Site properties, environmental factors, and crop identify influence soil bacterial communities more than municipal biosolid application

Reducing the environmental impact of Canadian field crop agriculture, including the reliance on conventional synthesised fertilisers, are key societal targets for establishing long-term sustainable practices. Municipal biosolids (MSB) are an abundant, residual organic material, rich in phosphate, nitrogen and other oligo-nutrients, that could be used in conjunction with conventional fertilisers to decrease their use. Though MBS have previously been shown to be an effective fertiliser substitute for different crops, including corn and soybean, there remain key knowledge gaps concerning the impact of MBS on the resident soil bacterial communities in agro-ecosystems. We hypothesised that the MBS fertiliser amendment would not significantly impact the structure or function of the soil bacterial communities, nor contribute to the spread of human pathogenic bacteria, in corn or soybean agricultural systems. In field experiments, fertiliser regimes for both crops were amended with MBS, and compared to corn and soybean plots with standard fertiliser treatments. We repeated this across four different agricultural sites in Quebec, over 2021 and 2022. We sampled MBS-treated, and untreated soils, and identified the composition of the soil bacterial communities via 16S rRNA metabarcoding. We found no indication that the MBS fertiliser amendment altered the structure of the soil bacterial communities, but rather that the soil type and crop identities were the most significant factors in structuring the bacterial communities. Moreover, there was no evidence that the MBS-treated soils were enriched in potential human bacterial pathogens over the two years of our study. Our analysis indicates that not only can MBS function as substitutes for conventional, synthesised fertilisers, but that they also do not disrupt the structure of the resident soil bacterial communities in the short term. Finally, we suggest that the use of MBS in agro-ecosystems poses no greater concern to the public than existing soil bacterial communities. This highlights the significant role MBS could potentially have in reducing the use of conventional industrial fertilisers and improving agricultural production, without risking environmental contamination.

Biosolids, an important route for transporting poly- and perfluoroalkyl substances from wastewater treatment plants into the environment: A systematic review

The pervasive presence of poly- and perfluoroalkyl substances (PFAS) in diverse products has led to their introduction into wastewater systems, making wastewater treatment plants (WWTPs) significant PFAS contributors to the environment. Despite WWTPs' efforts to mitigate PFAS impact through physicochemical and biological means, concerns persist regarding PFAS retention in generated biosolids. While numerous review studies have explored the fate of these compounds within WWTPs, no study has critically reviewed their presence, transformation mechanisms, and partitioning within the sludge. Therefore, the current study has been specifically designed to investigate these aspects. Studies show variations in PFAS concentrations across WWTPs, highlighting the importance of aqueous-to-solid partitioning, with sludge from PFOS and PFOA-rich wastewater showing higher concentrations. Research suggests biological mechanisms such as cytochrome P450 monooxygenase, transamine metabolism, and beta-oxidation are involved in PFAS biotransformation, though the effects of precursor changes require further study. Carbon chain length significantly affects PFAS partitioning, with longer chains leading to greater adsorption in sludge. The wastewater's organic and inorganic content is crucial for PFAS adsorption; for instance, higher sludge protein content and divalent cations like calcium and magnesium promote adsorption, while monovalent cations like sodium impede it. In conclusion, these discoveries shed light on the complex interactions among factors affecting PFAS behavior in biosolids. They underscore the necessity for thorough considerations in managing PFAS presence and its impact on environmental systems.

A LC-MS/MS method for the simultaneous quantification of 17 opioids in biosolids

The solid product of wastewater treatment plants is commonly used as a fertiliser to increase sustainability and waste reuse. It has undergone extensive treatment to remove high nutrient loads, pathogens and heavy metals but the extensive matrix of household chemicals, pesticides and pharmaceuticals remains, untargeted by most treatment technologies. These compounds, particularly pharmaceuticals, have been detected in biosolids with there being evidence of uptake by plants. With the current opioid pandemic in North America and overprescription, a simple method is required for the extraction of opioids from a solid medium as to ascertain the concentrations the environment is exposed to. A sonication-liquid-liquid extracted method was developed where biosolids were suspended in water and extracted using ethyl acetate before analysis on LC MS/MS. Sodium and potassium chloride were compared along with acidic and alkaline conditions. The optimised method utilised NaCl at a pH of 12 and was validated for 17 opioids, achieving linearity >0.987, 86-113% matrix effect and 0.1-10 μg/kg limits of detection. Upon analysis of biosolids destined for agriculture, 14 opioids were detected across all samples in a concentration range of 1-289 μg/kg.

Fertilisation of agricultural soils with municipal biosolids: Glyphosate and aminomethylphosphonic acid inputs to Québec field crop soils

Municipal biosolids (MBS) are suggested to be abundant, sustainable, inexpensive fertilisers, rich in phosphorus and nitrogen. However, MBS can also contain glyphosate and phosphonates that can degrade to AMPA. Glyphosate-based herbicides (GBH) are used in field crops all over the world. Most glyphosate generally degrades within a few weeks, mainly as aminomethylphosphonic acid (AMPA). AMPA is more persistent than glyphosate, and can accumulate from one crop year to the next. AMPA is phytotoxic even to glyphosate-resistant crops. The aims of this study were to assess whether MBS applications constitute: 1) an additional source of glyphosate and AMPA to agricultural soils with respect to GBH, 2) a significant source of trace metals, and 3) a partial replacement of mineral fertilisation while maintaining similar yields. To this end, four experimental agricultural sites were selected in Québec (Canada). Soil samples (0-20 cm) were collected to estimate the as yet unmeasured contribution of MBS application to glyphosate and AMPA inputs in agricultural soils. MBS applied in 2021 and 2022 had mean concentrations of 0.69 ± 0.53 μg glyphosate/dry g and 6.26 ± 1.93 μg AMPA/dry g. Despite the presence of glyphosate and AMPA in MBS, monitoring of these two compounds in corn and soybean crops over two years showed no significant difference between plots treated with and without MBS applications. For the same site, yields measured at harvest were similar between treatments. MBS application could thus represent a partial alternative to mineral fertilisers for field crops, while limiting the economic and environmental costs associated with their incineration and landfilling. It is also an economic advantage for agricultural producers given the possibility of using fewer mineral fertilisers and therefore reducing the environmental impact of their use.

Heavy metals drive microbial community assembly process in farmland with long-term biosolids application

Biosolids are considered an alternative to chemical fertilizers due to their rich nutrients. However, long-term biosolids application can lead to heavy metals accumulation, which severely affects soil microbial community compositions. The factors influencing soil microbial community assembly were explored under a 16-year long-term experiment with biosolids applications. Our results indicated that biosolids application significantly increased fungal richness while not for bacterial and arbuscular mycorrhizal (AM) fungal richness. Besides, biosolids application significantly affected soil bacterial, fungal compositions and AM fungal community. Soil microorganisms were clustered into different modules with bacterial and AM fungal communities were affected by both organic matter and heavy metals, while fungal communities were affected by heavy metals (Cr, Ni, and As). The soil bacterial community assembly was dominated by stochastic processes while the fungal and AM fungal community assemblies were mainly driven by deterministic processes. Random forest analysis showed that heavy metals were identified as major drivers (Hg, Cu, Cd, and Zn for bacteria, Pb and Cr for fungi, and As and Ni for AM fungi) of the community assembly process. Overall, our study highlights the significant role of heavy metals in shaping microbial community dynamics and gives a guide for controlling biosolids application.

Nutrient transport, shear strength and hydraulic characteristics of topsoils amended with mulch, compost and biosolids

Anthropogenic disturbance of soils can disrupt soil structure, diminish fertility, alter soil chemical properties, and cause erosion. Current remediation practices involve amending degraded urban topsoils lacking in organic matter and nutrition with organic amendments (OA) to enhance vegetative growth. However, the impact of OAs on water quality and structural properties at rates that meet common topsoil organic matter specifications need to be studied and understood. This study tested three commonly available OAs: shredded wood mulch, leaf-based compost, and class A Exceptional Quality stabilized sewage sludge (or biosolids) for nutrient (nitrogen and phosphorus) water quality, soil shear strength, and hydraulic properties, through two greenhouse tub studies. Findings showed that nitrogen losses to leachate were greater in the biosolids amended topsoils compared to leaf-compost, mulch amended topsoils, and control treatments. Steady-state mean total nitrogen (N) concentrations from biosolids treatment exceeded typical highway stormwater concentrations by at least 25 times. Soil total N content combined with the carbon:nitrogen ratio were identified to be the governing properties of N leaching in soils. Study soils, irrespective of the type of amendment, reduced the applied (tap) water phosphorus (P) concentration of ∼0.3 mg-P/L throughout the experiment. Contrary to the effects on N leaching, P was successfully retained by the biosolids amendment, due to the presence of greater active iron contents. A breakthrough mechanism for P was observed in leaf compost amended soil, where the effluent concentrations of P continued to increase with each rainfall application, possibly due to an saturation of soil adsorption sites. The addition of OAs also improved the strength and hydraulic properties of soils. The effective interlocking mechanisms between the soil and OA surfaces could provide soil its required strength and stability, particularly on slopes. OAs also improved soil fertility to promote turf growth. Presence of vegetative root zones can further reinforce the soil and control erosion.

