Effect of tetracycline on nitrogen removal in Moving Bed Biofilm Reactor (MBBR) System. - Related Documents




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804401.0000Effect of tetracycline on nitrogen removal in Moving Bed Biofilm Reactor (MBBR) System. The effect of tetracycline (TC) on nitrogen removal in wastewater treatment plants has become a new problem. This study investigated the effects of TC on nitrogen removal using a Moving Bed Biofilm Reactor system. The results showed that there was no significant effect on nitrogen removal performance when the concentration of TC was 5 mg/L, and that the total nitrogen (TN) removal efficiency could reach 75-77%. However, when the concentration of TC increased to 10 mg/L, the denitrification performance was affected and the TN removal efficiency decreased to 58%. The abundance of denitrifying bacteria such as those in the genus Thauera decreased, and TC-resistant bacteria gradually became dominant. At a TC concentration of 10 mg/L, there were also increases and decreases, respectively, in the abundance of resistance and denitrification functional genes. The inhibitory effect of TC on denitrification was achieved mainly by the inhibition of nitrite-reducing bacteria.202235007308
804310.9998Effect of tetracycline on bio-electrochemically assisted anaerobic methanogenic systems: Process performance, microbial community structure, and functional genes. Bio-electrochemically assisted anaerobic methanogenic systems (An-BES) are highly effective in wastewater treatment for methane production and degradation of toxic compounds. However, information on the treatment of antibiotic-bearing wastewater in An-BES is still very limited. This study therefore investigated the effect of tetracycline (TC) on the performance, microbial community, as well as functional and antibiotic resistance genes of An-BES. TC at 1 and 5 mg/L inhibited methane production by less than 4.8% compared to the TC-free control. At 10 mg/L TC, application of 0.5 and 1.0 V decreased methane production by 14 and 9.6%, respectively. Under the effect of 1-10 mg/L TC, application of 1.0 V resulted in a decrease of current from 42.3 to 2.8 mA. TC was mainly removed by adsorption; its removal extent increased by 19.5 and 32.9% with application of 0.5 and 1.0 V, respectively. At 1.0 V, current output was not recovered with the addition of granular activated carbon, which completely removed TC by adsorption. Metagenomic analysis showed that propionate oxidizing bacteria and methanogens were more abundant in electrode biofilms than in suspended culture. Antibiotic resistance genes (ARGs) were less abundant in biofilms than in suspended culture, regardless of whether voltage was applied or not. Application of 1.0 V resulted in the enrichment of Geobacter in the anode and Methanobacterium in the cathode. TC inhibited exoelectrogens, propionate oxidizing bacteria, and the methylmalonyl CoA pathway, leading to a decrease of current output, COD consumption, and methane production. These findings deepen our understanding of the inhibitory effect of TC in An-BES towards efficient bioenergy recovery from antibiotic-bearing wastewater, as well as the response of functional microorganisms to TC in such systems.202235533856
791520.9998Deciphering antibiotic resistance genes and microbial community of anammox consortia under sulfadiazine and chlortetracycline stress. The responses of anammox consortia to typical antibiotics sulfadiazine (SDZ) and chlortetracycline (CTC) were evaluated on the aspects of general performance, microbial activity, diversity and abundance of antibiotic resistance genes (ARGs), and microbial host of ARGs in anammox system. Results showed the anammox consortia had a stable performance and great resistance to 10 mg/L of SDZ, while 1 mg/L of CTC induced an unrecoverable inhibitory influence on nitrogen removal performance and anammox activity without any special treatment. The absolute abundances of anammox functional genes (nirS, hzsA and hdh) were stimulated by the acclimation to SDZ stress, however, they were much lower than the initial levels under CTC stress. In anammox consortia, ARGs comprised 18 types (94 subtypes) derived from over 20 genera. Strikingly, the anammox bacteria (AnAOB) "Ca. Brocadia" occupied 46.81% of the SDZ resistance genes (sul1 and sul2) and 38.63% of CTC resistance genes (tetX, tetG and rpsJ), and thus were identified as the dominant antibiotic resistance bacteria (ARB). Therefore, harboring the corresponding ARGs by AnAOB could be the primary protective mechanism to interpret the resistance of anammox consortia to antibiotics stress. Meanwhile, co-occurring of ARGs in anammox consortia suggested the synergistic cooperation of different ARGs could be an essential strategy to alleviate the SDZ and CTC stress. The present study proposed a new interpretation of possible mechanism that cause antibiotic resistance of anammox consortia.202235259594
