Land Application Of Biosolids Research Articles

Surveillance of PFAS in sludge and biosolids at 12 water resource recovery facilities.

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 21ng/g (dry), while they were detected at 151ng/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.

Biosolids management and utilizations: A review

Biosolids, derived from wastewater treatment processes, have garnered increasing attention as a valuable resource due to their rich organic and inorganic constituents, which can be beneficially utilized in multiple sectors, including agriculture, civil engineering, and energy recovery. The present review article begins by providing an overview of biosolids, including their production methods and classification based on treatment processes. Subsequently, the chemical composition of biosolids is explored, highlighting the diverse array of organic and inorganic components present. The characterization techniques employed for analyzing biosolids, such as spectroscopy, chromatography, and microscopy, are thoroughly discussed, emphasizing their role in determining the quality and suitability of biosolids for different applications. Furthermore, the environmental impacts associated with biosolids disposal are extensively examined. This includes the potential risks posed by heavy metals, pathogens, and emerging contaminants, as well as strategies for mitigating these risks through proper treatment and management practices. In addition to environmental considerations, the article explores the various products that can be derived from biosolids. These include organic matter-rich soil amendments for agricultural applications, inorganic nutrient supplements for enhancing plant growth, and the potential for energy recovery through anaerobic digestion and thermal conversion technologies. The utilization of biosolids in civil engineering projects, such as landfill capping and construction materials, is promising. Land application of biosolids also can have economic and waste management benefits (e.g., conservation of landfill space; reduced demand on non-renewable resources like phosphorus; and a reduced demand for synthetic fertilizers).

Emerging organic contaminants in the soil-plant-receptor continuum: transport, fate, health risks, and removal mechanisms.

There is a lack of comprehensive reviews tracking emerging organic contaminants (EOCs) within the soil-plant continuum using the source-pathway-receptor-impact-mitigation (SPRIM) framework. Therefore, this review examines existing literature to gain insights into the occurrence, behaviour, fate, health hazards, and strategies for mitigating EOCs within the soil-plant system. EOCs identified in the soil-plant system encompass endocrine-disrupting chemicals, surfactants, pharmaceuticals, personal care products, plasticizers, gasoline additives, flame retardants, and per- and poly-fluoroalkyl substances (PFAS). Sources of EOCs in the soil-plant system include the land application of biosolids, wastewater, and solid wastes rich in EOCs. However, less-studied sources encompass plastics and atmospheric deposition. EOCs are transported from their sources to the soil-plant system and other receptors through human activities, wind-driven processes, and hydrological pathways. The behaviour, persistence, and fate of EOCs within the soil-plant system are discussed, including sorption, degradation, phase partitioning, (bio)transformation, biouptake, translocation, and bioaccumulation in plants. Factors governing the behaviour, persistence, and fate of EOCs in the soil-plant system include pH, redox potential, texture, temperature, and soil organic matter content. The review also discusses the environmental receptors of EOCs, including their exchange with other environmental compartments (aquatic and atmospheric), and interactions with soil organisms. The ecological health risks, human exposure via inhalation of particulate matter and consumption of contaminated food, and hazards associated with various EOCs in the soil-plant system are discussed. Various mitigation measures including removal technologies of EOCs in the soil are discussed. Finally, future research directions are presented.

A comparison of Tier 1, 2, and 3 methods for quantifying nitrous oxide emissions from soils amended with biosolids