Occurrence, fate, and remediation for per-and polyfluoroalkyl substances (PFAS) in sewage sludge: A comprehensive review

Addressing per-and polyfluoroalkyl substances (PFAS) contamination is an urgent environmental concern. While most research has focused on PFAS contamination in water matrices, comparatively little attention has been given to sludge, a significant by-product of wastewater treatment. This critical review presents the latest information on emission sources, global distribution, international regulations, analytical methods, and remediation technologies for PFAS in sludge and biosolids from wastewater treatment plants. PFAS concentrations in sludge matrices are typically in hundreds of ng/g dry weight (dw) in developed countries but are rarely reported in developing and least-developed countries due to the limited analytical capability. In comparison to water samples, efficient extraction and cleaning procedures are crucial for PFAS detection in sludge samples. While regulations on PFAS have mainly focused on soil due to biosolids reuse, only two countries have set limits on PFAS in sludge or biosolids with a maximum of 100 ng/g dw for major PFAS. Biological technologies using microbes and enzymes present in sludge are considered as having high potential for PFAS remediation, as they are eco-friendly, low-cost, and promising. By contrast, physical/chemical methods are either energy-intensive or linked to further challenges with PFAS contamination and disposal. The findings of this review deepen our comprehension of PFAS in sludge and have guided future research recommendations.

Comparison of ATR-FTIR and NIR spectroscopy for identification of microplastics in biosolids

Biosolids are considered a potentially major input of microplastics (MPs) to agricultural soils. Our study aims to identify the polymeric origin of MPs extracted from biosolid samples by comparing their Attenuated Total Reflection (ATR) - Fourier-transform infrared (FTIR) spectra with the corresponding near-infrared (NIR) spectra. The reflectance spectra were preprocessed by Savitzky-Golay (SG), first derivative (FD) and compared with analogous spectra acquired on a set of fifty-two selected commercial plastic (SCP) materials collected from readily available products. According to the results portrayed in radar chart and built from both ATR-FTIR and NIR spectral datasets, the MPs showed high correlations with polymers such as polyethylene (LDPE, HDPE), polyethylene terephthalate (PET), polystyrene (PS), polypropylene (PP) and polyamide (PA), determined in SCP samples. Each unknown MP sample had on average three or more links to several types of SCP, according to the correlation coefficients for each polymer ranging from 0.7 up to 1. The comparison analysis classified the majority of MPs as composed mainly by LDPE/HDPE, according to the top correlation coefficients (r > 0.90). PP and PET were better identified with NIR than ATR-FTIR. In contrast to ATR-FTIR analysis, NIR was unable to identify PS. Based on these results, the primary sources of MPs in the biosolids could be identified as discarded consumer packaging (containers, bags, bottles) and fibers from laundry, disposable glove, and cleaning cloth. SYNOPSIS: Microplastics (MPs) are considered contaminants of emerging concern. This study compares two simple and fast spectroscopy techniques to identify microplastics in the biosolid matrix.

A high-throughput analytical method for complex contaminant mixtures in biosolids

Biosolids are rich in organic matter and other nutrients that contribute to environmental and agricultural sustainability by improving soil textural and biological properties and enhancing plant growth when applied to agricultural crops. Land application of biosolids encourages resource recovery and circumvents drawbacks associated with landfilling or incineration. However, biosolids contain numerous chemicals at trace levels, and quantitative analysis of such mixtures in this complex matrix is crucial for understanding and managing application risks. There are currently few analytical methods available that are capable of extracting and quantifying a large range of the emerging contaminants found in biosolids. In this study, a simplified, rapid, and robust method of analysis was developed and validated for a high-priority organic contaminant mixture of 44 endocrine disrupting compounds known to occur in biosolids. Analytes consisted of chemicals from many classes with a wide range of physiochemical properties (e.g., log Kow values from -1.4 to 8.9). The biosolids extraction and cleanup protocol was validated for 42 of the targeted compounds. The UPLC-MS2 parameters were validated for all 44 organic contaminants targeted for study. From the two batches of biosolids tested using this analytical method, most of the targeted contaminants (86%) were detected with 100% frequency at concentrations ranging from 0.036 to 10,226 μg/kg dw. Performance results highlighted that internal standards alone could not negate biosolids matrix effects; thus, internal standards and the standard addition method were used for residue quantification. This was the first study to detect and quantify 6PPD-q in biosolids, and the first to quantify lidocaine and 11 other chemicals in biosolids using a single analytical method. This method may be expanded for analysis of additional chemicals in biosolids and comparable matrices.

A review of the influence of heat drying, alkaline treatment, and composting on biosolids characteristics and their impacts on nitrogen dynamics in biosolids-amended soils

Application of biosolids to agricultural land has gained increasing attention due to their rich nutrient content. There are a variety of treatment processes for converting sewage sludge to biosolids. Different treatment processes can change the physicochemical properties of the raw sewage sludge and affect the dynamics of nutrient release in biosolids-amended soils. This paper reviews heat drying, alkaline treatment, and composting as biosolids treatment processes and discusses the effects of these treatments on biosolid nitrogen (N) content and availability. Most N in the biosolids remain in organic forms, regardless of biosolids treatment type but considerable variation exists in the mean values of total N and mineralizable N across different types of biosolids. The highest mean total N content was recorded in heat-dried biosolids (HDB) (4.92%), followed by composted biosolids (CB) (2.25%) and alkaline-treated biosolids (ATB) (2.14%). The mean mineralizable N value was similar between HDB and ATB, with a broader range of mineralizable N in ATB. The lowest N availability was observed in CB. Although many models have been extensively studied for predicting potential N mineralization in soils amended with organic amendments, limited research has attempted to model soil N mineralization following biosolids application. With biosolids being a popular, economical, and eco-friendly alternative to chemical N-fertilizers, understanding biosolids treatment effects on biosolids properties is important for developing a sound biosolids management system. Moreover, modeling N mineralization in biosolids-amended soils is essential for the adoption of sustainable farming practices that maximize the agronomic value of all types of biosolids.

Occurrence, spatiotemporal trends, fate, and treatment technologies for microplastics and organic contaminants in biosolids: A review

This review provides a comprehensive overview of the occurrence, fate, treatment and multi-criteria analysis of microplastics (MPs) and organic contaminants (OCs) in biosolids. A meta-analysis was complementarily analysed through the literature to map out the occurrence and fate of MPs and 10 different groups of OCs. The data demonstrate that MPs (54.7% occurrence rate) and linear alkylbenzene sulfonate surfactants (44.2% occurrence rate) account for the highest prevalence of contaminants in biosolids. In turn, dioxin, polychlorinated biphenyls (PCBs) and phosphorus flame retardants (PFRs) have the lowest rates (<0.01%). The occurrence of several OCs (e.g., dioxin, per- and polyfluoroalkyl substances, polycyclic aromatic hydrocarbons, pharmaceutical and personal care products, ultraviolet filters, phosphate flame retardants) in Europe appear at higher rates than in Asia and the Americas. However, MP concentrations in biosolids from Australia are reported to be 10 times higher than in America and Europe, which required more measurement data for in-depth analysis. Amongst the OC groups, brominated flame retardants exhibited exceptional sorption to biosolids with partitioning coefficients (log Kd) higher than 4. To remove these contaminants from biosolids, a wide range of technologies have been developed. Our multicriteria analysis shows that anaerobic digestion is the most mature and practical. Thermal treatment is a viable option; however, it still requires additional improvements in infrastructure, legislation, and public acceptance.

Quality and risk management frameworks for biosolids: An assessment of current international practice

Biosolids, a product of wastewater treatment, provide a valuable resource, but to optimize the use of this resource it is necessary to manage risks posed to public health and the environment. Key requirements include identifying contaminant sources and providing barriers to ensure containment and treatment while maintaining the viability and value of biosolids products. Responsibility for managing biosolids is the remit of many stakeholders but primarily it rests with private and public wastewater facilities. The global variabilities in the way biosolids resources are acknowledged, applied, and managed are substantial. For example, some countries are increasing incineration because of their ability to remove contaminants while others have experienced a proportional decrease in incineration dependent on industrial resources or regarding resource recovery costs and needs. Some jurisdictions focus on energy recovery and others on land application. A risk management framework is a tool that may provide a suitable holistic approach to biosolids management. With this focus, current instruments in practice globally to manage biosolids were assessed for the degree to which they have adopted a risk management framework. To form a basis for this assessment a set of criteria was established by concept mapping several internationally recognized standards. Guidelines for a range of developed and developing countries were then assessed against these criteria. That process enabled the identification of which current practices were holistic in terms of applying biosolids risk management principles from production to end-use. Through this process, risk management gaps and vulnerabilities were identified. The results reveal that the incorporation of risk standards into risk management frameworks around the world is variable for the presence of risk criteria and the scale of detail provided. Contaminant concentrations need perspective within the changing risk landscape for stakeholders and the environment while jointly the opportunities and contaminant challenges require solutions that balance risks.

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.

