Ozonation and UV(254)(nm) radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater. - Related Documents




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781801.0000Ozonation and UV(254)(nm) radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater. Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV(254nm) radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, bla(TEM), sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV(254)(nm) treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.201727072309
718310.9998Evaluation of five antibiotic resistance genes in wastewater treatment systems of swine farms by real-time PCR. Antibiotics are widely used in livestock for infection treatment and growth promotion. Wastes from animal husbandry are a potential environmental source of antibiotic-insensitive pathogens, and the removal efficiency of the resistance genotypes in current wastewater treatment plants (WWTPs) is unknown. In this study, quantitative PCR was used for evaluating antibiotic resistance genes in wastewater treatment processes. Six wastewater treatment plants in different swine farms were included in this study, and five antibiotic resistance genes (ARGs) were tested for each treatment procedure. All of the tested ARGs including tetA, tetW, sulI, sulII, and blaTEM genes were detected in six swine farms with considerable amounts. The results showed that antibiotic resistance is prevalent in livestock farming. The ARG levels were varied by wastewater treatment procedure, frequently with the highest level at anaerobic treatment tank and lowest in the activated sludge unit and the effluents. After normalizing the ARG levels to 16S rRNA gene copies, the results showed that ARGs in WWTP units fluctuated partly with the quantity of bacteria. Regardless of its importance in biodegradation, the anaerobic procedure may facilitate bacterial growth thus increasing the sustainability of the antibiotic resistance genotypes. After comparing the copy numbers in influx and efflux samples, the mean removal efficiency of ARGs ranged between 33.30 and 97.56%. The results suggested that treatments in the WWTP could partially reduce the spread of antibiotic-resistant bacteria, and additional procedures such as sedimentation may not critically affect the removal efficiency.201425064719
718520.9998Relationship between modification of activated sludge wastewater treatment and changes in antibiotic resistance of bacteria. Biological treatment processes at wastewater treatment plants (WWTPs), which are the most common methods of sewage treatment, could cause selective elimination and/or changes in the proportions of phenotypes/genotypes within bacterial populations in effluent. Therefore, WWTPs based on activated sludge used in sewage treatment constitute an important reservoir of enteric bacteria which harbour potentially transferable resistance genes. Together with treated wastewater, these microorganisms can penetrate the soil, surface water, rural groundwater supplies and drinking water. Because of this, the aim of this study was to determine the impact of various modification of sewage treatment (the conventional anaerobic/anoxic/oxic (A2/O) process, mechanical-biological (MB) system, sequencing batch reactors (SBR), mechanical-biological system with elevated removal of nutrients (MB-ERN)) on the amount of antibiotic resistant bacteria (ARB) (including E. coli) and antibiotic resistance genes (ARGs) in sewage flowing out of the 13 treatment plants using activated sludge technology. There were no significant differences in ARB and ARGs regardless of time of sampling and type of treated wastewater (p > 0.05). The highest percentage of reduction (up to 99.9%) in the amount of ARB and ARGs was observed in WWTPs with MB and MB-ERN systems. The lowest reduction was detected in WWTPs with SBR. A significant increase (p < 0.05) in the percentage of bacteria resistant to the new generation antibiotics (CTX and DOX) in total counts of microorganisms was observed in effluents (EFF) from WWTPs with A2/O system and with SBR. Among all ARGs analyzed, the highest prevalence of ARGs copies in EFF samples was observed for sul1, tet(A) and qepA, the lowest for bla(TEM) and bla(SHV). Although, the results of presented study demonstrate high efficiency of ARB and ARGs removal during the wastewater treatment processes, especially by WWTPs with MB and MB-ERN systems, EFF is still an important reservoir of ARGs which can be transferred to other microorganisms.201829791883
