the negative effects of these compounds on human health and ecosystems. Recently, PFASs were found in wastewater treatment plant solids (sewage sludge), and laboratory and field studies indicate that PFASs can leach from these solids. Since land application of these solids, also known as biosolids, is a common practice to fertilize and improve soil conditions, it is important to understand how solids management and treatment practices affect the presence of PFASs in biosolids. Additionally, little is known about how exposure to natural environments may affect the potential leaching of PFASs from biosolids once they are applied to soil. This research project will work with wastewater treatment plants to experimentally determine the effects of sewage sludge management practices on the amount and types of PFASs that end up in the biosolids. This project will also study environmental factors, such as temperature, rainfall, and biological decomposition, that may impact the release of PFASs into the environment following land application of biosolids. In addition to better understanding the fate of PFAS in biosolids, the outcomes of the project will likely lead to better sludge management practices that minimize possible PFAS exposure to soil ecosystems. The project will include outreach efforts to improve the understanding of PFASs and land-application of biosolids for middle school, high school, and university students.The main objective of this collaborative research project is to understand how solid characteristics and water quality affect PFAS desorption from sewage-derived solids. The proposed research will be the first effort to systematically identify solid phase characteristics and water quality factors that govern PFASs sorption capacity in sewage solids. The focus on sewage-derived sludge, namely secondary and anaerobic digester sludges and biosolids, provides a same-sourced solid that substantially changes in character over its production and its use. This proposal will combine PFASs sorption isotherm and edge experiments, conducted in concert with sewage-derived solid and leachate characterization and microbial assessments, to identify the critical factors governing PFASs sorption. The central hypotheses in this study are as follows: 1) sewage-derived solids protein contents will be the key solid phase characteristics that affects PFASs sorption capacity, and that sorption capacity will generally decrease with microbiological processing; 2) the presence of increased dissolved polyvalent cation concentration will increase PFASs sorption capacity, particularly for the longer chain length compounds; and 3) the abiotic sequential leaching weathering process will deplete the hydrophilic components of the biosolids, rendering the remaining biosolids with a more hydrophobic character and thus increased PFASs sorption capacity. If successful, this project will provide valuable information that will aid in the safe use of biosolids produced from recycling sewage waste, enabling a sustainable method of resource recovery from the Nation's wastewater treatment processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.