Tracing the origins of plastics in biosolids: The role of sewerage pipe materials and trade waste

Plastics are ubiquitous in virtually every environment on earth. While the specific sources of plastics entering wastewater are not well known, growing evidence suggests sewage sludge (biosolids) can be a sink for plastics. One potential source could be the sewerage pipe materials used to transport sewage between premises and wastewater treatment plants (WWTPs). To evaluate the significance of sewerage piping as a source of biosolids plastics concentrations, we compared the proportion of the total network (by length and surface area) of polyethylene (PE), polyvinylchloride (PVC), and polypropylene (PP) pipes from 10 WWTPs against their biosolids mass concentrations (mg plastic/g biosolid). Among the 10 catchments, the percentage of the network consisting of PP piping ranged from 0 to 1 %, with 0.8-21 % for PE, and 8-73 % for PVC. Biosolids plastics concentrations ranged from 0.09 to 8.62 mg/g (mg plastic/g biosolid) for PP and PE, respectively. For all three plastics, there was no significant Pearson correlation (r < 0.4) between the biosolids concentration (dry weight mg/g) and the proportion of the network material of the sewerage piping as plastic (either length or surface area). A comparison of trade waste entering a subset of 6 WWTP showed the highest biosolid principal components analysis (PCA) associations between loads of plastics (g/day) and automotive wash bays, general manufacturing, hospitals, laboratories, food manufacturing, laundry and dry cleaning, and cooling towers. A stepwise regression analysis indicated pipe length and surface area, as well as automotive wash bays and food manufacturing may be significant. While our data gave mixed results on the attribution of the sources of plastics entering WWTPs, it suggests that sewerage infrastructure and trade waste may play some role. Future studies should investigate the leachability of sewerage infrastructure and contributions from specific trade waste categories to determine their significance in plastics entering WWTPs.

Reducing biosolids from a membrane bioreactor system: Assessing the effects on carbon and nutrient removal, membrane fouling and greenhouse gas emissions

This study presents the effects on carbon and nutrient removal, membrane fouling and greenhouse gas (GHG) emissions of an Oxic-Settling-Anaerobic (OSA) - Membrane Bioreactor (MBR) pilot plant fed with real wastewater. The influence of three sludge return internal ratios (IR) was investigated by testing 45, 75 and 100%. The results showed that with the increase of IR, the biological sludge production substantially decreased by 85.8% due to the combination of cell lysis and endogenous metabolism. However, a worsening of ammonia removal efficiencies occurred (from 94.5 % to 84.7 with an IR value of 45 and 100%, respectively) mostly due to the ammonia release caused by cell lysis under anaerobic conditions. The N2O emission factor increased with the rise of IR (namely, from 2.17% to 2.54% of the total influent nitrogen). In addition, a variation of carbon footprint (CF) (0.78, 0.62 and 0.75 kgCO2eq m-3 with 45, 75 and 100% IR, respectively) occurred with IR mainly due to the different energy consumption and carbon oxidation during the three periods. The study's relevance is to address the optimal operating conditions in view of reducing sludge production. In this light, the need to identify a trade-off between the advantages of reducing sludge production and the disadvantages of increasing membrane fouling and GHG emissions must be identified in the future.

Quantifying the removal of polybrominated diphenyl ethers (PBDEs) in physical, chemical, and biological sludge treatment systems

Polybrominated diphenyl ethers (PBDE) are priority contaminants historically used as flame retardants. PBDEs are known to occur in wastewater biosolids posing potential concerns with the beneficial land application of the biosolids. This study evaluated the removal of 21 congeners in nine full-scale sludge treatment systems including pelletization (P), alkaline stabilization (AS), and aerobic (AE) and anaerobic (AN) digestion. It is the first study to conduct a mass balance analysis of a broad spectrum of PBDEs during physical, chemical, and biological sludge treatment. The PBDE congener pattern in raw sludge and biosolids samples was consistent with commercial formulations. The fully brominated congener BDE-209 dominated biosolids from all sites with an average concentration of 620 ng/g dry weight (dw), followed by BDE-99 (173 ng/g dw) and BDE-47 (162 ng/g dw). Mass balance analysis on the P and AS processes showed no change in PBDE mass flows with treatment. However, aerobic and anaerobic digestion processes reported significant levels of removal and formation of individual congeners, though the results were not consistent between facilities. One aerobic digestion process (AE2) reported an overall average removal of 48%, whereas the other (AE1) reported very high levels of accumulation of tri- and tetraBDE congeners. Similarly, there were significant variations in PBDE behavior across the five anaerobic digestion plants studied. The plant with the longest solids retention time (SRT) (AN1) reported a moderate removal (50%) of overall PBDE loading and lower congeners, whereas other plants (AN2-AN5) showed significant low (-19%) to high (-166%) levels of formation of lower congeners. The results suggest that reduced SRTs result in formation of lower congeners while extended SRTs can lead to moderate removal of some PBDEs. Conventional sludge treatment result in low to moderate PBDE removal and advanced thermal conversion technologies may be needed to improve the contaminant removal during sludge treatment.

Agronomic and phytotoxicity test with biosolids from anaerobic CO-DIGESTION with temperature and micro-organism phase separation, based on sewage sludge, vinasse and poultry manure

This study deals with energy and agronomic valorisation by anaerobic co-digestion with temperature and microorganism phase separation of sewage sludge, vinasse and poultry manure, with the aim of achieving an integral waste management, obtaining bioenergy and biofertilizer that returns nutrients to the soil in a natural way. The yields obtained were 40 mL H2/gVS and 391 mLCH4/gVS. The resulting effluent showed more than 98 % removal of E. coli and Total Coliforms, as well as total removal of Salmonella. The results obtained in the phytotoxicity tests showed that all the proportions studied had phytostimulant and phytonutrient properties, with 20 % having the highest germination index (GI) with mean values of 145.30 %. Finally, the agronomic trial carried out with strawberry crops (Fragaria sp.) showed that the addition of this biosolid has fertilising properties and can be used as an agronomic amendment, with an increase of 145 % in fresh weight and 102.5 % in dry weight, and fruit production doubled with respect to the control. The ANOVA statistical study corroborated that there were significant differences in crop growth when applying different proportions of biofertilizer in the fertilizer. Therefore, these results show that this technology is promising and would contribute environmentally, socially and economically to the transfer towards a circular economy model.

Wastewater recovery for sustainable agricultural systems in the circular economy - A systematic literature review of Life Cycle Assessments

Water availability and quality are known to affect agricultural production and nutrition. The aim of this study was to elaborate a systematic literature review of the most sustainable ways of wastewater treatment towards achieving circular economy (CE) in agro-industry activities. From the SLR, the authors selected twenty-seven papers that they classified into the three research themes of recovery of wastewater into irrigation water, extraction of sludge for production of bio-based compounds, and recovery of nutrients for soil amendment, including recovering of feeds for aquaculture, and recovery of nutrient biosolids for soil amendment. Results underlined that the recovery of nutrients biosolids for soil amendment can generate a GWP gain up to - 37 kg CO2-eq. So, the review highlighted that wastewater recovery for multiple purposes can be truly effective for the environmental sustainability of agricultural systems, and that LCA is a valid tool to assess and improve that sustainability. Under this perspective, this SLR's findings can stimulate public administrations at national and local scales in their planning and funding activities towards implementing circular bioeconomy paths based upon wastewater recovery for a sustainable, resilient agriculture. Overall, the authors believe that their article was effective in overviewing the current wastewater recovery paths in the CE context, and in highlighting key methodological aspects and findings of the reviewed LCAs, to advance the specialised literature and knowledge, and to guide practitioners for future LCA applications in the field. Finally, through its main findings, the article effectively contributes to the whole research project which it is part of and which the authors are deeply involved in. That research is performed under the Progetto GRINS "Growing Resilient, Inclusive and Sustainable" thanks to a PNRR M4C2- Investment 1.3 - GRINS with the aim of "Building a dataset for the circular economy of the main Italian production systems".

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.

Per- and polyfluoroalkyl substances (PFAS) in Canadian municipal wastewater and biosolids: Recent patterns and time trends 2009 to 2021

The concentrations of per- and polyfluoroalkyl substances (PFAS) were determined in raw influent, final effluent, and treated biosolids at Canadian wastewater treatment plants (WWTPs) to evaluate the fate of PFAS through liquid and solids trains of typical treatment process types used in Canada and to assess time trends of PFAS in wastewater between 2009 and 2021. Data for 42 PFAS in samples collected from 27 WWTP across Canada were used to assess current concentrations and 48 WWTPs were included in the time trends analysis. Although regulated and phased-out of production by industry since the early 2000s and late 2000s/early2010s, respectively, perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and other long-chain PFAS continue to be widely detected in Canadian wastewater and biosolids. Short-chain PFAS that are not currently regulated in Canada were also widely detected. In general, elevated concentrations of several PFAS were observed at WWTPs that receive landfill leachate. Except for PFOS, concentrations of long-chain perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs) generally decreased over time in influent, effluent, and biosolids, which is attributable to industrial production phase-outs and regulations. Concentrations of PFOS did not decrease over time in wastewater media. This indicates that regulatory action and industrial phase-outs of PFOS are slow to be reflected in wastewater. Concentrations of short-chain PFCAs in wastewater influent and effluent consistently increased between 2009 and 2021, which reflect the use of short-chain PFAS as replacements for phased-out and regulated longer-chained PFAS. Short-chain PFAS were infrequently detected in biosolids. Continued periodic monitoring of PFAS in wastewater matrices in Canada and throughout the world is recommended to track the effectiveness of regulatory actions, particularly activities to address the broad class of PFAS.

