Organic Contaminants in Chinese Sewage Sludge: A Meta-Analysis of the Literature of the Past 30 Years

Analysis of perfluorinated compounds in sewage sludge and hydrochar by UHPLC LTQ/Orbitrap MS and removal assessment during hydrothermal carbonization treatment

Wastewater treatment plants have been recognized as important sinks for per- and polyfluoroalkyl substances (PFAS) because of their ineffectiveness in removing them reflecting both water and sewage sludge discharge routes. Hydrothermal treatment represents an alternative technology for treating sludge to recover energy and other valuable products. In this study, 15 PFAS were determined in sludge and hydrochar substrates using sonication-solid phase extraction procedure and analyzed using LC-Orbitrap-High Resolution-MS/MS. The method was fully validated, exhibiting very good linearity, recoveries in the range of 48 to 126 %, low detection and quantification limits with expanded uncertainty and precision below 32 % and 21.9 %, respectively. The method was applied to sludge samples from the WWTP of Ioannina city (Greece), as well as to hydrothermally treated samples under various conditions. The most abundant PFAS were PFHxA (0.5-38.3 ng g-1) and PFOS (4.4-22.1 ng g-1). Finally, the hydrothermally treated sludge samples spiked with PFAS presented removal efficiencies for total PFAS of 86.9 %, 91.8 % and 95.7 % at three spiking levels namely 10, 50 and 200 ng g-1, respectively. Results indicated that PFCAs were almost completely removed, except for PFOA, while the concentrations of PFSAs increased in the produced hydrochar with the formation of several intermediates, as detected by HR-LC-MS/MS. The results of this study demonstrate the effect of hydrothermal treatment to the fate of PFAS in sewage sludge and contribute for further studies on design and scale up of hydrothermal carbonization technology as a management option for safer disposal of municipal wastewater sludge.

Global performance and trends of research on emerging contaminants in sewage sludge: A Bibliometric Analysis from 1990 to 2023

The pervasive occurrence of emerging contaminants (ECs) in sewage sludge (SWS) poses significant safety challenges concerning the processing, disposal, and secure application, ultimately jeopardizing both human health and the ecological environment. To comprehensively comprehend the evolutionary trajectories, present state, and research advancements in the field of ECs in SWS, a systematic was conducted, scrutinizing the annual publication quantity, disciplinary distribution, core authors, involved nations/regions, pertinent keywords, and citation status of 2082 research publications related to ECs in SWS from 1990 to 2023. The results indicate a substantial upward trajectory in the research literature pertaining to ECs in SWS. The study of ECs in SWS encompasses 78 disciplines, including Environmental Sciences, Environmental Engineering, and Water Resources. China, Spain, and the USA ranked among the top three countries in terms of both total publications and citation frequency. The majority of publications were published in reputable high-impact journals such as Science of the Total Environment, Chemosphere, and Bioresource Technology. Based on high-frequency keywords, co-occurrence networks of keywords, and keywords burst analysis, it is found that the occurrence and environment behavior of ECs in SWS (ARGs, microplastics, PPCPs, and POPs), the detection and analytical methods, the impact on SWS treatment and disposal processes, and the accumulation and ecological risks in plants and soil during SWS land utilization, are the main research directions and hot topics in this field. In the future, the study of the impact of SWS treatment technologies on ECs removal is expected to receive increased research attention.

Occurrence and Prioritization of Human Androgen Receptor Disruptors in Sewage Sludges Across China

The global practice of reusing sewage sludge in agriculture and its landfill disposal reintroduces environmental contaminants, posing risks to human and ecological health. This study screened sewage sludge from 30 Chinese cities for androgen receptor (AR) disruptors, utilizing a disruptor list from the Toxicology in the 21st Century program (Tox21), and identified 25 agonists and 33 antagonists across diverse use categories. Predominantly, natural products 5α-dihydrotestosterone and thymidine emerged as agonists, whereas the industrial intermediate caprolactam was the principal antagonist. In-house bioassays for identified disruptors displayed good alignment with Tox21 potency data, validating employing Tox21 toxicity data for theoretical toxicity estimations. Potency calculations revealed 5α-dihydrotestosterone and two pharmaceuticals (17β-trenbolone and testosterone isocaproate) as the most potent AR agonists and three dyes (rhodamine 6G, Victoria blue BO, and gentian violet) as antagonists. Theoretical effect contribution evaluations prioritized 5α-dihydrotestosterone and testosterone isocaproate as high-risk AR agonists and caprolactam, rhodamine 6G, and 8-hydroxyquinoline (as a biocide and a preservative) as key antagonists. Notably, 16 agonists and 20 antagonists were newly reported in the sludge, many exhibiting significant detection frequencies, concentrations, and/or toxicities, demanding future scrutiny. Our study presents an efficient strategy for estimating environmental sample toxicity and identifying key toxicants, thereby supporting the development of appropriate sludge management strategies.

Effect-directed analysis of androgenic compounds from sewage sludges in China

The safety of municipal sewage sludge has raised great concerns because of the accumulation of large-scale endocrine disrupting chemicals in the sludge during wastewater treatment. The presence of contaminants in sludge can cause secondary pollution owing to inappropriate disposal mechanisms, posing potential risks to the environment and human health. Effect-directed analysis (EDA), involving an androgen receptor (AR) reporter gene bioassay, fractionation, and suspect and nontarget chemical analysis, were applied to identify causal AR agonists in sludge; 20 of the 30 sludge extracts exhibited significant androgenic activity. Among these, the extracts from Yinchuan, Kunming, and Shijiazhuang, which held the most polluted AR agonistic activities were prepared for extensive EDA, with the dihydrotestosterone (DHT)-equivalency of 2.5 - 4.5 ng DHT/g of sludge. Seven androgens, namely boldione, androstenedione, testosterone, megestrol, progesterone, and testosterone isocaproate, were identified in these strongest sludges together, along with testosterone cypionate, first reported in sludge media. These identified androgens together accounted for 55 %, 87 %, and 52 % of the effects on the sludge from Yinchuan, Shijiazhuang, and Kunming, respectively. This study elucidates the causative androgenic compounds in sewage sludge and provides a valuable reference for monitoring and managing androgens in wastewater treatment.

Drivers distinguishing of PAHs heterogeneity in surface soil of China using deep learning coupled with geo-statistical approach

Although numerous studies have reported the influencing factors of polycyclic aromatic hydrocarbons (PAHs) in surface soil from source, process or soil perspectives, the mechanism of PAHs heterogeneity in surface soil are still not well understood. In this study, the effects of 16 PAHs in surface soil of China sampled between 2003 and 2020 with their 17 "source-process-sink" factors at 1 km resolution (N = 660)) were explored using deep learning (eXtreme Gradient Boosting) to mine key information from complex dataset under the optimized parameters (i.e., learning rate = 0.05, maximum depth = 5, sub-sample = 0.8). It was observed that top five factors of 16 PAH had the largest cumulative contribution (i.e., from 84.8% to 98.1%) on their soil concentrations. PAH emission was the predominant driver, and its effect on soil PAH increases with increasing logKow. Soil was the second driver, in which clay can promote the partition of PAHs with low or middle logKow. However, sand can accumulate those congeners with high logKow. Moreover, the deep learning plus geo-statistical models (with low deviation for testing dataset (N = 283)) were capable of predicting soil PAH concentrations using their drivers with high accuracy. This study improved the understanding of the environmental fate and spatial variability of soil PAHs, as well as provided a novel technique (i.e., deep learning coupled with geo-statistics) for accurate prediction of soil pollutants.

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.