Municipal biosolids are a nitrogen (N)-rich agricultural fertilizer which may emit nitrous oxide (N2O) after rainfall events. Due to sparse empirical data, there is a lack of biosolids-specific N2O emission factors to determine how land-applied biosolids contribute to the national greenhouse gas inventory. This study estimated N2O emissions from biosolids-amended land in Canada using Tier 1, Tier 2 (Canadian), and Tier 3 (Denitrification and Decomposition model [DNDC]) methodologies recommended by the Intergovernmental Panel on Climate Change (IPCC). Field data was from replicated plots at 8 site-years between 2017 and 2019 in the provinces of Quebec, Nova Scotia and Alberta, Canada, representing three distinct ecozones. Municipal biosolids were the major N source for the crop, applied as mesophilic anaerobically digested biosolids, composted biosolids, or alkaline-stabilized biosolids alone or combined with an equal amount of urea-N fertilizer to meet the crop N requirements. Fluxes of N2O were measured during the growing season with manual chambers and compared to N2O emissions estimated using the IPCC methods. In all site-years, the mean emission of N2O in the growing season was greater with digested biosolids than other biosolids sources or urea fertilizer alone. The emissions of N2O in the growing season were similar with composted or alkaline-stabilized biosolids, and no greater than the unfertilized control. The best estimates of N2O emissions, relative to measured values, were with the Tier 3 > adapted Tier 2 with biosolids-specific correction factors > standard Tier 2 = Tier 1 methods of the IPCC, according to the root mean square error statistic. The Tier 3 IPCC method was the best estimator of N2O emissions in the Canadian ecozones evaluated in this study. These results will be used to improve methods for estimating N2O emissions from agricultural soils amended with biosolids and to generate more accurate GHG inventories.

Agronomic impacts of new regulations governing land application of Class B biosolids in Florida

AbstractAlthough land application of biosolids is an attractive option for beneficial reuse, it represents a complex challenge for government and private organizations. This 3‐year field study evaluated the agronomic impacts of reduced biosolids rates imposed by new regulations in Florida on bahiagrass (Paspalum notatum Flugge) herbage accumulation and nutritive value. Treatments consisted of a factorial combination of two phosphorus (P) sources (triple superphosphate and biosolids) applied at 0 (control), 20 (low), 40 (intermediate), and 60 kg total P ha−1 (high). Triple superphosphate plots received the same nitrogen (N) load (from ammonium nitrate) as the corresponding biosolids treatments. Bahiagrass herbage accumulation increased with increasing P and associated N rates. Bahiagrass annual herbage accumulation ranged from 2120 kg ha−1 in 2022 to 6970 kg ha−1 in 2020 and was 33%–80% less than previously published data. This was likely due to the reduced biosolids rates that did not supply sufficient N and P to sustain adequate forage production. Lesser herbage accumulation will likely lead to greater application of inorganic fertilizers, which generally have greater environmental footprint than biosolids. Biosolids generally resulted in either similar or greater bahiagrass crude protein, in vitro digestible organic matter, and tissue mineral concentrations than inorganic fertilizer. Similarly, no differences in bahiagrass N and P recovery between biosolids and inorganic fertilizer were observed. This study, along with a significant body of literature, demonstrated that biosolids have considerable fertilizer value and can be an effective alternative to commercial inorganic fertilizer while also providing environmental and economic benefits.

Accumulation of microplastics in soil after long-term application of biosolids and atmospheric deposition

Land-applied biosolids can be a considerable source of microplastics in soils. Previous studies reported microplastics accumulation in soils from biosolid application, however, little is known about the contribution of atmospherically deposited microplastics to agricultural soils. In this study, we quantified and characterized microplastics in soils that have been amended with biosolids over the past 23 years. We also collected atmospheric deposition samples to determine the amount and type of plastics added to soils through atmospheric input over a period of about 2 years. Soil samples were taken from a replicated field trial where biosolids have been applied at rates of 0, 4.8, 6.9, and 9.0 t/ha every second crop. The biosolids were anaerobically digested and dewatered, and were applied by spreading onto the soil surface. Soil and atmospheric samples were extracted for microplastics by Fenton's reaction to remove organic matter followed by flotation in a zinc chloride solution to separate plastic from soil particles. Samples were analyzed for microplastics by optical microscopy and Laser Direct Infrared Imaging Analysis (LDIR). The mean number of microplastics identified from biosolids samples was 12,000 particles/kg dry biosolids. The long-term applications of biosolids to the soil led to mean plastics concentrations of 383, 500, and 361 particles/kg dry soil in the 0–10 cm depth for low, medium, and high biosolids application rates, respectively. These plastic concentrations were not significantly different from each other, but significantly higher than those found in non biosolids-amended soil (117 particles/kg dry soil). The dominant plastic types by number found in biosolids were polyurethane, followed by polyethylene, and polyamide. The most abundant plastics in soil samples were polyurethane, polyethylene terephthalate, polyamide, and polyethylene. Atmospheric deposition contributed to 15 particles/kg dry soil per year and was mainly composed of polyamide fibers. This study shows that long-term application of biosolids led to an accumulation of microplastics in soil, but that atmospheric deposition also contributes a considerable input of microplastics.