791330.9998Response of the partial denitrification coupled with anaerobic ammonia oxidation system to disinfectant residues stress. The extensive use of disinfectants, especially NaClO, has resulted in chlorine disinfectant residues entering and impairing the biological treatment system. This study combined with long-term stress and transient shock of chlorine residues to comprehensively evaluate the variations of nitrogen removal performance, microbial community and antibiotic resistance genes composition in the PD/A system. The results showed that low concentration NaClO had no obvious harm to the system, but high concentration (>1 mg/L) NaClO would destroy the nitrogen removal performance of PD/A system. Interestingly, microorganisms in biofilm were more resistant to chlorine residues than that in sludge. Anaerobic ammonia oxidizing bacteria suffered more harm than denitrifying microorganisms, and chlorine residues mainly inhibited the process of converting N(2)H(4) to N(2) in anammox reaction. In addition, this study found that sludge showed a more significant increase in ARGs abundance and risk than biofilm. Moreover, risk assessments indicated that chlorine residues increased the risk of ARGs in PD/A systems.202540010223
790240.9998Determination of the lower limits of antibiotic biodegradation and the fate of antibiotic resistant genes in activated sludge: Both nitrifying bacteria and heterotrophic bacteria matter. Antibiotics can be biodegraded in activated sludge via co-metabolism and metabolism. In this study, we investigated the biodegradation pathways of sulfamethoxazole (SMX) and antibiotic resistant genes' (ARGs) fate in different autotrophic and heterotrophic microorganisms, by employing aerobic sludge, mixed sludge, and nitrifying sludge. A threshold concentration of SMX activating the degradation pathways in the initial stage of antibiotics degradation was found and proved in different activated sludge systems. Heterotrophic bacteria played an important role in SMX biodegradation. However, ammonia-oxidizing bacteria (AOB) had a faster metabolic rate, which was about 15 times higher than heterotrophic bacteria, contributing much to SMX removal via co-metabolism. As SMX concentration increases, the amoA gene and AOB relative abundance decreased in aerobic sludge due to the enrichment of functional heterotrophic bacteria, while it increased in nitrifying sludge. Microbial community analysis showed that functional bacteria which possess the capacity of SMX removal and antibiotic resistance were selected by SMX pressure. Potential ARGs hosts could increase their resistance to the biotoxicity of SMX and maintain system performance. These findings are of practical significance to guide antibiotic biodegradation and ARGs control in wastewater treatment plants.202234799165
792350.9998Effect of ultrasonic and ozone pretreatment on the fate of enteric indicator bacteria and antibiotic resistance genes, and anaerobic digestion of dairy wastewater. In this study, the effect of ultrasound (US), ozone and US combined with ozone (US/ozone) pretreatments on the fate of enteric indicator bacteria and antibiotic resistance genes (ARGs), and anaerobic digestion (AD) of dairy wastewater was investigated. The pretreatment conditions included US power 200 W, ozone concentration 4.2 mg O(3)/L, and pretreatment time 0-30 min. The results showed that US/ozone pretreatment was effective in the inactivation of enteric indicator bacteria. Total coliforms and enterococci were reduced by 99% and 92% after 30 min US/ozone pretreatment. Pretreatments could not decrease ARGs in absolute concentration, but could decrease ARGs in relative abundance. In the subsequent AD process, methane production increased more than 10% with 20 min ozone or 20 min US/ozone pretreatments. Pretreatment-AD together obviously inhibited the enrichment of ARGs in relative abundance. This study provided a pretreatment way to enhance methane production and to prevent the enrichment of ARGs.202133186838
