A review on the fate and effects of contaminants in biosolids applied on land: Hazards and government regulatory policies

Analysis of multi-class unregulated organic compounds in soil and biosolids using LC-MS/MS

Numerous unregulated organic compounds (UOCs) including pharmaceuticals, opioids, and personal care products (PCPs) end up in wastewater. UOC presence in biosolids (a wastewater treatment byproduct), which are applied to soil for different reasons raises environmental and health risk concerns. In this study, two multi-class extraction methods were developed and validated to target 111 UOCs from 8 different major families simultaneously in biosolids and biosolids-impacted soil. One method (M-SPE) is a modified version of EPA 1694, that uses triple solid-liquid extraction and solid phase extraction (SPE). The second method (EMR) is a super-fast method consisting in a single solvent extraction and EMR (enhanced matrix removal)-Lipid dispersive SPE. M-SPE performed better overall with 72 and 54 UOCs extracted with 50-130% recovery for soil and biosolids, respectively, compared to EMR for which only 49 and 43 UOCs achieved within the same range, respectively. EMR performed particularly well for the extraction of low concentration opioids from biosolids. The use of ENVI-Carb as an additional cleanup step and its potential to sorb analytes was also evaluated. Although >75% sorption of 27 UOCs occurred, ENVI-Carb (graphitized carbon) was needed to sufficiently clean extracts prior to injection to avoid precipitation and protect analytical systems. Application of these methods to environmental samples resulted in detection of some flame retardants, opioids, pharmaceuticals, PCPs and phthalates totaling 30 and 26 UOCs in biosolids and soil historically applied with biosolids, respectively. This methodology will be an asset to determining UOC concentrations in biosolids and biosolids-impacted soils.

Developmental programming: Sex-specific effects of prenatal exposure to a real-life mixture of environmental chemicals on liver function and transcriptome in sheep

Humans are chronically exposed to a mixture of environmental chemicals (ECs), many with metabolic and endocrine disrupting potential, contributing to non-communicable disease burden. Understanding the effects of chronic exposure to low-level mixtures of ECs requires an animal model that reflects real-world conditions, lags behind studies on single ECs. Biosolids, from wastewater treatment, offers a real-life model to investigate the developmental health risks from EC mixtures. Prenatal biosolids exposure studies have documented metabolic perturbations including heavier thyroid glands in male fetuses and reduced bodyweight in prepubertal male lambs followed by catchup growth. We hypothesized that maternal preconceptional and gestational exposure of sheep to biosolids programs sex-specific transcriptional and functional changes in the offspring liver. Ewes (F0) were grazed on either inorganic fertilizer (C) or biosolids-treated pastures (BTP) preconception till parturition. All lambs (n = 15/group with male n = 7/group and females n = 8/group) were raised on Control pastures until euthanasia at 9.5 weeks. Next generation sequencing of liver RNA and DESeq2 was used to identify exposure-specific differentially expressed genes (DEG) and sex-differentially expressed genes (SDG). Liver function was assessed with markers of oxidative stress, triglyceride and fibrosis markers. Control lambs exhibited 647 SDGs confirming the inherent sexual dimorphism in hepatic gene expression. A sex-stratified analysis identified 10 DEG, mostly affecting metabolism, in male and none in female lambs. Biosolids exposure diminished the sexual dimorphism in hepatic gene expression barring 41 genes, potentially due to the increase in androgenic steroids found in F0 maternal circulation. Additionally, BTP male lambs showed elevated plasma triglyceride and a trend towards increased liver triglyceride concentrations. The identified effects of prenatal exposure to low-dose mixture of ECs via biosolids, in a precocial species paralleling human developmental patterns holds translational importance for understanding the sexually dimorphic origin of non-communicable diseases.

Advancing sustainable agriculture through multi-omics profiling of biosolids for safe application: A review

