Grantee Research Project Results
2022 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, 2021 through July 31,2022
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 3 effort includes progress on all six objectives from writing manuscripts to additional experiments including the electrochemical oxidation of PFAS in synthesized solutions and wastewater treatment plant centrate and landfill leachate; evaluating the effect of drinking water treatment residuals (DWTRs) on plant uptake of PFAS in pot studies, PFAS leachate from biosolids mitigation studies and quantifying changes in PFAS profiles and concentrations pre and post Cambi thermal hydrolysis.
For Obj. 1 (centrate treatment, UIC lead) and Obj. 2 (landfill treatment, UIC lead), we focused on evaluating the effects that dissolved wastewater constituents have on electrochemical oxidation of PFAS in centrate solutions using a Ti4O7 tubular reactive electrochemical membrane (REM) reactor. Synthetic solutions consisted of per- and polyfluoroalkyl acids (PFAAs) such as perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), and perfluorohexanesulfonic acid (PFHxS) with different background electrolytes representative of constituents found in centrate wastewater. Results showed between 81 to 87% removal of PFOA in ~60 s of electrolysis time, and the kinetics for PFOA oxidation (initial concentration = 0.6 mM) were not significantly affected by the presence of other PFAS (i.e., PFHxA and PFHxS). The observed surface area-normalized first order rate constants (kobs) at an anodic potential of 3.2 V/SHE were (2.3 ± 0.8) x 10-5 and (2.8 ± 0.4) x 10-5 m/s in the absence and presence of other PFAS, respectively. Electrochemical oxidation of PFOA was also investigated in an ionic mixture representative of wastewater centrate that was concentrated by nanofiltration. The removal of PFOA decreased to 41% and kinetics were no longer first-order. Additional single salt experiments determined that NaHCO3, (NH4)2HPO4, and NaCl electrolytes all inhibited PFOA oxidation, with removals of 58.5, 42.1, and 64.9 %, respectively. Linear sweep voltammetry (LSV) scans showed that NaHCO3 significantly blocked the oxygen evolution reaction compared to the other electrolytes, which suggested an interaction of HCO3- ions with the Ti4O7 surface that also inhibited PFOA oxidation. Kinetic modeling indicates inhibition is occurring over time due to surface blockage. To resolve intermediate product formation, electrochemical oxidation of 8 mM PFOA in a NaClO4 background electrolyte was conducted for which > 99% PFOA was removed at an electrolysis time of 44 s with intermediate PFAS production (i.e., PFHpA, PFHxA, PFPeA, PFBA) accounting for ~38% of the PFOA degraded. Products were consistent with a sequential removal of -CF2 groups. Additional work focused on pretreatment of landfill leachate samples prior to PFAS oxidation. Coagulation as a function pH and FeCl3 concentrations was studied. Chemical oxygen demand (COD) decreased from approximately 10-fold after coagulation. In general, removal increased with PFAA chain length with the maximum removal observed for PFOS (97%) and no removal of PFBS and PFBA. The 3:3 fluorotelomer carboxylic acid (3:3 FTCA) was produced during the coagulation process with the maximum 3:3 FTCA produced (20 ± 6 times the initial value) at pH 6 with 4 g FeCl3/L.
For Obj. 4 and 5 (UF, Purdue lead) Desorption of resident PFAAs from the WTRs was negligible for carboxylic acids, though some desorption of sulfonic acids, particularly PFOS, was detected. ACH-WWTR was further evaluated for its potential to attenuate additional PFAAs added to a biosolid-derived porewater matrix. Sorption was highest for long chain PFAAs and subsequent desorption of the adsorbed PFAAs ranged from 0% to no more than 26%. ACH-WTR effectiveness to reduce PFAS leachate concentrations is being evaluated in transient flow sandy low organic matter soil columns containing biosolids with and without either 1 wt % ACH WTRs or 1.5 wt% biochar Simulated rain events were invoked weekly for four months to date (2.7 pore volume per week). Current data reflects greater attenuation for most PFAS in the ACH-WTR and biochar treatments compared to the biosolids only columns.
For Obj. 6 (Purdue lead), sample extraction and injections for the Cambi THP system samples were completed and added a sampling plan for a second larger-scale Cambi thermal hydrolysis system with additional points throughout the treatment train including individual input sources in some cases and in additional biosolids processing steps. All but a few samples have now been collected and extracted and now awaiting injection. We are wrapping up data and preparing manuscripts on the PFAS changes at key points in a typical anaerobic digestion wastewater treatment as well as the PFAS changes in the ATAD and SNDR processes.
Future Activities:
Much of this last year on will focus on manuscript writing and submission. Some ongoing experimental work will continue including (1) elucidating the mechanism of PFOA removal during electrochemical oxidation and optimizing PFOA removal in a tandem separation/oxidation treatment system; (2) execute some final bench scale partitioning work intended to help clarify trends observed in the plant uptake data; (3) complete the current biosolids-sorbent-amended column studies; and (4) finish the Cambi thermal hydrolysis treatment studies.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 14 publications | 4 publications in selected types | All 4 journal articles |
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Broadbent E, Gravesen C, Choi Y, Lee L, Wilson P, Judy J. Effects of drinking water treatment residual amendments to biosolids on plant uptake of per- and polyfluoroalkyl substances. JOURNAL OF ENVIRONMENTAL QUALITY 2023; |
R839640 (2022) |
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Gravesen C, Lee L, Cho Y, Silveria M, Judy J. PFAS release from wastewater residuals as a function of composition and production practices. ENVIRONMENTAL POLLUTION 2023;322(121167). |
R839640 (2022) |
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Gravesen C, Lee L, Alukkal C, Openiyi E, Judy J. Per-and polyfluoroalkyl substances in water treatment residuals:Occurrence and desorption. JOURNAL OF ENVIRONMENTAL QUALITY 2023;. |
R839640 (2022) |
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Supplemental Keywords:
electrochemical oxidation, trace organics, sorption/desorptionProgress 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.