Comprehensive assessment of microplastics in Australian biosolids: Abundance, seasonal variation and potential transport to agroecosystems

Striving towards a circular economy, the application of treated sewage sludge (biosolids) to land is an opportunity to improve the condition of the soil and add essential nutrients, in turn reducing the need for fertilisers. However, there is an increasing concern about microplastic (MP) contamination of biosolids and their transport to terrestrial ecosystems. In Australia, agriculture is the largest biosolids end-user, however, there is limited understanding of MPs in Australian biosolids. Also, while the method to isolate MPs from biosolid is established, a need to extract and analyse MPs more efficiently is still pressing. In this study, we comprehensively quantified and characterised MPs in 146 biosolids samples collected from thirteen wastewater treatment plants (WWTPs) including different seasons. We have optimised an oxidative-enzymatic purification method to overcome current limitations for MP identification in complex samples and accurately report MPs in biosolids. This method enabled removal of >93 % of dry weight of organic material and greatly facilitated the MPs instrumental analysis. The concentration of MPs (>20 µm) in all biosolids samples ranged from 11 to 150 MPs/g dry weight. Abundance of MPs was affected by seasons with higher abundance of MPs usually found during cold and wet seasons. Despite seasonal variations, polyethylene terephthalate, polyurethane and polymethyl methacrylate were the most abundant polymers. Smaller MPs (20 to 200 µm) comprised >70 % of all detected MPs with a clear negative linear relationship observed between MP size and abundance. Per capita concentration of MPs in biosolids across all studied WWTPs was 0.7 to 21 g MPs per person per year. Therefore, biosolids are an important sink and source of MPs to agroecosystems, emphasising the need to more comprehensively understand the fate, impact and risks associated with MPs on agricultural soils.

Per- and polyfluoroalkyl substances (PFAS) in final treated solids (Biosolids) from 190 Michigan wastewater treatment plants

Trends in concentration, distribution, and variability of per- and polyfluoroalkyl substances (PFAS) in biosolids are characterized using an extensive dataset of 350 samples from 190 wastewater treatment plants (WWTPs) across Michigan. All samples are comprised of final treated solids generated at the end of the wastewater treatment process. Concentrations of both individual and Σ24 PFAS are lognormally distributed, with Σ24 PFAS concentrations ranging from 1-3200 ng/g and averaging 108 ± 277 ng/g dry wt. PFAS with carboxyl and sulfonic functional groups comprise 29% and 71% of Σ24 PFAS concentrations, respectively, on average. Primary sample variability in concentration is associated with long-chain PFAS with higher tendency for partitioning to biosolids. Short-chain carboxylic compounds, most notably PFHxA, are responsible for secondary concentration variability. Usage of FTSA and PFBS replacements to long-chain sulfonic compounds also contributes to variance in biosolids concentrations. Sulfonamide precursor compounds as a collective group are detected at a similar frequency as PFOS and often have higher concentrations. Trends in PFAS enrichment for individual PFAS vary at least 3 orders-of-magnitude and generally increase with compound hydrophobicity; however, partitioning of PFAS onto solids in WWTPs is a complex process not easily described nor constrained using experimentally-derived partitioning coefficients.

A case study of biosolids from wastewater treatment plants in Western Greece

The great interest of modern societies in the reuse of wastes opens up new horizons in the field of wastewater, as well. In particular, the treated sludge resulting from a Wastewater Treatment Plant (WWTP) is dealed with a new perspective in the context of circular economy. The aim of this study is the characterization of its complex matrix, and the evaluation for reuse. Biosolids (BS) collected from four urban WWTPs in the Western region of Greece i.e. Agrinio (AG), Amaliada (AM), Aegio (AE) and Itea (IT). Analytical and spectroscopical methods namely TGA, ICP-OES, Fluorescence, SEM/EDS, XRD, FT-IR and NMR were the means that served this purpose. SEM along with XRD proved the amorphous nature of BS. The dominant metals detected in the samples are: Fe, Zn, Mn, with concentrations which meet the guidelines included in 86/278/EEC Directive. The inorganic load is of great importance, along with their humic acid content, adding value at the samples as fertilizers. BS appeared to be rich in organic matter with long aliphatic chains and numerous functional groups, as capturedin FT-IR spectra. The applied methods form an analytical protocol of the BS mapping, highlighting its potential as a material to be utilized in agriculture.

Identification of microplastics extracted from field soils amended with municipal biosolids

Microplastic particles in arable soil are expected to impact the environment and potentially human health. The application of municipal biosolids (MBs) to agricultural land presents a further dilemma in that biosolids act as a fertilizer for crop growth, and a disposal pathway for wastewater treatment plants. They are also a direct path for emerging contaminants, such as microplastics to enter the terrestrial environment. Reliable methods are needed to identify and quantify microplastics, found in agricultural soils to determine how microplastics are being cycled in the terrestrial environment. In this study, we developed a method for extracting microplastics from soil, and characterized their composition and identity for particles sized 5 μm to 2 mm. Method development was initially completed using natural soils spiked with microplastics and MBs, followed by the analyses of soil sampled from an agricultural field where MBs were recently applied at a rate of 13 tons dw/ha. The procedures that used the spiked samples showed that microplastics can be reliably extracted from soil in a laboratory setting, and identified and semi-quantified by thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR). However, when the same methods were applied to the soil samples collected from the agricultural field, reproducibility became a challenge, as the number and type of microplastics changed even within the same soils (i.e., collected the same day from the same exact location). The variation in reproducibility observed between laboratory and field samples underscores the significant heterogeneity present in the environment. This heterogeneity, in turn, affects the identification and quantity of microplastics detected, a phenomenon observed even when comparing different fields within a single treatment regimen.

Effects of sodium sulfide concentration on the solid and solution chemistry of a biosolids slurry for phosphorus recovery and reuse

Municipal biosolids contain organic and inorganic phosphorus (P) that could be recovered for reuse as P fertilizer. Inorganic P compounds include iron phosphates that precipitate and/or adsorbed phosphate ions as a consequence of soluble iron addition in order not to exceed total phosphorus (TP) emission limits. The inorganic orthophosphate (o-Pi) minerals within biosolids can have low solubilities. One P recovery strategy is to maximize the dissolution of o-Pi from biosolids for reuse. Dissolving iron phosphates in biosolids by adding sodium sulfide was assessed as an o-Pi dissolution strategy. 10 % w/w biosolids slurries with a total phosphorus (TP) of 0.97 ± 0.03 mmol P/dry g were mixed with sulfide/TP (S2-/TP) molar ratios from 0 to 4 for up to 96 h. The maximum o-Pi concentration (48 ± 7 mM, or 42 ± 6 % of TP) was obtained for 4 S2-/TP after 24 h at room temperature (RT). Iron concentrations measured by colorimetry (ferrozine) reduced from 0.6 ± 0.1 mM to less than 0.01 mM (S2-/TP > 1). X-ray diffraction and FTIR suggest that sulfide treatment preferentially dissolved amorphous o-Pi-containing solids, vivianite, and minerals with iron, aluminum, phosphate, sulfate, and other subsitutions. Poorly crystalline erdite (NaFeS2 ·2H2O) was detected in products after S2-/TP treatment ratios ≥ 2. Incubation at RT or 37 °C did not affect the o-Pi concentrations for 0 or 4 S2-/TP over 47 h. Sulfide addition could also increase the risk of construction material corrosion, and reduce the efficiency of P recovery by precipitation. There are disadvantages to using sulfide to dissolve o-Pi from biosolids as a potential P recovery process.

Preconceptional and in utero exposure of sheep to a real-life environmental chemical mixture disrupts key markers of energy metabolism in male offspring

Over recent decades, an extensive array of anthropogenic chemicals have entered the environment and have been implicated in the increased incidence of an array of diseases, including metabolic syndrome. The ubiquitous presence of these environmental chemicals (ECs) necessitates the use of real-life exposure models to the assess cumulative risk burden to metabolic health. Sheep that graze on biosolids-treated pastures are exposed to a real-life mixture of ECs such as phthalates, per- and polyfluoroalkyl substances, heavy metals, pharmaceuticals, pesticides, and metabolites thereof, and this EC exposure can result in metabolic disorders in their offspring. Using this model, we evaluated the effects of gestational exposure to a complex EC mixture on plasma triglyceride (TG) concentrations and metabolic and epigenetic regulatory genes in tissues key to energy regulation and storage, including the hypothalamus, liver, and adipose depots of 11-month-old male offspring. Our results demonstrated a binary effect of EC exposure on gene expression particularly in the hypothalamus. Principal component analysis revealed two subsets (B-S1 [n = 6] and B-S2 [n = 4]) within the biosolids group (B, n = 10), relative to the controls (C, n = 11). Changes in body weight, TG levels, and in gene expression in the hypothalamus, and visceral and subcutaneous fat were apparent between biosolid and control and the two subgroups of biosolids animals. These findings demonstrate that gestational exposure to an EC mixture results in differential regulation of metabolic processes in adult male offspring. Binary effects on hypothalamic gene expression and altered expression of lipid metabolism genes in visceral and subcutaneous fat, coupled with phenotypic outcomes, point to differences in individual susceptibility to EC exposure that could predispose vulnerable individuals to later metabolic dysfunction.