Identifying sources of antibiotic resistance genes in the environment using the microbial Find, Inform, and Test framework.

Antimicrobial resistance (AMR) is an increasing public health concern for humans, animals, and the environment. However, the contributions of spatially distributed sources of AMR in the environment are not well defined. To identify the sources of environmental AMR, the novel microbial Find, Inform, and Test (FIT) model was applied to a panel of five antibiotic resistance-associated genes (ARGs), namely, erm(B), tet(W), qnrA, sul1, and intI1, quantified from riverbed sediment and surface water from a mixed-use region. A one standard deviation increase in the modeled contributions of elevated AMR from bovine sources or land-applied waste sources [land application of biosolids, sludge, and industrial wastewater (i.e., food processing) and domestic (i.e., municipal and septage)] was associated with 34-80% and 33-77% increases in the relative abundances of the ARGs in riverbed sediment and surface water, respectively. Sources influenced environmental AMR at overland distances of up to 13 km. Our study corroborates previous evidence of offsite migration of microbial pollution from bovine sources and newly suggests offsite migration from land-applied waste. With FIT, we estimated the distance-based influence range overland and downstream around sources to model the impact these sources may have on AMR at unsampled sites. This modeling supports targeted monitoring of AMR from sources for future exposure and risk mitigation efforts.

High potential of coupling the source-separation and incineration promotion to reduce costs based on city-level cost-benefit analysis of municipal solid waste management strategies in China

To screen the optimum strategy of municipal solid waste (MSW) management toward the goal “zero-waste city” in China, in this study, a tailored system including six indicators of waste of land resource, greenhouse gas emissions, human toxicity, energy recovery, biomass recovery, and paper/plastic recovery were developed and total costs were quantified based on city-level cost-benefit analysis considering the city socioeconomic characteristics. Results show that the systemic change scenario which couples the MSW source-separation, incineration promotion, and biosolid land application has the best performance in total net cost reduction by US$154 billion during 2021–2030, of which US$80 billion is external cost. Due to the change in external cost of land resources, the marginal cost of MSW treatment varies significantly with city groups, with megalopolises being 3 times as other city groups. The high external cost of land resources further underscores the importance of reducing the final landfilled waste mass for megalopolises.

A Path to a Reduction in Micro and Nanoplastics Pollution

Microplastics (MP) are plastic particles less than 5 mm in size. There are two categories of MP: primary and secondary. Primary or microscopic-sized MP are intentionally produced material. Fragmentation of large plastic debris through physical, chemical, and oxidative processes creates secondary MP, the most abundant type in the environment. Microplastic pollution has become a global environmental problem due to their abundance, poor biodegradability, toxicological properties, and negative impact on aquatic and terrestrial organisms including humans. Plastic debris enters the aquatic environment via direct dumping or uncontrolled land-based sources. While plastic debris slowly degrades into MP, wastewater and stormwater outlets discharge a large amount of MP directly into water bodies. Additionally, stormwater carries MP from sources such as tire wear, artificial turf, fertilizers, and land-applied biosolids. To protect the environment and human health, the entry of MP into the environment must be reduced or eliminated. Source control is one of the best methods available. The existing and growing abundance of MP in the environment requires the use of multiple strategies to combat pollution. These strategies include reducing the usage, public outreach to eliminate littering, reevaluation and use of new wastewater treatment and sludge disposal methods, regulations on macro and MP sources, and a wide implementation of appropriate stormwater management practices such as filtration, bioretention, and wetlands.

