Efficient workflow for suspect screening analysis to characterize novel and legacy per- and polyfluoroalkyl substances (PFAS) in biosolids

Evaluation of PFAS extraction and analysis methods for biosolids

Per- and polyfluoroalkyl substances (PFAS) in the environment is a growing concern leading to a focus on PFAS occurrence in biosolids, a byproduct of wastewater treatment processes, often applied to improve soil health. This led to the need for analytical method development for assessing PFAS in biosolids. This study compares three methods for PFAS quantitation, evaluating solvent extraction, clean-up techniques, and final injection solvents. Three biosolids examined included not stabilized, anaerobically digested, and activated sludge with long-term lagoon-stabilized solids, resulting in differing properties. One method is a methanolic extraction with ENVI-Carb clean-up (ME), modified by adding isopropanol (ME-P) to the injection vial to prevent emulsification that can occur with more complex biosolids matrices. The second method was the U.S. EPA 1633 method involving additional solid-phase extraction (SPE) and filtration while the third method was Quick Easy Cheap Effective Rugged and Safe (QuEChERS), yet to be tested on biosolids. Method performance was evaluated based on instrument precision, limit of quantitation (LOQ), and extraction recoveries. PFAS concentrations and recoveries were similar for Me-P and 1633 methods while QuEChERS performed poorly. Method 1633 exhibited better reproducibility with lower relative standard deviations but had higher LOQ values due to sample dilution. Most LOQs ranged between 0.06 and 0.3 μg/kg across methods, while recovery of spiked native PFAS ranged between 70 and 130 % in most cases. Methanol-based mobile phases resulted in better peak shape. ME-P excelled in overall cost-effectiveness showing superior extraction efficiency with fewer operational steps compared to other methods for PFAS quantitation in biosolids.

Examining environmental matrix effects on quantitative non-targeted analysis estimates of per- and polyfluoroalkyl substances

Non-targeted analysis (NTA) is commonly used for the detection and identification of emerging pollutants, including many per- and polyfluoroalkyl substances (PFAS). While NTA outputs are often non-quantitative, concentration estimation is now possible using quantitative non-targeted analysis (qNTA) approaches. To date, few studies have examined matrix effects on qNTA performance, and little is therefore known about the implications of matrix effects on qNTA results and interpretations. Using a set of 19 PFAS, we examined the impacts of drinking water (DW) and waste-activated sludge matrices on qNTA performance across three qNTA approaches: one structure-independent approach based on "global" surrogates and two structure-dependent approaches based on "expert-selected" surrogates and predicted ionization efficiency (IE) regression. The performance of each qNTA approach was examined separately for the PFAS prepared in pure solvent, DW extract, and sludge extract using leave-one-out modeling. Performance was evaluated using previously defined qNTA metrics that describe predictive accuracy, uncertainty, and reliability. The studied sample matrices had minimal effects on qNTA accuracy and larger effects on qNTA uncertainty and reliability. Using solvent-based surrogate data to inform matrix-based estimations yielded lower uncertainty, but also lower reliability, emphasizing that uncertainty must be considered in context of reliability. No single qNTA approach uniformly performed best across all comparisons. Since the IE regression and global surrogates approaches proved most reliable, we recommended them for future qNTA applications. This study highlights the importance of examining multiple performance metrics and utilizing matrix-matched surrogate data in qNTA studies.

Comprehensive Evaluation of the Analytical Efficiency of Combustion Ion Chromatography for Per- and Polyfluoroalkyl Substances in Biological and Environmental Matrices

Combustion ion chromatography (CIC) has emerged as a valuable tool for determining fluorine content attributable to per- and polyfluoroalkyl substances (PFAS) in biological and environmental samples. The total organofluorine (TOF) data from CIC complement information obtained by targeted analyses using liquid chromatography-tandem mass spectrometry (LC-MS/MS) because TOF includes PFAS that may not be captured by targeted techniques. However, the effect of different PFAS types (chain lengths, head groups, etc.) and matrices on combustion efficiency has not been systematically evaluated. Comparison of C4-C12 PFAS using equimolar quantities of fluorine (5.27 nmol F) demonstrated statistically equivalent CIC responses, indicating uniform combustion across chain lengths. Further, signals resulting from combustion times ranging from 7.5 to 15 min were statistically equivalent. However, fluorotelomer alcohols (FTOHs) exhibited losses due to volatility, requiring the use of an activated carbon sorbent to improve analytical signals. Matrix variations exhibited no change in PFAS combustion efficiency across chain lengths in water, blood, and biosolids. Total fluorine results from CIC analysis of real blood and biosolid samples were compared to targeted LC-MS/MS results. This study highlights the strengths and limitations of CIC as an important complement to targeted PFAS analysis and provide guidance for optimizing application-specific conditions and interpreting CIC results.