719430.9998Response of antibiotic resistance genes in constructed wetlands during treatment of livestock wastewater with different exogenous inducers: Antibiotic and antibiotic-resistant bacteria. This work aimed to study the behavior of antibiotic resistance genes (ARGs) in constructed wetlands with different exogenous inducers additions (oxytetracycline and its resistant bacteria) by high-throughput quantitative polymerase chain reaction. Results indicated that constructed wetlands have the potential to reduce ARGs relative abundances in wastewater, and the total ARGs removal efficiency could exceed 60%. ARGs profile in the effluent differed from that in the influent, and that did not directly reflect the export of dominant ARGs in wetland biofilms. Meanwhile, the highest levels of detected numbers and relative abundances of ARGs were 43 and 3.35 × 10(-1) for control system and 44 and 6.40 × 10(-1) for treatment system, respectively, which meant that ARGs generation in wetlands were inevitable, and antibiotic and antibiotic-resistant bacteria from wastewater could indeed promote ARGs abundance in the system. Compared to the single roles of inducers, their synergistic role had a more significant influence on ARGs relative abundance.202032652450
781940.9998Ozone treatment of conditioned wastewater selects antibiotic resistance genes, opportunistic bacteria, and induce strong population shifts. An ozone treatment system was investigated to analyze its impact on clinically relevant antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs). A concentration of 0.9±0.1g ozone per 1g DOC was used to treat conventional clarified wastewater. PCR, qPCR analyses, Illumina 16S Amplicon Sequencing, and PCR-DGGE revealed diverse patterns of resistances and susceptibilities of opportunistic bacteria and accumulations of some ARGs after ozone treatment. Molecular marker genes for enterococci indicated a high susceptibility to ozone. Although they were reduced by almost 99%, they were still present in the bacterial population after ozone treatment. In contrast to this, Pseudomonas aeruginosa displayed only minor changes in abundance after ozone treatment. This indicated different mechanisms of microorganisms to cope with the bactericidal effects of ozone. The investigated ARGs demonstrated an even more diverse pattern. After ozone treatment, the erythromycin resistance gene (ermB) was reduced by 2 orders of magnitude, but simultaneously, the abundance of two other clinically relevant ARGs increased within the surviving wastewater population (vanA, blaVIM). PCR-DGGE analysis and 16S-Amplicon-Sequencing confirmed a selection-like process in combination with a substantial diversity loss within the vital wastewater population after ozone treatment. Especially the PCR-DGGE results demonstrated the survival of GC-rich bacteria after ozone treatment.201627058129
781750.9998Effect of alkaline treatment on pathogens, bacterial community and antibiotic resistance genes in different sewage sludges for potential agriculture use. Alkaline treatment is widely used to reduce pathogens in sewage sludge in developing countries and guarantee that it is safe for use in agriculture. The aim of this study was to investigate the effect of alkaline treatment applied to waste-activated (WAS) and Upflow Anaerobic Sludge Blanket (UASB)-sludge on the bacterial community, pathogens (viable helminths eggs and Salmonella spp), and antibiotic resistance genes (ARG). The bacterial community structure was examined through denaturing gel gradient electrophoresis (DGGE), targeting 16S rRNA genes. Polymerase chain reaction (PCR) was applied to evaluate the presence of several ARGs. The conducted alkaline experiment consisted of adding hydrated lime (Ca(OH)(2)) to sewage sludges. Samples were taken before and after 2, 24, 48, and 72 hours of treatment. Alkaline treatment changed considerably the bacterial community structure and after 24 hours, shifts in bacterial profiles were more pronounced in the UASB sludge sample than in WAS. Some bacteria remained under extreme pH conditions (pH > 12), such as Azospira oryzae and Dechloromonas denitrificans in the WAS samples, and Geothrix and Geobacter in the UASB sludge samples. The values of pathogens and indicators in the sludge after 24 hours of alkaline treatment meet sanitary law regulations and thus the sludges could have the potential to agricultural distribution. It is important to highlight that ARG, which are not currently present in sanitary regulations, were detected in the sludge samples after the alkaline treatment, which could be a concern for human health.202030051768
731160.9998Sludge as a potential important source of antibiotic resistance genes in both the bacterial and bacteriophage fractions. The emergence and prevalence of antibiotic resistance genes (ARGs) in the environment is a serious global health concern. ARGs found in bacteria can become mobilized in bacteriophage particles in the environment. Sludge derived from secondary treatment in wastewater treatment plants (WWTPs) constitutes a concentrated pool of bacteria and phages that are removed during the treatment process. This study evaluates the prevalence of ARGs in the bacterial and phage fractions of anaerobic digested sludge; five ARGs (blaTEM, blaCTX-M, qnrA, qnrS, and sul1) are quantified by qPCR. Comparison between the wastewater and sludge revealed a shift in the prevalence of ARGs (blaTEM and sul1 became more prevalent in sludge), suggesting there is a change in the bacterial and phage populations from wastewater to those selected during the secondary treatment and the later anaerobic mesophilic digestion of the sludge. ARGs densities were higher in the bacterial than in the phage fraction, with high densities in both fractions; particularly for blaTEM and sul1 (5 and 8 log10 gene copies (GC)/g, respectively, in bacterial DNA; 5.5 and 4.4 log10 GC/g, respectively, in phage DNA). These results question the potential agricultural uses of treated sludge, as it could contribute to the spread of ARGs in the environment and have an impact on the bacterial communities of the receiving ecosystem.201424873655
