Occurrence and removal of antibiotics and antibiotic resistance genes in natural and constructed riverine wetlands in Beijing, China

Performance of ultrafiltration-ozonation for municipal wastewater reclamation under rainstorm conditions: Impacts of DOM surge on micropollutant removal and associated risks

This study investigated the impacts of rainstorms on the performance of a combined ultrafiltration (UF)-ozonation (O3) process for micropollutant removal and risk mitigation during municipal wastewater reclamation. Results reveal that the rainstorm triggered a substantial surge in dissolved organic matter (DOM) in secondary effluent, primarily composed of protein-like substances and terrestrial humus. Meanwhile, 12 commonly detected pharmaceuticals and personal care products (PPCPs) were found at concentrations slightly lower than in normal weather, ranging from 5.0 to 545.0 ng L-1. Following the rainstorm, the overall removals of PPCPs spanned a wide range of 14.8 %-77.7 %, where a significantly lower retention of high molecular-weight pollutants (e.g., ≥ 400 Da) was observed for UF. For the ozonation unit, the removals remained comparable, while the relative contribution of radical oxidation increased. This shift was related to the enhanced generation of HO• and/or other reactive species, driven by the enrichment of unsaturated proteins (originating from upstream sludge loss) as precursors. Higher concentrations of disinfection by-products (DBPs), reaching up to 1372.5 μg L-1, were observed in chlorinated effluents after the rainstorm, ascribing to the elevated content of terrestrial humus persisting through the treatments. While the risks associated with PPCPs were negligible, the formed DBPs posed considerable risks to human health (with cancer risk at 10-5) and aquatic ecosystem (with risk quotient up to 13.6), particularly post ozonation. These findings highlight the role of rainstorm-fueled DOM in reclaimed water quality and provide insights into ensuring reclaimed water safety under different weather conditions.

Management strategies to reduce microbial mercury methylation in constructed wetlands: Potential routes and future challenges

Constructed wetlands (CWs) are widely recognized as the potential hotspots for producing highly toxic methylmercury (MeHg). This presents an obstacle to the widespread application of CWs. A comprehensive discussion on strategies to control mercury methylation in CWs is currently lacking. This review highlighted the potential impacts of differences in oxygen supply and consumption in various CWs, the characteristics of influent quality, the interactions between different substrates and mercury (including mercury adsorption, reduction), and plants on microbial mercury methylation in CWs. We also proposed the potential strategies for human intervention in regulating or controlling microbial mercury methylation in CWs, including oxygenation, nitrate inhibition, selection of substrates with high adsorption capacity, weak reducibility and low organic matter release, and plant management. Knowledge summarized in this review would help achieve a comprehensive understanding of various research gaps in previous studies and point out future research directions by focusing on CWs types, influent quality, substrates selection and plants management, to reduce the mercury methylation in CWs.

Insights into the impact of different phytoremediation strategies on antibiotic resistance genes at the metagenomic level in real scenarios

Engineered phytoremediation strategies provide cost effective options for eliminating antibiotics and antibiotic resistance genes (ARGs) from wastewater. However, there is a knowledge gap in understanding the impact of these phytoremediation strategies on the on the diversity and composition of ARGs as well as the key driving biotic and biological factors of ARGs at the metagenomic level in real scenarios. Through metagenomic sequencing, this study demonstrates that phytoremediation with Iris pseudacorus L., Myriophyllum verticillatum L., Eichhornia crassipes (Mart.) Solms and Oenanthe javanica (Bl. DC) significantly alters the pattern of antibiotic resistome. This study is the first to reveal, at the omics level, that phytoremediation enhances the diversity of ARGs (3.2 %∼11.6 % improvement), despite reducing their absolute abundances. Furthermore, this study highlights that plant varieties have a significant impact on the performance of phytoremediation in mitigating ARGs. The non-dominant bacterial taxa, specifically Verrucomicrobia, Planctomycetes, and Actinobacteria, play a crucial role in shaping the pattern of the antibiotic resistome during the wastewater treatment. The changes in the total organic carbon, total nitrogen and antibiotics robustly influence the environmental behaviors of antibiotic resistome and microbiome. In summary, this study gives insight into the impact of different phytoremediation strategies on mitigating ARGs at the omics level in real scenarios.

Jointly considering multi-medium and full-cycle to better reveal distribution and removal of antibiotic resistance genes in long-term constructed wetland

Constructed wetlands (CWs) have been proven to effectively remove antibiotic resistance genes (ARGs) at different experimental scales; however, there is still a lack of researches on the removal and monitoring of ARGs during the actual operation of full-scale CWs. To fill this gap, this study selected the Annan constructed wetland in Beijing as a case study and utilized quantitative sequencing, metagenomic analysis, and other technical methods to determine characteristics of ARGs in CWs during different operating periods. Furthermore, we analysed the overall removal characteristics of ARGs in the CW during different operating periods and differences of ARG distribution in three media. The dominant ARGs in the CW were quinolone, β-lactam and tetracycline, with subtypes of tufA and fusA. ARG distributions are significantly influenced by anthropic activities and seasonal changes. Three periods of the CW had good removal effects on special ARGs, but there were differences in the removal characteristics of different types and subtypes of ARGs. The CW had removal effects on four types of ARGs (such as multidrugs), 16 types of fusidic acid, and nine types of ARGs (such as bleomycin) during the dormancy, start-up, and operation periods, respectively. Among ARG subtypes, the CW had removal effects on 37, 53, and 51 subtypes during the dormancy, start-up, and operation periods, respectively. The subtypes that were removed mainly included those containing tetracycline, efflux pump, and β-lactam, mcr-1, and mcr-5 (colistin ARGs). For individual parts of CWs, the removal effects on the total abundance of ARGs were as follows: forebay > surface flow wetland > subsurface flow wetland. These findings provide insights for optimizing the purification efficiency of CWs for ARGs.

Antibiotic resistomes and ecological risk elimination in field-scale constructed wetland revealed by integrated metagenomics and metatranscriptomics

Constructed wetlands (CWs) are identified as significant ecological systems for the potential control of antibiotic resistance genes (ARGs) in the environment. However, the precise mechanisms governing removal, persistence, expression, and associated risks of ARGs during wetland treatment remain poorly understood. In this study, the distribution, mobility, expression, and hosts of ARGs in water, sediments, and plants of a field-scale CW and its parallel natural river were systematically investigated through metagenomic and metatranscriptomic approaches. Results showed that both the abundance and diversity of ARGs in water gradually decreased along the way of CW, reaching a final abundance removal rate of 72.28 % in the effluent. Source tracking analysis indicted that the reduction of ARGs in water was mainly achieved by the dynamic accumulation of ARGs in sediments and plants of the CW. Proteobacteria were identified as primary hosts for ARGs, particularly in sediments and plants during CW treatment. Moreover, although ESKAPE pathogens carrying multiple ARGs persisted in all media throughout the CW treatment, ARG expression levels and risk of water were also significantly decreased after CW treatment. Collectively, our comprehensive multi-omics study would enhance the understanding of ARG removal by CWs, offering insights for controlling antimicrobial resistance in wastewater treatment system.

The fate of sulfamethoxazole in microcosms of the macrophyte Schoenoplectus californicus and its impact on microbial communities

Sulfamethoxazole is a widely used antibiotic frequently found as an environmental pollutant. It can alter microbial communities and increase antibiotic resistance, becoming a public health risk. Constructed wetlands have the potential for removing sulfamethoxazole from polluted waters, but the role of different macrophytes in this process is not well understood. We investigated the fate of sulfamethoxazole and its effect on bacterial communities in microcosms containing Schoenoplectus californicus, an altitude-tolerant macrophyte. Within the first 10 h after introducing sulfamethoxazole (initial concentration 5 mg/L) to the microcosms, the concentration in the liquid phase significantly differed between microcosms with and without S. californicus. However, over the long term (15 and 30 days post-addition), the removal percentage (around 75%) in the liquid phase was not significantly influenced by S. californicus, indicating that sediments might be primarily responsible for removing the antibiotic. The presence of S. californicus promoted algae growth in the microcosms, and we determined that algae contributed to sulfamethoxazole removal from the liquid phase, likely through adsorption. Additionally, we characterized bacterial communities in the microcosm sediments via nanopore sequencing to identify changes following sulfamethoxazole addition. The relative abundance of Proteobacteria increased from 37-46% to 48-99% with the addition of the antibiotic. Conversely, the relative abundance of cyanobacteria decreased significantly after sulfamethoxazole was added (from 17 to 35% to less than 2%), suggesting it may serve as a biological marker for sulfamethoxazole pollution. In addition, the functional profile of the community was estimated from taxonomic diversity using PICRUST.