Advancing sustainable agriculture through multi-omics profiling of biosolids for safe application: A review

Biosolids, derived from wastewater treatment processes, are valuable resources for soil amendment in agriculture due to their nutrient-rich composition. However, various contaminants of concern (CEC) such as pharmaceuticals, per-and poly-fluoroalkyl substances, endocrine disruptive chemicals, surfactants, pathogens, nanoplastics, and microplastics, are also reported in biosolids. The use of biosolids for agriculture may introduce these CEC into the soil, which raises concerns about their environmental and human health impacts. Moreover, the presence of pathogens (Escherichia coli, Salmonella sp., Shigella, Giardia, Rotavirus, etc.) even after treatment calls for microbial profiling of biosolids, especially in developing countries. Multi-omics approaches can be used as powerful tools for characterizing microbial communities and highlighting metabolic pathways. Moreover, these approaches also help in predicting the ecological and agronomic effects of biosolids application in agricultural soils. This review discusses the advantages and challenges of using biosolids in agriculture, considering the range of different CEC reported in biosolids. Moreover, the current legislation for the use of biosolids in agriculture is also presented, highlighting the limitations with respect to guidelines for emerging contaminants in biosolids. Furthermore, the role of the multi-omics approach in biosolids management, focusing on genomics, transcriptomics, proteomics, and metabolomics is also assessed. Multi-omics also allows for real-time monitoring, ensuring continuous optimization of biosolids towards changing environmental conditions. This dynamic approach not only enhances the safe use, but also enhances the sustainability of waste management practices, minimizing the negative effects. Finally, the future research directions for integrating the multi-omics approach into biosolid management practices are also suggested. The need for updating the legislative framework, continued innovation to promote sustainable and robust agricultural systems, bringing the process closer to the principles of a circular bioeconomy is also empahasized.

Simultaneous targeted and non-targeted analysis of contaminants in fertilizers in Quebec, Canada

In this study, an LC-MS based analytical method was developed and validated for the simultaneous targeted analysis (14 bisphenols and 14 plasticizers) and suspect screening of other plastic-related contaminants in various types of fertilizers. The ultrasound-assisted extraction method showed overall satisfactory performances, achieving a median absolute recovery of 85 % for the target compounds in different types of fertilizers. The method was applied to sixteen different types of fertilizers, including fertilizing residual materials (n = 8 types), one cattle manure, and seven mineral fertilizers collected in Quebec, Canada in 2022 and 2023. Relatively higher levels of the targeted bisphenols and plasticizers were detected in some fertilizing residual materials, such as municipal biosolids and deinking residues. 4-Hydroxyphenyl 4-isoprooxyphenylsulfone (D-8) and bis(2-ethylhexyl) phthalate (DEHP) were dominant contaminants in these matrixes, with concentrations up to 35.6 and 64.7 μg g-1 dw, respectively. A non-targeted workflow was successfully applied to municipal biosolids and deinking residues, and >30 contaminants were identified across multiple chemical families at level 1 identification confidence, with most of them previously unreported in various types of fertilizers. For example, new color developers, N-(2-((Phenylcarbamoyl)amino)phenyl)benzenesulfonamide (NKK-1304) and 2,4-bis(phenylsulfonyl)phenol (DBSP), were reported in deinking residues. This work illustrates the complexity of the contaminant mixtures in fertilizers such as municipal biosolids and deinking residues.

Understanding the impact of pre-digestion thermal hydrolysis process on PFAS in anaerobically digested biosolids

