Grantee Research Project Results
2021 Progress Report: Decreasing polyfluoroalkyl substances (PFASs) in municipal wastewater effluent and minimizing release from land-applied biosolids
EPA Grant Number: R839640Title: Decreasing polyfluoroalkyl substances (PFASs) in municipal wastewater effluent and minimizing release from land-applied biosolids
Investigators: Lee, Linda S. , Chaplin, Brian , Judy, Jonathan
Institution: Purdue University , University of Florida , University of Illinois at Chicago
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2019 through July 31, 2022 (Extended to July 31, 2023)
Project Period Covered by this Report: August 1, 2020 through July 31,2021
Project Amount: $899,960
RFA: Practical Methods to Analyze and Treat Emerging Contaminants (PFAS) in Solid Waste, Landfills, Wastewater/Leachates, Soils, and Groundwater to Protect Human Health and the Environment (2018) RFA Text | Recipients Lists
Research Category: Human Health , Water , Drinking Water , Water Quality , PFAS Treatment
Objective:
Our overall goal is to reduce PFAS loads in water resource and recovery facilities (WRRFs) and mitigate PFAS release from biosolids such that both the beneficial use of biosolids and water quality are protected.
Progress Summary:
Year 2 efforts included progress on all six objectives including experiments on the electrochemical oxidation of PFAS in synthesized solutions and wastewater treatment plant centrate; characterizing wastewater treatment plant centrate and one landfill leachate; conducting PFAS mitigation studies using alum drinking water treatment residuals (DWTRs) and biochar from pyrolyzed Class A biosolids; final data collection on the improved extraction and analysis of 57 PFAS from several biosolids, measurement of several biosolids characteristics and PFAS release concentrations in support of evlauting trends between characteristics and treatment processes. We were able to overcome the challenges we faced with getting leachate as well as DWTRs. We were able to get on leachate this past year for Dr. Chaplin (this project) for the treatment objectives and Dr. Guelfo at Texas Tech (a different STAR project) to achieve some of her objectives. We have one more landfill leachate coming to us to complete our treatment objectives. We had some residual challenges this past year as well induced by COVID restrictions and supply chain interruptions, but overall nothing compared to Year 1.
For Obj. 1 (centrate treatment) and Obj. 2 (landfill treatment), we completed the Ti4O7 tubular reactive electrochemical membrane (REM) reactor and testing for PFAS oxidation using synthetic solutions followed by testing on municipal wastewater treatment plant centrate. PFOA oxidation experiments in synthetic solutions at 40 mA/cm2 and different concentrations (0.1 to 10 µM) achieved similar removals (96-99%) over 80 seconds of electrolysis time. Production of short chain intermediates was observed, indicating sequential removal of CF2 groups. The total PFAS concentration decreased following 2nd-order kinetics (decreasing rates with increasing PFAS concentration), which indicated adsorption effects were likely important during PFOA oxidation and that a preconcentration step would be beneficial. Therefore, wastewater centrate was concentrated 10-fold using nanofiltration and then electrochemically oxidized at a current density of 30 mA/cm2 in a 100% recycle-mode experiment for 233 seconds of electrolysis time yielding 83% removal of total PFAS. Removal of PFOA was 93.3%, PFBA and 5:3 FTA was > 99.9%; and PFHxS was > 99.3%. Both PFHxA and PFPeA production as intermediates resulted in only a 38% decrease in PFHxA and a ~4.2-fold increase in PFPeA. Landfill leachate was collected and characterized; PFAS totaled ~18,000 ng/L with similar concentrations of long chain and short chain PFAS. PFBS degradation was investigated in a 240 mM NaClO4 electrolyte at a current density of 30 mA/cm2. PFBS removal was ~48% after 82 seconds of electrolysis time, compared to 20% for the open circuit potential control. Ongoing work is focused on increasing the reactivity of the REM by catalyst deposition to achieve complete removal of short chain PFAS compounds during electrochemical oxidation of both centrate and leachate solutions.
For Obj. 3, a subset of 12 biosolids were characterized. A total of 34 PFAS of the 57 PFAS quantified were present in one or more of the solids evaluated. Solids-porewater partition coefficients for shorter-chain PFAS showed positive correlations to protein content while % OM correlated better to partitioning of the longer chain PFAS. Both Fe and Al oxide content also positively correlated with PFAS biosolids-porewater partition coefficients. Additional synthesis of the data is ongoing to derive a predictive tool that includes the main factors driving PFAS release (partitioning) from these materials.
For Obj. 4, we characterized several drinking water treatment residuals (DWTRs) including five Al-based, two Ca-base, and one Fe-based DWTRs. Total native PFAS concentrations ranged from < method detection limits to ~34 µg kg-1. PFOS was the most commonly detected PFAS in 6 of the 8 DWTRs, followed by PFHxA, PFOA, and L-PFHxS. The highest concentration was in a DWTR derived from an aluminum chlorohydrate (ACH) coagulant and was used to treat wastewater (WW) rather than drinking water prior to pumping the treated WW into the aquifer. The PFAS sorption capacity and desorption trend was evaluated for this ACH-based DWTR. High concentrations of PFAS with ≥ 6 perfluorocarbons were ~100% sorbed from biosolids porewater amended when using > 5 g/L ACH-based residuals. This ACH-based residual shows high promise for use in mitigating PFAS leaching from biosolids, thus is now the target of one treatment at the field-scale on a different EPA grant.
For Obj. 5 (Purdue lead), we achieved 100% sorption of PFAS with perfluorocarbon chain lengths ≥ 7 achieved with biochar at a mass to porewater volume ratio of 0.1.
For Obj. 6 (Purdue lead), we have analyzed monthly samples of pre- and post-digest sludge as well as some locations within the treatment trains from a newly installed Cambi thermal hydrolysis system. Sample extraction is partially complete and undergoing data processing.
Future Activities:
Obj. 1 and 2: We will focus on increasing the reactivity of the REM by catalyst deposition to achieve complete removal of short chain PFAS compounds during electrochemical oxidation of both centrate and leachate solutions. Obj 3. We will finish data synthesis and prepare/submit manuscript, and graduate one PhD student. Obj. 4 and 5: We will continue characterizing the mitigation potential of a subset of DWTRs and the one biochar including sorption from biosolid-derived porewater, PFAS release from biosolids compared to biosolids mixed with DWTRs, and completion of tomato plant uptake experiments examining the effect of DWTR application on PFAS and phosphorus uptake. Graduate one MS student. Obj. 6: We will complete our analysis of the Cambi thermal hydrolysis process on PFAS concentrations. Across all objectives, we are targeting a 6 to 7 manuscripts for submission in this next year.
Journal Articles:
No journal articles submitted with this report: View all 28 publications for this projectSupplemental Keywords:
abiotic remediation, trace organics, availabilityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.