Tetracycline and quinolone contamination mediate microbial and antibiotic resistant gene composition in epiphytic biofilms of mesocosmic wetlands

The fate and ecological impact of antibiotics on aquatic ecosystems have not been properly elucidated in mesocosm wetlands scale. This study explored how tetracyclines (TCs, including tetracycline TC and oxytetracycline) and fluoroquinolones (QNs, including ciprofloxacin CIP and levofloxacin) affect mesocosm wetlands vegetated by V. spiralis, focusing on their impact on epiphytic biofilm microbial communities and antibiotic resistance genes (ARGs). Results showed that submerged plants absorbed more antibiotics than sediment. Both TCs and QNs disrupted microbial communities in different ways and increased eukaryotic community diversity in a concentration-dependent manner (2-4 mg/L for CIP, 4-8 mg/L for TC). TCs mainly inhibited epiphytic bacteria, while CIP increased bacterial phyla abundance. TC reduced Cyanobacteriota, Acidobacteriota, and Patescibacteria but increased Bacillota, Bacteroidota, and Armatimonadota. In contrast, CIP reduced Bacteroidota, Cyanobacteriota, and Gemmatimonadota but increased Bacillota, Planctomycetota, and Acidobacteriota. Significant differences in ARG profiles were observed between QNs and TCs, with TCs having a more substantial effect on ARGs due to their stronger impact on bacterial communities. Both antibiotics raised ARG levels with higher concentrations, particularly for multidrug resistance, tetracyclines, trimethoprim, sulfonamides, aminoglycosides, and fosfomycin, emphasizing their role in antimicrobial resistance. The study suggests that antibiotics can either stimulate or inhibit ARGs depending on their effects on bacterial communities. This study provides key evidence on the ecological mechanisms underlying the impact of TCs and QNs on epiphytic microbes of mesocosm wetlands.

Responses of soil antibiotic resistance genes to the decrease in grain size of sediment discharged into Dongting Lake, China

Sediment or soil in wetlands is regarded as an important sink of antibiotic resistance genes (ARGs). However, there are no studies on the effects of sediment changes (which caused changes in soil texture) on soil ARGs in wetland. Here, we collected topsoil samples from 12 study sites that were deposited in early (prior to the 1970s) or recent years to reveal the responses of soil ARGs to the decrease in grain size of sediment discharged into Dongting Lake. The results indicated that it caused significant increases in clay content, soil organic matter (SOM), moisture, and bacterial abundance. The absolute abundance of 38 % ARG subtypes, 62 % ARG types, and the total ARG concentrations showed a significant increase. The composition of ARG profiles also showed significant changes. For mobile genetic elements (MGEs), the levels of plasmid, insertional, and transposase were significantly elevated. Notably, clay content, moisture, SOM, and bacterial abundance presented very strong positive correlation with most ARG and total ARG abundance. The contributions of physicochemical characteristics and bacterial abundance to ARG variations were ranked as follows: 16S rRNA > SOM > moisture > pH > soil texture (clay, sand and silt) > nitrate nitrogen > ammonium nitrogen. Bacterial abundance, SOM, moisture, and soil texture were the primary environmental parameters contributing to the soil ARG variations in this research. These changes of ARGs may pose risks to ecosystems and public health.

Spatiotemporal distribution of ecological risk of antibiotics in seven major river basins of China: An optimized multilevel assessment approach

Antibiotics have been recognized as emerging pollutants due to their ecological and human health risks. This paper aims to enhance the ecological risk assessment (ERA) framework for antibiotics, to illustrate the distribution of these risks across different locations and seasons, and to identify the antibiotics that pose high ecological risk. This paper focuses on 52 antibiotics in seven major basins of China. Relying on the optimized approach of ERA and antibiotic monitoring data published from 2017 to 2021, the results of ERA are presented in multilevel. Across the study area, there are marked variations in the spatial distribution of antibiotics' ecological risks. The Huaihe River Basin, the Haihe River Basin, and the Liaohe River Basin are the top three in the ranking of present ecological risks. The research results also reveal significant differences in temporal variation, underscoring the need for increased attention during certain seasons. Ten antibiotics with high contribution rates to ecological risk are identified, which is an important reference to formulate an antibiotic control list. The multilevel results provided both risk values and their ubiquities across a broad study region, which is a powerful support for developing ecological risk management of antibiotics.

Urban agglomerations as an environmental dimension of antibiotics transmission through the "One Health" lens

The spatiotemporal distributions of antibiotics in different media have been widely reported; however, their occurrence in the environmental dimension of the Chinese urban agglomerations has received less attention, especially in bioaccumulation and health risks of antibiotics through the "One Health" lens. The review presents the current knowledge on the environmental occurrence, bioaccumulation, as well as health exposure risks in urban agglomerations through the "One Health" lens, and identifies current information gaps. The reviewed studies suggested antibiotic concentrations in water and soil were more sensitive to social indicators of urban agglomerations than those in sediment. The ecological risk and resistance risk of antibiotics in water were much higher than those of sediments, and the high-risk phenomenon occurred at a higher frequency in urban agglomerations. Erythromycin-H2O (ETM-H2O), amoxicillin (AMOX) and norfloxacin (NFC) were priority-controlled antibiotics in urban waters. Tetracyclines (TCs) posed medium to high risks to soil organisms in the soil of urban agglomerations. Health risk evaluation based on dietary intake showed that children had the highest dietary intake of antibiotics in urban agglomerations. The health risk of antibiotics was higher in children than in other age groups. Our results also demonstrated that dietary structure might impact health risks associated with target antibiotics in urban agglomerations to some extent.

Constructed wetlands as neglected fixed source of microplastics and antibiotic resistance genes in natural water bodies?

The pollution status and the harm caused by microplastics and antibiotic resistance genes (ARGs) in aquatic ecosystems have been a growing concern. The presence of microplastics could accelerate the transfer and spread of ARGs. Before sewage reaches natural water bodies, microplastics and ARGs need to be eliminated through specific processes. Constructed wetlands are currently an effective and environmentally friendly wastewater treatment process. Research has shown significant effectiveness in removing microplastics and ARGs. Microplastics and ARGs can be removed through processes such as adsorption, capture, adhesion, and biodegradation. However, long-term continuous operation could lead to constructed wetlands becoming significant reservoirs of microplastics and ARGs. Inflow loads and seasonal variations in constructed wetlands may result in the reintroduction of persistent microplastics and ARGs into the receiving water body, establishing the constructed wetland as a continuous source of these pollutants in the receiving water body. The key to the widespread application of constructed wetlands lies in solving this challenging problem. Therefore, although constructed wetlands serve as a green strategy for removing microplastics and ARGs, there are still many gaps in our knowledge. Based on the current accumulation of microplastics and ARGs in constructed wetlands, this paper summarizes the removal of microplastics and ARGs in existing constructed wetlands and explores the interaction between them. Additionally, it proposes suggestions for optimizing the process and improving the reliability of monitoring microplastics and ARGs in sewage.

Multidrug resistance and class 1 integron presence in Escherichia coli isolates from a polluted drainage ditch's water

The impact of contamination of water drainage ditches in the development of antibiotic-resistant bacteria has been scarcely studied in Mexico. In this regard, 101 isolates of E. coli were obtained from water samples from a ditch in Sinaloa, during one year. The antimicrobial resistant profiles, the presence of the class 1 integron and evolutionary relationship of intI1 sequences were determined. The 47.5% of strains were resistant and 5.9% multidrug resistant (MDR) with an average multiple antibiotic resistance index value of 0.45. The highest resistance was registered with β-lactam (39.6%) and quinolone (9.9%). The intI1 gene was detected in 11.9% of the isolates, and no association with MDR was found. Sequence were associated with human and animal host isolates. MDR E. coli isolates with intI1 gene highlight the potential risk of the ditch's water to human health. An attenuation effect of MDR E. coli isolates in the outlet water was observed.

Integrons, transposons and IS elements promote diversification of multidrug resistance plasmids and adaptation of their hosts to antibiotic pollutants from pharmaceutical companies

Plasmids are important vehicles for the dissemination of antibiotic resistance genes (ARGs) among bacteria by conjugation. Here, we determined the complete nucleotide sequences of nine different plasmids previously obtained by exogenous plasmid isolation from river and creek sediments and wastewater from a pharmaceutical company. We identified six IncP/P-1ε plasmids and single members of IncL, IncN and IncFII-like plasmids. Genetic structures of the accessory regions of the IncP/P-1ε plasmids obtained implied that multiple insertions and deletions had occurred, mediated by different transposons and Class 1 integrons with various ARGs. Our study provides compelling evidence that Class 1 integrons, Tn402-like transposons, Tn3-like transposons and/or IS26 played important roles in the acquisition of ARGs across all investigated plasmids. Our plasmid sequencing data provide new insights into how these mobile genetic elements could mediate the acquisition and spread of ARGs in environmental bacteria.