Per- and poly-fluoroalkyl substances (PFAS) present in biosolids are influenced by their source, treatment processes, and the dynamics of water resource recovery facilities (WRRF). Understanding these effects is vital for informed decisions in treatment process selection, however, comprehensive studies are sparse. This study examined the impact of anaerobic digestion (AD) and the addition of a thermal hydrolysis process (THP) before AD on PFAS in the solids stream at a WRRF. Targeted analysis of 58 PFAS (linear and branched) and suspect screening of the solid stream before and after AD as well as THP, with the total PFAS (ΣPFAS) concentrations ranging between 244 and 566 μg/kgdw. Precursor and intermediate PFAS, mainly di-substituted polyfluoroalkyl phosphate esters (diPAPs) followed by fluorotelomer carboxylic acids (FTCAs), were the dominant contributors (62-96 mol % ΣPFAS) in all 5 sample types. AD impacts were observed both before and after deploying THP altering the relative contribution of different PFAS classes through biotransformation, with an increase in PFCAs and a decrease in diPAPs. However, we observed that THP reduced the % of precursor conversion as well as conversion of the FTCA intermediates in the AD process as evidenced by a substantial increase in FTCAs post-THP + AD and lower PFCA generation compared to AD only. Total PFAS organofluorine (∑FPFAS) decreased by 28% pre- and post-AD, which on total fluorine (TF) showed a larger reduction to 43%. Fluoride was <3% of the TF in all cases, thus, the greater reduction in TF vs ∑FPFAS could be volatile losses of PFAS and other non-PFAS F-containing molecules. After THP installation, a 32% decrease in (∑FPFAS) was observed in the combined THP-AD system whereas adjusted total organofluorine increased by ∼43%. Overall, achieving higher solids handling capacity and energy neutrality with the THP addition did not lead to a significant difference in quantifiable PFAS concentrations compared to AD-only.

Neurotoxic Effects of Mixtures of Perfluoroalkyl Substances (PFAS) at Environmental and Human Blood Concentrations

Per- and polyfluoroalkyl substances (PFAS) may cause various deleterious health effects. Epidemiological studies have demonstrated associations between PFAS exposure and adverse neurodevelopmental outcomes. The cytotoxicity, neurotoxicity, and mitochondrial toxicity of up to 12 PFAS including perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, 6:2 fluorotelomer sulfonic acid (6:2 FTSA), and hexafluoropropylene oxide-dimer acid (HPFO-DA) were tested at concentrations typically observed in the environment (e.g., wastewater, biosolids) and in human blood using high-throughput in vitro assays. The cytotoxicity of all individual PFAS was classified as baseline toxicity, for which prediction models based on partition constants of PFAS between biomembrane lipids and water exist. No inhibition of the mitochondrial membrane potential and activation of oxidative stress response were observed below the cytotoxic concentrations of any PFAS tested. All mixture components and the designed mixtures inhibited the neurite outgrowth in differentiated neuronal cells derived from the SH-SY5Y cell line at concentrations around or below cytotoxicity. All designed mixtures acted according to concentration addition at low effect and concentration levels for cytotoxicity and neurotoxicity. The mixture effects were predictable from the experimental single compounds' concentration-response curves. These findings have important implications for the mixture risk assessment of PFAS.

Suspect screening of per-and polyfluoroalkyl substances in paper by selective and non-selective extraction with UHPLC-Q orbitrap MS

Non-targeted analysis and suspect screening of per- and polyfluoroalkyl substances (PFAS) in various matrices have gained traction with advancements in accurate mass analytical instruments. This study employed ultra-high performance liquid chromatography coupled to quadrupole orbitrap high-resolution mass spectrometry for PFAS suspect screening of paper grades used in the paper recycling chain. The samples were prepared using two extraction techniques; selective accelerated solvent extraction with weak anionic exchange solid-phase extraction and non-selective ultrasonic-assisted extraction. A suspect screening protocol was established to tentatively identify suspected PFAS against spectral databases using a systematic approach of peak filtering and study-specific thresholds for reporting, linked to a confidence level. The possible prevalence of previously unreported PFAS in several paper materials across the various collection sites in the paper recycling chain was inferred by the common detection of short-chain polyfluoroalkyl ketones and diketones in the paper recycling chain. The suspect screening tentatively identified 41 unique PFAS, with 3 common to both pre-treatment techniques. The detection of unique PFAS by the two sample pre-treatment techniques highlighted the significance of both selective and non-selective extraction in PFAS screening endeavours. Further, it showed the importance of understanding the acquisition mechanisms employed in mass spectrometry where data-dependent acquisition triggered fragmentation in certain identified compounds, and not in others. The tentatively identified PFAS indicated that there were several previously unreported PFAS in the paper recycling chain and that additional studies were required to investigate their abundance, possible persistence, bioaccumulation and toxicity, in relation to their functional groups and carbon chains.

