Grantee Research Project Results

2020 Progress Report: Decreasing polyfluoroalkyl substances (PFASs) in municipal wastewater effluent and minimizing release from land-applied biosolids

EPA Grant Number: R839640
Title: 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, 2019 through July 31,2020
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: Drinking Water , Water Quality , Human Health , Water , PFAS Treatment

Progress Summary:

Year 1 efforts included completing and approval of our quality assurance and data management plans, acquisition of centrate, landfill leachate, WTRs, biosolids, experimental set-up, method optimization, enhancing the SOP for PFAS extraction and analysis for biosolids, target and nontarget screening of PFAS occurrence in several biosolids and a centrate, and some experiments addressing objectives several of our objectives. For centrate treatment (UIC lead), we focused on experimental nanofiltration (NF) and reactive electrochemical membrane (REM) reactor setup, electrode synthesis/characterization, NF performance, general and PFAS characterization of centrate, and initial reactivity testing. We found that a total of 404 ng/L of poly and perfluoroalkyl substances (PFAS) were contained in the analyzed centrate solution and 62% of the total PFAS consisted of PFBS. Initial oxidation experiments of a synthetic centrate solution using the REM reactor in single-pass mode (hydraulic residence time ~17s) resulted in > 90% removal of PFHpA, PFBS, PFHxS, and PFHpA at a current density of 66 mA/cm². However, PFBS was only removed by 41% at 66 mA/cm², which was attributed to its known recalcitrance to oxidation. We (UF lead) secured 6 total WTRs, of which 3 are Al-based, 1 Fe-based and 2 Ca-based and 38 biosolids of varying origin and production processes. We have characterized 16 biosolids for % organic matter, dissolved organic carbon (DOC), relative aromaticity of DOC using a SUVA₂₅₄ measurement, and oxalate extractable Fe and Al. An initial multivariate analysis indicates PFAA partitioning between biosolids and porewater for PFBA and PFHxA are influenced by DOC, SUVA₂₅₄, OM%, and oxalate extractable Al while PFOA release was only correlated with DOC and SUVA₂₅₄. We (Purdue lead) did an initial pyrolysis treatment on one Class A 2006-2007 biosolid (875 mg/kg SPFAAs) at 350 °C under low oxygen conditions. Some PFAA concentrations increased in the biochar due to mass reduction. However, PFAA release into porewater, which was initially in the 6 to 1200 ppt range for the different PFAAs, diminished to less than 7 ppt for each PFCA and no release of PFSAs above limits of quantitation. Evaluation of additional treatments including pre- and post-digest sludge (mostly anaerobic digestion) from a municipal wastewater treatment plant producing Class B biosolids to compare with an upcoming Cambi thermal hydrolysis process being implemented to produce Class A biosolids. We found that the concentrations of the PFAS being quantified (currently 36) increased significantly (~2 times) due largely due to increases in 5:3 FTA in all samples as well as L-N-MeFOSAA and PFPeA in some of the monthly samples, which are all known products of microbial degradation of precursors. A similar assessment was done for a single sample set for evaluating biosolids pre and post the autothermal aerobic digestion (ATAD) process. Post treatment PFAS levels led to increased concentrations of both PFCAs and PFSAs indicating precursor breakdown in the ATAD process with total PFAS quantified increasing by ~5 times. This is most likely due to aerobic microbial processes rather than the temperatures given they were relatively low (65-70 °C). The PFAAs that increased the most were PFBA, PFHxA and PFOA..

Future Activities:

For treatment of centrate and landfill leachate, we (UIC lead) will focus on benchmarking the removal of PFAS with the NF membrane/REM system for a variety of centrate and landfill leachate solutions. Based on these results we will determine if additional pretreatment is necessary. The REM reactor is currently being redesigned to improve the fluid dynamics and prevent leaking in the system. We will test both single-pass and recycle-mode operation strategies with the REM to determine an optimal mode of operation to improve PFAS removal. We will also explore catalyst addition (e.g., Bi-SnO₂) to enhance PFAS removal. We (UF lead) will complete the characterization of the collected biosolids to expand and finalize our multi-variate analysis of the relationship between biosolids characteristics and PFAS partitioning. We will characterize the oxalate extractable Al, Fe, and Ca, the total Al, Fe, and Ca, the OM%, and the PFAS of our WTR materials. We (Purdue lead) will conduct sorption-desorption experiments for the biosolid-based biochar of PFAS additions to see how well the biochar can capture incoming PFAS, e.g., PFAS released from unaltered biosolids. Future TOP assay results and suspect screening will allow us to evaluate the occurrence and % transformation of a suite of precursors. We will complete the TOP assays, suspect screening and pore-water assays for completing our evaluation of the treatment processes we are evaluating for changes in PFAS presence and distribution. The team will also be preparing and submitting at least two manuscripts as follows: (1) PFAS extraction and analysis methods for biosolids with varying properties that affect their extraction behavior; and (2) PFAS in WTRs, and submit conduct PFAS analysis of WTRs. In addition, we will begin drafting manuscripts on the effect of treatment processes (Cambi and ATAD) on PFAS occurrence and distribution; biosolid property correlation with PFAS partitioning, and the PFAS treatment in centrate work.

Journal Articles:

No journal articles submitted with this report: View all 14 publications for this project

Supplemental Keywords:

abiotic remediation, trace organics, availability

Progress and Final Reports:

Original Abstract

The 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.