Biosolids, derived from wastewater treatment processes, are valuable resources for soil amendment in agriculture due to their nutrient-rich composition. However, various contaminants of concern (CEC) such as pharmaceuticals, per-and poly-fluoroalkyl substances, endocrine disruptive chemicals, surfactants, pathogens, nanoplastics, and microplastics, are also reported in biosolids. The use of biosolids for agriculture may introduce these CEC into the soil, which raises concerns about their environmental and human health impacts. Moreover, the presence of pathogens (Escherichia coli, Salmonella sp., Shigella, Giardia, Rotavirus, etc.) even after treatment calls for microbial profiling of biosolids, especially in developing countries. Multi-omics approaches can be used as powerful tools for characterizing microbial communities and highlighting metabolic pathways. Moreover, these approaches also help in predicting the ecological and agronomic effects of biosolids application in agricultural soils. This review discusses the advantages and challenges of using biosolids in agriculture, considering the range of different CEC reported in biosolids. Moreover, the current legislation for the use of biosolids in agriculture is also presented, highlighting the limitations with respect to guidelines for emerging contaminants in biosolids. Furthermore, the role of the multi-omics approach in biosolids management, focusing on genomics, transcriptomics, proteomics, and metabolomics is also assessed. Multi-omics also allows for real-time monitoring, ensuring continuous optimization of biosolids towards changing environmental conditions. This dynamic approach not only enhances the safe use, but also enhances the sustainability of waste management practices, minimizing the negative effects. Finally, the future research directions for integrating the multi-omics approach into biosolid management practices are also suggested. The need for updating the legislative framework, continued innovation to promote sustainable and robust agricultural systems, bringing the process closer to the principles of a circular bioeconomy is also empahasized.

Opportunities and challenges of using human excreta-derived fertilizers in agriculture: A review of suitability, environmental impact and societal acceptance

Human excreta-derived fertilizers (HEDFs) are organic fertilizers made from human excreta sources such as urine and feces. HEDFs can contribute to a sustainable and circular agriculture by reuse of valuable nutrients that would otherwise be discarded. However, HEDFs may contain contaminants such as pharmaceuticals, persistent organic compounds, heavy metals and pathogens which can negatively affect plant, water and soil quality. Moreover, consumer prejudice, farmer hesitance and strict regulations can discourage utilization of HEDFs. Here, we conducted a thorough review of published literature to explore the opportunities and challenges of using HEDFs in agricultural systems by evaluating the suitability of human excreta as a nutrient source, their typical contaminant composition, how they affect the quality of crops, soils and water and their societal impact and acceptance. We found that HEDFs are suitable nutrient-rich fertilizers, but may contain contaminants. Processing treatments increase the fertilizer quality by reducing these contaminants, but they do not remove all contaminants completely. Regarding the environmental impacts of these fertilizers, we found overall positive effects on crop yield, soil nutrients, plant-soil-microbe interactions and plant pathogen suppression. The use of HEDFs reduces water contamination from sewage waste dumping, but nutrient leaching dependent on soil type may still affect water quality. We found no increased risks with human pathogens compared to inorganic fertilizers but identified processing treatment as well as crop and soil type significantly affect these risks. Lastly, we found that public acceptance is possible with clear regulations and outreach to inform consumers and farmers of their multi-faceted benefits and safe usage after processing treatments. In summary, this review emphasizes the great potential of HEDFs and its positive impacts on society, especially in regions where conventional fertilizers are scarce, while also stressing the need for adaptation to specific soils and crops.

Innovative Approach to Sustainable Fertilizer Production: Leveraging Electrically Assisted Conversion of Sewage Sludge for Nutrient Recovery

Efforts addressing sludge management, food security, and resource recovery have led to novel approaches in these areas. Electrically assisted conversion of sludge stands out as a promising technology for sewage sludge valorization, producing nitrogen and phosphorus-based fertilizers. The adoption of this technology, which could lead to a fertilizer circular economy, holds the potential to catalyze a transformative change in wastewater treatment facilities toward process intensification, innovation, and sustainability. This paper provides insights into the economic aspects of the technology, policy considerations, and challenges involved in realizing the potential of electrified processes for sludge valorization. To demonstrate the impact of the technology, a case study for its implementation in the United States assuming the municipal wastewater treatment plants market is discussed. It was found that electrically assisted sludge conversion could enable the recovery of nitrogen and phosphorus from waste, representing up to 9% of the nitrogen and 32% of the phosphorus consumption of the U.S. for fertilizer use. This technology also enables full electrification and modularization of the process, thereby presenting significant economic and environmental opportunities.