Influence of water chemistry and operating parameters on PFOS/PFOA removal using rGO-nZVI nanohybrid

Graphene and zero-valent-iron based nanohybrid (rGO-nZVI NH) with oxidant H2O2 can remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) through adsorption-degradation in a controlled aquatic environment. In this study, we evaluated how and to what extent different environmental and operational parameters, such as initial PFAS concentration, H2O2 dose, pH, ionic strength, and natural organic matter (NOM), influenced the removal of PFOS and PFOA by rGO-nZVI. With the increase in initial PFAS concentration (from 0.4 to 50 ppm), pH (3 to 9), ionic strength (0 to 100 mM), and NOM (0 to 10 ppm), PFOS removal reduced by 20%, 30%, 2%, and 6%, respectively, while PFOA removal reduced by 54%, 76%, 11%, and 33% respectively. In contrast, PFOS and PFOA removal increased by 10% and 41%, respectively, with the increase in H2O2 (from 0 to 1 mM). Overall, the effect of changes in environmental and operational parameters was more pronounced for PFOA than PFOS. Mechanistically, •OH radical generation and availability showed a profound effect on PFOA removal. Also, the electrostatic interaction between rGO-nZVI NH and deprotonated PFAS compounds was another key factor for removal. Most importantly, our study confirms that rGO-nZVI in the presence of H2O2 can degrade both PFOS and PFOA to some extent by identifying the important by-products such as acetate, formate, and fluoride.

PFΔScreen - an open-source tool for automated PFAS feature prioritization in non-target HRMS data

Per- and polyfluoroalkyl substances (PFAS) are a huge group of anthropogenic chemicals with unique properties that are used in countless products and applications. Due to the high stability of their C-F bonds, PFAS or their transformation products (TPs) are persistent in the environment, leading to ubiquitous detection in various samples worldwide. Since PFAS are industrial chemicals, the availability of authentic PFAS reference standards is limited, making non-target screening (NTS) approaches based on high-resolution mass spectrometry (HRMS) necessary for a more comprehensive characterization. NTS usually is a time-consuming process, since only a small fraction of the detected chemicals can be identified. Therefore, efficient prioritization of relevant HRMS signals is one of the most crucial steps. We developed PFΔScreen, a Python-based open-source tool with a simple graphical user interface (GUI) to perform efficient feature prioritization using several PFAS-specific techniques such as the highly promising MD/C-m/C approach, Kendrick mass defect analysis, diagnostic fragments (MS2), fragment mass differences (MS2), and suspect screening. Feature detection from vendor-independent MS raw data (mzML, data-dependent acquisition) is performed via pyOpenMS (or custom feature lists) with subsequent calculations for prioritization and identification of PFAS in both HPLC- and GC-HRMS data. The PFΔScreen workflow is presented on four PFAS-contaminated agricultural soil samples from south-western Germany. Over 15 classes of PFAS (more than 80 single compounds with several isomers) could be identified, including four novel classes, potentially TPs of the precursors fluorotelomer mercapto alkyl phosphates (FTMAPs). PFΔScreen can be used within the Python environment and is easily automatically installable and executable on Windows. Its source code is freely available on GitHub ( https://github.com/JonZwe/PFAScreen ).

Burning questions: Current practices and critical gaps in evaluating removal of per- and polyfluoroalkyl substances (PFAS) during pyrolysis treatments of biosolids

Concerns surrounding potential health and environmental impacts of per- and polyfluoroalkyl substances (PFAS) are growing at tremendous rates because adverse health impacts are expected with trace-level exposures. Extreme measures are required to mitigate potential PFAS contamination and minimize exposures. Extensive PFAS use results in the release of diverse PFAS species from domestic, industrial, and municipal effluents to wastewater, which partition to biosolids throughout secondary treatment. Biosolids generated during municipal wastewater treatment are a major environmental source of PFAS due to prevailing disposal practices as fertilizers. Pyrolysis is emerging as a viable, scalable technology for PFAS removal from biosolids while retaining nutrients and generating renewable, raw materials for energy generation. Despite early successes of pyrolysis in PFAS removal, significant unknowns remain about PFAS and transformation product fates in pyrolysis products and emissions. Applicable PFAS sampling methods, analytical workflows, and removal assessments are currently limited to a subset of high-interest analytes and matrices. Further, analysis of exhaust gases, particulate matter, fly ashes, and other pyrolysis end-products remain largely unreported or limited due to cost and sampling limitations. This paper identifies critical knowledge gaps on the pyrolysis of biosolids that must be addressed to assess the effectiveness of PFAS removal during pyrolysis treatment.

