Collaborative Research: ERASE-PFAS: Hydrothermal Treatment as a Strategy for Simultaneous PFAS Destruction and Recovery of Energy and Nutrients from Wastewater Residual Solids

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Per- and polyfluoroalkyl substances (PFAS) are fluorinated organic chemicals that are used in numerous consumer products and industrial applications. During the last decade, PFAS have emerged as priority pollutants due to increasing concerns about their persistence, stability, and toxicity to humans and other living organisms as they accumulate in the environment. The increasing detection of PFAS in sludge and biosolids from water resource recovery facilities (WRRFs) has raised serious concerns about using these solids in agriculture and farming as soil amendments, and sources of organic matter and nutrients. The goal of this collaborative project is to evaluate the use of hydrothermal liquefaction (HTL) as a platform technology to advance the simultaneous destruction of PFAS and recovery of liquid fuel and nutrients from sludge. The HTL process uses high temperature (250-350°C) and high pressure (100-250 bar) to break down PFAS-in sludge from WRRFs in a specially designed reactor. The proposed research will evaluate the effectiveness of HTL to remediate PFAS-laden sludges while producing liquid fuel and nutrients. The successful completion of this project will benefit society through the development of new fundamental knowledge and technology to advance the cost-effective remediation and management of PFAS-laden sludges from WRRFs. Additional benefits to society will be achieved through outreach and educational activities including the mentoring of a graduate student at Colorado School of Mines and a graduate student at the University of Illinois at Urbana-Champaign.The detection of PFAS in agricultural fields and farms where sludges were applied to the land has raised serious concerns about the land application of sludge, a farming practice commonly used to improve soil quality and crop yields. The goal of this collaborative research is to evaluate and advance the application of hydrothermal liquefaction (HTL) as an alternative technology for managing PFAS-laden sludges from water resource recovery facilities (WRRFs). This goal will be advanced through a combination of experiments and modeling efforts with a focus on two critical objectives: (1) identify HTL process conditions that ensure destruction of PFAS that accumulate in sludges from WRRFs; and (2) develop and apply a system modeling framework to optimize sludge valorization through the recovery of fuel and valuable products (e.g., nutrients) while safely destroying the PFAS contaminants. The proposed experiments will evaluate the destruction of PFAS and track the mass balances of the carbon, nitrogen, and phosphorus that are generated during sludge HTL. The results of the HTL experiments will inform and guide the development and validation of process modules that will be incorporated into QSDsan (Quantitative Sustainable Design for sanitation and resource recovery), an open-source modeling framework for optimizing resource recovery from wastewater and waste biomass. Model predictions that optimize resource recovery while destroying PFAS will then be validated with sludges and digested biosolids obtained from several WRRFs. The successful completion of this project has the potential for transformative impact through the development and validation of a new technology that addresses sludge PFAS contamination while advancing the recovery of valuable products. To implement the education and outreach activities of the project, the Principal Investigators (PIs) plan to leverage an existing REU program at Colorado School of Mines (CSM) to broaden participation in STEM education by recruiting students who have not previously participated in undergraduate research. In addition, the PIs plan to 1) conduct virtual workshops to support and broaden the use of QSDsan modeling by the water research community and 2) develop summer camp activities on resource recovery from waste streams for K-6 students that will participate in a summer camp for children with dyslexia at CSM.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.