Legacy and emerging flame retardants in sediments and wastewater treatment plant-derived biosolids.

A baseline assessment of legacy and emerging flame retardant chemicals was performed in inland and transitional sediments as well as biosolids emanating from a selection of wastewater treatment plants (WWTPs) in Ireland. A selection of 24 polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and chlorinated organophosphate esters (Cl-OPEs) were quantified in: 81 inland and transitional sediment samples collected during 2023; 39 transitional sediments collected between 2018 and 2022; and 21 biosolid samples collected from 7 WWTPs over 4-month intervals in January, May, and September 2023. Highest concentrations of BDE-209 and several Cl-OPEs were detected in both sediment and biosolid samples, while most PCBs and penta-/octa-BDEs were comparatively low. Moderate levels of PBDEs and Cl-OPEs were detected in Irish sediments compared to similar studies conducted internationally. In biosolid samples, levels of BDE-209 were on the higher end of figured reported worldwide while levels of Σ8Cl-OPEs were the highest relative to comparable international studies. PCBs meanwhile are on the lower end of international levels for both biosolids and sediments. Based on available predicted no-effect concentrations (PNECs), the majority of compounds assessed were found to be of low-risk based on their levels in sediments with the exception of TCIPP (Risk Quotient - RQ = 1.354 = high risk) as well as EHDPP, TEHP, PCB-118, and PCB-52 (RQ = 0.948, 0.576, 0.446, and 0.257 respectively = moderate risk). Similar risk assessment could not be performed on contaminants in biosolids, though levels of BDE-209 were on the higher end of figured reported worldwide (avg = 3155 ng/g) while levels of Σ8Cl-OPEs were the highest relative to comparable international studies (avg8 = 3290 ng/g). As the legacy PBDEs and PCBs have been listed as persistent organic pollutants (POPs) and replacement flame retardants such as Cl-OPEs have been flagged by programmes such as human biomonitoring for EU (HBM4EU) and the NORMAN Network as chemicals of emerging concern, continued monitoring of these moderate and high-risk contaminants in sediments, as well as an investigation of potential contamination of the food chain through land-spreading of biosolids on agricultural lands, would be warranted.

Microplastics and per- and polyfluoroalkyl substances (PFAS) in landfill-wastewater treatment systems: A field study.

Landfills and wastewater treatment plants (WWTP) are point sources for many emerging contaminants, including microplastics and per- and polyfluoroalkyl substances (PFAS). Previous studies have estimated the abundance and transport of microplastics and PFAS separately in landfills and WWTPs. In addition, previous studies typically report concentrations of microplastics as particle count/L or count/g sediment, which do not provide the information needed to calculate mass balances. We measured microplastics and PFAS in four landfill-WWTP systems in Illinois, USA, and quantified mass of both contaminants in landfill leachate, WWTP influent, effluent, and biosolids. Microplastic concentrations in WWTP influent were similar in magnitude to landfill leachates, in the order of 102 µg plastic/L (parts-per-billion). In contrast, PFAS concentrations were higher in leachates (parts-per-billion range) than WWTP influent (parts-per-trillion range). After treatment, both contaminants had lower concentrations in WWTP effluent, although were abundant in biosolids. We concluded that WWTPs reduce PFAS and microplastics, lowering concentrations in the effluent that is discharged to nearby surface waters. However, partitioning of both contaminants to biosolids may reintroduce them as pollutants when biosolids are landfilled or used as fertilizer.

Preliminary human health risk assessment of antibiotic exposures in human waste handling occupations.