Water, Water Everywhere, but Every Drop Unique: Challenges in the Science to Understand the Role of Contaminants of Emerging Concern in the Management of Drinking Water Supplies

The protection and management of water resources continues to be challenged by multiple and ongoing factors such as shifts in demographic, social, economic, and public health requirements. Physical limitations placed on access to potable supplies include natural and human-caused factors such as aquifer depletion, aging infrastructure, saltwater intrusion, floods, and drought. These factors, although varying in magnitude, spatial extent, and timing, can exacerbate the potential for contaminants of concern (CECs) to be present in sources of drinking water, infrastructure, premise plumbing and associated tap water. This monograph examines how current and emerging scientific efforts and technologies increase our understanding of the range of CECs and drinking water issues facing current and future populations. It is not intended to be read in one sitting, but is instead a starting point for scientists wanting to learn more about the issues surrounding CECs. This text discusses the topical evolution CECs over time (Section 1), improvements in measuring chemical and microbial CECs, through both analysis of concentration and toxicity (Section 2) and modeling CEC exposure and fate (Section 3), forms of treatment effective at removing chemical and microbial CECs (Section 4), and potential for human health impacts from exposure to CECs (Section 5). The paper concludes with how changes to water quantity, both scarcity and surpluses, could affect water quality (Section 6). Taken together, these sections document the past 25 years of CEC research and the regulatory response to these contaminants, the current work to identify and monitor CECs and mitigate exposure, and the challenges facing the future.

Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands

Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts' community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.

Insight into the spatiotemporal distribution of antibiotic resistance genes in estuarine sediments during long-term ecological restoration

In this study, we aimed to investigate the long-term spatiotemporal changes in hydrodynamics, antibiotics, nine typical subtypes of antibiotic resistance genes (ARGs), class 1 integron gene (intI1), and microbial communities in the sediments of a semi-enclosed estuary during ecological restoration with four treatment stages (influent (#1), effluent of the biological treatment area (#2), oxic area (#3), and plant treatment area (#4)). Ecological restoration of the estuary reduced common pollutants (nitrogen and phosphorus) in the water, whereas variations in ARGs showed noticeable seasonal and spatial features. The absolute abundance of ARGs at sampling site #2 considerably increased in autumn and winter, while it significantly increased at sampling site #3 in spring and summer. The strong intervention of biological treatment (from #1 to #2) and aerators (from #2 to #3) in the estuary substantially affected the distribution of ARGs and dominant antibiotic-resistant bacteria (ARB). The dominant ARB (Thiobacillus) in estuarine sediments may have low abundance but important dissemination roles. Meanwhile, redundancy and network analysis revealed that the microbial communities and intl1 were key factors related to ARG dissemination, which was affected by spatial and seasonal ecological restoration. A positive correlation between low flow velocity and certain ARGs (tetM, tetW, tetA, sul2, and ermC) was observed, implying that flow optimization should also be considered in future ecological restoration to remediate ARGs. Furthermore, the absolute abundance of ARGs can be utilized as an index to evaluate the removal capacity of ARGs by estuarine restoration.

Roles of substrates in removing antibiotics and antibiotic resistance genes in constructed wetlands: A review

Antibiotics and corresponding antibiotic resistance genes (ARGs) are emerging pollutants in wastewater that pose a significant threat to the environment and human health. Constructed wetlands (CWs) are a cost-effective technology for eliminating these pollutants through substrates, plants, and microorganisms. Detailed reviews of the roles of CW substrates on antibiotic and ARG removal and recent progress in the field are lacking. This paper reviews the mechanisms influencing antibiotic and ARG (intracellular and extracellular) removal in CWs, and natural, biomass, chemical, modified, industrial, novel, and combined substrates on their removal efficiencies. Generally, substrates remove antibiotics and ARGs mainly through adsorption, biodegradation, chemical oxidation, and filtration. Other mechanisms, such as photolysis, may also contribute to removal. Natural substrates (e.g., gravel, zeolite) are more frequently employed than other types of substrates. The removal performance of antibiotics and intracellular ARGs by zeolite was better than that of gravel through enhanced substrate adsorption, filtration, and biodegradation processes. Moreover, Mn ore showed promising high capability to remove high concentration of antibiotics through various removal pathways. In addition, combined substrates of soil/sand/gravel and other substrates further facilitate antibiotic removal. Future research is suggested to explore the mechanisms of competitive adsorption and redox-controlled biodegradation, investigate the effect of Fe/Mn oxides on the removal of antibiotics and ARGs via chemical oxidation, evaluate the removal of extracellular ARGs by CWs with different substrates, and investigate the effect of substrates on removal of antibiotics and ARGs in full-scale CWs.

Phytostabilization mitigates antibiotic resistance gene enrichment in a copper mine tailings pond

Mining-impacted environments are distributed globally and have become increasingly recognized as hotspots of antibiotic resistance genes (ARGs). However, there are currently no reports on treatment technologies to deal with such an important environmental problem. To narrow this knowledge gap, we implemented a phytostabilization project in an acidic copper mine tailings pond and employed metagenomics to explore ARG characteristics in the soil samples. Our results showed that phytostabilization decreased the total ARG abundance in 0-10 cm soil layer by 75 %, which was companied by a significant decrease in ARG mobility, and a significant increase in ARG diversity and microbial diversity. Phytostabilization was also found to drastically alter the ARG host composition and to significantly reduce the total abundance of virulence factor genes of ARG hosts. Soil nutrient status, heavy metal toxicity and SO₄^2- concentration were important physicochemical factors to affect the total ARG abundance, while causal mediation analysis showed that their effects were largely mediated by the changes in ARG mobility and microbial diversity. The increase in ARG diversity associated with phytostabilization was mainly mediated by a small subgroup of ARG hosts, most of which could not be classified at the genus level and deserve further research in the future.

Influencing factors of antibiotic resistance genes removal in constructed wetlands: A meta-analysis assisted by multivariate statistical methods

In order to control antibiotic resistance genes (ARGs) diffusion in constructed wetlands, it is critical to explore the main factors influencing ARGs removal and understand its mechanism. Despite the fact that numerous studies have been conducted to determine the factors influencing ARGs removal by constructed wetlands in recent years, attempts to use published data and incorporate them into a comprehensive comparison and analysis are still limited. A framework for literature collection, data extraction and statistical analysis (LDS) was constructed in this study. The main factors influencing antibiotics and ARGs removal by constructed wetlands were identified using this framework. The results showed that nutrients, types of constructed wetlands and hydraulic loading were the principal factors influencing the removal of most antibiotics. The principal factors influencing the most ARGs removal were mobile genetic elements, plants, volume of constructed wetlands and running time. After purification by constructed wetlands, the risk coefficient of antibiotics decreased significantly, while the relative abundance of most ARGs did not change significantly. The analysis results of linear mixed model showed that the relationship between antibiotics and ARGs in effluent was closer than that in influent. LDS framework provides a new platform for the study of influencing factors of pollutant removal based on data mining.

Ecological Risks of Antibiotics in Urban Wetlands on the Qinghai-Tibet Plateau, China

Although the ecological risks of antibiotics have been extensively researched globally, fewer studies have been conducted in sensitive and fragile plateau wetland ecosystems. To evaluate the ecological risk of antibiotics in plateau urban wetlands, 18 water samples, 10 plant samples, and 8 sediment samples were collected in March 2022 in the Xining urban wetlands on the Qinghai-Tibet Plateau. The liquid chromatography-electrospray ionization tandem mass spectrometry method was utilized to measure the concentrations of 15 antibiotics in three categories in three types of environmental media. Risk quotients were adopted to assess the ecological risk of antibiotics, and the principal component analysis-multiple linear regression model was used to analyze the source of antibiotics. The results showed that (1) the maximum concentrations of antibiotics in water samples, plants, and sediments reached 1220.86 ng/L, 78.30 ng/g, and 5.64 ng/g, respectively; (2) Tylosin (TYL), norfloxacin (NFX), ofloxacin (OFX), and ciprofloxacin (CFX) in water were at medium and high-risk levels, and OFX had the highest risk value, of 108.04; and (3) the results of source apportionment indicate that 58.94% of the antibiotics came from the Huangshui river and wastewater treatment plant (WWTP) near the wetlands. The current study may provide a reference for the risks and management of antibiotics in plateau urban wetlands.