The occurrence characteristics, removal efficiency, and risk assessment of polycyclic aromatic hydrocarbons in sewage sludges from across China

Sewage sludge is considered to be an important sink for polycyclic aromatic hydrocarbons (PAHs) in wastewater treatment plants and the potential risks from sludge contaminated with PAHs during land application has attracted attention. To identify the priority PAHs for control and enhance their removal from sludge, the occurrence characteristics, removal efficiency, and risk assessment of PAHs in sewage sludges from across China were analyzed. Data collection was from 2001 to 2023. Results showed that 16 PAHs were widely detected in Chinese sewage sludge with total amounts (∑16PAHs) between 0.06 and 34.93 mg kg dw-1. Fossil fuel, coal, and biomass combustion are main anthropogenic sources of PAHs in China. In general, phenanthrene (PHE), anthracene (ANT), fluorescein (FL), chrysene (CHR), pyrene (PYR), and benzo[b]fluoranthene (BbF) are regarded as the main components and PAHs with 3-5 rings dominate (84.01%-91.53%) sewage sludge in China. Although aerobic composting and anaerobic treatment significantly improve ∑16PAHs removal, sludge stabilization treatment only reduced the risk by a small amount, especially for high-molecular-weight (HMW) PAHs. The benzo[a]anthracene (BaA), benzo[a]pyrene (BaP), and dibenzo[a,h]anthracene (DahA) are proposed as the priority control contaminants for sewage sludge in China because they have consistently high-risk quotient (RQ) values of 2.42-7.47, 1.28-3.16, 1.06-1.83 before and after sludge stabilization, respectively. More attention should be paid to BaA, BbF, benzo[k]fluoranthene (BkF), BaP, DahA, and indeno[1,2,3-cd]pyrene (IcdP) in Beijing; ANT, BaA, and BaP in Shanghai; and BaA and BaP in Guanghzou. Although the toxic equivalent quotient (TEQ) for PAHs met the limit concentration requirements of the national standard, the potential health risks due to long-term exposure to HMW PAHs cannot be ignored because the incremental lifetime cancer risk (ILCR) was consistently in the risk threshold range (>1 × 10-6). Some suggestions on enhanced treatment approaches and land use standards are proposed to further alleviate the risk from HMW PAHs.

Chemicals of Emerging Arctic Concern in north-western Spitsbergen snow: Distribution and sources

Personal care products contain chemicals that are considered of emerging concern in the Arctic. In this study, a selected group of personal care products was investigated in the snowpack on north-western Spitsbergen. We report a preliminary study on the spatial and seasonal distribution of 13 ingredients commonly found in personal care products, including fragrance materials, UV filters, BHT and BPA. Possible sources and deposition processes are discussed. Experimental analyses utilizing GC-MS/MS, were complemented with outputs from the HYSPLIT transport and dispersion model. The results reveal the presence of all selected compounds in the snow, both in proximity to and distant from the research village of Ny-Ålesund. For some of these chemicals this is the first time their presence is reported in snow in Svalbard. These chemicals show different partitioning behaviours between the particulate and dissolved phases, affecting their transport and deposition processes. Additionally, concentrations of certain compounds vary across different altitudes. It is observed the relevance of long-range atmospheric transport during winter at most sites, and, regardless of the proximity to human settlements, snow concentrations can be influenced by long-distance sources. This study highlights the need for detailed information on CEACs' physical-chemical properties, considering their potential impact on fresh and marine waters during the snowmelt under climate change.

A 20-year shift in China's sewage sludge heavy metals and its feasibility of nutrient recovery in land use

Recycling resources from wastewater is even more important for developing a more sustainable society. Disposing sewage sludge, which accumulates most pollutants and resources in sewage, is the main challenge in wastewater pollution control and resource utilization. Heavy metals (HMs) are the greatest constraint limiting the application of sewage sludge to land as a sustainable use of this material. We conducted a meta-analysis of the concentrations of HMs in Chinese sewage sludge by combining data from studies published from 2000 to 2019 (N = 8477). Over this period, the reported concentrations of HMs in sewage sludge declined in three stages (a fluctuating stage, a slight decrease stage, and a rapid and stable decrease stage). The results revealed that economic development and environmental policy implementation were the main factors mitigating HM pollution in sewage sludge in China. Moreover, if environmental regulations were strengthened and HM pollution-mitigation strategies were made consistent, such that the proportion of sewage sludge applied to land in China could be increased from 18.6% to 48.0% (the proportion applied to land in the United States), the ecosystem services analysis showed that huge ecological-economic benefits could be realized (3.1 billion Chinese Yuan) and the use of fertilizers could be substantially reduced (the use of nitrogen fertilizers by 8.5% and the use of phosphate fertilizers by 18.1%). This review shows that China should formulate a unified policy and interdepartmental committee for sustainable application of sewage sludge to land and wastewater resource recycling management.

Review on heavy metal contaminants in freshwater fish in South India: current situation and future perspective

The primary natural resource we use in our daily lives for a variety of activities is freshwater for drinking and various developmental goals. Furthermore, the pace of human population increase worldwide is rising rapidly and has a great impact on the Earth's natural resources. Natural water quality has diminished owing to various anthropogenic activities. Water is crucial to the life cycle. On the other hand, chemical and agricultural industries pollute heavy metals. Acute and chronic diseases caused by heavy metals, such as slow metabolism and damage to the gills and epithelial layer of fish species, are divided into two categories. Pollutants can also harm liver tissues and result in ulceration as well as diseases such as fin rot, tail rot, and gill disease. The most prevalent heavy metals are As, Cr, Pb, and Hg, which are systemic toxicants that affect human health. These metals are categorized as carcinogens by the US Environmental Protection Agency and the worldwide agency for cancer research because they cause organ damage even at low exposure levels. The focus of the current study is to review various freshwater sources of heavy metal pollution.

Identification and Prioritization of Environmental Organic Pollutants: From an Analytical and Toxicological Perspective

Exposure to environmental organic pollutants has triggered significant ecological impacts and adverse health outcomes, which have been received substantial and increasing attention. The contribution of unidentified chemical components is considered as the most significant knowledge gap in understanding the combined effects of pollutant mixtures. To address this issue, remarkable analytical breakthroughs have recently been made. In this review, the basic principles on recognition of environmental organic pollutants are overviewed. Complementary analytical methodologies (i.e., quantitative structure-activity relationship prediction, mass spectrometric nontarget screening, and effect-directed analysis) and experimental platforms are briefly described. The stages of technique development and/or essential parts of the analytical workflow for each of the methodologies are then reviewed. Finally, plausible technique paths and applications of the future nontarget screening methods, interdisciplinary techniques for achieving toxicant identification, and burgeoning strategies on risk assessment of chemical cocktails are discussed.

Prioritization of risks posed by synthetic chemicals manufactured in China toward humans and the environment via persistence, bioaccumulation, mobility and toxicity properties

Over a third of the global chemical production and sales occurred in China, which make effective assessment and management for chemicals produced by China's chemical industry essential not just for China but for the world. Here, we systematical assessed the persistence (P), bioaccumulation (B), mobility (M) and toxicity (T) potency properties for the chemicals listed in Inventory of Existing Chemical Substances of China (IECSC) via experimental data retrieved from large scale databases and in silico data generated with well-established models. Potential PBT, PMT and PB&MT substances were identified. High risk potentials were highlighted for groups of synthetic intermediates, raw materials, as well as a series of biocides. The potential PBT and PMT synthetic intermediates and/or raw materials unique to the IECSC were dominated with organofluorines, for example, the intermediates used as electronic light-emitting materials. Meanwhile, the biocides unique to the IECSC were mainly organochlorines. Some conventional classes of insecticides, such as organochlorines and pyrethroids, were classified as being of high concern. We further identified a group of PB&MT substances that were considered to be both "bioaccumulative" and "mobile". Their properties and common substructures for several major clusters were characterized. The present results prioritized groups of substances with high potentials to cause adverse effects to the environment and humans, many of which have not yet been fully recognized.