718470.9998Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant. Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs' composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16 mJ/cm(2)) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly Acinetobacter and Streptococcus. Significant differences (p < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0-99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 10(7) copies/mL of intI1 gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.202235060061
718280.9998Effects of UV disinfection on phenotypes and genotypes of antibiotic-resistant bacteria in secondary effluent from a municipal wastewater treatment plant. To elucidate the effects of UV disinfection on antibiotic resistance in biologically-treated wastewater, we investigated the antibiotic resistance profiles, species of cultivable heterotrophic bacteria, and antibiotic-resistance genes (ARGs) in antibiotic-resistant bacteria before and after treatment. UV disinfection greatly changed the bacterial community structure and the antibiotic resistance in wastewater. The antibiotic resistance in wastewater samples was strongly associated with the bacterial community. The proportions of Gram-positive bacteria gradually increased with increasing UV fluence. The proportions of bacteria resistant to cephalexin, penicillin, and vancomycin all greatly decreased after UV treatment in both sampling events (July 2018 and January 2019), and those for bacteria resistant to ofloxacin, ciprofloxacin, and sulfadiazine increased, resulting from the alternative antibiotic resistance profiles among different genera. UV disinfection induced the selection of multi-antibiotic resistant (MAR) bacteria. For example, the MAR indices of Aeromonas, the dominant genus during the treatments, were significantly increased after UV irradiation (P < 0.05). The MAR index was also markedly increased (P < 0.05) at a fluence of 5 mJ/cm(2) in both events. In UV10 treatment, the bacterial community structure was greatly changed. The genera with relatively low MAR indices replaced that with high MAR indices, and became the dominant genera. As a result, the MAR indices of treated samples showed a decreased trend after 10 mJ/cm(2) UV irradiation. The detection frequencies of ARGs located on the chromosome varied mainly due to the evolution of the microbial community. The occurrence of ARGs (tetA, tetC, tetM, tetW, tetX, and sul1) located on plasmid DNA decreased after UV disinfection, and the average detection frequencies of tet and sul genes decreased by 15% and 6%, respectively (P < 0.05). Generally speaking, the effect of UV disinfection on the enrichment of antibiotic resistance is limited in this study, and horizontal gene transfer via the plasmids in surviving bacteria might be impaired due to the decreased abundance of ARGs on the plasmids.201930991178
725090.9998Effect of temperature on the fate of genes encoding tetracycline resistance and the integrase of class 1 integrons within anaerobic and aerobic digesters treating municipal wastewater solids. The objective of this research was to investigate the ability of anaerobic and aerobic digesters to reduce the quantity of antibiotic resistant bacteria in wastewater solids. Lab-scale digesters were operated at different temperatures (22 °C, 37 °C, 46 °C, and 55 °C) under both anaerobic and aerobic conditions and fed wastewater solids collected from a full-scale treatment facility. Quantitative PCR was used to track five genes encoding tetracycline resistance (tet(A), tet(L), tet(O), tet(W), and tet(X)) and the gene encoding the integrase (intI1) of class 1 integrons. Statistically significant reductions in the quantities of these genes occurred in the anaerobic reactors at 37 °C, 46 °C, and 55 °C, with the removal rates and removal efficiencies increasing as a function of temperature. The aerobic digesters, in contrast, were generally incapable of significantly decreasing gene quantities, although these digesters were operated at much shorter mean hydraulic residence times. This research suggests that high temperature anaerobic digestion of wastewater solids would be a suitable technology for eliminating various antibiotic resistance genes, an emerging pollutant of concern.201021058743