Tertiary Wastewater Treatment Processes Can Be a Double-Edged Sword for Water Quality Improvement in View of Mitigating Antimicrobial Resistance and Pathogenicity

Despite the high removal efficiency for chemical pollutants by tertiary wastewater treatment processes (TWTPs), there is no definite conclusion in terms of microbial risk mitigation yet. This study utilized metagenomic approaches to reveal the alterations of antibiotic resistance genes (ARGs), virulence factor genes (VFGs), their co-occurrence, and potential hosts during multiple TWTPs. Results showed that the TWTPs reduced chemical pollutants in wastewater, but the denitrifying biofilter (DB) significantly increased the absolute abundances of selected antibiotic-resistant bacteria and ARGs, and simultaneously elevated the relative abundances of ARGs and VFGs through the enrichment of multidrug resistance and offensive genes, respectively. Moreover, the co-occurrence of ARGs and VFGs (e.g., bacA-tapW, mexF-adeG) was only identified after the DB treatment and all carried by Pseudomonas. Then, the ultraviolet and constructed wetland treatment showed good complementarity for microbial risk reduction through mitigating antibiotic resistance and pathogenicity. Network and binning analyses showed that the shift of key operational taxonomic units affiliating to Pseudomonas and Acinetobacter may contribute to the dynamic changes of ARGs and VFGs during the TWTPs. Overall, this study sheds new light on how the TWTPs affect the antibiotic resistome and VFG profiles and what TWTPs should be selected for microbial risk mitigation.

Sample pretreatment and analytical methodology for the determination of antibiotics in swine wastewater and activated sludge

An analytical method for the simultaneous extraction and determination of eight veterinary antibiotics in swine wastewater and activated sludge was developed and validated based on the instrumental determination by liquid chromatography tandem quadrupole mass spectrometry. Ultrasound-assisted extraction and solid-phase extraction were introduced into the pretreatment procedure of the two complex environmental matrices. The critical steps involved in the sample pretreatment procedure and the instrumental analysis conditions were optimized progressively. Recoveries of the optimized method were good with 75.3-118.2% in wastewater and 82.8-130.1% in sludge. The absolute deviations of methods were lower than 11.7%, presenting a high reproducibility and precision. The limits of quantification for the eight pharmaceuticals in wastewater and sludge were 5-15 ng·L^-1 and 2-6 ng·g^-1, showing high sensitivity of the methods. The developed method has been successfully applied to evaluate the actual concentration levels of tetracyclines, quinolones, and sulfonamides in actual swine wastewater (maximum detected concentration of 87.377 μg·L^-1) and activated sludge (maximum detected concentration of 51242.3 ng·g^-1).

Insights into the fate of antibiotics in constructed wetland systems: Removal performance and mechanisms

Antibiotics have been recognized as emerging contaminants that are widely distributed and accumulated in aquatic environment, posing a risk to ecosystem at trace level. Constructed wetlands (CWs) have been regarded as a sustainable and cost-effective alternative for efficient elimination of antibiotics. This review summarizes the removal of 5 categories of widely used antibiotics in CWs, and discusses the roles of the key components in CW system, i.e., substrate, macrophytes, and microorganisms, in removing antibiotics. Overall, the vertical subsurface flow CWs have proven to perform better in terms of antibiotic removal (>78%) compared to other single CWs. The adsorption behavior of antibiotics in wetland substrates is determined by the physicochemical properties of antibiotics, substrate configuration and operating parameters. The effects of wetland plants on antibiotic removal mainly include direct (e.g., plant uptake and degradation) and indirect (e.g., rhizosphere processes) manners. The possible interactions between microorganisms and antibiotics include biosorption, bioaccumulation and biodegradation. The potential strategies for further enhancement of the antibiotic removal performance in CWs included optimizing operation parameters, innovating substrate, strengthening microbial activity, and integrating with other treatment technologies. Taken together, this review provides useful information for facilitating the development of feasible, innovative and intensive antibiotic removal technologies in CWs, as well as enhancing the economic viability and ecological sustainability.

Iron ore or manganese ore filled constructed wetlands enhanced removal performance and changed removal process of nitrogen under sulfamethoxazole and trimethoprim stress

Iron ore and manganese ore were used as substrate of constructed wetlands (CWs) to enhance nitrogen (N) removal. However, the N purification performance in CWs filled with iron or manganese ore under antibiotics stress needs further study. In this study, three groups of CWs filled with river sand, limonite (a kind of iron ore), and manganese ore sand were constructed, which were named as C-CWs, Fe-CWs, and Mn-CWs, respectively. The effect and mechanism of the composite antibiotics sulfamethoxazole (SMX) and trimethoprim (TMP) on N removal in CWs were investigated. While the addition of SMX and TMP inhibited about 40% nitrification and promoted about 25% denitrification in all CWs, Fe-CWs and Mn-CWs always had better N removal performance than C-CWs. Changes in microbial community structure in CWs indicated that the better N removal performance in Fe-CWs and Mn-CWs was attributed to the presence of more abundant and diverse N-associated bacteria, especially Fe- and Mn-driven autotrophic denitrifying bacteria. What's more, the addition of iron ore or manganese ore contributed to the better N removal performance with highest relative abundance of N-transferring bacteria under antibiotics stress.

The combined effect of an integrated reclaimed water system on the reduction of antibiotic resistome

The reuse of urban reclaimed water is conducive to alleviate the current serious shortage of water resources. However, antibiotic resistance genes (ARGs) in reclaimed water have received widespread attention due to their potential risks to public health. Deciphering the fate of ARGs in reclaimed water benefits the development of effective strategies to control resistome risk and guarantees the safety of water supply of reclaimed systems. In this study, the characteristics of ARGs in an integrated reclaimed water system (sewage treatment plant-constructed wetland, STP-CW) in Beijing (China) have been identified using metagenomic assembly-based analysis, as well as the combined effect of the STP-CW system on the reduction of antibiotic resistome. Results showed a total of 29 ARG types and 813 subtypes were found in the reclaimed water system. As expected, the STP-CW system improved the removal of ARGs, and about 58% of ARG subtypes were removed from the effluent of the integrated STP-CW system, which exceeded 43% for the STP system and 37% for the CW system. Although the STP-CW system had a great removal on ARGs, abundant and diverse ARGs were still found in the downstream river. Importantly, network analysis revealed the co-occurrence of ARGs, mobile genetic elements and virulence factors in the downstream water, implying potential resistome dissemination risk in the environment. Source identification with SourceTracker showed the STP-effluent was the largest contributor of ARGs in the downstream river, with a contribution of 45%. Overall, the integrated STP-CW system presented a combined effect on the reduction of antibiotic resistome, however, the resistome dissemination risk was still non-negligible in the downstream reclaimed water. This study provides a comprehensive analysis on the fate of ARGs in the STP-CW-river system, which would benefit the development of effective strategies to control resistome risk for the reuse of reclaimed water.

The potential of algae and aquatic macrophytes in the pharmaceutical and personal care products (PPCPs) environmental removal: a review

The presence of emerging contaminants, such as pharmaceuticals and personal care products (PPCPs), in aquatic environments has received increasing attention in the last years due to the various possible impacts on the dynamics of the natural environment and human health. In global terms, around 771 active pharmaceutical substances or their transformation products have been detected at levels above their respective detection limit. Additionally, 528 different compounds have been detected in 159 countries. Seeking to overcome potential ecotoxicological problems, several studies have been conducted using different technologies for PPCPs removal. Recently, the use of macro, microalgae, and aquatic macrophytes has been highlighted due to the excellent bioremediation capacity of these organisms and easy acclimatization. Thus, the present review aims to outline a brief and well-oriented scenario concerning the knowledge about the bioremediation alternatives of PPCPs through the use of macro, microalgae, and aquatic macrophytes. The characteristics of PPCPs and the risks of these compounds to the environment and human health are also addressed. Moreover, the review indicates the opportunities and challenges for expanding the use of biotechnologies based on algae and aquatic macrophytes, such as studies dedicated to relate the operational criteria of these biotechnologies with the main PPCPs removal mechanisms. Finally, algae and macrophytes can compose green and ecological biotechnologies for wastewater treatment, having great contribution to PPCPs removal.

