Metagenomic insights into dissemination of antibiotic resistance across bacterial genera in wastewater treatment

Socio-environmental externalities of sewage waste management

Conventional sewage management is expensive and inefficient, putting the environment and public health at risk, making access to sewage services difficult for everyone. Reusing sewage waste has agricultural and economic potential, but can contain harmful contaminants if not treated properly. This review is based on the hypothesis that the destination of sewage waste generates environmental and social externalities, which have not yet been widely compared. With the aim of identifying, from the literature, the socio-environmental externalities generated by different sewage waste management approaches, a systematic review of the literature was carried out, including 244 documents, with 50 % of these discussing impacts of conventional treatment and 37 % analyzing the reuse of waste. The main impacts and externalities were evaluated in three situations: untreated sewage, treated sewage, and reused waste. The results indicate that sewage waste has an underutilized economic value and can generate revenue, reduce operational costs and electricity expenses. Six negative externalities generated by conventional sewage treatment were identified: health costs; environmental cleaning; carbon offsetting; damage to tourism; damage to fishing and agriculture; and real estate depreciation. In reuse, there is a risk of two negative externalities: health costs and environmental cleaning, but two positive externalities were also identified: the reduction of phosphate rock mining and the neutralization of carbon credits. The complexity of the transition to sustainable sewage treatment practices is highlighted given the lack of consensus on the safe use of sewage waste, the lack of regulatory standardization, implementation costs and differences in regional parameters, highlighting the need for preliminary experimentation in a multidisciplinary and contextualized approach, considering comparative externalities among the available sewage waste management possibilities.

Mechanisms linking triclocarban biotransformation to functional response and antimicrobial resistome evolution in wastewater treatment systems

Evaluating the role of antimicrobials biotransformation in the regulation of metabolic functions and antimicrobial resistance evolution in wastewater biotreatment systems is crucial to ensuring water security. However, the associated mechanisms remain poorly understood. Here, we investigate triclocarban (TCC, one of the typical antimicrobials) biotransformation mechanisms and the dynamic evolution of systemic function disturbance and antimicrobial resistance risk in a complex anaerobic hydrolytic acidification (HA)-anoxic (ANO)/oxic (O) process. We mined key functional genes involved in the TCC upstream (reductive dechlorination and amide bonds hydrolysis) and downstream (chloroanilines catabolism) biotransformation pathways by metagenomic sequencing. Acute and chronic stress of TCC inhibit the production of volatile fatty acids (VFAs), NH4+ assimilation, and nitrification. The biotransformation of TCC via a single pathway cannot effectively relieve the inhibition of metabolic functions (e.g., carbon and nitrogen transformation and cycling) and enrichment of antimicrobial resistance genes (ARGs). Importantly, the coexistence of TCC reductive dechlorination and hydrolysis pathways and subsequent ring-opening catabolism play a critical role for stabilization of systemic metabolic functions and partial control of antimicrobial resistance risk. This study provides new insights into the mechanisms linking TCC biotransformation to the dynamic evolution of systemic functions and risks, and highlights critical regulatory information for enhanced control of TCC risks in complex biotreatment systems.

Metagenomic investigation of antibiotic resistance genes and resistant bacteria contamination in pharmaceutical plant sites in China

Pharmaceutical plant sites play a significant role in the dissemination of antibiotic resistance genes (ARGs) into the environment. It is imperative to comprehensively monitor of ARGs across various environmental media at these sites. This study focused on three pharmaceutical plants, two located in North China and one in South China. Through metagenomic approaches, we examined the composition, mobility potential, and bacterial hosts of ARGs in diverse media such as process water, groundwater, topsoil, soil cores, and pharmaceutical fermentation residues across diverse environmental matrices, including topsoil, soil cores, process water, groundwater, and pharmaceutical fermentation residues. We identified a wide array of ARGs, comprising 21 types and 740 subtypes, with process water exhibiting the highest abundance and diversity. Treatment processes varied in their efficacy in eliminating ARGs, and the clinically relevant ARGs should also be considered when evaluating wastewater treatment plant efficiency. Geographical distinctions in groundwater ARG distribution between northern and southern regions were observed. Soil samples from the three sites showed minimal impact from pharmaceutical activity, with vancomycin-resistance genes being the most prevalent. High levels of ARGs in pharmaceutical fermentation residues underscore the necessity for improved waste management practices. Metagenomic assembly revealed that plasmid-mediated ARGs were more abundant than chromosome-mediated ARGs. Metagenome-assembled genomes (MAGs) analysis identified 166 MAGs, with 62 harboring multiple ARGs. Certain bacteria tended to carry specific types of ARGs, revealing distinct host-resistance associations. This study enhances our understanding of ARG dissemination across different environmental media within pharmaceutical plants and underscores the importance of implementing strict regulations for effluent and residue discharge to control ARG spread.