7310100.9998Metagenomic Analysis Reveals Changes in Bacterial Communities and Antibiotic Resistance Genes in an Eye Specialty Hospital and a General Hospital Before and After Wastewater Treatment. The spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in hospital wastewater poses a great threat to public health, and wastewater treatment plants (WWTPs) play an important role in reducing the levels of ARB and ARGs. In this study, high-throughput metagenomic sequencing was used to analyze the bacterial community composition and ARGs in two hospitals exposed to different antibiotic use conditions (an eye specialty hospital and a general hospital) before and after wastewater treatment. The results showed that there were various potential pathogenic bacteria in the hospital wastewater, and the abundance and diversity of the influent ARGs in the general hospital were higher than those in the eye hospital. The influent of the eye hospital was mainly composed of Thauera and Pseudomonas, and sul1 (sulfonamide) was the most abundant ARG. The influent of the general hospital contained mainly Aeromonas and Acinetobacter, and tet39 (tetracycline) was the most abundant ARG. Furthermore, co-occurrence network analysis showed that the main bacteria carrying ARGs in hospital wastewater varied with hospital type; the same bacteria in wastewater from different hospitals could carry different ARGs, and the same ARG could also be carried by different bacteria. The changes in the bacterial community and ARG abundance in the effluent from the two hospitals showed that the activated sludge treatment and the direct chlorination disinfection can effectively remove some bacteria and ARGs in wastewater but have limitations. The species diversity increased significantly after the activated sludge treatment, while the direct chlorination disinfection did not increase the diversity. The activated sludge treatment has a better effect on the elimination of ARGs than the direct chlorination disinfection. In summary, we investigated the differences in bacterial communities and ARGs in wastewater from two hospitals exposed to different antibiotic usage conditions, evaluated the effects of different wastewater treatment methods on the bacterial communities and ARGs in hospital wastewater, and recommended appropriate methods for certain clinical environments.202235663906
7305110.9998Inactivation 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 (O(3))-based advanced wastewater treatment systems (O(3), O(3)/H(2)O(2), O(3)/UV, and O(3)/UV/H(2)O(2)) for the treatment of antimicrobials, antimicrobial-resistant bacteria (AMRB), and antimicrobial resistance genes (AMRGs) in wastewater from medical facilities. Our results indicated that the O(3)-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 log(10)) during hospital wastewater treatment. The inactivation and/or removal performances of these pollutants through the O(3)/UV and O(3)/UV/H(2)O(2) treatments were significantly (P < 0.05) better than those in the O(3) and O(3)/H(2)O(2) treatments. Altered taxonomic diversity of microorganisms based on 16S rRNA gene sequencing following the O(3)-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.202437777130
7571120.9998Ancient Oriental Wisdom still Works: Removing ARGs in Drinking Water by Boiling as compared to Chlorination. Antibiotic resistance genes (ARGs) in municipal drinking water may not be effectively removed during centralized treatment. To reduce potential health risks, water disinfection at the point-of-use scale is warranted. This study investigated the performance of boiling, a prevalent household water disinfection means, in response to ARGs contamination. We found that boiling was more efficient in inactivating both Escherichia coli and environmental bacteria compared to chlorination and pasteurization. Boiling of environmental bacteria suspension removed a much broader spectrum of ARGs and mobile genetic elements (up to 141 genes) than chlorination (up to 13 genes), such better performance was largely attributed to a stronger inactivation of chlorine-tolerant bacteria including Acinetobacter and Bacillus. Accumulation of extracellular ARGs was found during low-temperature heating (≤ 80°C) and in the initial stage of chlorination (first 3 min when initial chlorine was 5 mg/L and first 12 min when initial chlorine was 1 mg/L). These extracellular ARGs as well as the intracellular ARGs got removed as the heating temperature increased or the chlorination time prolonged. Under the same treatment time (30 min), high-temperature heating (≥ 90.1°C) damaged the DNA structure more thoroughly than chlorination (5 mg/L). Taking into account the low transferability of ARGs after DNA melting, boiling may provide an effective point-of-use approach to attenuating bacterial ARGs in drinking water and is still worth promoting in the future.202234910990