Pharmaceuticals and personal care products (PPCPs) in water, sediment and freshwater mollusks of the Dongting Lake downstream the Three Gorges Dam

Pharmaceuticals and personal care products (PPCPs) are a group of emerging anthropogenic pollutants. Here we investigated the occurrence and concentrations of 35 typical PPCPs in water, sediment, and freshwater mollusks (Hyriopsis cumingii, Unio douglasiae, Sinanodonta woodiana, Lamprotula leai and Corbicula fluminea) of the Dongting Lake downstream of the Three Gorges Dam. As results, 33 PPCPs were detected in water and sediment of the lake. Ketoprofen (not detected (ND)-292.8 ng/L, mean 91.1 ng/L) and roxithromycin (13.7-141.9 ng/L, mean 30.4 ng/L) were the primary PPCPs measured in lake water, while ibuprofen (ND-105.0 ng/g, mean 30.0 ng/g) and ketoprofen (ND-142.9 ng/g, mean 27.6 ng/g) were dominant in the sediment. Distinct seasonal difference in PPCP compositions was observed in both water and sediment of the Dongting Lake, potentially associated with the water-level fluctuations driven by the Three Gorges Dam operations. Ketoprofen and ibuprofen were also frequently detected in the soft tissues of freshwater mollusks, with concentrations of 42.5-1206.6 and 44.9-992.7 ng/g, respectively. Significant species-specific accumulation characteristics of PPCPs in mollusks were observed, with the highest total contents being reported for Corbicula fluminea (3.18 ± 1.13 μg/g). Moreover, gonads of mollusks were identified as the target organ to accumulate these compounds. Correlation analysis further revealed the strong associations of PPCP concentrations in mollusks with those in water and sediment, suggesting the importance of controlling dissolved and sedimentary bioavailability of PPCPs for ecological risk management in this freshwater lake ecosystems.

Antibiotic-Resistant Gene Behavior in Constructed Wetlands Treating Sewage: A Critical Review

The main objective of this review is to evaluate the performance of constructed wetlands (CWs) used to reduce antibiotic-resistant genes (ARGs) during sewage treatment. To accomplish this objective, statistical and correlation analyses were performed using published data to determine the influence of operational and design parameters on ARG reduction in CWs. The effects of design and operational parameters, such as different CW configurations, seasonality, monoculture and polyculture, support medium, and hydraulic retention time (HRT), on ARG removals, were analyzed. A comparison of ARG reduction under different CW configurations showed that the hybrid configuration of surface flow (SF)–vertical subsurface flow (VSSF) achieved the highest reductions, with values of 1.55 ulog. In this case, aeration is considered an important factor to reduce ARGs in CWs, and it should be considered in future studies. However, statistical analyses showed that the ARG reductions under different CW configurations were not significant (p > 0.05). The same behavior was observed when the effects of operational factors on ARG reductions were analyzed (p > 0.05). The results of this study show that CWs are not optimal technologies to reduce ARGs in sewage. The combination of CWs with advanced wastewater technologies can be a solution for enhancing ARG reduction and reducing the spread of antibiotic resistance.

Spatiotemporal dynamic changes of antibiotic resistance genes in constructed wetlands and associated influencing factors

A better understanding of the spatiotemporal dynamics and influencing factors of sulfonamide antibiotic resistance genes (ARGs) distribution in subsurface flow constructed wetlands is essential to improve the ARGs removal efficiency. The spatiotemporal dynamics of sulfonamide ARGs were explored in the vertical upflow subsurface flow constructed wetland (VUSFCW). The results showed that the absolute abundance of ARGs presented a trend of bottom layer > middle layer > top layer. The relative abundance of ARGs decreased significantly from the bottom layer to the middle layer, but increased in the top layer. The bottom layer was the main stage to remove ARGs. The absolute abundance of ARGs at each point in summer was significantly higher than that in winter. Based on the spatiotemporal distribution of ARGs, the internal mechanism of ARGs dynamic change was explored by the partial least square path analysis model. The results showed that physical-chemical factors, microorganisms and antibiotics indirectly affected the spatiotemporal distribution of ARGs mainly through mobile genetic elements. The indirect influence coefficients of physical-chemical factors, microorganisms and antibiotics on the spatiotemporal distribution of ARGs were 0.505, 0.221 and 0.98 respectively. The direct influence coefficient of MGEs on the spatiotemporal distribution of ARGs was 0.895. The results of network analysis showed that the potential host species of ARGs in summer were more abundant than those in winter. The selection mode of sulfonamide ARGs to potential hosts was nonspecific. There is a risk of sulfonamide ARGs infecting pathogens in VUSFCW. Fortunately, VUSFCW has proven effective in reducing the absolute abundance of ARGs and the potential risk of pathogens carrying ARGs. These findings provide a model simulation and theoretical basis for effectively reducing the threat of ARGs.

Occurrence and ecotoxicity of sulfonamides in the aquatic environment: A review

Rapid population growth and increasing demand for animal protein food have led to a continuous increase in global utilization of antibiotic. Sulfonamides (SAs) are ubiquitous in aquatic environments and pose an ecological risk owing to their large consumption and strong environmental persistence. Hence, this review focuses on the recent publications on 12 different SAs and provides a detailed summary of selected antibiotic concentrations in various water systems. We evaluated the ecotoxicity of SAs on organisms at different trophic level organisms and the environmental risks regarding aquatic systems. The results indicated that SA antibiotics were ubiquitous in aquatic environments at concentrations ranging from ng/L to μg/L. According to the data using standard ecotoxicity bioassays, algae were the most susceptible aquatic organisms for selected antibiotics, followed by crustaceans and fish. The risk data suggested that some antibiotics, such as sulfadiazine (SDZ), sulfamethoxazole (SMX), and sulfamethazine (SMZ) pose a great risk to the aquatic system. Based on the present review, it is necessary to strengthen the research into their ecotoxicity to marine systems and the chronic toxicity of antibiotic mixtures.

Occurrence and temporal variation of antibiotics and antibiotic resistance genes in hospital inpatient department wastewater: Impacts of daily schedule of inpatients and wastewater treatment process

The temporal variation of antibiotics and ARGs as well as the impact of daily schedule of inpatients on their regular occurrence in hospital wastewater (HWW) were previously obscure. In this study, the wastewater of the inpatient department pre- and posttreatment (hydraulic retention time = 8 h) was collected intraday and intraweek. The absolute concentrations of antibiotics/metabolites and ARGs in HWW were analyzed to investigate the temporal variations of their occurrence levels. Fluoroquinolones were the predominant drugs used in the inpatient department (681.30-881.66 ng/mL in the effluent) and the main contaminant in the outlet of the disinfection pond (538.29-671.47 ng/mL). Diurnal variations peaked at 19:00 for most antibiotics and ARGs, while the maximum of them occurred on weekends. Aminoglycoside resistance genes (AMRGs, 21.6-23000 copies/mL) and β-lactam resistance genes (BLGRs, 1.24-8500 copies/mL) were the dominant ARGs before and after treatment processing, respectively (p < 0.05). The significant removal rates (>50%) of most antibiotics and ARGs, as well as the integrase gene intI1 and 16S rRNA gene, were found to be subjected solely to the chloride disinfection process, suggesting the necessity of the self-contained wastewater treatment process. Meanwhile, the statistically significant correlation among antibiotics, ARGs, intI1, and 16S rRNA (p < 0.05) demonstrated that the risk of selective pressure, horizontal transfer and vertical propagation of ARGs in the effluent of the hospital was warranted. Principal component analysis (PCA) showed that the daily schedule of inpatients and wastewater treatment processes could markedly induce fluctuations in antibiotic and ARG levels in HWW, indicating that they should be considered an impact factor for environmental monitoring. This study demonstrated for the first time the temporal variations in the abundance and dissemination of antibiotics and ARGs in a semiclosed zone and provided new insight into the development of assessments of the associated ecological risk and human health.

Comparison and prioritization of antibiotics in a reservoir and its inflow rivers of Beijing, China

The occurrence of antibiotics in drinking water resources, like reservoirs, is of considerable concern due to their potential risks to ecosystem, human health, and antimicrobial resistance development. Here, we quantified 83 antibiotics in water and sediments of wet and dry seasons from the Miyun reservoir and its inflow rivers in Beijing, China. Twenty-four antibiotics were detected in water with concentrations of ND-11.6 ng/L and 19 antibiotics were observed in sediments with concentrations of ND-6.50 ng/g. Sulfonamides (SAs) were the dominated antibiotics in water in two seasons. SAs and quinolones (QNs) in wet season and macrolides (MLs) and QNs in dry season predominated in sediments. The reservoir and inflow rivers showed significant differences in antibiotic concentrations and compositions in water and sediments. As an important input source of reservoir, the river water showed significantly higher total antibiotic concentrations than those in the reservoir. In contrast, the reservoir sediments are the sink of antibiotics, and had higher total antibiotic concentrations compared with rivers. A prioritization approach based on the overall risk scores and detection frequencies of antibiotics was developed, and 3 (sulfaguanidine, anhydroerythromycin, and sulfamethoxazole) and 5 (doxycycline, sulfadiazine, clarithromycin, roxithromycin, and flumequine) antibiotics with high and moderate priority, respectively, were screened. The study provides a comprehensive insight of antibiotics in the Miyun Reservoir and its inflow rivers, and is significant for future monitoring and pollution mitigation of antibiotics.