The Effect of Municipal Biosolids on the Growth, Physiology and Synthesis of Phenolic Compounds in Ocimum basilicum L

The continuous development of drinking water networks is leading to the production of increasing amounts of waste water and sewage sludge. Secondary-treated sewage sludge is called biosolids and can be used as fertilizers in agriculture due to its rich nutrient content. The aim of this study was to evaluate the effects of biosolids mixed with an eroded soil on the morphology, physiology and synthesis of bioactive compounds in basil. The study was performed in pots under laboratory-controlled conditions. In total, four substrates were tested: S1 biosolids 100%, S2 biosolids 15% + eroded soil 85%, S3 eroded soil 100% and S4 control (commercial growing substrate). At the morphological level, a significant increase in plant height, number of branches, fresh biomass and dry biomass was found in the S2 variant. At the physiological level, photosynthesis and chlorophyll content did not vary significantly, but the quantum yield of PSII (ΦPSII) was significantly higher at S1 and S2. The oxidative status evaluated by determining the activity of SOD, POD and CAT enzymes was better in S2 and S3 compared to S3. Regarding the synthesis of bioactive compounds (rosmarinic acid, caffeic acid and gallic acid), it was stimulated in S1 and S2. In conclusion, biosolids application stimulated the stress response mechanisms in basil plants by increasing the quantum yield chlorophyll fluorescence and catalase activity, alleviating the negative effects of eroded soil.

Biofertilizers from wastewater treatment as a potential source of mineral nutrients for growth of amaranth plants

Exploring alternative fertilizers is crucial in agriculture due to the cost and environmental impact of inorganic options. This study investigated the potential of sewage-derived biofertilizers on the growth and physiology of Amaranthus cruentus plants. Various treatments were compared, including control treatments with inorganic fertilizer and treatments with biofertilizers composed of microalgae, biosolids and reclaimed water. The following traits were investigated: photosynthetic pigments, gas exchange, growth, and leaf nutrient concentrations. The results showed that the concentrations of N, P, Cu, Fe Zn and Na nutrients, in the dry microalgae and biosolids, were quite high for the needs of the plants. The wet microalgae presented high concentration of Cu, Fe and Zn nutrients while reclaimed water contained high concentration of N, K, Ca and S. Na and Zn nutrients increased in the leaf of plants treated with dry microalgae and biosolid, respectively. At the beginning of the flowering phase, total chlorophyll and carotenoids contents were lower for plants grown with wet microalgae while for plants grown with higher doses of biosolid or reclaimed water total chlorophyll was increased, and carotenoids were not affected. Lower photosynthetic pigments under wet microalgae resulted in lower photosynthetic rates. On the other hand, amendments with dry microalgae and biosolid increased photosynthetic rates with the biosolid being the most effective. Higher applications of biosolid, wet and dry microalgae produced a considerable increase in shoot biomass of amaranth, with the dry microalgae being the most effective. Additionally, reclaimed water obtained after tertiary treatment of sewage with microalgae and biosolids applied alone showed promising effects on plant growth. Overall, these findings suggest that organic fertilizers derived from sewage treatment have the potential to enhance plant growth and contribute to sustainable agricultural practices.

Tracing COVID-19 drugs in the environment: Are we focusing on the right environmental compartment?

The Coronavirus Disease 2019 (COVID-19) pandemic led to over 770 million confirmed cases, straining public healthcare systems and necessitating extensive and prolonged use of synthetic chemical drugs around the globe for medical treatment and symptom relief. Concerns have arisen regarding the massive release of active pharmaceutical ingredients (APIs) and their metabolites into the environment, particularly through domestic sewage. While discussions surrounding this issue have primarily centered on their discharge into aquatic environments, particularly through treated effluent from municipal wastewater treatment plants (WWTPs), one often overlooked aspect is the terrestrial environment as a significant receptor of pharmaceutical-laden waste. This occurs through the disposal of sewage sludge, for instance, by applying biosolids to land or non-compliant disposal of sewage sludge, in addition to the routine disposal of expired and unused medications in municipal solid wastes. In this article, we surveyed sixteen approved pharmaceuticals for treating COVID-19 and bacterial co-infections, along with their primary metabolites. For this, we delved into their physiochemical properties, ecological toxicities, environmental persistence, and fate within municipal WWTPs. Emphasis was given on lipophilic substances with log Kow >3.0, which are more likely to be found in sewage sludge at significant factions (25.2%-75.0%) of their inputs in raw sewage and subsequently enter the terrestrial environment through land application of biosolids, e.g., 43% in the United States and as high as 96% in Ireland or non-compliant practices of sewage sludge disposal in developing communities, such as open dumping and land application without prior anaerobic digestion. The available evidence underscores the importance of adequately treating and disposing of sewage sludge before its final disposal or land application in an epidemic or pandemic scenario, as mismanaged sewage sludge could be a significant vector for releasing pharmaceutical compounds and their metabolites into the terrestrial environment.

Desorption kinetic and sequential extraction of Pb and Zn in a contaminated soil amended with phosphate, lime, biochar, and biosolids

The mining and metallurgical industry sector activities often release potential toxic elements (PTE) surrounding exploitation area. We evaluated the addition of phosphate and lime using the dosage of 0.5:1, 1:1, and 2:1 molar ratio of PO43- and CO32- to the sum of PTE, respectively, and also, biochar and biosolids using the dosage of 2.5, 5, and 10% (m:m) to immobilize PTE in contaminated forest soil (Pb (270 mg kg-1) and Zn (858 mg kg-1)) near an abandoned mine site in Brazil. The desorption by stirred flow kinetics revealed that 15% of the total Zn and 12% Pb contents are mobile before any amendment application. Phosphate amendment decreased Pb desorption but increased Zn desorption. Biochar and biosolids immobilize high amounts of Zn and Pb because of their high cation exchange capacities and alkaline properties; however, 20% biosolid dose increased Pb desorption. X-ray absorption spectroscopy suggested Zn-kerolite as the major species in the contaminated soil, likely from mine dust. The change in Zn speciation after soil amendment addition indicated that biochar and lime kept a high proportion of Zn-Al species, whereas phosphate and biosolids led to more Zn-Fe species. Our results pointed out that lime might reduce both Pb and Zn mobilities; however, field trials are crucial to confirm the immobilization efficiency of lime and other amendments over long term.

The dynamics of boron when amending agricultural soil of the Mediterranean basin with biosolids: trials in leaching columns

There is mainly a lack of boron (B) in soils with low amounts of organic matter and in acidic and sandy soils. This is especially true in irrigated land or humid regions, where leaching can occur. The results from studying the amount of available B will reveal the status of B in the soil of a specific plot of land. The experimentation was performed as a controlled study using leaching columns. A container was placed at the end of the columns to collect the infiltrated water. Three treatments were performed by applying different amounts of biosolids (T40: 40,000 kg ha-1, T80: 80,000 kg ha-1, T120: 120,000 kg ha-1), as well as a blank test or control treatment (T0). We conclude that the mobility of B in soil was generally low despite the addition of organic matter and humidity to the soil. This is an indication that there is no clear risk of aquifers being contaminated with B or plants being impacted by toxicity due to this micronutrient.

Developmental programming: Impact of preconceptional and gestational exposure to a real-life environmental chemical mixture on maternal steroid, cytokine and oxidative stress milieus in sheep

BACKGROUND

Gestational exposure to environmental chemicals (ECs) is associated with adverse, sex-specific offspring health effects of global concern. As the maternal steroid, cytokine and oxidative stress milieus can have critical effects on pregnancy outcomes and the programming of diseases in offspring, it is important to study the impact of real-life EC exposure, i.e., chronic low levels of mixtures of ECs on these milieus. Sheep exposed to biosolids, derived from human waste, is an impactful model representing the ECs humans are exposed to in real-life. Offspring of sheep grazed on biosolids-treated pasture are characterized by reproductive and metabolic disruptions.

OBJECTIVE

To determine if biosolids exposure disrupts the maternal steroid, cytokine and oxidative stress milieus, in a fetal sex-specific manner.

METHODS

Ewes were maintained before mating and through gestation on pastures fertilized with biosolids (BTP), or inorganic fertilizer (Control). From maternal plasma collected mid-gestation, 19 steroids, 14 cytokines, 6 oxidative stress markers were quantified. Unpaired t-test and ANOVA were used to test for differences between control and BTP groups (n = 15/group) and between groups based on fetal sex, respectively. Correlation between the different markers was assessed by Spearman correlation.

RESULTS

Concentrations of the mineralocorticoids - deoxycorticosterone, corticosterone, the glucocorticoids - deoxycortisol, cortisol, cortisone, the sex steroids - androstenedione, dehydroepiandrosterone, 16-OH-progesterone and reactive oxygen metabolites were higher in the BTP ewes compared to Controls, while the proinflammatory cytokines IL-1β and IL-17A and anti-inflammatory IL-36RA were decreased in the BTP group. BTP ewes with a female fetus had lower levels of IP-10.

DISCUSSION

These findings suggest that pre-conceptional and gestational exposure to ECs in biosolids increases steroids, reactive oxygen metabolites and disrupts cytokines in maternal circulation, likely contributors to the aberrant phenotypic outcomes seen in offspring of BTP sheep - a translationally relevant precocial model.