Higher concentrations of microplastics in runoff from biosolid-amended croplands than manure-amended croplands

Land-applied municipal biosolids, produced from municipal wastewater treatment sludge, contributes to microplastics contamination in agroecosystems. The impacts of biosolids on microplastic concentrations in agricultural soil have been previously investigated, however, the potential for microplastics transport from biosolid-amended croplands has not been previously quantified. In this study, manure and biosolids were applied to field plots, runoff was collected following natural precipitation events and the potential of bacterial biofilm to grow on different microplastic morphologies was investigated. Higher concentrations of microplastics were detected in runoff from plots with land-applied biosolid in comparison with manure-amended and control plots. Fibers and fragments were the most frequently detected plastic morphologies in runoff, correlated with their decreased surface roughness. The potential of biosolids to contribute to microplastic contamination to U.S. surface waters was quantified which is among the first to quantify the potential for nonpoint source microplastic contamination of surface waters adjacent to agricultural production areas.

PFAS release from wastewater residuals as a function of composition and production practices

Per- and polyfluoroalkyl substances (PFAS) are a class of highly persistent contaminants that have been linked to human health effects at low exposure concentrations. Public concerns exist that land-application of biosolids may result in the release of PFAS into terrestrial and aquatic ecosystems. The relative importance of inorganic constituents such as Fe and Al, which are known to impact PFAS retention/release behavior in soils, on PFAS release from wastewater residuals (WWRs, i.e., biosolids and sewage sludges) is not well understood. Here, we examine native concentrations and WWR-water partition coefficients of a range of PFAS in the context of WWRs characteristics including oxalate-extractable Fe and Al, organic matter (OM), dissolved organic carbon, and total protein content. Total PFAS concentrations, which included perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, fluorotelomer sulfonates and some sulfonamides, ranged from ∼480 to 3500 μg PFAS kg−1 dry weight. PFAS WWR-water partition coefficients ranged from ∼10 to 20,000 L kg−1, consistent with the literature. PFAS partitioning was significantly correlated to oxalate extractable Al and Fe as well as bulk OM and protein content. These results have important implications for wastewater treatment facilities that recycle Al- and Fe-based drinking water treatment residuals in terms of both PFAS retention and loading.

Trace Element Uptake by Willows Used for the Phytoremediation of Biosolids.

The land application of biosolids can result in the unacceptable accumulation of Trace Elements (TEs) in agricultural soil and potentially introduce xenobiotics and pathogens into the food chain. Phytoremediation of biosolids aims to minimize this risk, while producing valuable biomass. Willows, well known to accumulate zinc (Zn), are used extensively in farming systems for soil conservation, shelter and as feed supplements with demonstrable health benefits. Potentially, biosolids phytoremediation could occur on marginal lands adjacent to farmlands where willows are grown for supplementary fodder. We aimed to determine the uptake and distribution of Zn and other TEs in willows grown on soils amended with biosolids and biosolids blended with biochar, with a view to their use as stock fodder. In the Canterbury Region, New Zealand, we grew Salix 'tangaio' (S. matsudana X S. alba) in a greenhouse trial and field study. The biomass production of the willows was unaffected by biosolids and increased by the biosolids+biochar mixture. The addition of 4% biosolids (w/w) to the soil resulted in a foliar Zn concentration of 600-1000 mg kg-1, some 25 times higher than the average New Zealand pasture. Zinc concentrations were highest in the bottom leaves and increased throughout the season. Biosolids addition doubled the copper (Cu) concentration to 10 mg kg-1. Adding biochar to the system reduced the plant uptake of Cu and to a lesser extent Zn, while cadmium (Cd) uptake was unaffected. For Cd, Cu, and Zn, plant uptake was a function of the Ca(NO3)2-extractable concentration, both in greenhouse experiments and the field trial. Future work should determine the changes in plant TE uptake over several growing seasons.