791460.9998Response of partial nitrification sludge to the single and combined stress of CuO nanoparticles and sulfamethoxazole antibiotic on microbial activity, community and resistance genes. Considering the inevitable release of antibiotics and nanoparticles (NPs) into the nitrogen containing wastewater, the combined impact of CuO NPs and sulfamethoxazole (SMX) antibiotic on partial nitrification (PN) process was investigated in four identical reactors. Results showed that the bioactivity of the aerobic ammonia-oxidizing bacteria (AOB) decreased by half after they were exposed to the combination of CuO NPs and SMX for short-term; however, there was no obvious variation in the bioactivity of AOB when they were exposed to either CuO NPs or SMX. During long-term exposure, the ammonia removal efficiency (ARE) of CuO NPs improved whereas that of SMX decreased, while the combination of CuO NPs and SMX significantly decreased ARE from 62.9% (in control) to 38.2% and had an unsatisfactory self-recovery performance. The combination of CuO NPs and SMX significantly changed the composition of microbial community, decreased the abundance of AOB, and significantly suppressed PN process. Reegarding the resistance genes, the CuO NPs-SMX combination did not improve the expression of copA, cusA, sul1 and sul2; however, it significantly induced the expression of sul3 and sulA.202032050397
804170.9998Insights into the microalgae-bacteria consortia treating swine wastewater: Symbiotic mechanism and resistance genes analysis. This study investigated the effects of microalgae-bacteria consortia (MBC) (Chlorella pyrenoidosa-activated sludge (AS)) treating swine wastewater with low C/N ratios. After co-culture, the removal rates of NH(4)(+)-N and PO(4)(3-)-P increased by 53.84% and 43.52%. Furthermore, the sulfamethoxazole (SMX) degradation rates in MBC were slightly higher than in the activated sludge process. Interestingly, the absolute abundance of antibiotic resistance genes (ARGs) in effluent from MBC is relatively less than in the AS process. C. pyrenoidosa has a negative zeta potential that allows bacteria to adhere to its surface. The concentrations of carbohydrates and proteins in extracellular polymeric substance (EPS) of MBC dramatically increased compared with the AS process. At the phylum level, Proteobacteria, Bacteroidota, and Cyanobacteria were the main bacteria, while Ascomycota and Basidiomycota were the primary fungi in MBC. Overall, those findings lead to a better understanding of the swine wastewater containing antibiotic treatment by MBC.202235217162
795980.9998Evolution of microbial community and antibiotic resistance genes in anammox process stressed by oxytetracycline and copper. The individual and combined impacts of copper ion (Cu(2+)) and oxytetracycline (OTC) on anaerobic ammonium oxidation (anammox) performance and its self-recovery process were examined. Experimental results showed that the anammox performance and activity of anammox bacteria were inhibited by 1.0 mg L(-1) OTC, Cu(2+) and OTC + Cu(2+), and both single and combined inhibitions were reversible. The abundance of functional genes and parts of antibiotic resistance genes (ARGs) were positively related to the dominant bacterium Ca. Kuenenia, implying that the recovery of the performance was associated with the progressive induction of potentially resistant species after inhibition. The above outcomes illustrated that anammox bacteria were stressed by metals and antibiotics, but they still could remove nitrogen at a rate higher than 20.6 ± 0.8 kg N m(-3) d(-1), providing guidance for engineering applications of anammox processes.202132949830
804290.9998Algal-bacterial consortium mediated system offers effective removal of nitrogen nutrients and antibiotic resistance genes. The sulfonamide antibiotic resistance genes (ARGs) especially sul1 was identified as the dominant in eutrophic water. The performance of Chlorella vulgaris-B. licheniformis consortium toward sul1 removal, total nitrogen (TN) removal, and the mechanism of sul1 removal was investigated. The removal efficiency of exogenous ARGs plasmids carrying sul1 reached (97.2 ± 2.3)%. The TN removal rate reached (98.5 ± 1.2)%. The enhancements of carbon metabolism, nitrogen metabolism, aminoacyl-tRNA biosynthesis, and glycoproteins had significant influences on sul1 and TN removals, under the premise of normal growth of algae and bacteria. The quantitative polymerase chain reaction (qPCR) results suggested that the absolute abundances of sul1 were low in algal-bacterial systems (0 gene copies/mL) compared with individual systems ((1 × 10(6) ± 15) gene copies/mL). The duplication of sul1 was inhibited in algal cells and bacterial cells. The algal-bacterial consortium seems to be a promising technology for wastewater treatment with a potential to overcome the eutrophication and ARGs challenges.202236049708