Exposure to biosolids in human waste handling occupations is associated with a risk for illness due to microbial infections. Although several years of exposure to biosolids might be hypothesized to be a prophylaxis against infection, the risks associated with infections from antibiotic-resistant organisms can also be a potential concern. Therefore, this study aimed to conduct a screening level risk assessment by deriving occupational exposure limits (OELs) characterizing the risks of adverse health effects among workers in human waste handling occupations with a focus on exposure to two pharmaceuticals commonly found in biosolids: ciprofloxacin (CIP) and azithromycin (AZ). Epidemiological and exposure studies of workers exposed to biosolids were identified through searches of major scientific databases. Screening OELs (sOELs) for these antibiotics were derived using a standardized methodology. The airborne concentrations of CIP and AZ antibiotics were determined using an exposure factors approach. The health-based exposure limits (i.e., sOELs) and the acceptable daily exposure (ADE) values for both of these antibiotics were derived as 80 µg/m3 and 12 µg/kg-day, respectively. An exposure factor approach suggested that inhalation route exposures to CIP and AZ are well below the sOELs and ADE daily doses, and likely too low to cause direct adverse health effects through antibiotic inhalation. A critical review of epidemiological studies on different occupations handling biosolids showed that the workers in industries with potential biosolids exposure have experienced an increased incidence of microbial-exposure-related illness. The health effects seen in the workers have been attributed to bacterial, viral, and protozoan infections. To the extent that bacteria are the pathogen of concern, it is not clear whether these bacteria are resistant to antibiotics commonly found in biosolids. It is also unclear whether the presence of antibiotics or antibiotic-resistant bacteria increases the susceptibility of these workers. Additional studies will provide more definitive estimates of inhalation and dermal exposures to CIP and AZ and could verify the exposure estimates in this study based on the literature and common exposure factors.

A critical review on emerging industrial applications of chars from thermal treatment of biosolids.

Thermochemical treatment is rapidly emerging as an alternative method for the management of stabilised sewage sludges (biosolids) to effectively reduce waste volume, degrade contaminants, and generate valuable products, particularly biochar and hydrochar. Biosolids-derived char has a relatively high concentration of heavy metals compared with agricultural chars but is still applied to land due to its beneficial properties and ability to retain metals. However, non-agricultural applications can provide additional economic and environmental benefits, promote sustainability and support a circular economy. This review identifies extensive non-agricultural opportunity for biosolids biochar, including adsorption, catalysis, energy storage systems, biological process enhancement, and as additives for rubber compounding and construction. Biosolids chars have received limited attention vs agricultural char, and we draw on both areas of literature, as well as evaluating differences between agricultural and biosolids chars. A key opportunity for biosolids biochar in comparison with other materials and agricultural chars is its sustainable and low-cost nature, relatively high metals content, improving catalyst properties, and ability to modify in various stages to tune it to specific applications. The specific opportunities for hydrochar have only received limited attention. Research needs to include better understanding of the benefits and limitations for specific applications, as well as adjacent drivers, including society, regulation, and market and economics.

Comparing occurrence of per- and polyfluoroalkyl substances (PFAS) in municipal biosolids and industrial wastewater sludge: A City of Los Angeles study.

Biosolids and sludge are what remain after the liquid fraction of wastewater is separated during wastewater treatment. These high organic content matrices are known to contain organic contaminants, a few of which are the hazardous and environmentally persistent per- and polyfluoroalkyl substances (PFAS). The current study investigates whether sludge from a treatment facility serving mostly industrial establishments and biosolids from a facility serving mostly domestic dwellings retain these 'forever chemicals' similarly. Using 31 markers covering different classes of PFAS, the sludge was found to contain higher levels of PFAS (869 ± 791 ng/g; 21 of 31) than biosolids (31 ± 7 ng/g, 11 of 31). The most abundant overall was perfluorooctane sulfonic acid (PFOS), mostly in sludge (range: 71-1300 ng/g versus 0-18 ng/g in biosolids). The large PFAS concentration variability in sludge was seasonal and sinusoidal. Sludge, additionally, contained all long chain PFAS, precursors (mostly surfactant ingredients and their transformation byproducts) and short chain PFAS (perhaps because of higher moisture content). By regression, the sludge is shown to consistently contain twice as much PFAS as biosolids when the same amounts are exposed to increasing levels of PFAS. Factors observed to cause differential PFAS retention between sludge and biosolids were moisture (98.6 % and 72.1 %, respectively), chain length, input quality (industrial versus residential) and functional group. Sulfonic acids for instance are one C atom shorter than carboxylates with similar occurrence in sludge and biosolids. More studies are needed to define the roles that organic carbon of sludge/biosolids, water chemistry, temperature and factors not considered here play in partitioning PFAS between the two matrices with respect to inputs. Existing Koc values could not help in explaining observed trends, but the ratio of biosolids-to-influent concentrations was found to correlate positively with PFAS size. Using influent in the ratio, and not effluent, is novel. SYNOPSIS: Sludge and biosolids are soil amendments; they contain hazardous and persistent PFAS. Methods of decoupling PFAS from these matrices start with understanding matrix-driven PFAS partitioning as shown here.