7195130.9998Insight into effect of high-level cephalexin on fate and driver mechanism of antibiotics resistance genes in antibiotic wastewater treatment system. In the study, antibiotic resistance genes (ARGs) were examined in wastewater and sludge samples to explore the effect of cephalexin (CFX) on the spreading and removal of ARGs in the Expanded Granular Sludge Bed (EGSB) reactor treating antibiotics wastewater. The result showed that the addition of CFX in the wastewater affected the removal amount of β-lactam ARGs and other types ARGs. Besides, the addition of CFX in the wastewater had no obviously effect on total concentration of targeted ARGs in the sludge, but it was related to the accumulation of some typical ARGs. Based on gene cassette array libraries analysis, the diversity of gene cassettes carried by intI1 gene was increased by the addition of CFX in the wastewater. Furthermore, the co-occurrence patterns between ARGs and bacterial genus were also investigated. The results showed the CFX in the wastewater not only affected the number of potential host bacteria of ARGs, but also changed the types of potential host bacteria of ARGs. The correlation analysis of ARG in influent, effluent and sludge showed that, for blaCTX-M, sul2, qnrS and AmpC genes, their removal amount in EGSB reactor treating antibiotic wastewater system might be enhanced by reducing their concentration in the sludge.202032505047
7229140.9998Occurrence of antibiotic-resistant bacteria and resistance genes in the urban water cycle. This study investigates the antibiotic resistance fate in the urban water cycle, evaluating the dynamics of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in three different full-scale wastewater treatment plants (WWTPs) and two drinking water treatment plants (DWTPs) located in the same geographical area (North-West of Italy). ARB (tetracycline-, ampicillin-, and sulfonamide-resistant bacteria) were quantified by plate counting and the abundances of selected ARGs (i.e., tetA, bla(TEM), and sulII) and intI1 gene were measured using quantitative real-time PCR (qPCR). Higher concentrations of ARB and ARGs were observed in the WWTPs with respect to the DWTPs identifying the WWTP as hotspot for the spread of antibiotic resistances. Although a significant reduction of ARB and ARGs was observed in WWTPs and DWTPs after the treatment, none of the detected ARB or ARGs was completely removed in drinking water. The stability of the antibiotic-resistant rates between inlet and outlet associated with the reduction of relative ARG abundances underlined that both the treatments (WWTs and DWTs) did not apply any selective pressure. The overall results highlighted the importance to investigate the antibiotic resistance dynamics in aquatic ecosystems involved in urban water cycle integrating the information obtained by culture-dependent method with the culture-independent one and the need to monitor the presence of ARB and ARGs mainly in drinking water that represents a potential route of transmission to human.202336527555
7093150.9998Class 1 integrase, sulfonamide and tetracycline resistance genes in wastewater treatment plant and surface water. Wastewater treatment plants are considered hot spots for multiplication and dissemination of antibiotic-resistant bacteria and resistance genes. In this study, we determined the presence of class 1 integron integrase and genes conferring resistance to tetracyclines and sulfonamides in the genomes of culturable bacteria isolated from a wastewater treatment plant and the river that receives the treated wastewater. Moreover, using PCR-based metagenomic approach, we quantified intI1, tet and sul genes. Wastewater treatment caused the decrease in the total number of culturable heterotrophs and bacteria resistant to tetracycline and sulfonamides, along with the decrease in the number of intI1, sul and tet gene copies per ml, with significant reduction of tet(B). On the other hand, the treatment process increased both the frequency of tetracycline- and sulfonamide-resistant bacteria and intI1-positive strains, and the relative abundance of all quantified antibiotic resistance genes (ARGs) and intI1 gene; in the case of tet(A) and sul2 significantly. The discharge of treated wastewater increased the number of intI1, tet and sul genes in the receiving river water both in terms of copy number per ml and relative abundance. Hence, despite the reduction of the number of ARGs and ARBs, wastewater treatment selects for bacteria with ARGs in effluent.201626519797
7816160.9998Reduction of antibiotic resistance determinants in urban wastewater by ozone: Emphasis on the impact of wastewater matrix towards the inactivation kinetics, toxicity and bacterial regrowth. This study investigated the impact of bench-scale ozonation on the inactivation of total cultivable and antibiotic-resistant bacteria (faecal coliforms, Escherichia coli, Pseudomonas aeruginosa, Enterococcus spp., and total heterotrophs), and the reduction of gene markers (16S rRNA and intl1) and antibiotic resistance genes (qacEΔ1, sul1, aadA1 and dfrA1) indigenously present in wastewater effluents treated by membrane bioreactor (MBR) or conventional activated sludge (CAS). The Chick-Watson model-predicted ozone exposure (CT) requirements, showed that higher CT values were needed for CAS- than MBR-treated effluents to achieve a 3-log reduction of each microbial group, i.e., ~30 and 10 gO(3) min gDOC(-1) respectively. Ozonation was efficient in inactivating the examined antibiotic-resistant bacteria, and no bacterial regrowth was observed after 72 h. The genes abundance decreased significantly by ozone, but an increase in their abundance was detected 72 h after storage of the treated samples. A very low removal of DOC was achieved and at the same time phyto- and eco-toxicity increased after the ozonation treatment in both wastewater matrices. The gene abundance, regrowth and toxicity results of this study may be of high environmental significance for comprehensive evaluation of ozone and may guide future studies in assessing these parameters for other oxidants/disinfectants.202134329111