Pyrolysis transports, and transforms, PFAS from biosolids to py-liquid

Per- and poly-fluoroalkyl substances (PFAS) in wastewater solids have resulted in bans on land application of biosolids, causing utilities to explore thermal treatment options.

Is PFAS from land applied municipal biosolids a significant source of human exposure via groundwater?

Per and polyfluoroakyl substances (PFAS) are emerging contaminants of critical concern commonly found in the bloodstream of most humans in the U.S. They are present in both Class A and B municipal biosolids. The potential for contamination of groundwater following land application of biosolids and subsequent leaching of PFAS through soil is one of several potential impacts that have generated discussions of possible bans on land application. In this commentary, we discuss the many factors that need to be considered to address the question: “Is PFAS from land applied biosolids a significant source of human exposure via groundwater?” The occurrence of PFAS in biosolids and biosolids-amended soils is discussed, as are the many factors that affect the potential for subsequent groundwater contamination. Additional critical factors are also noted.

Public Perceptions of Faecal Sludge Biochar and Biosolids Use in Agriculture

Full-scale pyrolysis of faecal sludge is a credible technology for the safe removal of pathogens and the concurrent creation of biochar, which has been shown to enhance crop productivity. Faecal sludge biochar has the potential to improve acidic, low nutrient soils and crop yield in developing nations more at risk of climate change and food insecurity. Little research has been conducted into public acceptance of faecal sludge biochar as a soil enhancer in agriculture. In this study of the public in Swansea, Wales, an online survey examines their awareness of, and comfort levels of eating food grown using biosolids, wood biochar and faecal sludge biochar. Our findings show that males were almost twice as likely than females to have a positive perception of biosolids (OR 1.91, p value 0.004) and faecal sludge biochar (OR 2.02, p value 0.03). Those in the oldest age group (65+) were almost five times more likely to have a positive view of faecal sludge biochar than the youngest age group (OR 4.88, p value 0.001). Deployment of faecal sludge biochar must overcome a “disgust effect” related to its human faecal origins. This factor must be centrally taken into account when implementing management and policy decisions regarding the land application of biosolids and faecal sludge biochar.

Ecological Risk Analysis for Benzalkonium Chloride, Benzethonium Chloride, and Chloroxylenol in US Disinfecting and Sanitizing Products.

Use of three topical antiseptic compounds-benzalkonium chloride (BAC), benzethonium chloride (BZT), and chloroxylenol (PCMX)-has recently increased because of the phaseout of other antimicrobial ingredients (such as triclosan) in soaps and other disinfecting and sanitizing products. Further, use of sanitizing products in general increased during the coronavirus (COVID-19) pandemic. We assessed the environmental safety of BAC, BZT, and PCMX based on best available environmental fate and effects data from the scientific literature and privately held sources. The ecological exposure assessment focused on aquatic systems receiving effluent from wastewater-treatment plants (WWTPs) and terrestrial systems receiving land-applied WWTP biosolids. Recent exposure levels were characterized based on environmental monitoring data supplemented by modeling, while future exposures were modeled based on a hypothetical triclosan replacement scenario. Hazard profiles were developed based on acute and chronic studies examining toxicity to aquatic life (fish, invertebrates, algae, vascular plants) and terrestrial endpoints (plants, soil invertebrates, and microbial functions related to soil fertility). Risks to higher trophic levels were not assessed because these compounds are not appreciably bioaccumulative. The risk analysis indicated that neither BZT nor PCMX in any exposure media is likely to cause adverse ecological effects under the exposure scenarios assessed in the present study. Under these scenarios, total BAC exposures are at least three times less than estimated effect thresholds, while margins of safety for freely dissolved BAC are estimated to be greater than an order of magnitude. Because the modeling did not specifically account for COVID-19 pandemic-related usage, further environmental monitoring is anticipated to understand potential changes in environmental exposures as a result of increased antiseptic use. The analysis presented provides a framework to interpret future antiseptic monitoring results, including monitoring parameters and modeling approaches to address bioavailability of the chemicals of interest. Environ Toxicol Chem 2022;41:3095-3115. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Extraction, analysis, and occurrence of per- and polyfluoroalkyl substances (PFAS) in wastewater and after municipal biosolids land application to determine agricultural loading