Effect of biosolid-derived dissolved organic matter on orthophosphate sorption to soils depends on clay mineralogy and solution composition

Dissolved organic matter (DOM) from biosolids can alter the sorption of orthophosphate (inorganic phosphorus (IP)) to soils and, therefore, affect the bioavailability of IP. It is not clear how clay mineralogy and solution composition interfere with DOM effects on IP sorption by soils. Hence, we studied the effect of DOM on IP sorption to five semi-arid soils dominated by either illite/smectite (I/S) or kaolinite clays. IP sorption isotherms were constructed in either NaCl or CaCl2 background solution, with and without the addition of DOM. The IP sorption capacity maxima (SMAX, Langmuir model) of the I/S soils were 33-102% higher in the presence of CaCl2, as compared to NaCl. Although DOM had no effect on the IP-SMAX in the presence of CaCl2, it increased the IP-SMAX by 35-59% in the presence of the NaCl solution. Surprisingly, DOM sorption to the I/S soils was 30-90% greater in the presence of a Na+-dominated solution, as compared to a Ca2+-dominated solution. In contrast to the I/S soils, the SMAX of the kaolinitic soil was not affected by the background electrolyte (Na+, Ca2+) or the addition of DOM. Furthermore, the addition of IP reduced the sorption of DOM to the kaolinitic soil (by up to 50%) in both background electrolyte solutions. These results highlight the contrasting roles of divalent and monovalent cations in conjunction with DOM in IP sorption to semi-arid I/S soils. We propose a new approach based on two conceptual mechanisms to explain the DOM's enhancement of IP sorption to I/S soils. (1) Under dispersion conditions in the Na+-dominated solutions, Ca2+-mediated DOM-IP complexes bind to the clay's negative planar surfaces. (2) Under flocculation conditions in the Ca+-dominated solutions, the distance between adjacent platelets decreases, reducing both the electronegative charge spillover and Ca2+ bridge-mediated DOM sorption. In contrast, the addition of DOM to kaolinite, a multi-platelet clay with a low isomorphic negative charge, reduces IP sorption due to competitive sorption on the clay's broken edges.

Potential ecotoxicological effects of silver nanoparticles and silver sulphide on the endogeic earthworm Aporrectodea caliginosa (Savigny 1826)

Silver nanoparticles (AgNPs) are increasingly used in consumer products and subsequently arrive in wastewater systems, accumulating as silver sulphide (Ag2S) in the resulting biosolids, which are commonly spread onto agricultural fields as a fertiliser. Experiments were performed to investigate the effect of AgNPs, using the endogeic earthworm Aporrectodea caliginosa as a test organism. In an acute toxicity experiment, A. caliginosa were exposed to soil containing different concentrations of AgNPs (0, 1, 5, 10, 50, 100, 250, 500, 750, and 1000 mg kg-1 dry soil) and Ag2S (0, 10, 50, 100, 500, and 1000 mg kg-1 dry soil). Earthworm biomass and mortality were monitored. Earthworms exposed to 500, 750 and 1000 mg kg-1 fresh AgNPs had mortality rates of 20%, 60% and 70%, respectively. Changes in biomass were directly related to AgNP concentration. Exposure to Ag2S did not affect biomass or mortality. Further experiments used 0, 10, 50, 100 and 250 mg kg-1 AgNPs and 0, 50, 100, 500, and 1000 mg kg-1 Ag2S to evaluate sublethal effects on A. caliginosa. Avoidance behaviour in a linear gradient was evaluated after 14 days. Earthworms significantly preferred soil that was free of either AgNPs or Ag2S. The same concentrations were used to assess effects on cocoon production of A. caliginosa exposed to AgNPs and Ag2S. In the first 3 months of AgNP exposure, higher concentrations had a negative effect on cocoon production, but this effect diminished thereafter. Ag2S had no discernible effect on reproduction. Overall, introduction of AgNPs into the soil through the application of biosolids appears to be of low concern to the tested endogeic earthworm.

Effective stabilization of per- and polyfluoroalkyl substances (PFAS) precursors in wastewater treatment sludge by surfactant-modified clay

The application of biosolids or treated sewage sludge containing per- and polyfluoroalkyl substances (PFAS) in agricultural lands and the disposal of sludge in landfills pose high risks to humans and the environment. Although PFAS precursors have not been regulated yet, their potential transformation to highly regulated perfluoroalkyl acids (PFAAs) may enable them to serve as a long-term source and make remediation of PFAAs a continuing task. Therefore, treating precursors in sewage sludge is even more, certainly not less, critical than treating or removing PFAAs. In this study, a green surfactant-modified clay sorbent was evaluated for its efficacy in stabilizing two representative PFAA precursors in sludge, e.g., N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA) and 6:2 fluorotelomer sulfonic acid (6:2 FTSA), in comparison with unmodified clay and powdered activated carbon (PAC). Results showed N-EtFOSAA and 6:2 FTSA exhibited distinct adsorption behaviors in the sludge without sorbents due to their different physicochemical properties, such as hydrophobicity and functional groups. Among the three sorbents, the modified clay reduced the water leachability of N-EtFOSAA and 6:2 FTSA by 91.5% and 95.4%, respectively, compared to controls without amendments at the end of the experiment (47 days). Within the same duration, PAC decreased the water leachability of N-EtFOSAA and 6:2 FTSA by 60.6% and 37.3%, respectively. At the same time, the unmodified clay demonstrated a poor stabilization effect and even promoted the leaching of precursors. These findings suggested that the modified clay had the potential for stabilization of precursors, while negatively charged and/or hydrophilic sorbents, such as the unmodified clay, should be avoided in the stabilization process. These results could provide valuable information for developing effective amendments for stabilizing PFAS in sludge or biosolids. Future research should evaluate the long-term effect of the stabilization approach using actual sludge from wastewater treatment facilities.

Occurrence and distribution of microplastics in long-term biosolid-applied rehabilitation land: An overlooked pathway for microplastic entry into terrestrial ecosystems in Australia

Wastewater treatment plants (WWTPs) efficiently eliminate over 98% of microplastics (MPs) from wastewater discharge, subsequently accumulating them in sludge. This sludge is frequently employed as fertilizer in agricultural practices or land rehabilitation. While there is significant research on biosolid application in agriculture, the discussion regarding its application in rehabilitating industrial zones and MPs contamination is limited. The current study investigates the abundance, distribution, and composition of MPs in rehabilitation land with long-term biosolid-application in Australia. Three minesite fields (designated 1-3), each with distinct biosolid application histories since 2011, 2012, and 2017, and a control field without any biosolid application history, were chosen for this study. The abundances of MPs in biosolid-applied fields 1-3 (6.04 ± 1.92 x 102 MP kg-1; 4.94 ± 0.73 x 102 MP kg-1; 2.48 ± 0.70 x 102 MP kg-1) were considerably higher compared to non-biosolid-applied field (0.70 ± 0.63 x 102 MP kg -1). This indicates that the application of biosolids significantly contributes to the presence of MPs in the soil. Moreover, the results suggest that with each successive application, the abundance of MPs increases. The abundance and size of MPs in both biosolid and non-biosolid soils decreased as the soil depth increased. Microbeads were dominant in soils where biosolids were applied (up to 61.9%), while fibres were dominant in non-biosolid soils (accounting for 85.7%). The distribution of plastic polymer types varied among fields and soil depths. Most MPs were microbeads of polyamide (PA), fragments of polyethylene (PE), foam of polystyrene (PS), and fibres of rayon. This research presents evidence that the extended utilization of biosolids results in elevated MP pollution in minesite rehabilitation land, highlighting a frequently overlooked origin of MP contamination in terrestrial settings. Additional evaluations needed to understand ecological risks of MPs in soil ecosystems affected by biosolid application.

Steps to circularity: Impact of resource recovery and urban agriculture in Seattle and Tacoma, Washington

Capturing the value in urban residuals (food scraps and wastewater) is a critical component of urban sustainability and a circular nutrient economy. Food production in urban areas has also been recognized as an important component of urban health. Data from two cities (Seattle and Tacoma, WA) with active resource recovery and community garden programs were used to quantify nutrient recovery and food production potential. Yield data from growth trials conducted using soil amendments produced from locally generated organic residuals were used to model yields in existing urban agriculture programs. Our survey showed much lower than expected volume of food scraps from both residential and multifamily housing for both cities. Nutrient generation rates from food scraps were estimated as 0.55-0.67 kg N and 0.09-0.11 kg P capita-1 yr-1. Recovery rates for Seattle with an established food scrap collection program were 0.21 kg N and 0.006 kg P capita-1 yr-1. Nutrient recovery from wastewater biosolids was higher; 1-1.67 kg N and 0.23-0.76 kg P capita-1 yr-1. Data on effluent quantity and nutrient concentrations from these programs suggests that effluent has a high potential for nutrient recovery (4.03-5 kg N and 0.3-0.5 kg P capita yr-1). Yield was modeled for kale (brassica oleracea) considering the number of people that could be fed per hectare for one year using a 67 g portion by comparing yields from synthetic fertilizer and residuals-based amendments in both high and low quality urban soils. The Tacoma biosolids potting soil yielded enough for 310 and 736 people ha-1 yr-1 for the high and low quality soils, respectively. The modeled food/yard compost produced from the food scraps yielded sufficient kale for 148 to 353 people ha-1 yr-1. Relative yield from fertilizer for the low and high quality soils was 15 and 263 people ha-1yr-1, respectively. Considering yield, enough biosolids are produced to meet 6.7-29.2% of the vegetable needs of each city. These results suggest that significant nutrients can be recovered using existing infrastructure. With enhanced nutrient capture from wastewater effluent, sufficient nutrients could be recovered to meet the N and P needs for food crops for the residents of each city.