Sediments alleviate the inhibition effects of antibiotics on denitrification: Functional gene, microbial community, and antibiotic resistance gene analysis

Both antibiotics and sediments can affect the denitrification in aquatic systems. However, little is known how antibiotics influence the denitrification in the presence of sediments. Here, the effects of antibiotics (sulfamethoxazole, tetracycline and ofloxacin) on denitrification in the absence and presence of sediments were investigated. The influencing mechanisms were revealed by quantifying the denitrification functional genes (DNGs), 16S-seq of bacteria, and antibiotic resistance genes (ARGs). The results showed that the presence of antibiotics inhibited NO₃-N reduction by decreasing the abundances of narG, nirK, nosZ, total DNGs, and denitrifying bacteria. However, the inhibition effect was alleviated by sediments, which promoted the growth of bacteria and decreased the selective pressure of antibiotics as the vector of bacteria and antibiotics, thus increasing the abundances of denitrifying bacteria and all the DNGs. Partial least-squares path model disclosed that antibiotics had negative effects on bacteria, ARGs and DNGs, while sediments had negative effects on ARGs but positive effects on bacteria and DNGs. The network analysis further revealed the close relation of the genera Bacillus, Acinetobacter, and Enterobacter with the ARGs and DNGs. The findings are helpful to understand the denitrification in antibiotic-polluted natural waters.

A review on the ecotoxicological effect of sulphonamides on aquatic organisms

Antibiotics are extensively used to treat human and animal diseases and are especially used in animal production to promote the growth performance of livestock and aquatic animals. Sulphonamides, as important drugs for aquatic animals, are often used in aquaculture to prevent and treat diseases. However, various antibiotics found in the aquatic environment exhibit varying degrees of toxicity to aquatic organisms. Antibiotics in wastewater produced in industrial and agricultural processes are not thoroughly removed by sewage treatment and are released into water, which results in varying degrees of pollution of the surrounding water environment, forcing people to pay attention towards the ecosystem. Several studies have investigated the impact of antibiotics on aquatic organisms in water environment; however, only a few studies have investigated the underlying mechanism. Antibiotics persisting in an aquatic environment for a long time can cause genotoxicity and histopathological changes in various aquatic organisms. Therefore, this paper reviews the sources of antibiotics in aquatic environment, the pollution status of sulfonamides in aquatic environment at home and abroad, and focuses on the research status of ecotoxicological effects of sulfonamides on aquatic organisms. Because there are not only antibiotic pollution, but also many other pollutants, such as heavy metals, micro plastics and other chemicals, it will be a challenge to determine the combined effects of antibiotics or other pollutants on aquatic organisms in future environmental toxicity studies.

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Sulphonamides are ubiquitously detected in the water environment.

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Sulfamethoxazole is one of the least efficient antibiotics removed in wastewater treatment plants.

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Interaction of sulphonamides with other antibiotics needs more attention.

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Multigeneration studies related to the water environment are needed.

Quantifying the contribution rates of sulfonamide antibiotics removal mechanisms in constructed wetlands using multivariate statistical analysis

The removal of antibiotics in subsurface flow constructed wetlands is performed through various removal mechanisms, such as adsorption, hydrolysis, microbial degradation and plant uptake. However, the contribution rates of the removal mechanisms in constructed wetlands are still not well studied. This study conducted a series of experiments and used multivariate statistical analysis to determine contribution rates for substrate adsorption, hydrolysis, and microbial degradation. Multiple stepwise regression analysis indicated that specific surface area and salt content were the main factors influencing sulfonamide adsorption, while temperature and pH were the main factors influencing sulfonamide hydrolysis. Variance partitioning analysis showed that the influence of physical-chemical factors was greater than that of nutrients on the microbial community. Partial least squares path analysis showed that the path coefficients of microbial degradation, adsorption and hydrolysis for sulfonamides removal in vertical subsurface flow constructed wetlands were 0.6339, 0.3608 and 0.0351, respectively, while the corresponding path coefficient were 0.5658, 0.4707 and 0.1079 in horizontal subsurface flow constructed wetlands, respectively. This means that microbial degradation contributes the most to the removal of sulfonamides in subsurface flow constructed wetlands. Enhanced microbial degradation may be a powerful measure to improve the removal of sulfonamides. These results will be helpful for understanding the removal mechanism of antibiotics and will provide a definite direction for pertinently improving sulfonamide removal efficiency in constructed wetlands.

A Review on Occurrence and Spread of Antibiotic Resistance in Wastewaters and in Wastewater Treatment Plants: Mechanisms and Perspectives

This paper reviews current knowledge on sources, spread and removal mechanisms of antibiotic resistance genes (ARGs) in microbial communities of wastewaters, treatment plants and downstream recipients. Antibiotic is the most important tool to cure bacterial infections in humans and animals. The over- and misuse of antibiotics have played a major role in the development, spread, and prevalence of antibiotic resistance (AR) in the microbiomes of humans and animals, and microbial ecosystems worldwide. AR can be transferred and spread amongst bacteria via intra- and interspecies horizontal gene transfer (HGT). Wastewater treatment plants (WWTPs) receive wastewater containing an enormous variety of pollutants, including antibiotics, and chemicals from different sources. They contain large and diverse communities of microorganisms and provide a favorable environment for the spread and reproduction of AR. Existing WWTPs are not designed to remove micropollutants, antibiotic resistant bacteria (ARB) and ARGs, which therefore remain present in the effluent. Studies have shown that raw and treated wastewaters carry a higher amount of ARB in comparison to surface water, and such reports have led to further studies on more advanced treatment processes. This review summarizes what is known about AR removal efficiencies of different wastewater treatment methods, and it shows the variations among different methods. Results vary, but the trend is that conventional activated sludge treatment, with aerobic and/or anaerobic reactors alone or in series, followed by advanced post treatment methods like UV, ozonation, and oxidation removes considerably more ARGs and ARB than activated sludge treatment alone. In addition to AR levels in treated wastewater, it examines AR levels in biosolids, settled by-product from wastewater treatment, and discusses AR removal efficiency of different biosolids treatment procedures. Finally, it puts forward key-points and suggestions for dealing with and preventing further increase of AR in WWTPs and other aquatic environments, together with a discussion on the use of mathematical models to quantify and simulate the spread of ARGs in WWTPs. Mathematical models already play a role in the analysis and development of WWTPs, but they do not consider AR and challenges remain before models can be used to reliably study the dynamics and reduction of AR in such systems.

Comparison of the elimination effectiveness of tetracycline and AmpC β-lactamase resistance genes in a municipal wastewater treatment plant using four parallel processes

Municipal wastewater treatment plants (mWWTPs), considered reservoirs of antibiotic resistance genes (ARGs), are selected to compare the contributions of technology and process to ARG removal. Fifteen ARGs (tetA, tetB, tetC, tetE, tetG, tetL, tetM, tetO, tetQ, tetS, tetX, MOX, CIT, EBC, and FOX) and two integron genes (intI1, intI2) were tracked and detected in wastewater samples from a large-scale mWWTP with four parallel processes, including three biological technologies of AAO (anaerobic-anoxic-oxic), AB (adsorption-biodegradation), and UNITANK, two different disinfection technologies, and two primary sedimentation steps. The results showed that ARGs were widely detected, among which tetA and tetM had the highest detection rate at 100%. AAO was the most effective process in removing ARGs, followed by the AB and UNITANK processes, where the separation step was critical: 37.5% AmpC β-lactamase genes were reduced by the secondary clarifier. UV disinfection was more efficient than chlorination disinfection by 47.0% in ARG removal. Both disinfection and primary sedimentation processes could effectively remove integrons, and the swirling flow grit chamber was a more effective primary settling facility in total ARG removal than the aerated grit chamber. The tet genes and AmpC β-lactamase genes were significantly correlated with the water quality indexes of BOD5, CODCr, SS, TP, TOC, pH and NH4+-N (p < 0.05). In addition, the correlation between efflux pump genes and AmpC β-lactamase genes was strongly significant (r2 = 0.717, p < 0.01). This study provides a more powerful guide for selecting and designing treatment processes in mWWTPs with additional consideration of ARG removal.

