Per‐ and polyfluoroalkyl substances (PFAS) are refractory anthropogenic chemicals and current treatment processes at municipal water resource recovery facilities (WRRFs) cannot efficiently degrade them, hence, these chemicals cycle through the environment. Certain PFAS can be concentrated in biosolids from WRRFs and are commonly land applied for beneficial reuse. Given recent advances in measurement of PFAS, documentation of the range of concentrations in pre‐stabilized sludge and stabilized biosolids is critical to evaluating treatment best practices and assessing potential human health and ecological risks. In this study, pre‐stabilized sludge and post‐stabilized biosolids samples were collected from 12 major WRRFs across the United States. PFAS were analyzed using Environmental Protection Agency (EPA) Method SW846‐3500C/537.1, and Draft EPA Method 1633, by one commercial laboratory and two university research laboratories, respectively. Results comparison among laboratories demonstrated statistical differences in PFAS concentrations among split samples. For example, 5:3 FTCA (fluorotelomer carboxylic acid) concentrations in post‐stabilized sludge at Lab 1 were measured at 21 ng/g (dry), while they were detected at 151 ng/g (dry) in Lab 3. Further, higher PFAS concentrations were observed in post‐stabilized biosolids compared to pre‐stabilized sludges, regardless of the laboratory or analysis method, even when solids destruction through solids stabilization was considered. Further research is required to refine methods for analyses of PFAS in sludge and biosolids samples from WRRFs prior to being used for development of regulatory actions as well as understanding how various treatment protocols could impact concentrations of PFAS in land‐applied biosolids.

Per‐ and polyfluoroalkyl substances (PFAS) are being studied in all environmental matrices because of their ubiquitous presence and adverse human health impacts. This study conducted a surveillance of 27 water resource recovery facilities throughout the United States and Canada to screen the range of PFAS concentrations in pre‐stabilized sludge and post‐stabilized product. Among the 27 water resource recovery facilities, 82% use anaerobic digestion and the rest use chemical stabilization and/or incineration for sludge stabilization. Forty PFAS compounds were evaluated by US Environmental Protection Agency Method SW846/537.1, and four and nine compounds were reported in the pre‐stabilized sludge and post‐stabilized product, respectively. Concentrations of reported compounds in pre‐stabilized sludge and post‐stabilized product varied from 5 to 33 ng/g dry basis and 2 to 220 ng/g dry basis, respectively. 3‐Perfluoropentylpropanoic acid (5:3 FTCA) and perfluorooctanesulfonic acid (PFOS) were the most frequently observed compounds, and PFAS concentrations in the post‐stabilized products were generally higher than the corresponding pre‐stabilized sludge. Practitioner Points: Among the 40 target PFAS, four were above reporting limit in the pre‐stabilized sludge and nine in the post‐stabilized product. Incineration ash (post‐stabilized product) samples did not have any reportable PFAS. 5:3 FTCA and PFOS were the two frequently observed compounds; concentrations were higher in the post‐stabilized product compared to the pre‐stabilized sludge. PFPeA and PFHxA were the only two short chain perfluoroalkyl carboxylic acids reported. PFOA was reported in only one of the 54 samples evaluated.

Performic acid (PFA) has emerged as a promising disinfectant for wastewater effluents and combined sewer overflows (CSOs), offering strong microbial inactivation with minimal formation of harmful disinfection byproducts (DBPs). This review systematically evaluates existing research on PFA performance across primary effluent, CSOs, and secondary effluent, emphasizing microbial inactivation kinetics, exposure modeling, DBP formation, and toxicity, while identifying knowledge gaps. Compared with traditional disinfectants such as free chlorine, chlorine dioxide, chloramines, and peracetic acid, PFA demonstrates comparable or superior bacterial inactivation while generating substantially lower concentrations of regulated halogenated DBPs. PFA also generates diverse oxygenated and nitrogen-containing transformation products, with PAA behaving similarly, whereas chlorine and chloramines form more persistent halogenated and nitrogenous byproducts. Disinfection efficacy of PFA varies across microbial groups, with enterococci, spores, and protozoan cysts demonstrating greater resistance, consistent with patterns observed for other disinfectants. However, PFA achieves faster inactivation at equivalent doses. Studies indicate that integral CT (ICT)-based models more accurately describe PFA inactivation under real wastewater conditions by capturing disinfectant decay and non-ideal hydraulics. DBP formation during PFA disinfection remains low, with halogenated DBPs detected only at high PFA concentrations (≥30 mg/L), and no nitrosamine formation reported. Acute toxicity assays show low ecotoxicity, although responses differ among species. Despite these promising findings, research gaps remain regarding PFA reactivity with complex wastewater matrices, inactivation of human enteric viruses and resistant bacterial spores, environmental fate of transformation products, and long-term ecological impacts. Overall, this review highlights PFA's strong potential as a safer, effective disinfectant for wastewater treatment and identifies critical areas for future investigation to support full-scale implementation.

This study evaluated thermal and thermo-alkaline post-treatment of digested cattle manure (DCM) as a strategy to increase methane recovery and improve the flexibility of biogas systems within hybrid renewable energy alternatives. A 10 L mesophilic CSTR was operated for 311 days, producing lignin-rich digestate that was subjected to a statistically designed range of post-treatment conditions varying temperature (50–90 °C), pH (8–12), and contact time (6–24 h). Biomethane potential assays and lignocellulosic fractionation were used to determine changes in solubilization, biodegradability, and methane production kinetics. Thermal treatment provided modest improvements, reaching 84 mg SCOD g⁻¹ PCOD solubilization and a 26 mL CH₄ g⁻¹ COD increase in methane yield. Thermo-alkaline treatment produced substantially higher enhancements, with the most severe condition (90 °C-pH 12–24 h) achieving 493 mg SCOD g⁻¹ PCOD solubilization, 66% removal of structural carbohydrates, and a 60.2 mL CH₄ g⁻¹ COD increase in methane yield, corresponding to a 16% rise in biodegradability and a twofold increase in methane production rate. Gompertz modeling indicated accelerated kinetics and minimal lag time. A strong linear correlation (R² = 0.90) between severity index and solubilization supported predictable scalability. These results demonstrate that thermo-alkaline hydrolysis can significantly enhance post-digestion methane recovery and strengthen the role of agricultural biogas in integrated renewable energy systems. The techno-economic analysis revealed that, despite higher operating costs for thermo-alkaline post-treatment than for the control, the main drivers are chemical costs and the price of renewable energy, and thus the application of post-treatment as a sustainable solution for animal manure treatment will likely improve as renewable energy prices increase in the future.