Sensitivity and consistency of long- and short-read metagenomics and epicPCR for the detection of antibiotic resistance genes and their bacterial hosts in wastewater

Wastewater surveillance is a powerful tool to assess the risks associated with antibiotic resistance in communities. One challenge is selecting which analytical tool to deploy to measure risk indicators, such as antibiotic resistance genes (ARGs) and their respective bacterial hosts. Although metagenomics is frequently used for analyzing ARGs, few studies have compared the performance of long-read and short-read metagenomics in identifying which bacteria harbor ARGs in wastewater. Furthermore, for ARG host detection, untargeted metagenomics has not been compared to targeted methods such as epicPCR. Here, we 1) evaluated long-read and short-read metagenomics as well as epicPCR for detecting ARG hosts in wastewater, and 2) investigated the host range of ARGs across the wastewater treatment plant (WWTP) to evaluate host proliferation. Results highlighted long-read revealed a wider range of ARG hosts compared to short-read metagenomics. Nonetheless, the ARG host range detected by long-read metagenomics only represented a subset of the hosts detected by epicPCR. The ARG-host linkages across the influent and effluent of the WWTP were characterized. Results showed the ARG-host phylum linkages were relatively consistent across the WWTP, whereas new ARG-host species linkages appeared in the WWTP effluent. The ARG-host linkages of several clinically relevant species found in the effluent were identified.

Inactivation of antibiotic-resistant bacteria in hospital wastewater by ozone-based advanced water treatment processes

The emergence and spread of antimicrobial resistance (AMR) continue on a global scale. The impacts of wastewater on the environment and human health have been identified, and understanding the environmental impacts of hospital wastewater and exploring appropriate forms of treatment are major societal challenges. In the present research, we evaluated the efficacy of ozone (O3)-based advanced wastewater treatment systems (O3, O3/H2O2, O3/UV, and O3/UV/H2O2) for the treatment of antimicrobials, antimicrobial-resistant bacteria (AMRB), and antimicrobial resistance genes (AMRGs) in wastewater from medical facilities. Our results indicated that the O3-based advanced wastewater treatment inactivated multiple antimicrobials (>99.9%) and AMRB after 10-30 min of treatment. Additionally, AMRGs were effectively removed (1.4-6.6 log10) during hospital wastewater treatment. The inactivation and/or removal performances of these pollutants through the O3/UV and O3/UV/H2O2 treatments were significantly (P < 0.05) better than those in the O3 and O3/H2O2 treatments. Altered taxonomic diversity of microorganisms based on 16S rRNA gene sequencing following the O3-based treatment showed that advanced wastewater treatments not only removed viable bacteria but also removed genes constituting microorganisms in the wastewater. Consequently, the objective of this study was to apply advanced wastewater treatments to treat wastewater, mitigate environmental pollution, and alleviate potential threats to environmental and human health associated with AMR. Our findings will contribute to enhancing the effectiveness of advanced wastewater treatment systems through on-site application, not only in wastewater treatment plants (WWTPs) but also in medical facilities. Moreover, our results will help reduce the discharge of AMRB and AMRGs into rivers and maintain the safety of aquatic environments.

Application of high-throughput sequencing technologies and analytical tools for pathogen detection in urban water systems: Progress and future perspectives

The ubiquitous presence of pathogenic microorganisms, such as viruses, bacteria, fungi, and protozoa, in urban water systems poses a significant risk to public health. The emergence of infectious waterborne diseases mediated by urban water systems has become one of the leading global causes of mortality. However, the detection and monitoring of these pathogenic microorganisms have been limited by the complexity and diversity in the environmental samples. Conventional methods were restricted by long assay time, high benchmarks of identification, and narrow application sceneries. Novel technologies, such as high-throughput sequencing technologies, enable potentially full-spectrum detection of trace pathogenic microorganisms in complex environmental matrices. This review discusses the current state of high-throughput sequencing technologies for identifying pathogenic microorganisms in urban water systems with a concise summary. Furthermore, future perspectives in pathogen research emphasize the need for detection methods with high accuracy and sensitivity, the establishment of precise detection standards and procedures, and the significance of bioinformatics software and platforms. We have compiled a list of pathogens analysis software/platforms/databases that boast robust engines and high accuracy for preference. We highlight the significance of analyses by combining targeted and non-targeted sequencing technologies, short and long reads technologies, sequencing technologies, and bioinformatic tools in pursuing upgraded biosafety in urban water systems.