Fate of per- and polyfluoroalkyl substances at a 40-year dedicated municipal biosolids land disposal site

The fate of per- and polyfluoroalkyl substances (PFAS) was evaluated at a site where municipal biosolids have been applied annually for 38 years as a waste management strategy. Soil cores (1.8 m in 30-cm sections), groundwater from four wells, and biosolids applied in 2022 were analyzed for PFAS (54 targeted, 17 semi-quantified) using liquid chromatography high resolution mass spectrometry including suspect screening. Total PFAS concentrations decreased with soil depth from 1700 ng/g to 2.06 ng/g. PFAS distribution in 2022 biosolids were 60 mol% perfluoroalkyl acid (PFAA) precursors and intermediates. The surface soil was dominated by long-chain PFAAs (67-76 mol%) reflecting precursor degradation after biosolids application. Presence of semi-quantified intermediates further reflects precursor degradation in surface soil. Long-chain PFAAs diminished with depth while short-chain PFAAs increased with up to 98 and 96 mol% short-chain PFAAs in the bottom depth and groundwater, respectively. PFAS distribution with depth is consistent with chain-length dependent sorption-impacted transport and the high organic carbon content of the surface soil (15.2 % OC) which subsequently decreased with depth (~2-3 % OC at >60 cm). High organic carbon content in the upper horizon is likely from decades of high biosolids application rates, which contributed to minimizing leaching of long-chain PFAS. While the well within the dedicated land disposal is not drinking water, for comparison only, PFAS concentrations in this well only marginally exceeded the EU drinking water directive for total PFAS and a few individual short-chain PFAS, but did exceed tenfold, the USEPA drinking water standard for PFOA.

Terrestrial bioassays for assessing the biochemical and toxicological impact of biosolids application derived from wastewater treatment plants

Wastewater treatment plants (WWTP) are facilities where municipal wastewater undergoes treatment so that its organic load and its pathogenic potential are minimized. Sewage sludge is a by-product of this process and when properly treated is preferentially called "biosolids". These treatments may include some or most of the following: thickening, dewatering, drying, digestion, composting, liming. Nowadays it is almost impossible to landfill biosolids, which however can well be used as crop fertilizers. Continuous or superfluous biosolids fertilization may negatively affect non-target organisms such as soil macro-organisms or even plants. These effects can be depicted through bioassays on terrestrial animals and plants. It has been shown that earthworms have been affected to various degrees on the following endpoints: pollutants' bioaccumulation, viability, reproduction, avoidance behavior, burrowing behavior. Collembola have been affected on viability, reproduction, avoidance behavior. Other terrestrial organisms such as nematodes and diplopods have also shown adverse health effects. Phytotoxicity have been caused by some biosolids regimes as measured through the following endpoints: seed germination, root length, shoot length, shoot biomass, root biomass, chlorophyll content, antioxidant enzyme activity. Very limited statistical correlations between pollutant concentrations and toxicity endpoints have been established such as between juvenile mortality (earthworms) and As or Ba concentration in the biosolids, between juvenile mortality (collembola) and Cd or S concentration in the biosolids, or between phytotoxicity and some extractable metals in leachates or aquatic extracts from the biosolids; more correlations between physicochemical characteristics and toxicity endpoints have been found such as between phytotoxicity and ammonium N in biosolids or their liquid extracts, or between phytotoxicity and salinity. An inverse correlation between earthworm/collembola mortality and stable organic matter has also been found. Basing the appropriateness of biosolids only on chemical analyses for pollutants is not cost-effective. To enable risk characterization and subsequent risk mitigation it is important to apply a battery of bioassays on soil macro-organisms and on plants, utilizing a combination of endpoints and established protocols. Through combined analytical quantification and toxicity testing, safe use of biosolids in agriculture can be achieved.

Influence of microplastic contamination on the dissipation of endocrine disrupting chemicals in soil environment

Microplastic (MP) contamination is in the spotlight today, yet knowledge of their interaction with other organic contaminants in the soil environment is limited. Concerns extend to endocrine disrupting chemicals (EDCs), known for their potential to interfere with the hormonal systems of organisms and for their persistence and widespread presence in the environment. In this study, the most frequently occurring EDCs were monitored both in alluvial soil and in soil contaminated with different MPs commonly found in soil media, polyethylene, polyamide, and polystyrene. Bisphenol A and parabens were the most rapidly dissipating compounds, followed by triclosan and triclocarban, with the latter showing poor degradation. Per- and polyfluoroalkyl substances (PFAS) showed high persistence as concentrations remained nearly constant throughout the experiment. Although they fitted well with first-order dissipation kinetics, most showed biphasic behavior. The co-occurrence of MPs in the soil influenced the kinetic behavior in most cases although the differences were not very marked. MPs could impact sorption-desorption processes, affecting contaminant mobility and bioavailability to organisms in soil. These findings strengthen evidence for the influence of MPs on the behavior of soil contaminants such as EDCs, not only as vectors or sources of contaminants but by affecting dissipation kinetics.