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Land application of sewage sludge as a pathway for emerging contaminants: a comparative review of microplastics, PFAS, and pharmaceuticals.
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This review summarizes existing research on three contaminants found in sewage sludge spread on farmland: microplastics, PFAS chemicals, and pharmaceutical residues. It compares how each behaves in soil, finding they differ in persistence and mobility, and concludes that current treatment methods and regulations do not fully address these differences.
Agricultural application of treated sewage sludge supports nutrient and organic matter recovery but can also transfer emerging contaminants retained in or associated with sludge during wastewater treatment to soil. This review evaluates microplastics (MPs), per- and polyfluoroalkyl substances (PFAS), and pharmaceutical residues across their sources, sludge association, treatment response, agricultural loading, environmental fate, exposure pathways, potential effects, and regulation. Evidence identified through targeted searches of the Web of Science Core Collection and Scopus was integrated using a structured narrative review and comparative qualitative synthesis. These groups share a sludge-to-soil pathway but exhibit fundamentally different environmental profiles. MPs are retained mainly through physical association with solids and remain environmentally relevant through persistence, fragmentation, and size-dependent redistribution. PFAS behavior reflects compound-specific partitioning, the high persistence of many perfluoroalkyl acids (PFAAs), precursor transformation, and the greater mobility of many shorter-chain PFAAs under some soil conditions. Pharmaceutical residues show compound-specific variation in sorption, degradation, transformation, mobility, biological activity, and plant uptake. Conventional sludge treatments often redistribute contaminants or modify measured profiles without establishing destructive removal. High-temperature thermal processes may achieve greater destruction of some contaminants under suitable operating conditions, but transformation-aware whole-process mass balances remain necessary. Existing European Union and US sludge frameworks remain centered largely on conventional pollutants, although PFAS-related assessment and management are developing. The comparison demonstrates that occurrence alone does not establish risk and that a single uniform monitoring or management framework is inadequate. Class-specific monitoring, treatment evaluation, and long-term field evidence are needed to support environmentally defensible land application.
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Perfluoroalkyl and polyfluoroalkyl substances in sewage sludge: challenges of biological and thermal treatment processes and potential threats to the environment from land disposal
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This review summarizes data on PFAS (per- and polyfluoroalkyl substances, also known as 'forever chemicals') found in sewage sludge, which is commonly spread on farmland. Current biological and thermal treatment methods struggle to fully remove these persistent chemicals from sludge. While focused on PFAS rather than microplastics, the findings are relevant because both contaminants accumulate in sludge and enter the food chain when that sludge is applied to agricultural soil.
Assessing emerging and priority micropollutants in sewage sludge: environmental insights and analytical approaches
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Researchers reviewed the presence of emerging pollutants, including microplastics, pharmaceuticals, and industrial chemicals, in sewage sludge that is commonly applied to agricultural land. They found that current analytical methods are improving but still face challenges in detecting these contaminants at low concentrations in complex sludge samples. The study highlights the environmental risks of spreading pollutant-laden sludge on farmland and calls for better monitoring standards.
Emerging contaminants in biosolids: Presence, fate and analytical techniques
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Researchers reviewed how "emerging contaminants" — including pharmaceuticals, PFAS (forever chemicals), flame retardants, and microplastics — behave in sewage sludge (biosolids) and wastewater treatment plants, and how they can transform into potentially more toxic breakdown products. The review evaluated detection methods and called for better regulation and advanced analytical tools to track these pollutants as they move through water treatment systems and into the environment.
A review on the fate and effects of contaminants in biosolids applied on land: Hazards and government regulatory policies
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This review examines the contaminants, including microplastics and persistent organic pollutants, that remain in treated sewage sludge (biosolids) when it is applied to farmland as fertilizer. These pollutants can accumulate in soil and potentially enter crops and groundwater, creating exposure pathways to humans. The authors argue that current government regulations on biosolid use, particularly in the US, are outdated and need updating to address emerging contaminants like microplastics.
Fate of microplastics in sewage sludge and in agricultural soils
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Researchers reviewed how microplastics accumulate in sewage sludge at wastewater treatment plants and then spread into agricultural soils when that sludge is applied as fertilizer, finding that sludge treatment processes can alter microplastic size and shape but do not eliminate them. The review calls for standardized methods to study how different sludge treatments affect microplastic properties and their downstream risks to soil health.
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