PFAS in biosolids: Accumulation characteristics and fate profiles after land application.

The land application of biosolids as a management practice is considered a beneficial use for improving crop yield and reducing the need for other fertilizers. PFAS enter wastewater treatment plants through collection networks, including industrial discharges, the use of PFAS-containing products, and runoff. Therefore, PFAS may be present in biosolids derived from sewage sludge. The objectives of this study were to evaluate PFAS levels in biosolids samples collected at two wastewater treatment plants operated by the Miami Dade Water and Sewer Department (MDWASD): (1) the South District Wastewater Treatment Plant (SDWWTP) which received landfill leachate and (2) the Central District Wastewater Treatment Plant (CDWWTP). Sludge samples were collected after thickening, anaerobic digestion, and dewatering processes. The samples were subjected to batch leaching tests for 30 days. After the leaching tests, the PFAS levels in the liquid and solid fractions were analyzed for 40 PFAS. The findings show that during the aeration process (i.e., activated sludge process), PFAS are removed from the wastewater and accumulate on the solids. When the thickened sludge is digested, some PFAS are released to the liquid phase as the volatile solids decompose. During the dewatering process by centrifugation, PFAS that are partitioned to the liquid phase are removed, reducing PFAS content in the dewatered biosolids. Of the 40 PFAS analyzed, 24 were detected in leachate or solid residue samples. Samples from the SDWWTP had higher levels of PFAS due to the contribution from landfill leachate discharged to this facility. The partitioning of PFAS between the liquid phase and solid residue after 30 days of mixing indicates that the majority of PFAS in the biosolids are highly soluble and have a high tendency to be mobilized (by runoff, irrigation, precipitation) after land application. The fate profiles of PFAS biosolids were evaluated in terms of their solubility and retardation characteristics.

Transport and Accumulation of Microplastics from Biosolids to Australian Agricultural Soils: Detection of Microplastics Down to 1 µm.

The shift toward sustainable agriculture involves replacing inorganic fertilizers with organic alternatives like biosolids. However, concerns arise over emerging contaminants, such as microplastics (MPs), which remain largely unregulated. Despite their common use in Australia, the transfer of MPs from biosolids to agricultural soils remains largely unknown. Herein, we have investigated the abundance, characteristics, and transport of MPs resulting from biosolids application in two Queensland agricultural sites. MP concentrations were significantly higher in biosolid-amended soils (average of 1137 MPs/kg) than in reference sites (average of 36 MPs/kg), correlating with the volume, time since application, and frequency of biosolids application. MPs > 25 µm were predominantly polyethylene, polypropylene, and poly(methyl methacrylate) fragments (up to 85%). Fibers constitute only 15-30% of MPs and mainly in larger sizes (average 1011 µm), whereas fragments (average 188 µm) and beads (average 72 µm) had smaller size ranges. Despite analytical challenges using Raman spectroscopy, detected smaller MPs (1-25 µm) were fragments composed of polyethylene, polypropylene, and poly(vinyl alcohol). This study provides the first report of MPs down to 1 µm in Australian agricultural soils. Our findings suggest a need to assess the long-term impact of MPs in biosolids on soil health and food safety. We call on policymakers to consider the implementation of effective MP source control strategies and the development of guidelines for acceptable biosolids application rates.

Biogeochemical stability of organic covers and mine wastes under climate change simulated mesocosms.