Per- and polyfluoroalkyl substances in Chinese surface waters: A review

The contamination of surface waters in China with Per- and polyfluoroalkyl (PFASs) has been extensively studied in recent decades, however, almost all studies have been conducted in small areas and/or limited samples, which are not representative of the nationwide contamination of surface water environments with PFASs. In this study, attempt was made to provide a comprehensive report about PFASs pollution in Chinese surface water based on the PRISMA. By analyzing 111 papers published between 2006 and 2022, we provide a systematic review of the pollution of PFASs in surface water environments in China. The results show that 26 PFASs contaminants were detected at least once in China's surface water environment and were mainly concentrated in the eastern part of China. Most surface water environments in China had mean PFASs concentrations below 100 ng/L. The most polluted place was the Xiaoqing River, where sampling results in 2020 showed PFASs concentrations as high as 25,429 ng/L, followed by the Tangxun Lake, the Xi River, the Daling River, the Majia River, the Baiyangdian Lake, the Liuxi River, the Jiaolai River, the Tuo River and the Zhimai River. The Xiaoqing River also has the highest concentration of the novel pollutant, with concentrations of HFPO-TA and HFPO-DA as high as 1039 ng/L and 164 ng/L. Based on the source analysis, fluoropolymer manufacturing plants are the main source of PFASs pollutants in surface water. The results of the base risk analysis using risk quotients value (RQ) method show that the RQ values of the Xiaoqing River, the surface water near Bohai Bay, the Majia River and the Tuo River PFOA are 36.9, 7.7, 3.6 and 2.1 respectively, which are high risk areas and require enhanced control. This study provides information on surface waters contaminated by PFASs nationwide, and the results can be used as a reference for the development of pollution control and management strategies for PFASs in surface waters in China.

Nitrogen and boron co-doped lignin biochar for enhancing calcium peroxide activation toward organic micropollutants decontamination in waste activated sludge and related microbial structure dynamics

This study synthesized dual heteroatom nitrogen and boron-co-doped lignin-based biochar (NB-LGBC) for calcium peroxide (CP) activation to enhance the removal of organic micropollutants (OMPs), namely, 4-nonylphenol (4-NP) from waste activated sludge (WAS). NB-LGBC/CP enhanced 4-NP degradation by arriving at 83 % removal in 12 h. The NB-LGBC/CP system degraded 4-NP via a synergistic interaction (HO•, O₂^•- radicals, and singlet oxygen) and electron transfer due to the N-B-C bonding configurations. Results of fluorescence excitation-emission matrix (FEEM) analysis revealed significantly increase in biodegradable organics from treated WAS mixture. NB-LGBC/CP treatment enriched alkaliphilic bacterium associated with the predominance of the genus Desulfonatronum within the phylum Proteobacteria in the WAS, which improved the biological treatment capacity of 4-NP. Thus, NB-LGBC in HR-CAOP will be a novel approach for WAS decontamination.

Formation of organic chloride in the treatment of textile dyeing sludge by Fenton system

In the oxidation treatment of textile dyeing sludge, the quantitative and transformation laws of organic chlorine are not clear enough. Thus, this study mainly evaluated the treatment of textile dyeing sludge by Fenton and Fenton-like system from the aspects of the influence of Cl^-, the removal of polycyclic aromatic hydrocarbons (PAHs) and organic carbon, and the removal and formation mechanism of organic chlorine. The results showed that the organic halogen in sludge was mainly hydrophobic organic chlorine, and the content of adsorbable organic chlorine (AOCl) was 0.30 mg/g (dry sludge). In the Fenton system with pH=3, 500 mg/L Cl^-, 30 mmol/L Fe²⁺ and 30 mmol/L H₂O₂, the removal of phenanthrene was promoted by chlorine radicals (•Cl), and the AOCl in sludge solid phase increased to 0.55 mg/g (dry sludge) at 30 min. According to spectral analysis, it was found that •Cl could chlorinate aromatic and aliphatic compounds (excluding PAHs) in solid phase at the same time, and eventually led to the accumulation of aromatic chlorides in solid phase. Strengthening the oxidation ability of Fenton system increased the formation of organic chlorines in liquid and solid phases. In weak acidity, the oxidation and desorption of superoxide anion promoted the removal and migration of PAHs and organic carbon in solid phase, and reduced the formation of total organic chlorine. The Fenton-like system dominated by non-hydroxyl radical could realize the mineralization of PAHs, organic carbon and organic chlorines instead of migration. This paper builds a basis for the selection of sludge conditioning methods.

Occurrence and emission of polycyclic aromatic hydrocarbons from water treatment plant sludge in Taiwan

The concentrations level and distribution of 16 US EPA polycyclic aromatic hydrocarbon (PAHs) from the water treatment plant (WTP), sewage treatment plant (STP), and industrial water treatment plant (ITP) sludge in Taiwan were determined and then assessed the sources, and potential toxicity (carcinogenic polycyclic aromatic hydrocarbons [CPAHs] and toxic BaP equivalent [TEQ]). Results indicated that the total concentrations of PAHs ranged between 58 and 16,436 μg/kg dw. Among the 17 samples, the 2-4 ring of total PAHs were the predominant compound in three kinds of treatment plant (> 60%). Especially, ITP1 owns 95.8% of 2-4 ring of total PAHs and ITP3 owns 54% of five- and six-ring of total PAHs. The molecular indices and principal component analysis (PCA) were used to determine the source contributions, with the results showing that the contributions of combustion/grass, coal or wood combustion and combustion/ liquid (oil) fossil fuel combustion. A PAH toxicity indicated by TEQ was 2.5-506 μg TEQ/g dw. Although, the results indicated that these were not recommended for land applications, but analyses are beneficial to develop effective management strategies for controlling PAH discharge in treatment plants and establishing strategies for its reuse in managing pollutants.

Nationwide Occurrence and Unexpected Severe Pollution of Fluorescent Brighteners in the Sludge of China: An Emerging Anthropogenic Marker

Fluorescent brighteners (FBs) are a group of mass-produced dyestuff chemicals that have been extensively used for decades. However, knowledge of their occurrence in municipal wastewater treatment plants on a large geographical scale remains unknown. Herein, we implemented the first nationwide survey for wastewater-derived FBs in sludge across major cities in China. All 25 target FBs were detected in the nationwide sludge. Ionic FBs exhibited much higher concentrations than nonionic FBs. The total sludge concentrations of 25 FBs (∑₂₅FBs) ranged from 7300 to 1,520,000 ng/g, with a median of 35,300 ng/g. A clear geographical distribution of significantly higher concentrations of FBs was found in East and Central China than in West China (p < 0.05). The sludge concentrations of ∑₂₅FBs were correlated well with the gross domestic product (GDP) and population size at the provincial level in China (p < 0.05), demonstrating the significance of anthropogenic impacts on FB levels in urban sludge. The nationwide annual emission of total FBs into sludge in China is estimated to be 835 tons/year, of which 134 tons/year is directly released into sludge-applied soils. Our work highlights another new class of chemicals that significantly contribute to the chemical mixtures in urban sludge and thus require immediate attention.

The impact of endocrine disrupting compounds and carcinogens in wastewater: Implications for breast cancer

The incidence of breast cancer is often associated with geographic variation which indicates that a person's surrounding environment can be an important etiological factor in cancer development. Environmental risk factors can include exposure to sewage- or wastewater, which consist of a complex mixture of pathogens, mutagens and carcinogens. Wastewater contains primarily carbonaceous, nitrogenous and phosphorus compounds, however it can also contain trace amounts of chemical pollutants including toxic metal cations, hydrocarbons and pesticides. More importantly, the contamination of drinking water by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds. Organic solvents and other pollutants often found in wastewater have been detected in various tissues, including breast and adipose tissues. Furthermore, these pollutants such as phenolic compounds in some detergents and plastics, as well as parabens and pesticides can mimic estrogen. High estrogen levels are a well-established risk factor for estrogen-receptor (ER) positive breast cancer. Therefore, exposure to wastewater is a risk factor for the initiation, progression and metastasis of breast cancer. Carcinogens present in wastewater can promote tumourigenesis through various mechanisms, including the formation of DNA adducts, gene mutations and oxidative stress. Lastly, the presence of endocrine disrupting compounds in wastewater can have negative implications for ER-positive breast cancers, where these molecules can activate ERα to promote cell proliferation, survival and metastasis. As such, strategies should be implemented to limit exposure, such as providing funding into treatment technologies and implementation of regulations that limit the production and use of these potentially harmful chemicals.