7605170.9998Inactivation of antibiotic resistant bacteria and their resistance genes in sewage by applying pulsed electric fields. We evaluated the suitability of pulsed electric field (PEF) technology as a new disinfection option in the sewage treatment plants (STPs) that can inactivate antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). It was shown that PEF applied disinfection could inactivate not only vancomycin-resistant enterococci (VRE), but also vanA resistance gene. Cultivable VRE could be effectively inactivated by PEF applied disinfection, and were reduced to below the detection limit (log reduction value of VRE > 5 log). Although the vanA also showed a reduction of more than 4 log, it remained in the order of 10(5) copies/mL, suggesting that ARGs are more difficult to be inactivated than ARB in PEF applied disinfection. Among parameters in each applying condition verified in this study, the initial voltage was found to be the most important for inactivation of ARB and ARGs. Furthermore, frequency was a parameter that affects the increase or decrease of the duration time, and it was suggested that the treatment time could be shortened by increasing the frequency. Our results strongly suggested that PEF applied disinfection may be a new disinfection technology option for STPs that contributes to the control of ARB and ARGs contamination in the aquatic environments.202234879573
7021180.9998Metagenomic insights into dissemination of antibiotic resistance across bacterial genera in wastewater treatment. The aim of this study was to evaluate the impacts of conventional wastewater treatment processes including secondary treatment and chlorination on the removal of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB), and to assess the association of ARGs with their potential hosts in each treatment process. The results showed chlorination with subinhibitory concentration (<8 mg/L) resulted in an increased ARB number in the disinfection effluent. qPCR analysis indicated secondary treatment increased relative abundance of ARGs in remaining bacteria whereas disinfection reduced the relative abundance of those genes effectively. Metagenomic analysis revealed a significant shift of dominating bacterial genera harboring ARGs. Along the treatment train, 48, 95 and 80 genera were identified to be the ARG carriers in primary effluent, secondary effluent, and disinfection effluent, respectively. It was also found that secondary treatment increased the diversity of potential ARG hosts while both secondary treatment and chlorination broadened the host range of some ARGs at the genus level, which may be attributed to the spread of antibiotic resistance across bacterial genera through horizontal transfer. This study highlights the growing concerns that wastewater treatment plants (WWTPs) may disseminate ARGs by associating this effect to specific treatment stages and by correlating ARGs with their bacterial hosts.202133453487
7022190.9998Fate of antibiotics, antibiotic-resistant bacteria, and cell-free antibiotic-resistant genes in full-scale membrane bioreactor wastewater treatment plants. The removal of antibiotics, antibiotic-resistant bacteria (ARB), and cell-free antibiotic-resistant genes (ARGs) and the microbial community of ARB were investigated in detail to understand their fate and provide valuable information on the feasibility of full-scale membrane bioreactor (MBR). The potential risks of cell-free ARGs to the receiving environment were discovered. High influent antibiotic concentration could inhibit the microbial activity of MBR sludge, whereas good antibiotic removal could be maintained because of relatively long solid retention time and high biomass retention. Approximately 61.8%-77.5% of the total antibiotics were degraded, and 22.5%-38.2% of the total antibiotics were adsorbed by MBR sludge on average. The individual antibiotic removal presented intense discrepancy because of the chemical construction and distribution coefficient of antibiotics. Aeromonas exhibited specific antibiotic resistance to ampicillin and erythromycin, Escherichia became the predominant genera in kanamycin-ARB and tetracycline-ARB, and Klebsiella and Bacteroides were the particular genera that exhibited distinct antibiotic resistance to ciprofloxacin. A significant correlation was found between cell-free ARG abundance and ARB content, and relatively high effluent cell-free ARG abundance facilitated the proliferation and transmission of ARB. The impacts of the receiving environment to eliminate the ecological risks and severe threats to human health should be investigated because of the low decay ratio and long-term persistence of cell-free ARGs.202031986335