Mine environments in boreal and sub-boreal zones are expected to experience extreme weather events, increases in temperature, and shifts in precipitation patterns. Climate change impacts on geochemical stability of tailings contaminants and reclamation structures have been identified as important climate-related challenges to Canadian mining sector. Adapting current reclamation strategies for climate change will improve long-term efficiency and viability of mine tailings remediation/restoration strategies under a changing climate. Accordingly, mesocosm experiments were conducted to investigate associations of climate-driven shifts in microbial communities and functions with changes in the geochemistry of organic covers and underlying tailings. Our results show that warming appears to significantly reduce C:N of organic cover and promote infiltration of nitrogen into deeper, unoxidized strata of underlying tailings. We also observed an increase in the abundance of some nitrate reducers and sulfide oxidizers in microbial communities in underlying tailings. These results raise the concern that warming might trigger oxidation of sulfide minerals (linked to nitrate reduction) in deeper unoxidized strata where the oxygen has been eliminated. Therefore, it would be necessary to have monitoring programs to track functionality of covers in response to climate change conditions. These findings have implications for development of climate resilient mine tailings remediation/restoration strategies.

Vermistabilization of excess sludge employing Eisenia fetida: Earthworm histopathological alterations and phytotoxicity evaluation.

The aim of this work was to stabilize excess sludge (ES) coming from a wastewater treatment plant (WWTP) by vermistabilization and to evaluate ecotoxicological effects over the earthworm species Eisenia fetida. Three mixtures were made up in triplicate using different volume ratios of ES and soil (S) (100% ES, 70:30% ES:S and 30:70% ES:S in wet weight basis). Earthworms were added in order to compare vermicomposting vs. natural stabilization. The mixtures were monitored over 130 days through physical, chemical, pathological and biological analysis, following quality standards depicted in the US EPA 40 CFR Part 503, local regulations and background studies. Histopathological samples were processed as biomarkers of acute and chronic toxicity on earthworms, and germination assays were performed at the end of the experiment to assess phytotoxicity. In terms of pathogen depletion comparing initial and final values from each treatment, the mixtures with higher ES proportions (70 and 100%) with earthworms were the most efficient ones registering 64.8 and 75.5% of reduction of fecal coliforms (FC) respectively, while the lowest ES proportion with earthworms (30%) showed 54.7%. Final pathogens content in all the treatments with earthworms were significantly lower (ranged from 1360 to 1760 MPN g total solids-1) than the values registered in treatments without earthworms (ranged from 2400 to 4000 MPN g total solids-1) (p < 0.05). However, none of the treatments attained class A categorization (FC ≤ 1000 MPN g total solids-1) in terms of FC. Also, values of mean cocoon production and hatched juveniles along time were significantly higher in the treatments with 100 and 70% ES (p < 0.05), while the higher mean adult biomass was detected in the treatment with 30% ES. Volatile solids decrease ranged between 8.45 and 22.34% in treatments with earthworms and all values of specific oxygen uptake rate were below 1.5 mg O2 h -1 g total solids -1. There were not negative effects over behavior or reproduction of E. fetida adults, nor the presence of external and internal injuries. Final products from mixtures with earthworms presented a humus-like structure, were odorless and reached maturity values -presenting no phytotoxicity-with significant differences between germination index values of treatments with and without earthworms (p < 0.05). Vermistabilization is a successful eco-technology to sanitize excess sludge, acquiring an added-value material and contributing to its revalorization as organic amendments or fertilizers in soils within the circular economy framework and the United Nations' Sustainability Development Goals.

Elimination of microplastics, PFAS, and PPCPs from biosolids via pyrolysis to produce biochar: Feasibility and techno-economic analysis.

Biosolids from municipal wastewater treatment contain many contaminants of emerging concern, including microplastics (MPs), per- and polyfluoroalkyl substances (PFAS), pharmaceuticals and chemicals from personal care products (PPCPs). Many of these contaminants have very slow biotic or abiotic degradation rates and have been shown to have human and ecological health impacts. Application of biosolids to agriculture, a common disposal method, can result in extended environmental contamination. An approach for eliminating the contaminants is pyrolysis, which can also generate biochar, enhancing carbon sequestration as a side-benefit. We pyrolyzed biosolid samples from an operating facility at various temperatures from 400 to 700 °C with a 2-hour residence time. We then evaluated contaminant removal, which in many cases was 100 %, with only a few residuals. No trace of PFAS was detectable even at 400 °C. Overall mass removal of PPCPs, including PFAS, was over 99.9 %. MP removal via pyrolysis ranged from 91 to 97 %. The biochar contains significant amounts of Fe and P, which make it a useful fertilizer amendment. The techno-economic analysis indicates that pyrolysis may generate significant cost savings, and revenue from the sale of biochar, sufficient to more than cover the investment and operating costs of the dryer and pyrolysis unit.