Chlorine disinfection modifies the microbiome, resistome and mobilome of hospital wastewater - A nanopore long-read metagenomic approach

The aim of the present study was to analyze changes in the microbiome, resistome, and mobilome of hospital wastewater (HWW) induced by disinfection with chlorine compounds. Changes in bacterial communities and specific antibiotic resistance genes (ARGs) in HWW were determined with the use of a nanopore long-read metagenomic approach. The main hosts of ARGs in HWW were identified, and the mobility of resistance mechanisms was analyzed. Special attention was paid to the prevalence of critical-priority pathogens in the HWW microbiome, which pose the greatest threat to human health. The results of this study indicate that chlorine disinfection of HWW can induce significant changes in the structure of the total bacterial population and antibiotic resistant bacteria (ARB) communities, and that it can modify the resistome and mobilome of HWW. Disinfection favored the selection of ARGs, decreased their prevalence in HWW, while increasing their diversity. The mobility of the HWW resistome increased after disinfection. Disinfection led to the emergence of new drug resistance mechanisms in previously sensitive bacterial taxa. In conclusion, this study demonstrated that HWW disinfected with low (sublethal) concentrations of free chlorine significantly contributes to the mobility and transfer of drug resistance mechanisms (including critical mechanisms) between bacteria (including pathogens).

Contribution of wastewater to antimicrobial resistance: A review article

OBJECTIVES

Antimicrobial resistance (AMR) is a global challenge that has raised concern globally, owing to its detrimental effects on the health and economy of countries. The ever-growing threat of AMR and sources of AMR are still being investigated. Wastewater plays an important role as a habitat for bacteria and an environment conducive to gene transfer. The primary aim of this review was to highlight the contribution of wastewater to AMR.

METHODS

Evidence of AMR in wastewater was drawn from literature published in the last 10 years, from 2012 to 2022.

RESULTS

Wastewater from agricultural practices, pharmaceutical manufacturing plants, and hospital effluents was established to promote AMR. Furthermore, stress factors such as the presence of antibiotics, heavy metals, pH, and temperature initiate and propagate AMR in bacteria living in wastewater. AMR in bacteria from wastewater was established to be either natural or acquired. Wastewater treatment techniques such as membrane filtration, coagulation, adsorption, and advanced oxidation processes have been used to remove resistant bacteria with varying success levels.

CONCLUSION

Wastewater is a major contributor to AMR, and an understanding of its role in AMR is necessary to find a lasting solution. In this regard, the spread of AMR in wastewater should be considered a threat that requires a strategy to stop further damage.

Quantification and antibiotic resistance risk assessment of chlorination-residual viable/VBNC Escherichia coli and Enterococcus in on-site hospital wastewater treatment system

On-site hospital wastewater treatment system widely applying chlorination has been regarded as an important barrier to curb the dissemination of antibiotic resistance. Chlorination-residual viable and viable but non-culturable (VBNC) bacteria probably lead to overestimate the effect of disinfection, while their antibiotic resistance risks imported from hospital effluents to municipal pipe network may be ignored. In this study, we quantified viable/VBNC Escherichia coli and Enterococcus in chlorination of an on-site hospital wastewater treatment system and assessed their antibiotic resistance risks. The numbers of viable/VBNC Escherichia coli and Enterococcus in raw wastewater were detected as high as 5.76-6.34/5.76-6.33 and 5.44-5.76/5.44-5.75 log₁₀(cells/mL). Meanwhile, high proportions of antibiotic-resistant Escherichia coli and Enterococcus to culturable Escherichia coli and Enterococcus were observed, especially carrying ampicillin resistance (22.25-41.70 % and 28.09-54.05 %). Chlorination could remove 0.44-1.88-/0.43-1.88- and 0.29-1.29-/0.28-1.28-log of viable/VBNC and complete culturable Escherichia coli and Enterococcus, but cause antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) to be released outside cells, and possibly further enhance the antibiotic resistance of viable bacteria. Low detections of antibiotics suggested that the occurrence of antibiotic-resistant bacteria (ARB) may not be accompanied by the corresponding antibiotics. Different sampling months had some impacts on above results, while the results were basically stable at different sampling times of hospital daily working period. The high release rates (11.26-13.02 and 11.59-12.98 log₁₀(cells/h)) and cumulative amounts (15.41-16.12 and 15.75-16.14 log₁₀(cells)) of chlorination-residual viable/VBNC Escherichia coli and Enterococcus indirectly assessed the potential risks of bacterial antibiotic resistance entering municipal pipe network. Additionally, the contributions from the corresponding antibiotic ceftazidime, ciprofloxacin, and vancomycin with the cumulative amounts of 2.57-4.85, 5.73-7.50, and 5.21-7.14 kg should also be taken seriously. Residual chlorine could serve as an important signal indicator for the risk assessment.