8093100.9997Acidic conditions enhance the removal of sulfonamide antibiotics and antibiotic resistance determinants in swine manure. Manure pH may vary depending on its inherent composition or additive contents. However, the effect of pH on the fate of antibiotics and antibiotic resistance determinants in manure remains unclear. This work demonstrated that pH adjustment promoted the removal of different sulfonamide antibiotics (SAs) within swine manure under incubation conditions, which increased from 26-60.8% to 75.0-86.0% by adjusting the initial pH from neutral (7.4) to acidic (5.4-4.8). Acidification was also demonstrated to inhibit the accumulation of antibiotic resistance genes in manure during incubation. Acidified manure contained both lower absolute and relative abundances of sul1 and sul2 than those at a neutral pH like 7.4. Further investigation indicated that acidification promoted the reduction of sul genes in manure by restricting sulfonamide-resistant bacteria (SRB) proliferation and inhibiting IntI1 accumulation. Furthermore, pH adjustment significantly influenced the composition of the manure bacterial community after incubation, which increased Firmicutes and decreased Proteobacteria. Close relationships were observed between pH-induced enrichment of the Firmicutes bacterial phylum, enhanced SAs degradation, and the fates of antibiotic resistance determinants. Overall, lowering the pH of manure promotes the degradation of SAs, decreases sul genes and SRB, and inhibits horizontal sul gene transfer, which could be a simple yet highly-effective manure management option to reduce antibiotic resistance.202032302890
7901110.9997Responses of antibiotic resistance genes and microbial community in the microalgae-bacteria system under sulfadiazine: Mechanisms and implications. Microalgae-bacteria system is an emerging alternative for sustainable wastewater treatment. Exploring the structure and diversity of microbial community in microalgae-bacteria system under sulfadiazine stress can contribute to the understanding of the sulfadiazine behavior in environments. Furthermore, as important carriers of antibiotic resistance genes (ARGs), microalgae can influence the profiles of ARGs either directly or indirectly through the secretion of metabolites. However, the effects of sulfadiazine on ARGs dissemination of microalgae-bacteria systems remain underreported. Herein, the impacts of sulfadiazine (1 mg/L) on the structural diversity and metabolic activity of microorganisms were examined in microalgae-bacteria systems. Results showed that microalgae-bacteria system could remove NH(4)(+)-N better (about 72.3 %) than activated sludge system, and hydrolysis was the first step in sulfadiazine degradation. A high level of intI1 (5.7 × 10(4) copies/mL) was detected in the initial media of the microalgae-bacteria system. Microalgae could hamper the rate of horizontal gene transfer activation. Compared with activated sludge system, the abundance of sul genes (sul1, sul2, sul3, and sulA) was significantly lowered after treating with microalgae-bacteria system. Additionally, the number of proteins and the sum of polysaccharides in the extracellular polymeric substances of the activated sludge system were lower than those of the microalgae-bacteria system. Microalgae can alter microbial communities. The genus Rozellomycota predominated all samples. Fungi with relatively high abundance increased in the microalgae-bacteria system, including Dipodascaceae, Rhodotorula, and Geotrichum. These results offer valuable insights into the application processes involving microalgae-bacteria system.202540602895
8092120.9997Effect of pH on the mitigation of extracellular/intracellular antibiotic resistance genes and antibiotic resistance pathogenic bacteria during anaerobic fermentation of swine manure. Effects of various initial pH values (i.e., 3, 5, 7, 11) during anaerobic fermentation of swine manure on intracellular and extracellular antibiotic resistance genes (iARGs and eARGs) and ARG-carrying potential microbial hosts were investigated. The abundance of almost all iARGs and eARGs decreased by 0.1-1.7 logs at pH 3 and pH 5. The abundance of only three iARGs and eARGs decreased by 0.1-0.9 logs at pH 7 and pH 11. Under acidic initial fermentation conditions (pH 3 and pH 5), the ARG removal effect was more pronounced. Acidic conditions (pH 3 and pH 5) significantly reduced the diversity and abundance of the microbial community, thereby eliminating many potential ARG hosts and antibiotic-resistant pathogenic bacteria (ARPB). Therefore, the study results contribute to the investigation of the effects of swine manure anaerobic fermentation on the removal and risk of contamination of ARGs and ARPB.202336746211