Occurrence and transformation of heavy metals during swine waste treatment: A full scale study

This study tracked the fate of nine detected heavy metals in an industrial swine farm with integrated waste treatment, including anoxic stabilization, fixed-film anaerobic digestion, anoxic-oxic (A/O), and composting. Results show that heavy metals exhibited different transformation behaviors in the treatment streamline with Fe, Zn, Cu and Mn as the most abundant ones in raw swine waste. The overall removal of water-soluble heavy metals averaged at 30 %, 24 % and 42 % by anoxic stabilization, anaerobic digestion and A/O unit, respectively. In particular, anoxic stabilization could effectively remove Cu, Mn and Ni; while A/O unit was highly effective for Fe, Cr and Zn elimination from water-soluble states. As such, the environmental risk of liquid products for agricultural irrigation decreased gradually to the safe pollution level in swine waste treatment. Furthermore, heavy metals in the solid (slurry) phase of these bioprocesses could be immobilized with the passivation rate in the range of 42-70 %. Nevertheless, heavy metals preferably transformed from liquid to biosolids to remain their environmental risks when biosolids were used as organic fertilizer in agriculture, thereby requiring effective strategies to advance their passivation in all bioprocesses, particularly composting as the last treatment unit.

Pulp mill biosolids mitigate soil greenhouse gas emissions from applied urea and improve soil fertility in a hybrid poplar plantation

Pulp mill biosolids (hereafter 'biosolids') could be used as an organic amendment to improve soil fertility and promote crop growth; however, it is unclear how the application of biosolids affects soil greenhouse gas emissions and the mechanisms underlying these effects. Here, we conducted a 2-year field experiment on a 6-year-old hybrid poplar plantation in northern Alberta, Canada, to compare the effects of biosolids, conventional mineral fertilizer (urea), and urea + biosolids on soil CO2, CH4 N2O emissions, as well as soil chemical and microbial properties. We found that the addition of biosolids increased soil CO2 and N2O emissions by 21 and 17%, respectively, while urea addition increased their emissions by 30 and 83%, respectively. However, the addition of urea did not affect soil CO2 emissions when biosolids were also applied. The addition of biosolids and biosolids + urea increased soil dissolved organic carbon (DOC) and microbial biomass C (MBC), while urea addition and biosolids + urea addition increased soil inorganic N, available P and denitrifying enzyme activity (DEA). Furthermore, the CO2 and N2O emissions were positively, while the CH4 emissions were negatively associated with soil DOC, inorganic N, available phosphorus, MBC, microbial biomass N, and DEA. In addition, soil CO2, CH4 and N2O emissions were also strongly associated with soil microbial community composition. We conclude that the application of the combination of biosolids and chemical N fertilizer (urea) could be a beneficial approach for both the disposal and use of pulp mill wastes, by reducing greenhouse gas emissions and improving soil fertility.

Influence of biosolids and sewage effluent application on sitagliptin soil sorption

Biosolids and sewage effluent application to agricultural fields is becoming a win-win practice as both an economical waste management strategy and a source of nutrients and organic matter for plant growth. However, these organic wastes contain a variety of trace chemicals of environmental concern such as pharmaceuticals and personal care products (PPCPs), which may pose a risk to agricultural fields and ecosystems. This work aims to investigate the sorption of sitagliptin on four agricultural soils, evaluate the effects of biosolids and sewage effluent application, and elucidate the main sorption mechanism of the pharmaceutical on soils. The sorption study revealed that the sorption capacities of sitagliptin on different soils were positively related to the contents of soil organic matter and negatively associated with soil pH values. The application of biosolids and sewage effluent decreased the sorption capacity of sitagliptin, which may be attributed to the loading of dissolved organic matter derived from organic wastes. The Freundlich isotherm model demonstrated that the addition of biosolids from 0 to 100 % (W/W) consistently decreased the sorption affinity (Kf) of sitagliptin from 1.69 × 102 to 3.82 × 101 mg(1-n) Ln kg-1. Sewage application at 0, 10, 50, and 100 % (V/V) also reduced the Kf values from 1.69 × 102 to 9.17 × 101 mg(1-n) Ln kg-1. Attenuated Total Reflection (ATR)-Infrared (IR) spectroscopy analyses suggested that electrostatic interactions between carbonyl and amino groups of sitagliptin and the negatively charged soil surface are the main sorption mechanisms. In a co-solute system, the sorption affinity of sitagliptin on the soil decreased with increasing metformin concentrations, suggesting that competitive sorption may reduce the sorption capacity of individual contaminants in soil systems containing multiple PPCPs.

Investigation on removal of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) using water treatment sludge and biochar

This work assessed the adsorption performance of three common PFAS compounds (PFOA, PFOS and PFHxS) on two water treatment sludges (WTS) and two biochars (commercial biomass biochar and semi-pilot scale biosolids biochar). Of the two WTS samples included in this study, one was sourced from poly-aluminium chloride (PAC) and the other from alum (Al2(SO4)3). The results of experiments using a single PFAS for adsorption reinforced established trends in affinity - the shorter-chained PFHxS was less adsorbed than PFOS, and the sulphates (PFOS) were more readily adsorbed than the acid (PFOA). Interestingly, PAC WTS, showed an excellent adsorption affinity for the shorter chained PFHxS (58.8%), than the alum WTS and biosolids biochar at 22.6% and 41.74%, respectively. The results also showed that the alum WTS was less effective at adsorption than the PAC WTS despite having a larger surface area. Taken together, the results suggest that the hydrophobicity of the sorbent and the chemistry of the coagulant were critical factors for understanding PFAS adsorption on WTS, while other factors, such as the concentration of aluminium and iron in the WTS could not explain the trends seen. For the biochar samples, the surface area and hydrophobicity are believed to be the main drivers in the different performances. Adsorption from the solution containing multiple PFAS was also investigated with PAC WTS and biosolids biochar, demonstrating comparable performance on overall adsorption. However, the PAC WTS performed better with the short-chain PFHxS than the biosolids biochar. While both PAC WTS and biosolids biochar are promising candidates for adsorption, the study highlights the need to explore further the mechanisms behind PFAS adsorption, which could be a highly variable source to understand better the potential for WTS to be utilized as a PFAS adsorbent.

Biosolids application enhances the growth of Aloe vera plants and provides a sustainable practice for nutrient recirculation in agricultural soils

In the present study, the fertilization potential of biosolids (sewage sludge; SS) for the cultivation of Aloe vera plants was investigated using block design. Pot experiments were conducted in this study using 50, 100, 150, and 200 g/kg of SS. Results showed that SS-fertilized soils significantly (p < 0.05) affected the proximate, biochemical, and heavy metal parameters of A. vera plants. In particular, the T4 treatment gave the best results with maximum plant height 62.21 ± 0.10 cm, number of leaves per plant 18.00 ± 4.00, shoot-to-root ratio 6:1, fresh weight 1972.10 ± 0.07 g per plant, dry weight 175.49 ± 0.15 g per plant, total chlorophyll content (TCC) 0.41 ± 0.02 mg/g fwt., carotenoids 0.25 ± 0.04 mg/g, total flavonoids 7.55 ± 0.05 mg/g, total tannins 3.87 ± 0.06 µg/g, ascorbic acid 532.14 ± 0.10 µg/g, superoxide dismutase (SOD) 46.28 ± 0.19 µg/g, catalase (CAT) 119.23 ± 0.17 µg/g, salicylic acid 3.05 ± 0.12 mg/ml and anthraquinones 0.45 ± 0.04 mg/ml, respectively. The proximate plant characteristics were 96.25 ± 2.71% moisture content, crude protein 0.93 ± 0.05%, crude fiber 5.78 ± 0.44%, crude lipid 3.25 ± 0.02%, lignin 10.74 ± 0.30%, cellulose 13.56 ± 1.06%, hemicellulose 7.24 ± 0.14%, ash 8.75 ± 0.03%, and carbohydrate contents 52.18 ± 1.10% in comparison with control treatment. The bioaccumulation factor showed that heavy metal accumulation was in the order of Cd < Ni < Cu < Pb < Cr < Zn < Fe. The prediction models developed on the basis of soil properties showed good fitness results for the prediction of heavy metal uptake by A. vera plants. The study presented a sustainable approach for managing SS in an eco-friendly way while producing good-quality A. vera plants.

Target and Suspect Screening Integrated with Machine Learning to Discover Per- and Polyfluoroalkyl Substance Source Fingerprints

This study elucidates per- and polyfluoroalkyl substance (PFAS) fingerprints for specific PFAS source types. Ninety-two samples were collected from aqueous film-forming foam impacted groundwater (AFFF-GW), landfill leachate, biosolids leachate, municipal wastewater treatment plant effluent (WWTP), and wastewater effluent from the pulp and paper and power generation industries. High-resolution mass spectrometry operated with electrospray ionization in negative mode was used to quantify up to 50 target PFASs and screen and semi-quantify up to 2,266 suspect PFASs in each sample. Machine learning classifiers were used to identify PFASs that were diagnostic of each source type. Four C5-C7 perfluoroalkyl acids and one suspect PFAS (trihydrogen-substituted fluoroethernonanoic acid) were diagnostic of AFFF-GW. Two target PFASs (5:3 and 6:2 fluorotelomer carboxylic acids) and two suspect PFASs (4:2 fluorotelomer-thia-acetic acid and N-methylperfluoropropane sulfonamido acetic acid) were diagnostic of landfill leachate. Biosolids leachates were best classified along with landfill leachates and N-methyl and N-ethyl perfluorooctane sulfonamido acetic acid assisted in that classification. WWTP, pulp and paper, and power generation samples contained few target PFASs, but fipronil (a fluorinated insecticide) was diagnostic of WWTP samples. Our results provide PFAS fingerprints for known sources and identify target and suspect PFASs that can be used for source allocation.