Given the ubiquitous detection of per- and polyfluoroalkyl substances (PFAS) within numerous soil and water environmental compartments, there is a need for global understanding of current methodologies for extracting water, solids, polar organic chemical integrative samplers (POCIS), and plant tissue for these substances. This study provides details of several current extraction methods, demonstrates the use of POCIS in monitoring these compounds in a wastewater environment, and provides evidence of detectable levels of certain PFAS compounds within Midwestern municipalities and agroecosystems. Validated extraction procedures help characterize occurrence and release of 18 PFAS in a midwestern wastewater treatment plant (WWTP), surface water, runoff after land application of biosolids to agricultural test plots, infiltration into topsoil, and uptake by grain sorghum. Of the compounds measured, 14 PFAS were detected at least at one sampling site or type. The average total (Σ PFAS) dissolved phase time-weighted average (TWA) concentration in wastewater influent, effluent and in the upstream and downstream effluent mixing zone (EMZ) sites in the receiving stream, respectively, were 27.9, 132, 37.7, and 71.4 ng L−1. Long-chain PFAS dominated most of the aqueous compartments, and perfluoroalkyl acids (PFAAs) occurred in the WWTP and receiving surface waters. Total Σ14 PFAS measured in municipal biosolids applied to soils were 22.9 ng g−1 dw with long-chain PFAS comprising 77.5% of the cumulative PFAS mass. Perfluorooctanesulfonic acid (PFOS) was the most abundant compound detected in biosolids at the highest concentration (9.40 ng g−1 dw). Accumulation in WWTP biosolids was estimated to occur at a rate of 72.8 g day−1 dw based on the difference between influent and effluent time weighted average concentrations. PFAS were detected in both surface soil and runoff after land application of biosolids, but also in control plots consistent with background PFAS contamination. PFAS concentrations in surface runoff decreased over time from plots treated with biosolids. These results provide evidence of the introduction of PFAS to agroecosystems from wastewater effluent and land application of biosolids in the Midwest.

The Effects of Five-Year Biosolid Application on the Diversity and Community of Soil Arthropods

Land application of biosolids is a beneficial form of management, although heavy metal contamination is a major concern. Biosolid application can shape the abundance, species richness, and community structure of arthropods, which are important regulators of soil processes. We investigated the effect of the five-year (2012–2017) application of domestic biosolids at 0, 15, 30, and 45 ton ha−1 on the soil properties, enzyme activity, heavy metal concentrations, abundance, and diversity of soil arthropods in degraded sandy soil. The results showed that the application of a high amount of biosolids resulted in an increase in soil organic carbon of 2.6 times and in the water content of 2.8 times compared with CK (no biosolids). The total metal concentrations of Cr, Ni, Cu, Zn, Cd, and Pb increased by 6.6%, 3.2%, 6.6%, 7.7%, 13.3%, and 22.5%, respectively, compared with CK in soil (p > 0.05). The activities of seven enzymes, which mainly participate in carbon (C), nitrogen (N), phosphate (P), and sulfur (S) transformation, increased by 1.53%~122.7%, indicating that the soil function did not change under biosolid application. The number of individual arthropods collected from a square meter of soil changed from 0 to 2560. The total abundance of arthropods increased from 1.2 to 4 times under biosolid application (p < 0.05), but biosolid application had no effects on simple measures of richness and diversity (Shannon–Weaver index). Multivariate ordination techniques showed a significant shift of the arthropod community structure under biosolid application due to differing responses of several taxa to the biosolids. Redundancy analysis highlighted the influential role of soil chemical properties (soil organic C, total N, water content, microbial biomass, and pH) and cadmium in shaping the soil arthropod structure. These results suggest that long-term biosolid application with limited heavy metal concentrations does not have detrimental effects on soil arthropods or microbial-related soil function.