7543130.9997Aerobic granular sludge for swine wastewater treatment: Implications for antibiotic and antibiotic resistance gene elimination. Swine wastewater (SW) contains high levels of traditional pollutants, antibiotics, and antibiotic resistance genes (ARGs), necessitating effective elimination. Two parallel aerobic granular sludge (AGS) reactors, R(1) and R(2), were constructed and optimized for treating SW from two pig farms, identified as SW(1) and SW(2). R(2) showed higher antibiotic removal efficiency, particularly in the removal of sulfonamides, while fluoroquinolones tended to adsorb onto the sludge. Process optimization by introducing an additional anoxic phase enhanced denitrification and reduced effluent ARG levels, also aiding in the improved removal of fluoroquinolones. The nitrite-oxidizing bacteria (NOB) Nitrospira accumulated after the treatment process, reaching 12.8 % in R(1) and 14.1 % in R(2), respectively. Mantel's test revealed that pH, NH(4)(+)-N, and Mg significantly affected ARGs and microbial community. Sulfadiazine and sulfamethazine were found to significantly impact ARGs and the microbial communities. This study provides innovative insights into the application of AGS for the treatment of real SW.202439153702
7549140.9997Fate of antibiotic resistance genes during sludge anaerobic fermentation: Roles of different sludge pretreatment. Excess sludge, the primary by-product of wastewater treatment plants, is the source and sink of antibiotic resistance genes (ARGs). Sludge pretreatments are an indispensable pathway to improve the resource recovery and harmfulness for anaerobic digestion sludge. However, fewer studies have compared the effects of different pretreatment technologies on the distribution of ARGs during anaerobic sludge digestion. Here, this study established seven anaerobic digesters, and four typical ARGs and one integrase gene of class 1 integron (intI1) regarded as the representative mobile genetic elements (MGEs) were examined during the whole anaerobic digestion process. It was found anaerobic digestion could effectively remove ARGs with about 70.86% removal rate of total ARGs. Among these pretreatments, the reduce efficiency of ARGs was the highest in 50 °C pretreatment, followed by oxidant, and the last was acid-alkaline. The microbial community analysis demonstrated the microbial community structure, including ARGs hosts and antibiotic resistant bacteria, was significantly changed and influenced by high temperature pretreatment. In addition, high temperature and K(2)S(2)O(8) observably decrease the level of ROS production. Macro transcriptome analysis indicated that sludge pretreatment, except for 50 °C pretreatment, up-regulated the genes relevant to lyases and transferase, but down-regulated the genes responsible for peroxidase, antioxidant enzymes and T4SS gene. This study emphasized and compared the different sludge pretreatments on the fate of ARGs in anaerobic sludge, and highlighted concerns regarding the environmental and health risks to our society.202439393457
8084150.9997Metagenomic insights into effects of carbon/nitrogen ratio on microbial community and antibiotic resistance in moving bed biofilm reactor. This study investigated the effects of carbon/nitrogen (C/N) ratio on microbial community in moving bed biofilm reactor (MBBR) using metagenomic analysis, and the dynamic changes of relevant antibiotic resistance genes (ARGs) were also analyzed. The results showed that under low C/N ratio, MBBR exhibited average removal rates of 98.41 % for ammonia nitrogen and 75.79 % for total nitrogen. Metagenomic analysis showed low C/N ratio altered the structure of biofilm and water microbiota, resulting in the detachment of bacteria such as Actinobacteria from biofilm into water. Furthermore, sulfamethazine (SMZ)-resistant bacteria and related ARGs were released into water under low C/N ratio, which lead to the increase of SMZ resistance rate to 90%. Moreover, most dominant genera are potential hosts for both nitrogen cycle related genes and ARGs. Specifically, Nitrosomonas that carried gene sul2 might be released from biofilm into water. These findings implied the risks of antibiotic resistance dissemination in MBBR under low C/N ratio.202438901747
7916160.9997Effects of combined antibiotics on nitrification, bacteria and antibiotic resistance genes in activated sludge: Insights from legacy effect of antibiotics. The effect of combined antibiotics exposure on nitrogen removal, microbial community assembly and proliferation of antibiotics resistance genes (ARGs) is a hotspot in activated sludge system. However, it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics. In this study, the effects of combined sulfamethoxazole (SMX) and trimethoprim (TMP) pollution on activated sludge under legacy of SMX or TMP stress with different doses (0.005-30 mg/L) were investigated to clarify antibiotic legacy effects. Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal (∼70%) occurred. Based on the full-scale classification, the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa (CAT) and conditionally rare or abundant taxa (CRAT). Rare taxa (RT) were the keystone taxa in the microbial network, and the responses of hub genera were also affected by the legacy of antibiotic stress. Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria (Pseudomonas, Thaurea and Hydrogenophaga) were enriched under legacy of high dose, as were the key denitrifying genes (napA, nirK and norB). Furthermore, the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect. While, some shared hosts (eg., Citrobacter) and hub ARGs (eg., mdtD, mdtE and acrD) were identified. Overall, antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.202337225384