Metagenomic surveillance of antibiotic resistome in influent and effluent of wastewater treatment plants located on the Qinghai-Tibetan Plateau

As hotspots for the dissemination of antibiotic resistance genes (ARGs), wastewater treatment plants (WWTPs) have attracted global attention. However, there lacks a sufficient metagenomic surveillance of antibiotic resistome in the WWTPs located on the Qinghai-Tibet Plateau. Here, metagenomic approaches were used to comprehensively investigate the occurrence, mobility potential, and bacterial hosts of ARGs in influent and effluent of 18 WWTPs located on the Qinghai-Tibet Plateau. The total ARG relative abundances and diversity were significantly decreased from influent to effluent across the WWTPs. Multidrug, bacitracin, sulfonamide, aminoglycoside, and beta-lactam ARGs generally consisted of the main ARG types in effluent samples, which were distinct from influent samples. A group of 72 core ARGs accounting for 61.8-95.8 % of the total ARG abundances were shared by all samples. Clinically relevant ARGs mainly conferring resistance to beta-lactams were detected in influent (277 ARGs) and effluent (178 ARGs). Metagenomic assembly revealed that the genetic location of an ARG on a plasmid or a chromosome was related to its corresponding ARG type, demonstrating the distinction in the mobility potential of different ARG types. The abundance of plasmid-mediated ARGs accounted for a much higher proportion than that of chromosome-mediated ARGs in both influent and effluent. Moreover, the ARGs co-occurring with diverse mobile genetic elements in the effluent exhibited a comparable mobility potential with the influent. Furthermore, 137 metagenome-assembled genomes (MAGs) assigned to 13 bacterial phyla were identified as the ARG hosts, which could be effectively treated in most WWTPs. Notably, 46 MAGs were found to carry multiple ARG types and the potential pathogens frequently exhibited multi-antibiotic resistance. Some ARG types tended to be carried by certain bacteria, showing a specific host-resistance association pattern. This study highlights the necessity for metagenomic surveillance and will facilitate risk assessment and control of antibiotic resistome in WWTPs located on the vulnerable area.

A sludge bulking wastewater treatment plant with an oxidation ditch-denitrification filter in a cold region: bacterial community composition and antibiotic resistance genes

Bacterial community structure of activated sludge directly affects the stable operation of WWTPS, and these bacterial communities may carry a variety of antibiotic resistance genes (ARGs), which is a threat to the public health. This study employed 16S rRNA gene sequencing and metagenomic sequencing to investigate the bacterial community composition and the ARGs in a sludge bulking oxidation ditch-denitrification filter WWTP in a cold region. The results showed that Trichococcus (20.34%), Blautia (7.72%), and Faecalibacterium (3.64%) were the main bacterial genera in the influent. The relative abundances of norank_f_Saprospiraceae and Candidatus_Microthrix reached 10.24% and 8.40%, respectively, in bulking sludge, and those of norank_f_Saprospiraceae and Candidatus_Microthrix decreased to 6.56 and 7.10% after the anaerobic tank, indicating that the anaerobic tank had an inhibitory effect on filamentous bacteria. After 20 mJ/cm² UV disinfection, about 540 bacterial genera, such as Romboutsia (7.99%), Rhodoferax (7.98%), and Thermomonas (4.13%), could still be detected in the effluent. The ARGs were 345.11 ppm in the influent and 11.20 ppm in the effluent; 17 subtypes, such as sul1, msrE, aadA5, ErmF, and tet(A), could be detected throughout the entire process. These ARG subtypes were persistent ARGs with a high health risk. Network analysis indicated that the changes in filamentous bacteria norank_f_Saprospiraceae abundance mainly contributed to the abundance shift of MexB, and Acinetobacter mainly increased the abundance of drfA1. These results above will provide theoretical support for the sludge bulking and ARGs controls of WWTPs in cold regions.