Structural and antimicrobial property changes of veterinary antibiotics in thermal treatment

Agricultural application contributes major consumption of antibiotics worldwide. As veterinary antibiotics are poorly metabolized by animals, most of them end up in agricultural waste, which is increasingly subject to thermal treatment, such as torrefaction, pyrolysis, etc. However, there is a lack of research on their thermal decomposition mechanisms and products elucidation. Therefore, this study investigated the thermal decomposition of four major veterinary antibiotics groups (β-lactams, tetracyclines, fluoroquinolones, sulfonamides) with emphasis on their thermal stability, structural transformation and antibacterial activity. Results show that thermal treatment can remove the parent antibiotics with their antibacterial activity except for gatifloxacin (GAT). Although the parent form of GAT was fully removed at 200 °C, its products showed significant antibacterial activity against E. coli. We present novel evidence that the PhO-CH₃ chemical bond on GAT preferentially brake to generate methyl radical, which underwent a substitution reaction at the para position of phenol. This reaction also occurred during the thermal decomposition of antibiotic analogues, balofloxacin and moxifloxacin, whose thermolysis products also showed significant antibacterial activity. Furthermore, these thermolysis products may present potentially cardiotoxic and pose higher risks to human health than their parent forms, based on the comparison with a group of drugs withdrawn from the market.

Antibiotic-resistant bacteria in hospital wastewater treatment plant effluent and the possible consequences of its reuse in agricultural irrigation

Wastewater from hospitals should be monitored precisely and treated properly before discharge and reuse to avoid epidemic and pandemic complications, as it contains hazardous pollutants for the ecosystem. Antibiotic residues in treated hospital wastewater effluents constitute a major environmental concern since they resist various wastewater treatment processes. The emergence and spread of multi-drug-resistant bacteria, that cause public health problems, are therefore always a major concern. The aims and objectives of this study were mainly to characterize the chemical and microbial properties of the hospital effluent of wastewater treatment plant (WWTP) before discharge to the environment. Special attention was paid to the presence of multiple resistant bacteria and the effects of hospital effluent reuse in irrigation on zucchini as an economically important plant. The risk of cell-free DNA carrying antibiotic resistance genes contained in the hospital effluent as a long-lasting hazard had been discussed. In this study, 21 bacterial strains were isolated from the effluent of a hospital WWTP. Isolated bacteria were evaluated for multi-drug resistance ability against 5 antibiotics (Tetracycline, Ampicillin, Amoxicillin, Chloramphenicol, and Erythromycin) at a concentration of 25 ppm. Out of them, three isolates (AH-03, AH-07, and AH-13) were selected because they recorded the highest growth in presence of tested antibiotics. Selected isolates were identified using 16S rRNA gene sequence homology as Staphylococcus haemolyticus (AH-03), Enterococcus faecalis (AH-07), and Escherichia coli (AH-13). Their susceptibility to ascending concentrations of tested antibiotics indicated that they were all susceptible at a concentration above 50 ppm. Results of the greenhouse experiment regarding the effect of hospital WWTP effluent reuse on zucchini plant fresh weights compared to that irrigated with fresh water indicated that the former recorded a limited increase in total fresh weights (6.2 g and 5.3 g/plant, respectively). Our results demonstrated the low impact of the reuse of Hospital WWTP effluent in agriculture irrigation compared to its greater risk in transferring multiple antibiotic bacteria and antibiotic resistance genes to soil bacteria through natural transformation.

Polycyclic aromatic hydrocarbons stimulate acidogenesis, acetogenesis and methanogenesis during anaerobic co-digestion of waste activated sludge and food waste

Polycyclic aromatic hydrocarbons (PAHs) have been reported to influence acetic acid production during anaerobic treatment. However, investigations of the impacts of PAHs on the anaerobic co-digestion of waste activated sludge and food waste are limited. Therefore, the effects of PAHs on anaerobic co-digestion were explored in this study. Four kinds of PAHs all exhibited positive contributions to methane production, especially phenanthrene. Mechanism exploration revealed that acidogenesis, acetogenesis, and methanogenesis were improved in the presence of phenanthrene, and acetotrophic methanogenesis had the greatest improvement with 69.4%. Dominant bacteria and archaea related to acetic acid and methane accumulation were changed by phenanthrene. Moreover, extracellular polymeric substances, coenzyme F₄₂₀, and McrA gene copy number were promoted by phenanthrene, which was beneficial for the generation of acetic acid and methane. Overall, this study provides new insights into the role of organic pollutants in the anaerobic co-digestion of solid wastes.

Evolution and Prospects in Managing Sewage Sludge Resulting from Municipal Wastewater Purification

Municipal sewage sludge is the residual material produced as a waste of municipal wastewater purification. It is a sophisticated multi-component material, hard to handle. For many years, it has been landfilled, incinerated, and widely used in agriculture practice. When unproperly discharged, it is very polluting and unhealthy. The rapidly increasing global amount of municipal sewage sludge produced annually depends on urbanization, degree of development, and lifestyle. Some diffused traditional practices were banned or became economically unfeasible or unacceptable by the communities. In contrast, it has been established that MSS contains valuable resources, which can be utilized as energy and fertilizer. The objective of the review was to prove that resource recovery is beneficially affordable using modern approaches and proper technologies and to estimate the required resources and time. The open sources of information were deeply mined, critically examined, and selected to derive the necessary information regarding each network segment, from the source to the final point, where the municipal sewage sludge is produced and disposed of. We found that developed and some developing countries are involved with ambitious and costly plans for remediation, the modernization of regulations, collecting and purification systems, and beneficial waste management using a modern approach. We also found that the activated sludge process is the leading technology for wastewater purification, and anaerobic digestion is the leading technology for downstream waste. However, biological technologies appear inadequate and hydrothermal carbonization, already applicable at full scale, is the best candidate for playing a significant role in managing municipal sewage sludge produced by big towns and small villages.

Microplastics contamination of groundwater: Current evidence and future perspectives. A review

Groundwater is a primary water source which supplies more than 2 billion people. The increasing population and urbanization of rural areas stresses and depletes the groundwater systems, reducing the groundwater quality. Among the emerging contaminants, microplastics (MPs) are becoming an important issue due to their persistency in the environment. Seepage through the pores and fractures as well as the interaction with colloidal aggregates can partially affect the MPs dynamics in the subsoil, making the detection of the MPs in the groundwater systems challenging. Based on literature, a critical analysis of MPs in groundwater is presented from a hydrogeological point of view. In addition, a review of the MPs data potentially affecting the groundwater systems are included. MPs in groundwater may have several sources, including the atmosphere, the interaction with surface water bodies, urban infrastructures, or agricultural soils. The characterization of both the groundwater dynamics and the heterogeneity of MPs is suggested, proposing a new framework named "Hydrogeoplastic Model". MPs detection methods aimed at characterizing the smaller fragments are necessary to clarify the fate of these contaminants in the aquifers. This review also aims to support future research on MP contamination in groundwater, pointing out the current knowledge and the future risks which could affect groundwater resources worldwide.

Adsorptive and photocatalytic remediation of hazardous organic chemical pollutants in aqueous medium: A review

The provision of clean water is still a major challenge in developing parts of the world, as emphasized by the United Nation Sustainable Development Goals (SDG 6), and has remained a subject of extensive research globally. Advancements in science and industry have resulted in a massive surge in the amount of industrial chemicals produced within the last few decades. Persistent and emerging organic pollutants are detected in aquatic environments, and conventional wastewater treatment plants have ineffectively handled these trace, bioaccumulative and toxic compounds. Therefore, we have conducted an extensive bibliometric analysis of different materials utilized to combat organic pollutants via adsorption and photocatalysis. The classes of pollutants, material synthesis, mechanisms of interaction, merits, and challenges were comprehensively discussed. The paper highlights the advantages of various materials used in the removal of hazardous pollutants from wastewater with activated carbon having the highest adsorption capacity. Dyes, pharmaceuticals, endocrine-disrupting chemicals, pesticides and other recalcitrant organic pollutants have been successfully removed at high degradation efficiencies through the photocatalytic process. The photocatalytic degradation and adsorption processes were compared by considering factors such as cost, efficiency, ease of application and reusability. This review will be good resource material for water treatment professionals/scientists, who may be interested in adsorptive and photocatalytic remediation of organic chemicals pollutants.