Biochar impacts on soil nitrogen and carbon dynamics in a Spodosol amended with biosolids and inorganic fertilizer

Despite evidence suggesting that biochar can retain nutrients, particularly nitrogen (N), and reduce the risks of transport, research on the co-application of biochar with organic and inorganic fertilizer sources is limited. Three laboratory studies (herein referred to as static incubation, column leaching, and batch sorption) were conducted to evaluate the impacts of two biochar materials (pine and grass biochar generated at temperatures of 800 and 400°C, respectively) on N and carbon (C) dynamics in soils amended with different N sources (ammonium nitrate, Class B, and Class AA biosolids). Nitrogen sources were applied at an equivalent rate of 180 kg N ha-1 while biochar was applied at a 1% (w/w) rate. Biochar effects on soil N and C dynamics were variable and dependent on biochar and N sources. A negligible but significant effect of pine biochar in reducing NH4 leaching was observed; however, both biochar materials were ineffective in reducing NO3 or inorganic N leaching. Reductions in leachate NH4 by pine biochar were attributed to relative greater ability of this material to retain NH4 than grass biochar. Both biochar materials exhibited no ability to sorb NO3 . Similarly, biochar had no effect on soil N2 O emissions. Class B biosolids resulted in greater N leaching and soil N2 O emissions compared to other fertilizers. This response was likely due to inherently high levels of inorganic N and moisture, which possibly favored denitrification. Further research is warranted to better understand the underlying mechanisms controlling soil N and C dynamics and responses to co-application with fertilizer sources.

Sexually dimorphic impact of preconceptional and gestational exposure to a real-life environmental chemical mixture (biosolids) on offspring growth dynamics and puberty in sheep

Humans are ubiquitously exposed to complex mixtures of environmental chemicals (ECs). This study characterised changes in post-natal and peripubertal growth, and the activation of the reproductive axis, in male and female offspring of sheep exposed to a translationally relevant EC mixture (in biosolids), during pregnancy. Birthweight in both sexes was unaffected by gestational biosolids exposure. In contrast to females (unaffected), bodyweight in biosolids males was significantly lower than controls across the peripubertal period, however, they exhibited catch-up growth eventually surpassing controls. Despite weighing less, testosterone concentrations were elevated earlier, indicative of early puberty in the biosolids males. This contrasted with females in which the mean date of puberty (first progesterone cycle) was delayed. These results demonstrate that developmental EC-mixture exposure has sexually dimorphic effects on growth, puberty and the relationship between body size and puberty. Such programmed metabolic/reproductive effects could have significant impacts on human health and wellbeing.

How many microplastic particles are present in Canadian biosolids?

Application of treated sewage sludge (biosolids) from wastewater treatment plants (WWTPs) to farmlands is an important pathway through which microplastic particles (MPs) enter terrestrial ecosystems. Yet, microplastic concentrations in Canadian biosolids have only been estimated in samples from four WWTPs previously. We aimed to fill this knowledge gap by quantifying microplastics in biosolids from 22 WWTPs located in nine provinces and two commercial fertilizer producers in Canada. All samples had substantial microplastic concentrations ranging from 228 to 1353 particles per gram dry weight (median = 636 particles), which are orders of magnitude greater than MPs reported from earlier investigations of biosolids from other countries. Fibers (median: 86%) were the most common type of MPs observed, followed by fragments (median: 13%). There were no statistically significant differences in the amount of microplastics observed in the biosolids from different geographical regions, WWTP types, and sludge treatment processes. This suggests that diverse combinations of local sewershed characteristics, site-specific treatment approaches, and daily flow at WWTPs may be influencing concentrations of microplastics in biosolids. Our results indicate that microplastic concentrations in biosolids are substantially higher than they are in other environmental matrices, and this has important implications to managing microplastic pollution in terrestrial ecosystems.

Emerging environmental health risks associated with the land application of biosolids: a scoping review

BACKGROUND

Over 40% of the six million dry metric tons of sewage sludge, often referred to as biosolids, produced annually in the United States is land applied. Biosolids serve as a sink for emerging pollutants which can be toxic and persist in the environment, yet their fate after land application and their impacts on human health have not been well studied. These gaps in our understanding are exacerbated by the absence of systematic monitoring programs and defined standards for human health protection.

METHODS

The purpose of this paper is to call critical attention to the knowledge gaps that currently exist regarding emerging pollutants in biosolids and to underscore the need for evidence-based testing standards and regulatory frameworks for human health protection when biosolids are land applied. A scoping review methodology was used to identify research conducted within the last decade, current regulatory standards, and government publications regarding emerging pollutants in land applied biosolids.

RESULTS

Current research indicates that persistent organic compounds, or emerging pollutants, found in pharmaceuticals and personal care products, microplastics, and per- and polyfluoroalkyl substances (PFAS) have the potential to contaminate ground and surface water, and the uptake of these substances from soil amended by the land application of biosolids can result in contamination of food sources. Advanced technologies to remove these contaminants from wastewater treatment plant influent, effluent, and biosolids destined for land application along with tools to detect and quantify emerging pollutants are critical for human health protection.

CONCLUSIONS

To address these current risks, there needs to be a significant investment in ongoing research and infrastructure support for advancements in wastewater treatment; expanded manufacture and use of sustainable products; increased public communication of the risks associated with overuse of pharmaceuticals and plastics; and development and implementation of regulations that are protective of health and the environment.

Long-duration monitoring and mass balance of PFAS at a wastewater treatment plant following the release of aqueous film-forming foam concentrate

Approximately 760 liters (200 gallons) of first-generation, PFOS-dominant, Aqueous Film-Forming Foam (AFFF) concentrate entered the sanitary sewer after an accidental release at the Kalamazoo/Battle Creek International Airport and migrated 11.4 km to the Kalamazoo Water Reclamation Plant. Near-daily sampling of influent, effluent, and biosolids generated a high-frequency, long-duration dataset used to understand the transport and fate of accidental PFAS releases to wastewater treatment plants, identify AFFF concentrate composition, and perform a plant-wide PFOS mass balance. Monitored influent concentrations exhibited sharp PFOS declines after 7 days post-spill, yet effluent discharges remained elevated due to return activated sludge (RAS) recirculation, resulting in the exceedance of Michigan's Surface Water Quality Value for 46 days. Mass balance estimates indicate 1.292 kg PFOS entering the plant and 1.368 kg leaving. Effluent discharge and sorption to biosolids account for 55% and 45% of estimated PFOS outputs, respectively. Identification of AFFF formulation and reasonable agreement between computed influent mass and reported spill volume demonstrates effective isolation of the AFFF spill signal and increases confidence in the mass balance estimates. These findings and related considerations provide critical insight for performing PFAS mass balances and developing operational procedures for accidental spills that minimize PFAS releases to the environment.

Diversity of virulence and antibiotic resistance genes expressed in Class A biosolids and biosolids-amended soil as revealed by metatranscriptomic analysis

Class A biosolids is a treated sewage sludge, commonly applied to agricultural fields, home lawns/gardens, golf courses, forests, and remediation sites around the world. This practice is of public and agricultural concern due to the possibility that biosolids contain antibiotic-resistant bacteria and fungal pathogens that could persist for extended periods in soil. This possibility was determined by metatranscriptomic analysis of virulence, antibiotic resistance, and plasmid conjugation genes, a Class A biosolids, organically managed soil, and biosolids-amended soil under realistic conditions. Biosolids harbored numerous transcriptionally active pathogens, antibiotic resistance genes, and conjugative genes that annotated mostly to Gram-positive pathogens of animal hosts. Biosolids amendment to soil significantly increased the expression of virulence genes by numerous pathogens and antibiotic-resistant genes that were strongly associated with biosolids. Biosolids amendment also significantly increased the expression of virulence genes by native soil fungal pathogens of plant hosts, which suggests higher risks of crop damage by soil fungal pathogens in biosolids-amended soil. Although results are likely to be different in other soils, biosolids, and microbial growth conditions, they provide a more holistic, accurate view of potential health risks associated with biosolids and biosolids-amended soils than has been achievable with more selective cultivation and PCR-based techniques.

Mass spectrometry imaging for biosolids characterization to assess ecological or health risks before reuse

Biosolids are byproducts of wastewater treatment. With the increasing global population, the amounts of wastewater to be treated are expanding, along with the amounts of biosolids generated. The reuse of biosolids is now accepted for diversified applications in fields such as agriculture, engineering, agro-forestry. However, biosolids are known to be potential carriers of compounds that can be toxic to living beings or alter the environment. Therefore, biosolid reuse is subject to regulations, mandatory analyses are performed on heavy metals, persistent organic pollutants or pathogens. Conventional methods for the analysis of heavy metals and persistent organic pollutants are demanding, lengthy, and sometimes unsafe. Here, we propose mass spectrometry imaging as a faster and safer method using small amounts of material to monitor heavy metals and persistent organic pollutants in different types of biosolids, allowing for ecological and health risk assessment before reuse. Our methodology can be extended to other soil-like matrices.