New and traditional methods for antibiotic resistance genes removal: Constructed wetland technology and photocatalysis technology

Antibiotic resistance genes (ARGs) are a new environmental contaminant that poses a major hazard to humans and the environment. This research discusses the methods and drawbacks of two ARG removal approaches, constructed wetlands (CWs) and photocatalysis. CWs primarily rely on the synergistic effects of substrate adsorption, plant uptake, and microbial processes to remove ARGs. The removal of ARGs can be influenced by wetland plants, substrate type, wetland type, and hydraulic conditions. The absolute abundance of ARGs in effluent decreased, but their relative abundance increased. Photocatalysis deactivates ARGs predominantly through reactive oxygen species, with removal effectiveness determined by catalyst type, radiation type, and radiation intensity. The drawback is that it exposes intracellular resistance genes, perhaps increasing the risk of ARG spread. To address the current shortcomings, this paper proposes the feasibility of combining a constructed wetland with photocatalysis technology, which provides a novel strategy for ARG removal.

Antibiotic resistant genes in the environment-exploring surveillance methods and sustainable remediation strategies of antibiotics and ARGs

Antibiotic Resistant Genes (ARGs) are an emerging environmental health threat due to the potential change in the human microbiome and selection for the emergence of antibiotic resistant bacteria. The rise of antibiotic resistant bacteria has caused a global health burden. The WHO (world health organization) predicts a rise in deaths due to antibiotic resistant infections. Since bacteria can acquire ARGs through horizontal transmission, it is important to assess the dissemination of antibioticresistant genes from anthropogenic sources. There are several sources of antibiotics, antibiotic resistant bacteria and genes in the environment. These include wastewater treatment plants, landfill leachate, agricultural, animal industrial sources and estuaries. The use of antibiotics is a worldwide practice that has resulted in the evolution of resistance to antibiotics. Our review provides a more comprehensive look into multiple sources of ARG's and antibiotics rather than one. Moreover, we focus on effective surveillance methods of ARGs and antibiotics and sustainable abiotic and biotic remediation strategies for removal and reduction of antibiotics and ARGs from both terrestrial and aquatic environments. Further, we consider the impact on public health as this problem cannot be addressed without a global transdisciplinary effort.

Occurrence and Quantitative Microbial Risk Assessment of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Sub-Catchment of the Yodo River Basin, Japan

The occurrence of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) in a sub-catchment of the Yodo River Basin, a representative water system of a drinking water source in Japan, was investigated. The chromogenic enzyme-substrate medium method was used for the detection of S. aureus and MRSA by the presence or absence of antimicrobials in the medium for viable bacteria in a culture-based setting. The contributions of S. aureus and MRSA from wastewater to the rivers were estimated based on mass flux-based analysis, and quantitative microbial risk assessment (QMRA) was further conducted for S. aureus and MRSA in river environments. The mean abundance of S. aureus and MRSA was 31 and 29 CFU/mL in hospital effluent, 124 and 117 CFU/mL in sewage treatment plant (STP) influent, 16 and 13 CFU/mL in STP effluent, and 8 and 9 CFU/mL in river water, respectively. Contribution of the pollution load derived from the target STP effluent to river water ranged from 2% to 25%. The QMRA showed that to achieve the established health benchmarks, the drinking water treatment process would need to yield 1.7 log₁₀ and 2.9 log₁₀ inactivation in terms of infection risk and disability-adjusted life year (DALY) indexes, respectively. These findings highlight the link between medical environment and the importance of environmental risk management for antimicrobial-resistant bacteria in aquatic environments.