Comparative meta-analysis of organic contaminants in sewage sludge from the United States and China

Characterizing the occurrence of organic contaminants (OCs) of environmental health concern in municipal sewage sludges is essential for safe handling and disposal of these abundant materials. This meta-analysis aimed to (i) summarize the extent of studies performed on the chemical composition of sewage sludges from China and the U.S., the world's two largest chemical producers, (ii) identify chemical groups of priority concern, (iii) quantitatively compare chemical abundance in sludge between nations, (iv) determine longitudinal contaminant accumulation trends in sludge, and (v) identify data gaps with regard to OC concentrations in sludge. A literature search was conducted on concentrations of OCs in U.S. sludges produced during treatment of domestic and industrial wastewater and compared statistically to contaminant levels in Chinese sludge abstracted from a recently established database. Longitudinal trends of OC occurrence were interpreted in the context of national chemical production, usage statistics, and regulations. A total of 105 studies on OCs in U.S. sewage sludge were found, while a total of 159 had been found in China. Among 1175 OCs monitored for, 23% of all analytes had been monitored in both countries (n = 269), 41% (n = 480) in China only, and the remaining 36% (n = 426) in the U.S. only. On average, concentrations of OCs were 4.0 times higher in U.S. than in Chinese sewage sludge, with the highest detection being observed for alkylphenol ethoxylates. Data from a new binational database on toxic OCs in sewage sludges suggest and reiterates the need for additional chemical monitoring in both countries, risk assessments for emerging OCs contained in sludges destined for application on land, and stronger enforcement of sludge disposal restrictions in China, where as much as 40% of sludge is currently being dumped improperly.

An improved method to predict polycyclic aromatic hydrocarbons in surface freshwater by reducing the input parameters

Predicting the concentration of polycyclic aromatic hydrocarbons (PAHs) in surface freshwater are critical for understanding their spatio-temporal distribution, regulation effectiveness, and the subsequent health risks. In this study, by exploring the correlation of PAHs concentrations in surface freshwater (C_PAHs) in China reported in the past twenty years with their emission (E_PAHs), a novel relationship of C_PAHs with E_PAHs and PAHs properties (i.e., logK_ow and S_w) was established. For PAHs individual, percent sample deviation between the measured concentrations and the calculated concentrations are in the range of 18% to 48%, suggesting that the calculated concentrations of PAHs are well consistent with the measured PAHs concentration in surface freshwater. Moreover, spatial distribution of predicted PAHs concentrations in surface freshwater of China is also matched well with measured ones. Compared with other environmental models, the established relationships in this work can reduce the number of model parameters from dozens to three, as well as decrease percent sample deviation from several orders of magnitude to less than 50%. The established relationship of PAHs concentrations in surface freshwater with E_PAHs, S_w, and logK_ow of PAHs, are valuable to facilitate the prediction of PAHs concentrations in surface freshwater by reducing monitoring costs.

Assessment of the occurrence of 455 pharmaceutical compounds in sludge according to their physical and chemical properties: A review

Sludge agronomical reuse is of major interest due to the beneficial contribution of nutrients. However, it implies the introduction of unregulated pharmaceuticals into amended-soils and creates a controversial issue about sludge management. To limit their dissemination, it is essential to identify the compounds of interest and understand their attenuation mechanisms through the sludge processes. This paper summarizes the knowledge on 455 investigated pharmaceuticals among 32 therapeutical categories in amendable sludge matrices. It contributes to enlarging the list of commonly quantified compounds to 305 residues including 84 additional compounds compared to previous reviews. It highlights that sorption appears as the main mechanism controlling the occurrence of pharmaceuticals in sludge matrices and shows the considerable residual levels of pharmaceuticals reaching several mg/kg in dry weight. Antibiotics, stimulants, and antidepressants show the highest concentrations up to 232 mg/kg, while diuretics, anti-anxieties or anticoagulants present the lowest concentrations reaching up to 686 µg/kg. Collected data show the increase in investigated compounds as antifungals or antihistamines, and underline emerging categories like antidiabetics, antivirals, or antiarrhythmics. The in-depth analysis of the substantial database guides onto the pharmaceuticals that are the most likely to occur in these amendable matrices to assist future research.

Current and Future Trends of Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons in Surface Water and Sediments of China: Insights from Their Long-Term Relationships between Concentrations and Emissions

In this study, we analyzed the temporal trend of polycyclic aromatic hydrocarbons (PAHs) in China using data reported over the past 20 years. We found that the total concentrations of low molecular weight PAHs (C_ΣLPAHs) in surface water and sediments were positively correlated with their total emissions (E_ΣLPAHs), which increased between 2000 and 2008, then decreased until 2017. Additionally, the total concentrations of high molecular weight PAHs (C_∑HPAHs) in surface water and sediments were positively correlated with their total emissions (E_ΣHPAHs), which increased significantly from 2000 to 2014 and then plateaued. Two future scenarios were assessed to explore C_∑LPAHs and C_∑HPAHs in surface water and sediments. PAH emissions were reduced by technological improvement in 2030 for coal consumption in Scenario 1 and for control of biomass burning in Scenario 2. Scenario 1 was more efficient than Scenario 2 in reducing C_∑HPAHs in the surface water and sediments of China for the areas where C_ΣHPAHs in surface water exceeded the annual average standard (i.e., 30 ng L^-1), with reductions of 38 and 24% in Scenarios 1 and 2, respectively. The observed relationships in this study can provide tools for emission reduction policies in the future.

Plant-scale hyperthermophilic composting of sewage sludge shifts bacterial community and promotes the removal of organic pollutants

The dissipation of toxic organic pollutants during plant-scale hyperthermophilic composting and the influence of microbial community remain unclear. The results of plant-scale hyperthermophilic composting of municipal sludge with green waste showed that the residual concentrations of polyaromatic hydrocarbons, phthalates, polybrominated diphenyl ethers were <5 mg/kg and decreased over time, with the removal percentages from 12.1% to 51.2% during seven days of composting. High-throughput sequencingreveals that hyperthermophilic composting significantly reduced the diversity (e.g., observed species, chao1 and Shannon index) of bacterial community, shifting their structure and functions. The relative abundances of dominant phyla Proteobacteria and Firmicutes declined significantly, while those of extremophilic and heat-resisting phyla Deinococcus-Thermus and Chloroflexi increased dramatically. Some genera capable of degrading organic pollutants presented stably in sludge composts. Moreover, hyperthermophilic composting enriched the bacterial functions related to degradation and metabolism of cellulose and xenobiotics pollutants, which promoted the dissipation of organic pollutants and humification.

Antibiotic tolerance and degradation capacity of the organic pollutant-degrading bacterium Rhodococcus biphenylivorans TG9T

Antibiotics are ubiquitous in soil due to natural ecological competition, as well as emerging contaminants due to anthropogenic inputs. Under environmental factors like antibiotic stress, some bacteria, including those that degrade environmental pollutants, can enter a dormant state as a survival strategy, thereby limiting their metabolic activity and function. Dormancy has a critical influence on the degradative activity of bacteria, dramatically decreasing the rate at which they transform organic pollutants. To better understand this phenomenon in environmental pollutant-degrading bacteria, we investigated dormancy transitions induced with norfloxacin in Rhodococcus biphenylivorans TG9^T using next-generation proteomics, proteogenomics, and additional experiments. Our results suggest that exposure to norfloxacin inhibited DNA replication, which led to damage to the cell. Dormant cells then likely triggered DNA repair, particularly homologous recombination, for continued survival. The results also indicated that substrate transport (ATP-binding cassette transporter), ATP production, and the tricarboxylic acid (TCA) cycle were repressed during dormancy, and degradation of organic pollutants was down-regulated. Given the widespread phenomenon of dormancy among bacteria involved in pollutant removal systems, this study improves our understanding of possible implications of antibiotic survival strategies on biotransformation of mixtures containing antibiotics as well as other organics.

Selective Removal of Phenolic Compounds by Peroxydisulfate Activation: Inherent Role of Hydrophobicity and Interface ROS

Selective removal of organic pollutants by advanced oxidation methods has been receiving increasing attention for environmental remediation. In this study, a novel catalyst, which can selectively oxidize phenolic compounds (PCs) based on their hydrophobicity, composed of metal-organic-framework-derived Fe/Fe₃O₄ and three-dimensional reduced graphene oxide (rGOF) is designed for peroxydisulfate (PDS) activation. This heterogeneous PDS activation system can completely degrade hydrophobic PCs within 30 min. By investigating the hydrophobic properties of eight representative PCs, a positive correlation between the hydrophobicity of PC and the reaction kinetics is reported for the first time. The selective removal stems from the strong interaction between highly hydrophobic PCs and the catalyst. Moreover, the mechanism investigation shows that the degradation reaction is triggered by interface reactive oxygen species (ROS). Our study reveals that the selective degradation of organic pollutants by PDS activation depends on the hydrophilic and hydrophobic properties of the pollutant and catalyst. The reported results provide new insights into a highly selective and efficient PDS activation system for organic pollutant removal.