A review on the fate and effects of contaminants in biosolids applied on land: Hazards and government regulatory policies

The increase in world population growth and its resultant increase in industrial production to meet its need, have continued to raise the volume of wastewater received by treatment plant facilities. This has expectedly, led to an upsurge in the volume of sewage sludge and biosolids generated from wastewater treatment systems. Biosolids are best managed by application on land because of their agronomic benefits. However, this usage has been discovered to negatively affect humans and impact the environment due to the accumulation of minute concentrations of contaminants still present in the biosolid after treatment, hence the need for government regulations. This review article examined the fate and effects of pollutants, especially persistent organic pollutants (PoPs) of concern and emerging contaminants found in biosolids used for land applications, and also discussed government regulations on biosolid reuse from the perspectives of the two major regulations governing biosolid land application-the EU's Sludge Directive and USEPA's Part 503 Rule, in an attempt to draw attention to their outdated contents since enactment, as they do not currently meet the challenges of biosolid land application and thus, require a comprehensive update. Any update efforts should focus on USEPA's Part 503 Rule, which is less stringent on the allowable concentration of biosolid pollutants. Furthermore, an update should include specific regulations on new and emerging contaminants and persistent organic pollutants (PoPs) such as microplastics, pharmaceutical and personal care products (P&PCPs), surfactants, endocrine-disrupting chemicals, flame retardants, pathogens, and organic pollutants; further reduction of heavy metal standard limits, and consideration of soil phosphate-metal interactions to regulate biosolid agronomic loading rate. Future biosolid research should focus on the concentration of TCS, TCC, and emerging pharmaceuticals, as well as Microplastic transport in biosolid-amended soils, soil-plant transfer mechanism, and metabolism of PFAs in the soils; all of which will inform government policies on biosolid application on land.

Quantitation of Total PFAS Including Trifluoroacetic Acid with Fluorine Nuclear Magnetic Resonance Spectroscopy

Fluorine nuclear magnetic resonance (19F-NMR) spectroscopy has been shown to be a powerful tool capable of quantifying the total per- and polyfluoroalkyl substances (PFAS) in a complex sample. The technique relies on the characteristic terminal -CF3 shift (-82.4 ppm) in the alkyl chain for quantification and does not introduce bias due to sample preparation or matrix effects. Traditional quantitative analytical techniques for PFAS, such as liquid chromatography-mass spectrometry (LC-MS) and combustion ion chromatography (CIC), contain inherent limitations that make total fluorine analysis challenging. Here, we report a sensitive 19F-NMR method for the analysis of total PFAS, with a limit of detection of 99.97 nM, or 50 μg/L perfluorosulfonic acid. To demonstrate the capabilities of 19F-NMR, the technique was compared to two commonly used methods for PFAS analysis: total oxidizable precursor (TOP) assay and LC-high resolution MS analysis for targeted quantification and suspect screening. In both cases, the 19F-NMR analyses detected higher total PFAS quantities than either the TOP assay (63%) or LC-MS analyses (65%), suggesting that LC-MS and TOP assays can lead to underreporting of PFAS. Importantly, the 19F-NMR detected trifluoroacetic acid at a concentration more than five times the total PFAS concentration quantified using LC-MS in the wastewater sample. Therefore, the use of 19F-NMR to quantify the total PFAS in highly complex samples can be used to complement classic TOP or LC-MS approaches for more accurate reporting of PFAS contamination in the environment.

Pyrolysis and Co-Combustion of Semi-Dry Sewage Sludge and Bituminous Coal: Kinetics and Combustion Characteristics

To reduce the energy consumption and cost of the drying of sewage sludge (SS) and to ensure stability during combustion, the pyrolysis and co-combustion characteristics of semi-dry SS after the dehydration of flocculant and bituminous coal (BC) were studied in this work. The results show that the decrease in moisture content accelerates the release of volatile substances, and the increase in heating rate can also enhance the release of water and volatile matters. Furthermore, in the co-combustion of semi-dry SS and BC, the increase in mixing ratio (from 0% to 60%) of semi-dry SS caused the ignition and burnout temperature to decrease from 481 °C to 214 °C and from 702 °C to 627 °C, respectively. During co-combustion, the infrared spectra showed that the temperature range of 300–700 °C was the main gas precipitation area, and the main gaseous products were CO2, NOx, SO2, and volatile organic pollutants (VOCs).