Distribution and characteristics of carbapenem-resistant and extended-spectrum β-lactamase (ESBL) producing Escherichia coli in hospital effluents, sewage treatment plants, and river water in an urban area of Japan

Occurrence of profiles of the carbapenem-resistant Escherichia coli (CRE-E) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-E) in an urban river in a sub-catchment of the Yodo River Basin, one of the representative water systems of Japan was investigated. We conducted seasonal and year-round surveys for the antimicrobial-resistant bacteria (AMRB) and antimicrobial-resistance genes (AMRGs) in hospital effluents, sewage treatment plant (STP) wastewater, and river water; subsequently, contributions to wastewater discharge into the rivers were estimated by analyses based on the mass flux. Furthermore, the characteristics of AMRB in the water samples were evaluated on the basis of antimicrobial susceptibility tests. CRE-E and ESBL-E were detected in all water samples with mean values 11 and 1900 CFU/mL in the hospital effluent, 58 and 4550 CFU/mL in the STP influent, not detected to 1 CFU/mL in the STP effluent, and 1 and 1 CFU/mL in the STP discharge into the river, respectively. Contributions of the pollution load derived from the STP effluent discharged into the river water were 1 to 21%. The resistome profiles for bla_IMP, bla_TEM, and bla_CTX-M genes in each water sample showed that AMRGs were not completely removed in the wastewater treatment process in the STP, and the relative abundances of bla_IMP, bla_TEM, and bla_CTX-M genes were almost similar (P<0.05). Susceptibility testing of antimicrobial-resistant E. coli isolates showed that CRE-E and ESBL-E detected in wastewaters and river water were linked to the prevalence of AMRB in clinical settings. These results suggest the importance of conducting environmental risk management of AMRB and AMRGs in the river environment. To our knowledge, this is the first detailed study that links the medical environment to CRE-E and ESBL-E for evaluating the AMRB and AMRGs in hospital effluents, STP wastewater, and river water at the basin scale on the basis of mass flux as well as the contributions of CRE-E and ESBL-E to wastewater discharge into the river.

How multi-walled carbon nanotubes in wastewater influence the fate of coexisting antibiotic resistant genes in the subsequent disinfection process

Wastewater treatment plants (WWTPs) are important hubs for the spread of antibiotic resistance genes (ARGs). Engineered nanoparticles, which was inevitably released to WWTPs, could change environmentally sensitive of antibiotic resistant bacteria (ARB). This would influence the fate of ARGs in subsequent disinfection process and consequent health risk. In this study, the ARGs fate of the effluent in conventional sodium hypochlorite (NaClO) disinfection process was investigated as multi-walled carbon nanotubes (MWCNTs) existed in sequencing batch reactor (SBR). The results showed the existence of MWCNTs in SBR could enhance the removal efficiency of intracellular 16S rRNA gene and intI1, extracellular intI1, sul2 and tetX in the effluent by NaClO. This is mainly due to the variation of bacterial physiological status, bacterial population structure and the activation of NaClO under the role of MWCNTs. MWCNTs in SBR could increase in membrane permeability of bacterial cells, which would be conducive to the penetration of chlorination to cytoplasm. MWCNTs in SBR also could change the bacterial population structure and induce the chlorine-sensitive bacteria; thus the potential hosts of ARGs in the effluent would be more easily inactivated by NaClO. Moreover, the residual MWCNTs in the effluent could activate NaClO to generate various free radical, which would enhance the oxidizing capacity of chlorination.

Submicron aerosols share potential pathogens and antibiotic resistomes with wastewater or sludge

Generation of size-segregated aerosols is an important eco-environmental problem in wastewater treatment plants (WWTPs), but the characteristics of potential pathogens and antibiotic resistomes in submicron aerosols (PM_1.0) were almost unknown. Here, 16S rRNA gene amplification and shotgun metagenome sequencing were respectively used to study the profiles of potential pathogens and antibiotic resistance genes (ARGs) in PM_1.0 from a full-scale WWTP. Acinetobacter and sul1 were respectively the predominant potential pathogens and ARG subtypes in PM_1.0 from aeration process. A total of 9 potential pathogens and 147 ARG subtypes, were shared among WWTP-PM_1.0, wastewater/sludge, and ambient air. Significant differences of potential pathogens or ARGs were found between WWTP-PM_1.0 and wastewater/sludge, however, wastewater/sludge had more crucial source contribution than the ambient air. Moreover, 13 potential pathogens and 40 ARG subtypes were easily aerosolized in PM_1.0 from at least one of the treatment units. ARGs were mainly harbored by Proteobacteria, and multidrug resistance genes were the most ARG type carried by potential pathogens. Taken together, this study indicates the prevalence of potential pathogens, ARGs, and ARG-carrying potential pathogens in WWTP-PM_1.0, which highlights the potential risk of PM_1.0 in spreading potential pathogens and antibiotic resistomes into the air environments.