Pretreatment, modification and applications of sewage sludge-derived biochar for resource recovery- A review

With the quick increase in industrialization and urbanization, a mass of sludge has been produced on the account of increased wastewater treatment facilities. Sewage sludge (SS) management has become one of the most crucial environmental problems because of the existence of various pollutants. However, SS is a carbon-rich material, which has favored novel technologies for biochar production, which can be utilized for dissimilar applications. This review systematically analyzes and summarizes the pretreatment, modification, and especially application of sewage sludge-derived biochar (SSBC), based on published literature. The comparative assessment of pretreatment technology such as pyrolysis, hydrothermal carbonization, combustion, deashing, and co-feeding is presented to appraise their appropriateness for SS resource availability and the production of SSBC. In addition, the authors summarize and analyze the current modification methods and divide them into two categories: physical properties and surface chemical modifications. The applications of SSBC as absorbent, catalyst and catalyst support, electrode materials, gas storage, soil amendment, and sold biofuel are reviewed in detail. Furthermore, the discussion about the existing problems and the direction of future efforts are presented at the end of each section to envisage SS as a promising opportunity for resources rather than a nuisance.

Aerobic granulation of nitrifying activated sludge enhanced removal of 17α-ethinylestradiol

The positive correlation between the nitrification activity of activated sludge and 17α-ethinylestradiol (EE2) removal has been widely reported. However, up to now the effect of the granulation of nitrifying activated sludge (NAS) on EE2 removal has not been determined. In this study, nitrifying granular sludge (NGS) exhibited more effective EE2 removal efficiency with 3.705 μgEE2∙(gMLSS∙h)^-1 in a sequential batch reactor (SBR). Through the artificial neural network (ANN) model and Spearman correlation analysis, nitrite accumulation was demonstrated to be the key factor affecting EE2 removal. Notably, under the same aeration condition (0.15 L/min), nitrite accumulation was more easily achieved in NGS because of its dense structure. Full-length 16S rRNA gene sequencing suggested that EE2 could strongly influence the microbial communities of NAS and NGS. NGS exhibited an increase in community diversity and richness, but NAS exhibited a decrease. In addition, the relative abundance of Nitrosomonas (ammonia-oxidizing bacteria, AOB) decreased considerably in both NAS and NGS, whereas the expression of amoA and nirK genes in Nitrosomonas was upregulated. It was suggested that Nitrosomonas was forced to regulate its gene expression to resist the negative effects of EE2. Denitrifying bacteria, such as Comamonas, were enriched in both NAS and NGS, and there were more species of heterotrophs that can degrade micropollutants in NGS with exposure to EE2. The transformation pathways of EE2 were uniform in NAS and NGS. Ammonia monooxygenase (AMO) in AOB directly biotransformed EE2 while reactive species produced by AOB chemically transformed EE2. Heterotrophs degraded EE2 and its transformation products (TPs) generated by AOB. According to TPs and microbial structure, NGS exhibited better performance than NAS regarding the collaborative removal of EE2 by AOB and heterotrophs. These results provide important information for the development and application of NGS to treat wastewater containing estrogen and high-strength ammonium.

Sewage Sludge as N-Fertilizers for Crop Production Enabling the Circular Bioeconomy in Agriculture: A Challenge for the New EU Regulation 1009/2019

The fertilizer framework in the European Union has recently been reviewed by EU Regulation 1009/2019 that excluded sewage sludge from the list of the possible constituents of organic fertilizers relying on their origin, not on their quality. This paper aimed to carry out a complete characterization of sewage sludge obtained from a pharmaceutical manufacturing process (PDSS) to demonstrate that sewage sludge obtained from a standardized and controlled manufacturing process can be safely recycled as organic fertilizer. The agronomic and environmental characteristics of the PDSS product were analyzed and compared to other organic fertilizers. Its fertilizing potential was also evaluated through plant growth trials. PDSS was characterized by a high concentration of total N (6.6% w/w), which was all present in organic form. PDSS also showed a low concentration of heavy metals, an absence of pathogens and low concentrations of organic contaminants. Plant growth trials showed that the PDSS was able to improve lettuce and carrot growth (+25 and +46% of dry weight compared to the unfertilized control), as well as their physiological status. Considering all the results, the exclusion of sewage sludge relying only on its origin and not on its quality appears to conflict with the principles of the circular bioeconomy.

Influence of sludge organic matter on elimination of polycyclic aromatic hydrocarbons (PAHs) from waste activated sludge by ozonation: Controversy over aromatic compounds

Ozonation has been widely used as a viable advanced oxidation process (AOP) for elimination of PAHs in waste activated sludge through effective sludge disintegration and abatement of organic pollutants. However, sludge organic matter (SOM) influences PAHs degradation during ozone treatment is still rarely understood. In this study, we investigated such an influence with the aid of solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy and the corresponding two-dimensional correlation analysis (2D-COS) strategy. The results showed that the degradation of SOM macromolecules in the order of aromatic substances > aliphatic carbon > α carbon > amides groups > O-alkyl upon ozone treatment. Moreover, the PAHs removal efficiency was positively correlated with the aromaticity of sludge (R² = 0.84-0.98), while negative associated with its aliphaticity (R² = 0.81-0.95). Lastly, humic acid (HA) was used as a proxy of aromatic SOM to further explore their interaction with PAHs in sludge matrix. The results revealed that freely dissolved (HA-D) and suspended particulates (HA-S) imposed distinctively different influence on ozone-based PAHs degradation. The HA-S facilitated the elimination of PAHs by 7.95 ± 0.11%, while those HA-D reduced the removal efficiency by 16.70 ± 0.13%.

Octanol-water partition coefficient (logKow) dependent movement and time lagging of polycyclic aromatic hydrocarbons (PAHs) from emission sources to lake sediments: A case study of Taihu Lake, China

Understanding the movement of polycyclic aromatic hydrocarbons (PAHs) from emission sources to sediments is important for achieving long-term pollution control of PAHs in sediments. In this study, by exploring the correlation of individual PAHs concentrations (C_PAHs) in Taihu Lake sediments reported in the past twenty years with their annual emissions (E_PAHs) in the lake region, it was observed that mean concentrations of PAHs with low logK_ow (i.e., logK_ow≤4.00) in Taihu Lake sediments were correlated best with their emissions without lagging between the sediment sampling time and the PAHs emitting time. However, for PAHs with middle logK_ow (i.e., 4.00<logK_ow≤4.57) or high logK_ow (i.e., logK_ow>4.57), their mean concentrations in sediments were correlated best with the emissions of PAHs emitted 1 or 2 years before the sediment sampling time. The longer lagging time of PAHs with middle or high logK_ow from emission sources to lake sediments could be attributed to their retardation in soils and river sediments around the lake. Moreover, the retardation in soils and river sediments is dependent on PAHs logK_ow and degradation half-life, indicating the dependence of PAHs concentration in sediments on their environmental behaviors, including sorption and degradation. K_ow dependent movement and the time lagging observed in Taihu Lake for PAHs from emission sources to sediments could be valuable for developing measures to control PAHs, especially for congeners with high logK_ow.