Size and polarity fractions of mobile organic matter from manure affect the sorption of sulfadiazine, caffeine and atenolol in soil.

Waste-derived organics introduced to soils along with pharmaceutical active compounds (PhAC) are a crude mixture of compounds occurring in various size and polarity fractions. They affect the sorption of PhACs to soil; however, the relevant knowledge is still insufficient. The effects of different size and polarity fractions of manure-derived mobile organic matter (<63 µm) on the sorption of sulfadiazine, caffeine and atenolol to five topsoils were investigated. Mobilization of the PhACs was strongest in the presence of dissolved organic matter (mDOM, <0.45 µm), with a reduction of Kd of sulfadiazine, caffeine and atenolol by mean factors of 0.66, 0.57 and 0.41, respectively. The mobilizing effects of colloidal organic matter (0.45-10 µm) were slightly smaller. Fine particulate organic matter (10-63 µm) reduced the sorption of the PhACs in slightly acidic soils (pH 6.0), but increased it in strongly acidic soil (pH 4.3). Furthermore, hydrophobic (HO-mDOM) and hydrophilic (HI-mDOM) fractions of mDOM reduced the sorption capacity but increased the sorption nonlinearity of PhACs in soils. Effects of HO-mDOM and HI-mDOM were PhAC specific. It is suggested to consider the varying impacts of mobile fractions in animal manure and/or treated wastewater in evaluating the fate and environmental relevance of associated PhACs.

Quantifying levels of per- and polyfluoroalkyl Substances (PFAS) in water and serum after contamination from agricultural biosolid application.

The National Academies of Sciences, Engineering, and Medicine recommends per- and polyfluoroalkyl substance (PFAS) blood testing for patients with risk of elevated exposure, and the Agency for Toxic Substances and Disease Registry (ATSDR) suggests PFAS blood testing based on exposure. Barriers to PFAS blood testing include cost, access to labs, and evolving laboratory methods. We quantify water and serum PFAS levels among a highly-exposed cohort in an area with groundwater contaminated by historical agricultural biosolid application. We compare the gold standard PFAS serum test with a commercial test and results from a one-compartment toxicokinetic model. Participants were adults (n = 30) whose household (n = 19) water had levels of the sum of six PFAS > 500 ng/L. Serum PFAS were measured using liquid chromatography-tandem mass spectrometry. Demographic and water consumption data were collected via telephone. Serum PFAS results from the commercial test were accessed via medical record. Statistical analysis included descriptive statistics and bivariate plots of serum levels. Perfluorohexanoic acid, perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorobutanesulfonic acid, perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonic acid (PFOS) were detected in 19 wells, and PFHpA, PFOA, PFNA, perfluorodecanoic acid, perfluoroundecanoic acid, PFHxS, and PFOS were detected in at least 19 participants' serum. In well water, PFOA and PFOS levels had geometric means (GMs) of 1749 ng/L (geometric standard deviation [GSD] 2.4) and 887 ng/L (GSD 19.7), respectively. In serum, PFOA and PFOS had GMs of 116.2 µg/L (GSD 13.5) and 58.3 µg/L (GSD 13.8), respectively. Our results are comparable with and had a wider mix of PFAS than other high-exposure cohorts. There was good agreement between the commercial and gold standard tests for PFOA, PFNA, and PFHxS, and mixed agreement between the gold standard test and modeled predictions, suggesting water-based toxicokinetic models of serum PFAS may be inadequate for assessing exposure in this population.

The state of the art in biosolids gasification.