Photo-Fenton-like degradation of antibiotics by inverse opal WO3 co-catalytic Fe2+/PMS, Fe2+/H2O2 and Fe2+/PDS processes: A comparative study

Advanced oxidation processes (AOPs) such as Fenton and Fenton-like process for pollutant removal have been widely reported. However, most papers choose one of the popular oxidants (H₂O₂, peroxymonosulfate (PMS) or peroxydisulfate (PDS)) as the oxidant via AOPs for pollutant degradation. The purpose of this work is to compare the degradation rates of the Fe²⁺/PMS, Fe²⁺/H₂O₂ and Fe²⁺/PDS processes. Furthermore, to solve the problem of slow regeneration of Fe²⁺, the visible light irradiation and inverse opal WO₃ cocatalyst were added to the Fenton/Fenton-like process. The IO WO₃ co-catalytic visible light assisted Fe²⁺/PMS, Fe²⁺/H₂O₂ and Fe²⁺/PDS processes greatly improved the degradation efficiency of norfloxacin (NOR), reaching about 30 times, 9 times and 12 times that of the homogeneous Fenton/Fenton-like process, respectively. On average, the TOC removal rates of PMS-based, H₂O₂-based and PMS-based processes for the five pollutants were 71.6%, 54.0%, and 59.6% within 60 min, and the corresponding co-catalyst treatment efficiencies were 0.215 mmol/g/h, 0.162 mmol/g/h, and 0.179 mmol/g/h, respectively. ¹O₂ and •O₂^- have been proven to play a vital role in the degradation of NOR via all the three IO WO₃ co-catalytic photo-Fenton-like processes. In addition, the effects of different reaction parameters on the activity of degrading norfloxacin were explored. The IO WO₃ co-catalytic visible light assisted Fe²⁺/PMS, Fe²⁺/H₂O₂ and Fe²⁺/PDS processes for removal of different persistent organic pollutants and norfloxacin in different actual wastewater have also been studied. Nonetheless, this study proves that IO WO₃ co-catalytic visible light assisted Fe²⁺/PMS, Fe²⁺/H₂O₂ and Fe²⁺/PDS processes could effectively remove antibiotics from wastewater.

Phenolic compounds promote the horizontal transfer of antibiotic resistance genes in activated sludge

Phenolic compounds are common organic pollutants in wastewater. During the wastewater treatment process, these compounds may influence the microbial community structure and functions. However, the impact of the phenolic compounds in the wastewater treatment plants on the horizontal transfer of antibiotic resistance genes (ARGs) has not been well assessed. In this study, we investigated the horizontal transfer of ARGs under the stress of phenolic compounds. The results showed that in pure culture bacteria system, p-nitrophenol (PNP), p-aminophenol (PAP) and phenol (PhOH) (10-100 mg/L) can significantly increase the horizontal transfer frequency of ARGs by 2.2-4.6, 3.6-9.4 and 1.9-9.0 fold, respectively. And, the RP4 plasmid transfer from Escherichia coli HB101 (E. coli HB101) to the bacteria in activated sludge increased obviously under the stress of phenolic compounds. Further investigation revealed that the PNP and PhOH at the concentration of 10-100 mg/L increased the production of reactive oxygen species and the permeability of cell membrane in the donor and recipient, which could be the causes of horizontal transfer of RP4 plasmid. In addition, it was also found that PNP, PAP and PhOH stress inhibit the expression of the global regulatory genes korB and trbA in the RP4 plasmid, and increase the expression level of the traF gene, thereby promoting the conjugative transfer of the RP4 plasmid. Taken together, these results improved our understanding of the horizontal transfer of ARGs under the stress of phenolic compounds and provided basic information for management of the systems that treat wastewater containing phenolic compounds.