Biochar Derived from Domestic Sewage Sludge: Influence of Temperature Pyrolysis on Biochars’ Chemical Properties and Phytotoxicity

The pyrolytic conversion of domestic sewage sludge (SS) into biochar is a promising method to reduce its large volume and recycle its high-value fuel gas as renewable energy and the use of its chemicals as soil fertilizers. Even though the effects of pyrolysis temperature on energy recovery have been extensively studied, little information has been found on nutrient recovery and biochar’s phytotoxicity before its reuse as a soil amendment. This study aims to investigate the ideal pyrolysis temperature that guarantees higher fertility levels as well as meeting quality standards for land disposal. Accordingly, air-dried domestic sewage sludge has been pyrolyzed at 260°C (PSS1), at 420°C (PSS2), and at 610°C (PSS3) with a residence time of 20, 40, and 60 minutes, respectively. The raw sewage sludge and the produced biochars have been analyzed to determine their volatile organic matter (VOM), mineral content (MC), nutrients’ level (total nitrogen TN, available phosphorus P, and potassium K), alkalinity (pH), and salinity (electrical conductivity EC and Na). The toxic effect of biochars derived from SS has been evaluated through the analysis of trace metals (Pb, Cr, Cd, Cu, and Zn) and their toxicity by measuring root elongation inhibition (REI). As expected, pyrolysis temperature has a significant impact on the biochars’ characteristics. This has been justified by higher VOM, TN, and P in the sewage sludge (SS) and the biochar (PSS1) produced at low temperature (260°C). However, higher pH, EC, Na, and K have been found in the biochars (PSS2 and PSS3) produced at higher temperature (420 and 610°C). The effect of pyrolysis temperature on trace metals concentrations has shown different patterns from one element to another, which indicates lower levels in the biochar (PSS2) produced at 420°C. As a result, the lowest REI has been observed in PSS2 compared to that in SS, PSS1, and PSS3, which highlights that 420°C is the ideal pyrolysis temperature for the safe reuse of SS as a soil amendment.

Enhancing biomethane production and pyrene biodegradation by addition of bio-nano FeS or magnetic carbon during sludge anaerobic digestion

Pyrene exerts toxic effects on methanogens during anaerobic digestion of sludge, thus affecting the efficiency of sludge treatment. This study evaluated the facilitated direct interspecific electron transfer (DIET) between bacteria and methanogens when bio-nano FeS or magnetic carbon is added into anaerobic reactors. Results showed that adding 200 mg/L bio-nano FeS or magnetic carbon clearly reduced the accumulation of short-chain fatty acids and avoided acidification during 25 days of anaerobic digestion. The methane productions were 98.38 L/kg total solid (TS) and 73.69 L/kg TS in the bio-nano FeS and magnetic carbon systems, respectively, which accelerated methane production by 58.1% and 33.4%, respectively, compared with the control system (40.26 L/kg TS). The pyrene removal rates reached 77.5% and 72.1% in the bio-nano FeS and magnetic carbon systems, whereas it was only 40.8% in the control system. Analysis of microbial community structure revealed that methanogens (e.g. Methanosarcina and Methanosaeta) and extracellular electron-transfer bacteria (e.g. Pseudomonas, Cloastridia, and Synergistetes) were enriched in the reactors added with bio-nano FeS or magnetic carbon. This result indicates that the addition of bio-nano FeS or magnetic carbon may promote the activity and growth of microorganisms to improve the efficiency of methane production and pyrene degradation by enhancing DIET.

Quantitative research on heavy metal removal of flue gas desulfurization-derived wastewater sludge by electrokinetic treatment

Flue gas desulfurization-derived wastewater sludge (FGD-WWS) has been produced increasingly in China and India etc., and its content of heavy metals (HMs) including Cd, Cr, Cu, Hg, Ni and Zn seriously exceeds the limits allowed. Developing the suitable disposal of FGD-WWS is therefore significantly important and necessary. The novel process of electrokinetic treatment combined with chemical pretreatment of HMs in FGD-WWS were proposed here to improve the removal efficiency. Results indicate that the effects of different pretreatment agents (citric acid (CA), ammonia, tetrasodium of N, N-bis (carboxymethyl) glutamic acid (GLDA), and rhamnolipid) on the ET of HMs were different. To investigate the mechanism of combined process, the transformation potential (TP), exchange potential (EP) and removal potential (RP) were calculated. Correlation analysis shows the correlation between TP and RP was higher than that between EP and RP, indicating that the removal efficiency is mainly affected by the fraction transformation of HMs. Electric field, pH and pretreatment agents are main factors causing fraction transformation and affecting TP. Focusing on fraction transformation is an efficient way to improve further the removal efficiency. The work is promisingly valuable for developing the technology of treating FGD-WWS.

Assessment of energy use and environmental impacts of wastewater treatment plants in the entire life cycle: A system meta-analysis

Wastewater treatment plants (WWTPs) play a critical role in the sustainable development of water resources due to its outstanding ability of removing pollutants from complex influent wastewater and generating clean and safe effluent. This paper innovatively adopted the meta-analysis method in view of published LCA studies to assess the energy use and environmental impacts of WWTPs during their life cycle. The search and screening process determined a useful data source with 54 LCA literatures covering 109 relevant case studies. The meta-analysis results revealed that, compared with other regions, the WWTPs in China have the higher intensity in terms of energy use, global warming potential (GWP), eutrophication potential (EP), acidification potential (AP), photochemical oxidation (PHO), freshwater ecotoxicity potential (FETP) and terrestrial ecotoxicity potential (TETP) categories, implying that the energy conservation and emission reduction strategies are necessary to wastewater treatment industry in China. Moreover, compared with A/A/O and CASS processes, the A/O process consumes less energy and results in lower GWP and AP intensity, but affects adversely the natural water-body protection due to undesirable treatment efficiency. Furthermore, the treatment capacities of medium and large scales (i.e. 5-20 × 10⁴ m³/d) are most reasonable sizes for WWTPs since their intensity of energy use, GWP, EP and AP are under a relatively low level. Finally, a strict effluent discharge standard is highly recommended from the perspective of protecting aquatic environment, although it leads to a higher energy consumption. The findings of this study could provide valuable references for promoting healthy and sustainable wastewater treatment industry.

Using Estrogenic Activity and Nontargeted Chemical Analysis to Identify Contaminants in Sewage Sludge

Diverse organic compounds, many derived from consumer products, are found in sewage sludge worldwide. Understanding which of these poses the most significant environmental threat following land application can be investigated through a variety of predictive and cell-based toxicological techniques. Nontargeted analysis using high-resolution mass spectrometry with predictive estrogenic activity modeling was performed on sewage sludge samples from 12 wastewater treatment plants in California. Diisobutyl phthalate and dextrorphan were predicted to exhibit estrogenic activity and identified in >75% of sludge samples, signifying their universal presence and persistence. Additionally, the application of an estrogen-responsive cell bioassay revealed reductions in agonistic activity during mesophilic and thermophilic treatment but significant increases in antagonism during thermophilic treatment, which warrants further research. Ten nontarget features were identified (metoprolol, fenofibric acid, erythrohydrobupropion, oleic acid, mestranol, 4'-chlorobiphenyl-2,3-diol, medrysone, scillarenin, sudan I, and N,O-didesmethyltramadol) in treatment set samples and are considered to have influenced the in vitro estrogenic activity observed. The combination of predictive and in vitro estrogenicity with nontargeted analysis has led to confirmation of 12 estrogen-active contaminants in California sewage sludge and has highlighted the importance of evaluating both agonistic and antagonistic responses when evaluating the bioactivity of complex samples.

Pilot-scale vermicomposting of sewage sludge mixed with mature vermicompost using earthworm reactor of frame composite structure

To improve the efficiency of sludge vermicomposting, a new cost-effective method is provided. It uses a new earthworm reactor with a frame composite structure for vermicomposting and reuses mature vermicompost to condition the sludge. Under the optimum conditions (proportion of earthworm droppings: 15%; thickness of sludge laying: 6 cm; moisture content of initial sludge mixture: 75%), the method of continuous operation described herein works well and presents three advantages compared with the traditional vermicomposting method: the short time required for vermicomposting (20.25 h); covering a small area (5 m2/t·d); and a low cost. In addition, the vermicompost obtained from sludge vermicomposting shows better stability and maturity (C/N: 14.96; GI: 86.42%; TOC: 188.5 mg/g; ash content: 516.2 mg/g). The investigation of the associated mechanisms, including 3D-EEM, TGA, SEM and microbial community analyses, revealed that the addition of mature vermicompost can speed up the progress of decomposition and humification of organic matter in sludge. The process of vermicomposting and adding mature vermicompost significantly modified the microbial community of sewage sludge, and the changes in microorganisms in vermicompost were related to the microorganisms in the earthworm gut.