Biosolids is a by-product of wastewater treatment that needs to be further processed. Traditional biosolids treatment and disposal technologies are inefficient under the current demanding standards. Thermochemical conversion technologies have been employed for biosolids management, with gasification being the most promising due to the production of syngas, a gaseous product that may be used for the production of energy or high-added-value substances through reforming reactions. Gasification is a complex thermochemical process; its performance and yield are strongly affected by the type of feedstock, but also by the system configuration and process conditions. Gasification usually takes place at temperatures between 700 and 1,200 °C, but it may also occur at lower temperatures (above 375 °C: supercritical water gasification) or at higher temperatures (above 3,000 °C: plasma gasification). The present review briefly presents the biosolids management practices, focusing on the gasification process and syngas treatment, while the state of the art in biosolids gasification is critically presented and discussed. A number of types of gasifiers (more frequently fluidized bed, but also fixed bed, rotary kiln, downdraft, etc.), gasifying agents, and operational conditions have been used for biosolids gasification. The key results of the study regarding biosolids gasification are: (i) the increase of temperature and equivalence ratio enhances the gasification performance, resulting in high syngas yield and quality, high cold gas efficiency, and low tar and char production; (ii) the calorific value of the obtained syngas tends to decrease with the increase of equivalence ratio; and (iii) the use of catalysts has been proven to substantially improve the gasification performance, compared to non-catalytic gasification. The proper selection of technical parameters determines the effectiveness of biosolids gasification, which is considered as a promising technology for the energy recovery from biosolids, so to upgrade wastewater treatment and improve environmental quality.

A method for the extraction of microplastics from solid biowastes including biosolids, compost, and soil for analysis by µ-FTIR.

Few methods exist detailing the extraction of microplastics from organic matrices. A validated method for the successful extraction of microplastics from solid biowastes including biosolids, compost, and soil for spectroscopic analysis by micro-Fourier transform infrared spectroscopy (µ-FTIR) was developed. Solid dry biowastes were first digested with a wet peroxide oxidation (WPO) with iron (II) solution and 30% hydrogen peroxide followed by sequential density separations with ultra-pure water and 1.8 g cm-3 NaI in an optimised sediment-microplastic isolation (SMI) unit. The average recoveries for spiked microplastics were 92, 95 and 98% for bagged compost, biosolids, and soil, respectively. This method ensures a high microplastic recovery by first chemically disintegrating biowaste aggregates without employing destructive methods like milling and allows for successful density separations where the settled fraction is isolated off from the supernatant, allowing thorough rinsing of the equipment and thus a greater transferal of particles into the vacuum filtering device. Minimal processing steps reduce the instance of introducing contamination and particle loss.•Digestion as a first step to disintegrate aggregates to release entrapped microplastics•Density separation with SMI unit with the method adapted for biowastes•Minimal steps to reduce contamination and particle loss.

Improving nutrients ratio in class A biosolids through vivianite recovery: Insights from a wastewater resource recovery facility.

Class A biosolids from water resource recovery facilities (WRRFs) are increasingly used as sustainable alternatives to synthetic fertilizers. However, the high phosphorus to nitrogen ratio in biosolids leads to a potential accumulation of phosphorus after repeated land applications. Extracting vivianite, an FeP mineral, prior to the final dewatering step in the biosolids treatment can reduce the P content in the resulting class A biosolids and achieve a P:N ratio closer to the 1:2 of synthetic fertilizers. Using ICP-MS, IC, UV-Vis colorimetric methods, Mössbauer spectroscopy, and SEM-EDX, a full-scale characterization of vivianite at the Blue Plains Advanced Wastewater Treatment Plant (AWTTP) was surveyed throughout the biosolids treatment train. Results showed that the vivianite-bound phosphorus in primary sludge thickening, before pre-dewatering, after thermal hydrolysis, and after anaerobic digestion corresponded to 8 %, 52 %, 40 %, and 49 % of the total phosphorus in the treatment influent. Similarly, the vivianite-bound iron concentration also corresponded to 8 %, 52 %, 40 %, and 49 % of the total iron present (from FeCl3 dosing), because the molar ratio between total iron and total incoming phosphorus was 1.5:1, which is the same stoichiometry of vivianite. Based on current P:N levels in the Class A biosolids at Blue Plains, a vivianite recovery target of 40 % to ideally 70 % is required in locations with high vivianite content to reach a P:N ratio in the resulting class A biosolid that matches synthetic fertilizers of 1:1.3 to 1:2, respectively. A financial analysis on recycling iron from the recovered vivianite had estimated that 14-25 % of Blue Plain's annual FeCl3 demand can potentially be met. Additionally, model simulations with Visual Minteq were used to evaluate the pre-treatment options that maximize vivianite recovery at different solids treatment train locations.