7918170.9997Robustness of the partial nitrification-anammox system exposing to triclosan wastewater: Stress relieved by extracellular polymeric substances and resistance genes. The partial nitrification-anammox (PN/A) process is a promising method for the treatment of municipal wastewater. It is necessary to clarify the responses of PN/A system to antimicrobial agent triclosan (TCS) widely existed in the influent of wastewater treatment plants. In this study, it was found that PN/A system was robust to cope with 0.5 mg/L TCS. Specifically, the control reactor reached 80% total nitrogen removal efficiency (TNRE) on day 107, while the reactor feeding with 0.5 mg/L TCS reached the same TNRE on day 84. The results of the activity test, high-throughput sequencing and DNA-based stable isotope probing showed that 0.5 mg/L TCS did not impede the performance of ammonia oxidizing archaea, ammonia oxidizing bacteria (Nitrosomonas) and anammox bacteria (Candidatus Brocadia and Ca. Kuenenia), but significant inhibited the nitrite oxidizing bacteria (Nitrospira and Ca. Nitrotoga) and denitrifying bacteria. The influent TCS led to the increase of EPS content and enrichment of four resistance genes (RGs) (intI1, sul1, mexB, and tnpA), which might be two principal mechanisms by which PN/A can resist TCS. In addition, functional bacteria carrying multiple RGs also contributed to the maintenance of PN/A system function. These findings improved the understandings of antimicrobial effects on the PN/A system.202234954146
7960180.9997Diversity evolution of functional bacteria and resistance genes (CzcA) in aerobic activated sludge under Cd(II) stress. An activated sludge sequencing batch reactor (SBR) was used to treat divalent cadmium (Cd(II)) wastewater for 60 d to investigate the overall treatment performance, evolution of the bacterial community, and abundance of the Cd(II) resistance gene CzcA and shifts in its potential host bacteria. During stable operation with a Cd(II) concentration of 20 mg/L, the average removal efficiencies of Cd(II) and chemical oxygen demand (COD) were more than 85% and that of total phosphorus was greater than 70%, while the total nitrogen (TN) was only about 45%. The protein (PN) content in the extracellular polymeric substances (EPS) increased significantly after Cd(II) addition, while polysaccharides displayed a decreasing trend (p < 0.05), indicating that EPS prefer to release PN to adsorb Cd(II) and protect bacteria from damage. Three-dimensional fluorescence spectral analysis showed that fulvic acid-like substances were the most abundant chemical components of EPS. The addition of Cd(II) adversely affected most denitrifying bacteria (p < 0.05), which is consistent with the low TN removal. In addition, quantitative polymerase chain reaction analysis revealed that CzcA gene abundance decreased as the Cd(II) concentration increased, possibly because expression of the CzcA gene was inhibited by Cd(II) stress. The majority of CzcA gene sequences were carried by Pseudomonas, making it the dominant genus among Cd(II)-resistant bacteria.201931514000
8082190.9997Deciphering the toxic effects of antibiotics on denitrification: Process performance, microbial community and antibiotic resistance genes. The extensive application of antibiotics, and the occurrence and spread of antibiotic resistance genes (ARGs) shade health risks to human and animal. The long-term effects of sulfamethoxazole (SMX) and tetracycline (TC) on denitrification process were evaluated in this study, with the focus on nitrogen removal performance, microbial community and ARGs. Results showed that low-concentration SMX and TC (<0.2 mg L(-1)) initially caused a deterioration in nitrogen removal performance, while higher concentrations (0.4-20 mg L(-1)) of both antibiotics had no further inhibitory influences. The abundances of ARGs in both systems generally increased during the whole period, and most of them had significant correlations with intI1, especially efflux-pump genes. Castellaniella, which was the dominant genus under antibiotic pressure, might be potential resistant bacteria. These findings provide an insight into the toxic effects of different antibiotics on denitrification process, and guides future efforts to control antibiotics pollution in ecosystems.202032250829