Performance of full scale constructed wetlands in removing antibiotics and antibiotic resistance genes

Additional treatment of wastewater, such as constructed wetlands (CWs), is a possible solution to reduce the discharge of antibiotics and antibiotic resistance genes (ARGs) from households and industry to the environment. This study aims to investigate the occurrence and removal of antibiotics and ARGs by two full scale CWs operated at different hydraulic retention times (HRT), namely 1 day and 3 days. Both CWs were receiving the same wastewater treatment plant (WWTP) effluent. Temporally and spatially distributed sampling of water and sediment was conducted for one year and samples were analyzed for antibiotics and ARGs by using LC-MS/MS and qPCR. Results showed that both CWs removed antibiotics significantly with a comparable overall removal of 28%-100%, depending on the type of antibiotics. However, some of the antibiotics showed higher concentration after the CW treatment. Five antibiotics (tiamulin, tylosin, oxytetracycline, sulfamethoxazole and trimethoprim) were the most abundant (>1500 ng/l on average) in winter. Meanwhile, ermB was the most abundant (average of 5.0 log) in winter compared to summer (average of 3.5 log). Other ARGs did not show a significant increase or decrease between winter and summer. ARGs were removed from the wastewater by 0.8 to 1.5 log. The HRT did not influence the removal of either the antibiotics or the ARGs. A strong correlation was found between sul genes and intI1. The results also revealed a positive and a negative relationship from sampling point 1 to sampling point 5: a positive relation between abundance of antibiotics, ARGs, and of NO₃-N, NH₄-N, TP, COD and a negative relation between antibiotics, ARGs and temperature. This relationship showed the effect between antibiotics and ARGs concentrations with physicochemical parameters and nutrients. The ability of CWs to reduce the input of micropollutants into the environment makes CWs a potential post treatment to WWTP.

Spatiotemporal distribution, source apportionment and combined pollution of antibiotics in natural waters adjacent to mariculture areas in the Laizhou Bay, Bohai Sea

The spatiotemporal distribution, source apportionment and combined pollution of 14 antibiotics in natural waters adjacent to mariculture farms of Laizhou Bay in the Bohai Sea were studied. The contribution proportion and quantity of each potential pollution source to antibiotics in natural water bodies were quantitatively described. The correlations between heavy metals and antibiotics and their underlying mechanisms in natural and aquaculture water environment were analyzed. Fourteen antibiotics were detected in natural water and sediment in the coastal area of Laizhou Bay. The maximum concentrations of sulfamethazine and trimethoprim in water reached tens or even hundreds of μg/L in winter. Trimethoprim was the main antibiotic in natural water bodies in winter and summer, and enrofloxacin was the principal antibiotic in sediments. Enrofloxacin, ciprofloxacin and oxytetracycline were detected in all underground water samples; thus, control of these antibiotics needs to be made a priority to mitigate groundwater contamination. PCA-MLR revealed that the potential sources of antibiotics in natural waters of Laizhou Bay include the mariculture wastewater (18.3%), the domestic sewage (63.3%) and the livestock wastewater (18.4%). Therefore, the antibiotic burden of Laizhou Bay was principally from the domestic sewage. In natural water, the concentration of Cu was positively correlated with antibiotics, which might be related to the common sources, the competitive adsorption in sediments and the easy complexation characteristic of Cu and antibiotics. Positive correlations among antibiotics and heavy metals were observed in mariculture sediments, while negative relationships were observed in natural sediments.

The Dual Role of Microplastics in Marine Environment: Sink and Vectors of Pollutants

This review is a follow-up to a previous review published in Journal of Marine Science and Engineeringon the issues of accumulation, transport, and the effects of microplastics (MPs) in the oceans. The review brings together experimental laboratory, mathematical, and field data on the dual role of MPs as accumulators of hydrophobic persistent organic compounds (POPs), and their release-effect in the marine ecosystem. It also examines the carrier role, besides POPs, of new emerging categories of pollutants, such as pharmaceuticals and personal care products (PPCPs). This role becomes increasingly important and significant as polymers age and surfaces become hydrophilic, increasing toxicity and effects of the new polymer-pollutant associations on marine food webs. It was not the intention to provide too many detailed examples of carriers and co-contaminants, exposed marine species, and effects. Instead, the views of two different schools of thought are reported and summarized: one that emphasizes the risks of transport, exposure, and risk beyond critical thresholds, and another that downplays this view.

Fate and removal of bacteria and antibiotic resistance genes in horizontal subsurface constructed wetlands: Effect of mixed vegetation and substrate type

This study aimed to investigate the influence of cropping method and substrate type on the fate and the removal of bacterial and antibiotic resistance genes (ARGs) indicators from primary wastewater by constructed wetlands (CWs) during startup and maturation stages. Four small-scale CWs differing in their plantation pattern (monoculture vs. polyculture) and substrate type were constructed and operated under field conditions. While for bacteria, the greatest impact of the cropping method and substrate type on removal was during the startup stage rather than the maturation stage, for ARGs, such impact was significant at both stages. During startup, the removal efficiencies of heterotrophic bacteria, fecal coliforms, E. coli, 16S rRNA genes and lacZ increased with the operation time. At maturation, the removal efficiencies were constant and were within the range of 89.2-99.4%, 93.7-98.9%, 89-98.8%, 94.1-99.6% and 92.9-98.7%, respectively. The removal efficiencies of intl1, tetM, intl1, sul1, ermB and total ARGs were also increased with the operation time. However, they were ARG type and configuration-dependent; at maturation they ranged between 50.7%-89.4%, 85.9%-97%, 49.6%-92.9%, 58.2%-96.7% and 79.9-94.3%, respectively. The tuff-filled serially planted CW was also the only one capable of removing these genes at similar high efficiency. Metagenomic analysis showed that none of the ARGs was among the most common ARGs in water and biofilm samples; rather most ARGs belonged to bacterial efflux transporter superfamilies. Although ARGs were removed, they were still detected in substrate biofilm and their relative concentrations were increased in the effluents. While the removal of both bacteria and ARGs was higher during summer compared to winter, the season had no effect on the removal pattern of ARGs. Hence, combination of the serial plantation with substrate having high surface area is a potential strategy that can be used to improve the performance of CWs.

Identification of transformation products to characterize the ability of a natural wetland to degrade synthetic organic pollutants

Natural wetlands have been recognized as a natural reactor for degradation and elimination of environmental pollutants. The Upo Wetland, the largest inland wetland in Korea, is mainly surrounded by agricultural lands and it is susceptible to contamination from excess nutrient loads and synthetic organic contaminants (SOCs) (e.g., pesticides). The aim of this study was to identify major SOCs in the wetland and evaluate their degradation. We used high resolution mass spectrometry (HRMS) with a two-step analysis approach (i.e., 1^st analysis for target measurement along with suspect and non-target screening (SNTS) and 2^nd analysis for complimentary suspect screening) to identify and quantify the transformation products (TPs) of the identified parent SOCs. Quantitative analysis of 30 targets, mainly including pesticides, showed that fungicides were the major SOCs detected in the wetland, accounting for about 50% of the composition ratio of the total SOCs quantified. Orysastrobin occurred at the highest mean concentration (>700 ng/L), followed by two other fungicides, carbendazim and tricyclazole. The first analysis (SNTS) tentatively identified 39 TPs (30 by suspect, 9 by non-target screening) of 14 parent pesticides. Additionally, the second analysis (complimentary suspect screening) identified 9 more TPs. Among the 48 total TPs identified, 7 were confirmed with reference standards. The identification of the remaining TPs had a high confidence level (e.g., level 2 or 3). Regarding transport though the wetland, most TPs showed greater peak area ratios (i.e., the relative portion of chromatographic area of the TPs to the parent compound) at the outlet point of the wetland compared to the inlet point. The risk quotient, which was calculated using the concentrations of parent compounds, decreased toward the outlet, demonstrating the degradation capacity of the wetland. The estimates for biodegradability, hydrophobicity, and toxicity by an in-silico quantitative structure-activity relationship (QSAR) model indicated a lower half-life, lower logD_OW, and greater effect concentration for most TPs compared to the parent compounds. Based on these results, we conclude that natural wetlands play a role as an eco-friendly reactor for degrading SOCs to form numerous TPs that are lower risk than the parent compounds.