Study on the fate of per- and polyfluoroalkyl substances during thermophilic anaerobic digestion of sewage sludge and the role of granular activated carbon addition.

Limited information is available on the removal of per- and polyfluoroalkyl substances (PFAS) in anaerobic digestion (AD). Τhe fate of six PFAS was studied in thermophilic bioreactors in the presence of granular activated carbon (GAC) and voltage application. Reactors with GAC exhibited lower concentrations of volatile fatty acids and higher methane production compared to those with and without the application of voltage. Analysis of PFAS in dissolved and solid phase showed that their distribution was dependent on perfluorocarbon chain length and functional group. Mass balances showed that PFAS were not removed during conventional AD or after applying voltage; however, significant removal (up to 61 ± 8 %) was observed in bioreactors with GAC for perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS). Biomass characterization showed that in these bioreactors, the relative abundance of Acinetobacter and Pseudomonas was higher, indicating their potential role in PFAS biotransformation.

Using organic amendments in disturbed soil to enhance soil organic matter, nutrient content and turfgrass establishment.

Disturbed soils, including manufactured topsoils, often lack physical and chemical properties conducive to vegetation establishment. As a result, efforts to stabilize disturbed soils with vegetation are susceptible to failure. Urban organic waste products such as wood mulch, composted leaf and yard waste, and biosolids are widely distributed as organic amendments that enhance sustainability and plant establishment. Correct use can be determined by examining soil properties such as pH; the concentration of soluble salts (SS); and plant available nutrients - particularly N, C and P; as well as root and shoot growth. This research examined the effects of three typical organic amendments on fertility, establishment, and nutrient loss. A manufactured topsoil was used as the base soil for all treatments, including a control unamended soil (CUT), and soil amended with either mulch (MAT), composted leaf and yard waste (LAT), or biosolids (BAT). A 2 % organic matter concentration increase was sought but not achieved due to difficulty in reproducing lab results at a larger scale. Results showed that LAT improved soil fertility, particularly N-P-K concentrations while maintaining a good C:N ratio, pH, and SS concentration. BAT was the most effective at enhancing shoot growth but results suggest that improved growth rates could result in increased maintenance. Additionally, biosolids were an excellent source of nutrients, especially N-P-K and S, but diminished root growth and N leachate losses indicate that N was applied in excess of turfgrass requirements. Therefore, biosolids could be used as fertilizer, subject to recommended rates for turfgrass establishment to prevent poor root growth and waterborne N pollution. To ensure establishment efforts are successful, MAT is not recommended without a supplemental source of soluble N. Altogether, study results and conclusions could inform others seeking to improve specifications for disturbed soil where turfgrass establishment is needed to stabilize soil.

Impact of long-term application of biosolids to surface water nitrogen in a working forest plantation in King County, Washington.

Forest fertilization with municipal biosolids has been shown to increase tree growth and enhance forest soils. However, there are concerns that nitrogen from the biosolids could impact surface waters through movement from subsurface flow. Here we analyzed data on soil and surface water nitrogen from a working tree plantation that has used biosolids for over three decades to see if there was evidence of N movement through the soil to surface waters. GIS (Geographic Information System) was used to map application units over time and LiDAR (Light Detection and Ranging) was used to delineate watersheds. The program is located in King County Washington with biosolids provided by the King County Wastewater Treatment program. We assembled records to determine if there is any evidence of movement of NO3- through soils or any enrichment in surface waters. While soils show evidence of NO3- enrichment following biosolids application with cumulative loading rates up to 26 Mg ha-1, this is generally limited to the 'A' soil horizon and does not increase linearly with increased biosolids loading rates. There was no indication of increased surface water NO3- concentration relative to biosolids application rates, with a small trend of decreasing water NO3- over time. Surface water NO3- concentration was not correlated with the fraction of the watershed area that had been amended with biosolids, and there was no observable increase in surface water NO3- with increased frequency of biosolids applications to the tree plantations. These results suggest that the current biosolids program is sufficiently protective of ground and surface waters. These observations suggest that biosolids application can be conducted on a large scale with multiple benefits and no discernible impact to surface waters.

