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Drug resistance poses a high risk to human health. Extensive use of non-antibiotic drugs contributes to antibiotic resistance genes (ARGs) transfer. However, how they affect the spread of broad-host plasmids in complex biological systems remains unknown. This study investigated the effect of metoprolol on the transfer frequency and host range of ARGs in both intrageneric and intergeneric pure culture systems, as well as in anammox microbiome. The results showed that environmental concentrations of metoprolol significantly promoted the intrageneric and intergeneric conjugative transfer. Initially, metoprolol induced excessive oxidative stress, resulting in high cell membrane permeability and bacterial SOS response. Meanwhile, more pili formation increased the adhesion and contact between bacteria, and the abundance of conjugation-related genes also increased significantly. Activation of the electron transport chain provided more ATP for this energy-consuming process. The underlying mechanism was further verified in the complex anammox conjugative system. Metoprolol induced the enrichment of ARGs and mobile genetic elements. The enhanced bacterial interaction and energy generation facilitated the high conjugative transfer frequency of ARGs. In addition, plasmid-borne ARGs tended to transfer to opportunistic pathogens. This work raises public concerns about the health and ecological risks of non-antibiotic drugs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The widespread use of surfactants raise challenges to biological wastewater treatment. Anaerobic ammonium oxidation (anammox) process has the potential to treat wastewater containing anionic surfactants, but the response of anammox consortia at the molecular level under long-term exposure is unclear. Using high-throughput sequencing and gene quantification, combined with molecular docking, the effect of sodium dodecyl sulfonate (SDS) on anammox consortia were investigated. Levels of reactive oxygen species (ROS) might be lower than the threshold of oxidative damage, while the increase of lactate dehydrogenase (LDH) represented the cell membrane damage. Decreased abundance of functional genes (hdh, hzsA and nirS) indicated the decrease of the anammox bacterial abundance. Trace amounts of N-acyl homoserine lactone (AHL, C6-HSL, C8-HSL and C12-HSL) contained in influent could induce endogenous quorum sensing (QS), which could regulate the correlation between functional bacteria to optimize the microbial community and strengthen the resistance of anammox consortia to SDS. In addition, the proliferation of disinfectant resistance genes might increase the environmental pathogenicity of sewage discharge. This work highlights the potential response mechanism of anammox consortium to surfactants and provides a universal microbial-friendly bioenhancement strategy based on QS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The inevitable introduction of biodegradable carbon sources (such as monosaccharides and volatile fatty acids) originating from pretreatment units might affect the performance of the mainstream anaerobic ammonium oxidation (anammox) process. Two model carbon sources (glucose and acetate) were selected to investigate their effects on granule-based anammox systems under mainstream conditions (70 mg total nitrogen (TN) L -1 , 15 °C). At a nitrogen loading rate of 2.87 ± 0.80 kg N m -3 d -1 , a satisfactory effluent quality (TN < 10 mg L -1 ) was achieved in the presence of glucose or acetate at a chemical oxygen demand (COD/N) ratio of 0.5. The contribution of anammox to nitrogen removal decreased with increasing COD/N ratio to 1.0 because the expression of anammox functional genes was inhibited, whereas the expression of denitrifying functional genes was promoted. However, the nitrogen removal efficiency of the two considered reactors was maintained above 80 %. Self-stratification of the microbial community along the reactor height facilitated a functional balance through the retention of anammox bacteria in granules but resulted in washout of denitrifying bacteria in flocs under a high-flow pattern. These findings highlighted the advantages of granule-based systems in the mainstream anammox process due to their inherent biomass self-segregation property and the need for the development of targeted biomass retention strategies., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The use of seawater to alleviate water shortages causes an increase of salinity in municipal pipe networks, posing challenges for biological wastewater treatment. The impacts of two compatible solutes on the anammox process under salt stress (20 g L -1 ) were compared here at the genetic and microbial levels. The findings revealed that both 0.3 mM glycine betaine (GB) and mannitol (MA) could alleviate the salt stress on anammox process, with GB exhibiting a better effect. Specifically, the addition of GB recovered the nitrogen removal efficiency (NRE) from 40 % to >80 % within 13 days. The addition of MA caused the reduction of the absolute abundance of hdh and hzsA, implying that 0.6 mM was not the optimal concentration. Moreover, salt stress induced an increase in the absolute abundance of nitrification functional genes and a decrease in the abundance of denitrification functional genes. Notably, compared with the initial level, the abundance of Candidatus Kuenenia increased by 7.1 % and 4.3 % after adding GB and MA, respectively. According to the network analysis, two compatible solutes promoted the bacterial interactions in anammox systems, which promoted the nitrogen circulation and further the nitrogen removal performance. This work provides a feasible strategy to relieve the salt stress on anammox process and then facilitates its application for treating saline wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

