Biotechnologies for removal of per- and polyfluoroalkyl substances (PFAS) in biosolids: Current status and challenges

Per- and polyfluoroalkyl substances (PFAS), widely recognized as "forever chemicals," pose significant environmental management challenges due to their persistence, mobility, and bioaccumulative behavior. Biosolids derived from wastewater treatment plants represent an important pathway for PFAS redistribution into terrestrial environments, particularly through land application. This review provides a comprehensive assessment of the global distribution, environmental behavior, toxicity, and biodegradation potential of PFAS in biosolids. A bibliometric analysis was conducted using the Web of Science database, and keyword co-occurrence mapping with VOSviewer was applied to evaluate research trends from 2018 to 2024. The findings indicate that research activity is concentrated in China (31%), Europe (30%), and North America (16%), with limited data available from South America, Oceania, and Africa, highlighting regional knowledge gaps. The environmental fate of PFAS in biosolids is governed by pH, temperature, redox conditions, and organic matter content, which influence sorption-desorption processes, mobility, and long-term persistence in soils. Biodegradation pathways include anaerobic reductive defluorination and aerobic oxidative transformation. Certain bacterial genera, such as Dehalobacter spp. and Gordonia spp., have demonstrated degradation efficiencies approaching 80-90% under optimized laboratory conditions. Fungal-mediated oxidative processes may further promote partial mineralization through enzymatic defluorination. In phytoremediation systems, long-chain PFAS preferentially accumulate in plant roots, whereas short-chain compounds exhibit greater mobility and translocation potential. Emerging remediation strategies integrating metagenomics, functional gene characterization, and enzyme-based treatments show promise for enhancing PFAS attenuation. However, substantial uncertainties remain regarding long-term bioaccumulation, biomagnification, and regulatory risk thresholds. Addressing these gaps is essential for developing science-based management strategies for PFAS-contaminated biosolids and protecting environmental and human health.