Application of next generation sequencing-based rapid detection platform for microbiological diagnosis and drug resistance prediction in acute lower respiratory infection

Background

Acute lower respiratory infections (ALRIs) have a high mortality rate. We aimed to apply a platform that rapidly detects 36 microorganisms and 49 antibiotic resistance markers in the clinical diagnosis of ALRI and drug resistance prediction.

Methods

Multicenter collection of clinical samples from patients with ALRIs was carried out from 2017 to 2018. Sputum culture (SC) was performed, which provided two outcomes: the detected pathogens and the resistance to different antibiotics. Additionally, each sputum sample was used to extract deoxyribonucleic acids (DNAs) followed by high-throughput sequencing.

Results

Eleven commonly observed pathogens were surveyed, and for all samples with positive SC results (137 cases), the overall coverage was 95.62% according to the sequencing results. The receiver operating characteristic (ROC) curve was drawn, and cutoff reads of the most frequently detected pathogens were acquired. Overall, sequencing exhibited significantly higher sensitivity in the detection of pathogens compared with the traditional SC method, with a generally satisfactory specificity. Furthermore, we investigated the correlation between antibiotic resistance gene phenotypes and the actual outcomes of the drug sensitivity test, and some significant correlations were found, especially for the resistance to Amikacin in the presence of blaOXA7.

Conclusions

Sequencing-based sputum metagenomics can reveal a profile of the lung pathogen microbiome. The sequencing method offers both sufficient accuracy and significantly higher sensitivity in the detection of pathogens, and can be at least a complementary approach to traditional SC reporting. The sequencing technique also revealed some novel potential correlations between the presence of different pathogens, as well as new antimicrobial-resistant genes.

Occurrence and distribution of five antibiotic resistance genes during the loading period in sludge treatment wetlands

The objectives of this study were to clarify the distribution as well as the removal mechanism of antibiotic resistance genes (ARGs) within three sludge treatment wetlands (STWs) during a loading period of two years. Three STW units were constructed and run during the loading period: Unit 1 (U1) built with aeration tubes, Unit 2 (U2) built with aeration tubes and reeds, and Unit 3 (U3) built with reeds only. All targeted ARGs, intI1, and 16S rRNA were detected in residual sludge in the order of magnitude: 16S rRNA>sul1>intI1>sul2>tetC>tetA>ermB. The abundance of the five targeted ARGs, intI1, and 16S rRNA increased in residual sludge, during the loading period, which may be due to the increase in bacteria caused by the continuous import of exogenous nutrients. However, STWs can also remove ARGs from sewage during the loading period and the mean removal efficiency of five resistance genes was 73.0%. The removal rates of intI1 and 16S rRNA were 73.5% and 78.6%, respectively. Positive correlations were detected in abundance of most ARGs and intI1, as well as 16S rRNA (P < 0.05), indicating intI1 plays a vital part in the propagation of ARGs. The removal of bacteria harboring these genes also occurs in the STW units.

Persistence of antibiotic resistance genes from river water to tap water in the Yangtze River Delta

Antibiotic resistance genes (ARGs) raise public concern as emerging contaminants. The abundance and variation of 11 ARGs, intI1 and 16S rRNA gene were deciphered using quantitative PCR (qPCR) in two drinking water treatment systems that include river, wetland, drinking water treatment plants (DWTPs) and tap water from the Yangtze River Delta. The influencing factors for ARG abundance in river water were also explored. All investigated genes were detected in river water and there was no significant difference between the two systems, with sulfonamide ARGs occupying the highest abundance. Temperature had a significant effect on the ARG distribution based on permutational multivariate analysis of variance (PERMANOVA). Further Spearman analysis demonstrated that temperature was strongly correlated with the abundance of sul1, sul2, tetA and tetC, and these genes were significantly correlated with environmental factors (including temperature, total organic carbon (TOC) and dissolved oxygen (DO)). Considering the frequency and abundance of ARGs, as well as their correlation with other genes, sul1, sul2, tetA and tetC could be used as indicators of ARGs in river water. No significant reduction was noted for the absolute abundance of ARGs from river water to wetland water. Principle coordinates analysis (PCoA) combined with PERMANOVA revealed that drinking water treatment was responsible for reducing 16S rRNA gene and ARG abundance resulting in 3-log reductions. However, it should be noted that after transportation of distribution pipeline, both 16S rRNA gene and ARGs still detected in tap water, which indicated persistence of ARGs and will require further research.

Enrichment of antibiotics in an inland lake water

Inland water is very susceptible to the input of pollutants. However, little is known about the occurrence of antibiotics in inland lakes. In this study, a total of 83 target antibiotics were quantified in water and sediment samples collected from the Qinghai Lake, the largest inland lake of China located on the northeast of Qinghai-Tibet plateau, and its inflowing rivers. The results showed that 27 and 25 antibiotics were detected in water and sediments, respectively, with the summed concentrations (SUM) of 1.14-17.3 ng/L and 0.72-8.31 ng/g. Compared with the input rivers, significantly higher levels of sulfonamides (SAs), quinolones (QNs), polyethers (PEs), and SUM in water samples were observed in Qinghai Lake water. The average proportions of SAs (50.9-52.7%) and QNs (22.0-28.3%) in Qinghai Lake water nearly doubled compared to those in input rivers. An enrichment factor (EF) was proposed to reveal the enrichment degree of antibiotics in Qinghai Lake compared to its input river water. Sulfaguanidine (SGD), flumequine (FLU), and nalidixic acid (NDA) were enriched in Qinghai Lake up to several ten times based on the calculated EF values, due to their persistence in such a cold saline lake. Risk assessment showed that most antibiotics except anhydrochlortetracycline (ACTC) had insignificant risks to aquatic organisms and antibiotic resistance selection in Qinghai Lake water. This study was the first to reveal the enrichment of antibiotics in Qinghai Lake water, and suggests the urgent need to investigate the possible long-term enrichment and environmental risks of antibiotics in inland lakes.

Biodegradation of sulfonamides in both oxic and anoxic zones of vertical flow constructed wetland and the potential degraders

The pollution of wastewater with antibiotics and antibiotics resistance genes has attracted public concerns about ecosystem and global health. Swine wastewater can contain high concentrations of antibiotics, especially sulfonamides, even after full-scale wastewater treatment. In this study, mesocosm-scale vertical flow constructed wetlands (VF-CWs) were applied to abate nutrients and antibiotics in swine wastewater containing sulfonamides. VF-CWs performed well in the removal of both nutrients and antibiotics. Sulfonamides did not influence total organic carbon (TOC) and total phosphorus (TP) removal, and even slightly enhanced NH₄⁺-N removal. High removal efficiencies (26.42-84.05%) were achieved for sulfadiazine (SDZ), sulfamethoxazole (SMX) and sulfamethazine (SMZ). Together with lab-scale sorption and biodegradation experiments, microbial degradation was found to be the most important removal mechanism for sulfonamides in VF-CWs. Sulfonamides addition increased bacterial alpha-diversity and changed microbial community structure. Moreover, antibiotics promoted antibiotic-resistant or -degrading bacteria. Bacillus, Geobacter and other seven genera were correlated with sulfonamides reduction under either aerobic or anaerobic condition. In summary, VF-CW is a suitable alternative for swine wastewater treatment, and biodegradation plays the key role in sulfonamides abatement. Main findings of the work. This was the first work to combine bacterial community analysis with microcosm experiments to uncover the major removal mechanism of sulfonamides in constructed wetlands.

Emerging pollutants-Part II: Treatment

Emerging pollutants (EPs) refer to a class of pollutants, which are emerging in the environment or recently attracted attention. EPs mainly include pharmaceutical and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), and antibiotic resistance genes (ARGs). EPs have potential threats to human health and ecological environment. In recent years, the continuous detections of EPs in surface and ground water have brought huge challenges to water treatment and also made the treatment of EPs become an international research hotspot. This paper summarizes some research results on EPs treatment published in 2019. This paper may be helpful to understand the current situations and development trends of EP treatment technologies.

Wetlands for environmental protection

This article presents an update on the research and practical demonstration of wetland-based treatment technologies for protecting water resources and environment covering papers published in 2019. Wetland applications in wastewater treatment, stormwater management, and removal of nutrients, metals, and emerging pollutants including pathogens are highlighted. A summary of studies focusing on the effects of vegetation, wetland design and operation strategies, and process configurations and modeling, for efficient treatment of various municipal and industrial wastewaters, is included. In addition, hybrid and innovative processes with wetlands as a platform treatment technology are presented.