Simulated leaching of PFAS from land-applied municipal biosolids at agricultural sites

Biosolids are an important resource for agricultural practice but have recently received increased focus as a potential source of per- and polyfluoroalkyl substances (PFAS) in the environment. Few studies have investigated the transport of PFAS through the unsaturated zone under conditions relevant to biosolids application sites. Herein, the unsaturated flow and transport model HYDRUS is used to evaluate the leaching of per- and polyfluoroalkyl substances (PFAS) from land-applied biosolids used in agricultural practice to determine the impacts of PFAS leaching on underlying groundwater resources. This numerical case study was based on conditions and operations at two test sites in central Illinois where biosolids were applied at agronomic rates and where PFAS contents and desorption characteristics were previously characterized. Each site possessed different vadose zone soil textural heterogeneity. Simulations were performed under actual present-day meteorological conditions and extended 150 years beyond the initial biosolids application. These long-term simulations demonstrate how soil equilibrium sorption/desorption processes within the biosolids-amended surface soils effectively control the transport rate of individual PFAS to groundwater. Air-water interfacial (AWI) adsorption, which is sometimes considered to be a significant source of PFAS retention in vadose zone soils, was observed to have minimal impacts on PFAS leaching rates within the biosolids-amended surface soils at these sites. Additionally, the impact of AWI adsorption was found to be most significant for PFAS transport within the underlying vadose zone soils when these soils were more texturally homogeneous and considerably less significant within the texturally heterogeneous soils represented herein. The results of multiple long-term simulations were used to develop an empirical equation that relates predicted maximum PFAS pore-water concentrations reaching the saturated zone with changes in PFAS concentrations in the biosolids-amended soil for various biosolids re-application events. This approach is shown to be very useful in developing site-specific PFAS soil screening levels and/or maximum leachate levels for PFAS in support of establishing best management practices (BMPs) for land application of biosolids.

Durable Plastic Goods: A Source of Microplastics and Chemical Additives in the Built and Natural Environments

Marine plastic pollution by single-use packaging is an emerging concern. However, more than half of all plastics manufactured are designed and utilized for longer-term uses (e.g., as indoor furnishings, insulation, electrical devices, conduits, and textiles). Such durable plastics are more likely to contain persistent, bioaccumulative, and toxic chemical additives (PBTs). Considerable additives and polymer fragments are released into enclosed indoor spaces over the service lives of these plastic products, with resultant human exposure, and then pass to wastewater treatment plants. However, globally only approximately half of all wastewaters receive any treatment. For affluent nations, efficiencies of removal of microplastics and PBTs of ≥90% are commonly quoted for effluents, but some wastewaters therein receive primary or less treatment. Regardless, PBTs and microplastics largely survive even sophisticated treatment, and most are deposited into settled solids. Such “biosolids” may then be repurposed to enrich soils due to their nutrient content. Associated contaminants may affect soil communities and later be dispersed via hydrologic and aeolian processes. To date, regulatory efforts have been insufficient to stem microplastic and additive emissions to air, water, and soils. Upgrading wastewater treatment to tertiary and excluding floating or primary settled solids from land-applied biosolids would substantially reduce releases of these contaminants.