Occurrence and dissipation mechanism of organic pollutants during the composting of sewage sludge: A critical review

Sewage sludge contains various classes of organic pollutants, limiting its land application. Sludge composting can effectively remove some organic pollutants. This review summarizesrecent researches on concentration changes and dissipation of different organic pollutants including persistent organic pollutants during sludge composting, and discusses their dissipation pathways and the current understanding on dissipation mechanism. Some organic pollutants like PAHs and phthalates were removed mainly through biodegradation or mineralization, and their dissipation percentages were higher than those of PCDD/Fs and PCBs. Nevertheless, some recalcitrant organic pollutants could be sequestrated in organic fractions of sludge mixtures, and their levels and ARG abundance even increased after sludge composting in some studies, posing potential risks for land application. This review demonstrated that microbial community and their corresponding degradation for organic pollutants were influenced by different pollutants, bulking agents, composting methods and processes. Further research perspectives on removing organic pollutants during sludge composting were highlighted.

Mechanisms of persulfate activation on biochar derived from two different sludges: Dominance of their intrinsic compositions

Sludge-derived biochar (SDBC) has been regarded as persulfate (PS) activator during the remediation of organic contamination. However, the complexity of sludge composition makes it difficult to predict the activity of SDBC and the efficacy of PS. To improve the understanding of how the composition of sludge regulated activity of its parent SDBC towards PS activation, we used two SDBCs derived from different sludges with significantly different organic compositions and metals. Results indicated the higher content of organic and nitrogen content in sludge led to higher polymerization and condensation of carbon layer and more moieties in SDBC1, whereas more Fe species (e.g. Fe-O, Fe²⁺ and Fe³⁺) formed in SDBC2. According to the results of phenol (PN) degradation in SDBC/PS, the apparent rate constants (k_obs) of SDBC2-700 (0.0037 min^-1) was 2 folds higher than that of SDBC1-700 (0.0016 min^-1), whereas the SDBC1-500 (6.0 ×10^-4 min^-1) exhibited higher k_obs than that of SDBC2-500 (4.9 ×10^-4 min^-1). The difference of PS activation by different SDBCs mainly relied on generated reactive oxygen species (ROS). The persistent free radicals (PFRs) and Fe species acted as redox sites for generated ROS, which were depended on the organic compositions and involved metals in used sludges.

Fate of emerging and priority micropollutants during the sewage sludge treatment - Part 2: Mass balances of organic contaminants on sludge treatments are challenging

This paper analyzes the fate of 71 priority and emerging organic contaminants all along the treatment trains of sewage sludge treatment facilities in Paris including dewatering by centrifugation, thermal drying and anaerobic digestion. It aimed at proposing and applying a mass balances calculation methodology to each process and pollutant. This data validation strategy demonstrated the complexity to perform representative inlet/outlet sampling and analysis campaigns at industrial scales regarding organic compounds and to propose options to overcome this issue. Centrifugation and drying processes only implied physical mechanisms as phase separation and water elimination. Hence, correct mass balance were expected observed for organic contaminants if sampling and analysis campaigns were representative. This was the case for hydrophobic and neutral compounds. For the other more hydrophilic and charged compounds, the mass balances were scarcely correct. Thus, the conventional sampling and analytical practices used with sludge should be questioned and adapted to better take into account the high heterogeneity of sludge and the evolution of matrix effect within sludge treatment processes on micropollutant determination. For the biological anaerobic digestion process where degradations can occur and removals can be observed, the mass balances were deeply interpreted for 60 contaminants. This process contributed to the elimination above 70% of 21 detected compounds including 16 pharmaceuticals, 2 phthalates, 2 hormones and 1 perfluorinated compound. Removals of domperidone, propranolol, escitalopram, lidocaine, verapamil and cefoperazone under this condition were reported for the first time.

Towards efficient elimination of polycyclic aromatic hydrocarbons (PAHs) from waste activated sludge by ozonation

Sewage sludge is one of the sinks for PAHs accumulation and concerns are growing regarding the environmental risk of the discharge of PAHs in waste activated sludge (WAS) as a major byproduct of sewage treatment. Here, we evaluated the effectiveness of ozone treatment to eliminate the 16 priority PAHs in WAS. The PAHs removal efficiency increased with ozone dosage and was strongly pH dependent. Even at ozone dosage of 40 mg O₃·g^-1, the PAHs removal efficiency at pH 9.0 (44.5%) was significantly higher than that observed at pH 5.0 and 200 mg O₃·g^-1 (41.7%). The pH-dependent elimination behavior of PAHs was attributed to the varying yield of hydroxyl radicals (OH) and degree of sludge disintegration (R² = 0.88-0.92). Over 96% of the PAHs were in the particulate flocs (PF) phase, while the fraction bound to the freely dissolved (FS) and dissolved and colloidal (DC) matters was negligible, indicating the need of WAS disintegration during ozonation to make PAHs more accessible to O₃ molecules and OH to initiate oxidation reactions. Failure of the three-compartment model to describe the PAHs sorption behavior in sludge matrix during ozonation implied that oxidation reaction occurred simultaneously with the partitioning of PAHs from PS to DC/FS fraction. Lastly, the results of the intermittent ozonation experiment demonstrated the interference of soluble organic compounds during PAHs degradation, particularly proteins and humic substances, as O₃ and OH scavengers. At ozone dosage of 120 mg O₃·g^-1 (pH 9.0), the PAHs removal efficiency was improved by 19.5% by intermittent ozonation, as compared to continuous ozonation under the same conditions.

Printing ink related chemicals, including synthetic phenolic antioxidants, organophosphite antioxidants, and photoinitiators, in printing paper products and implications for human exposure

Although synthetic antioxidants (AOs) and photoinitiators (PIs) are known to be used in printing inks, there are little data on residual concentrations in printing paper products. In the present study, twenty-five PIs, ten AOs, and six transformation products were analyzed in two types of printing paper products, magazines and paperboard food packaging materials, both of which are unavoidable everyday products in our life. Nine AOs and six transformation products can be detected in food packaging materials with total concentrations (geometric mean, GM) of 1.16 × 10⁴ ng/dm². Twenty-two PIs were detected in food packaging materials with total concentrations (GM) of 1.76 × 10⁴ ng/dm². These chemicals were also detected in magazines, albeit at low concentrations (GM of AOs: 466 ng/dm², GM of PIs: 1.17 × 10³ ng/dm²). Magazine front covers were found to have much higher concentrations of the target compounds than magazine inside pages. Tris(2,4-di-tert-butylphenyl) phosphate (AO168O), 2,6-di-tert-butyl-4-methylphenol (BHT), bisphenol A (BPA), and benzophenone (BP) were among the predominant chemicals in those printing paper products. Preliminary calculations suggest that dermal exposure to AOs (GM: 6.25 ng/day) and PIs (GM: 17.0 ng/day) via contact with printing paper products is a minor exposure pathway compared to food intake/dust ingestion and is exceedingly unlikely to cause adverse health effects.

Molecular characterization and environmental impacts of water-soluble organic compounds of bio-oil from the thermochemical treatment of domestic sewage sludge

Water-soluble organic compounds derived from bio-oil (WOCB) are regarded as potential risk sources of sludge thermochemical treatment. This study showed that 10.35 mg of water-soluble organic carbon and 1.32 mg of water-soluble organic nitrogen were released per gram of sludge when the final temperature of thermochemical treatment was 600 °C. WOCB was mainly formed at 300-500 °C. Furthermore, FT-ICR MS results indicated that high temperatures promoted deamination reactions, and low molecular weight (LMW) compounds with low oxygen number polymerized into aromatic compounds with increasing temperature. Noteworthily, WOCB released at 20-600 °C showed strong phytotoxicity to wheat. LMW compounds with lignin/carboxylic rich alicyclic molecules (CRAM)-like structures derived from low temperatures (200-400 °C) induced this inhibitory effect, but lipids containing nitrogen and sulfur from high temperatures (400-600 °C) can act as nutrients to promote wheat growth. This study provides theoretical support for the risk control and benefits assessments of sludge thermochemical treatment.