Effects on soil carbon storage from municipal biosolids application to agricultural fields.

This study investigated the influence of biosolid applications on soil carbon storage and evaluated nutrient management strategies affecting soil carbon dynamics. The research assessed alterations in soil pH, soil carbon stock, and soil nitrogen content within short-term and long-term biosolids-amended soils in Bible Hill, Nova Scotia, Canada, extending to a depth of 0-60 cm. The findings indicated an increase in soil pH with alkaline treatment biosolids (ATB) applications across both study sites, with a legacy effect on soil pH noted in the long-term biosolids-amended soil following a single ATB application over 13 years. Both sites demonstrated significant increases in soil total carbon (STC) and soil organic carbon (SOC) within the 0-30 cm soil depth after biosolid application, and soil inorganic carbon (SIC) accounted for approximately 5-10% of STC, specifically in the surface soil layer (0-15 cm). In the long-term study site, annual 14, 28 and 42 Mg ATB ha-1 treatments resulted in a substantial rise in soil carbon stock (59.5, 60.1 and 68.0 Mg C ha-1), marking a 25% increase compared to control soil. The SOC content in biosolids-amended soil showed a declining trend with increasing soil depth at both study sites. Notably, the carbon stock in the short-term site was observed in composted biosolids (COMP) > ATB > liquid mesophilic anaerobically digested biosolids (LMAD) from the 0-60 cm soil depth. Approximately 79-80% of the variation in SOC response at both sites was concentrated within the top 30 cm soil. Soil total nitrogen (STN) showed no significant differences at the short-term site, and STN in biosolids-amended soil decreased with increasing soil depth at the long-term site. Biosolids-induced C retention coefficients (BCR) for ATB remained consistent at both sites, ranging from -13% to 31.4% with a mean of 11.12%. BCR values for COMP ranged from 1.9% to 34.4% with a mean of 18.73%, while those for LMAD exhibited variability, spanning from -6.2% to 106.3% with a mean of 53.9%.

Analysis of effects and factors linked to soil microbial populations and nitrogen cycling under long-term biosolids application.

Information about impacts of long-term biosolids application on soil microbial populations and functional groups and N cycling is important for evaluating soil health and agroecosystem sustainability under long-term biosolids application. Mine spoil plots received annual biosolids application from 1973 to 2010 at low (16.8 Mg ha-1 yr-1), medium (33.6 Mg ha-1 yr-1), and high rates (67.2 Mg ha-1 yr-1). A no-biosolids control received chemical fertilizer at the agronomic rate. Soil samples were collected in three seasons per year spanning 2003-2005 for measuring soil moisture, pH, soil organic C (SOC), total and extractable heavy metals (Cd, Cu, Ni, Zn), NO3-, N mineralization potential (NMP), microbial biomass C (MBC), and populations of three N-cycling bacteria (NCB) groups: ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and denitrifying bacteria (DNB). Soil samples were collected again in 2008 and 2010 for quantifying total and extractable heavy metals, and in 2018 (eight years after biosolids applications ended) for measuring SOC, MBC, NMP, and microbial respiration. During 2003-2005, mean MBC was 315, 554, 794, and 1001 mg kg-1 in the control, low, medium, and high biosolids treatments, respectively. Populations of NCB did not differ among treatments. Biosolids application increased total and extractable metal concentrations but the effect of biosolids rates were much lower on extractable than total concentrations. Soil extractable Cd and Cu concentrations decreased from medium to high applications, likely due to complexing with biosolids organic matter. Partial least squares regression analysis identified a strong positive effect on MBC of SOC and a weak negative effect of Cu, explaining the strong net positive effect of biosolids on MBC. In 2018, the medium and high biosolids treatments maintained higher SOC, MBC, NMP, and microbial respiration than the control. This study provided further evidence that long-term biosolids application has positive effects on soil microbes that persist for years after ending application.