Metagenomic profiling of antibiotic resistance and virulence removal: Activated sludge vs. algal wastewater treatment system

Conventional activated sludge-based (CAS) wastewater treatment plants are known to be a source of antibiotic resistance genes (ARGs) and virulence genes (VGs). As an alternative, a single-step mixotrophic algal wastewater treatment (A-WWT) system is proposed here to effectively reduce ARGs and VGs in the final effluent while meeting all the discharge standards. In this study, we applied the metagenomic profiling approach to compare the A-WWT system against the CAS system in terms of removal efficacy of ARG and VGs. A total of 111 ARG and 93 VG subtypes belonging to 10 antibiotic resistant classes and 19 virulence classes were detected in this study. Although the CAS system reduced the relative abundance of most classes of ARGs (7 of 10) and VGs (11 of 19), 3 ARG classes and 7 VG classes had increased abundances. On the other hand, the A-WWT system reduced the relative abundance of all classes of ARGs and VGs, and effectively eliminated most subtypes of ARGs and VGs. In the CAS system, the bacterial genera carrying ARGs and VGs was expanded, and the diversity index was increased greatly, suggesting the occurrence of horizontal gene transfer (HGT). In contrast, the A-WWT system narrowed down the potential host range and decreased their diversity substantially. Results of this study highlight the potential risk of ARGs and VGs in CAS system and demonstrate the feasibility of the algal-based system in removing ARGs and VGs.

Risks, characteristics, and control strategies of disinfection-residual-bacteria (DRB) from the perspective of microbial community structure

The epidemic of COVID-19 has aroused people's particular attention to biosafety. A growing number of disinfection products have been consumed during this period. However, the flaw of disinfection has not received enough attention, especially in water treatment processes. While cutting down the quantity of microorganisms, disinfection processes exert a considerable selection effect on bacteria and thus reshape the microbial community structure to a great extent, causing the problem of disinfection-residual-bacteria (DRB). These systematic and profound changes could lead to the shift in regrowth potential, bio fouling potential, as well as antibiotic resistance level and might cause a series of potential risks. In this review, we collected and summarized the data from the literature in recent 10 years about the microbial community structure shifting of natural water or wastewater in full-scale treatment plants caused by disinfection. Based on these data, typical DRB with the most reporting frequency after disinfection by chlorine-containing disinfectants, ozone disinfection, and ultraviolet disinfection were identified and summarized, which were the bacteria with a relative abundance of over 5% in the residual bacteria community and the bacteria with an increasing rate of relative abundance over 100% after disinfection. Furthermore, the phylogenic relationship and potential risks of these typical DRB were also analyzed. Twelve out of fifteen typical DRB genera contain pathogenic strains, and many were reported of great secretion ability. Pseudomonas and Acinetobacter possess multiple disinfection resistance and could be considered as model bacteria in future studies of disinfection. We also discussed the growth, secretion, and antibiotic resistance characteristics of DRB, as well as possible control strategies. The DRB phenomenon is not limited to water treatment but also exists in the air and solid disinfection processes, which need more attention and more profound research, especially in the period of COVID-19.

Combat of antimicrobial resistance in municipal wastewater treatment plant effluent via solar advanced oxidation processes: Achievements and perspectives

This review aims to gather main achievements and limitations associated to the application of solar photocatalytic processes with regard to the removal of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from municipal wastewater treatment plant effluent (MWWTPE). Solar photocatalytic processes were chosen considering the context of developing tropical countries. Among these processes, solar photo-Fenton has been proved effective for the elimination of ARB from MWWTPE at neutral pH in bench and pilot scale and also under continuous flow. Yet, ARG removal varies as according to the gene. Irradiation intensity and matrix composition play a key role on treatment efficiency for this purpose. The use of sulfate radical in modified solar photo-Fenton is still incipient for ARB and ARG removal. Also, investigations related to ARB resistance profile and horizontal gene transfer rates after solar photo-Fenton treatment must be further analyzed. Regarding solar heterogeneous photocatalysis, TiO₂ and TiO₂-composites applied in suspension are the most commonly investigated for the removal of ARB and ARGs. Irradiation intensity, temperature and catalyst dosage affect treatment efficiency. However, most studies were performed in synthetic solutions using reduced sample volumes. Extended exposition times and addition of H₂O₂ to the system (solar/TiO₂/H₂O₂) are required to prevent bacteria regrowth and ensure ARG abatement. In addition, enhancement of TiO₂ with graphene or (semi)metals improved ARB elimination. Differences concerning irradiation intensity, matrix composition, catalyst dosage, and model ARB and ARGs used in studies analyzed in this review hinder the comparison of photocatalysts synthesized by various research groups. Finally, future research should aim at evaluating the efficiency of solar photocatalytic processes in real matrices originated from sewage treatment systems applied in developing countries; determining indicators of antimicrobial resistance in MWWTPE; and investigating ARB mutation rate as well as the removal of cell-free ARGs present in suspension in MWWTPE.