As a typical endocrine disruptor, bisphenol A (BPA) has been widely detected in various water bodies. Although the influence of BPA on traditional biological treatment system has been investigated, it is not clear whether it has potential impact on anaerobic ammonium oxidation (anammox) process. The short- and long-term influences of BPA on reactor operational performance, sludge characteristics and microbial community were investigated in this study. Results revealed that 1 and 3 mg L -1 BPA exhibited a limited adverse impact on granular sludge reactor performance. However, exposure of sludge under 10 mg L -1 BPA would cause an obvious inhibition on nitrogen removal rate from 10.3 ± 0.2 to 7.6 ± 0.4 kg N m -3 d -1 . BPA would affect granular sludge metabolic substance excretion and lead to effluent dissolved organic content increase. Both the microbial community and redundancy analysis showed that BPA exhibited a negative influence on Ca. Kuenenia but a positive correlation with SBR1031. Low BPA concentration appeared a limited impact on functional genes while 10 mg L -1 BPA would cause decline of hzsA and hdh abundances. The results of this work might be valuable for in-depth understanding the potential influence of endocrine disruptor on anammox sludge., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Antibiotics and antibiotic resistance genes (ARGs) have been recognized as emerging high-risk pollutants for human and animal health. This study systematically investigated the comprehensive effects of a typical antibiotic (sulfadimidine, SDM) in livestock and poultry breeding wastewater on the anammox process, with the aim of elucidating the intracellular and extracellular protective mechanisms of the anammox consortia to the antibiotic stress. Results revealed that the high-concentration SDM significantly reduced the specific anammox activity (SAA) by 37.8%. Changes in the abundance of Candidatus Kuenenia showed a similar trend with that of SAA, while other nitrogen-related microorganisms (e.g., Nitrosomonas and Nitrospira) contributed to the nitrogen removal especially during the inhibitory period. Resistance of the anammox consortia to SDM mainly depended on the protection of ARGs and EPS. Network analysis revealed the host range of eARGs was relatively larger than that of iARGs, and intI1 was closely associated with representative denitrifiers. In addition, metaproteomic analysis and molecular docking results indicated that abundant proteins in EPS could detain SDM in the extracellular matrix through forming complex via hydrogen bond. These findings provide a guidance for the stable operation of anammox process and ARGs transfer controlling., (Copyright © 2022 Elsevier B.V. All rights reserved.)

As one of the most promising autotrophic biological nitrogen removal technology, anaerobic ammonia oxidation (anammox) has gained intense attention for the past decades and several full-scale facilities have been implemented worldwide. However, anammox bacteria are easily affected by disturbed external environmental factors, which commonly leads to the fluctuations in reactor performance. The response of anammox sludge to external stress results in changes in components and structural characteristics of intracellular and extracellular polymer substances. Real-time and convenient spectral analysis of anammox sludge metabolites can give early warning of performance deterioration under external stresses, which is of great significance to the stable operation of bioreactor. This review summarized the research progress on characterizing the intracellular and extracellular metabolites of anammox sludge through spectroscopic techniques. The correlation between anammox sludge activity and its key metabolites was analyzed. Also, the limitations and future prospects of applying spectral analytical techniques for anammox bioreactor monitoring were discussed and outlooked. This review may provide valuable information for both scientific study and engineering application of anammox based nitrogen removal technology., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The effects of multiple antibiotics on the anaerobic ammonia oxidation (anammox) process were investigated. The resistance of the anammox system to high-concentration antibiotics was also demonstrated through gradual acclimation experiments. Inhibition of the anammox process (R 1 ) occurred when the concentrations of erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TC) were 0.1, 5.0 and 0.1 mg L -1 , respectively. The nitrogen removal efficiency (NRE) of R 1 was reduced from 97.2% to 60.7% within 12 days and then recovered to 88.9 ± 9.5% when the nitrogen loading declined from 4.52 ± 0.69 to 2.11 ± 0.58 kg N m -3 d -1 . Even when the concentrations of ERY, SMX and TC were as high as 1.0, 15.0 and 1.0 mg L -1 , respectively, R 1 maintained stable operation. The increases in the abundance of antibiotic resistance genes (ARGs) and in extracellular polymeric substances (EPS) content showed that the anammox process alleviated stress from multiple antibiotics mainly by producing ARGs and secreting EPS. The molecular docking simulation results illustrated the potential binding sites between ammonium transporter and different antibiotics. The upregulation of functional gene expression and the stable abundance of Candidatus Kuenenia in R 1 compared with that in the control suggested that the R 1 reactor generally maintained more stable long-term operation. This work provides a new understanding of the application of the anammox process to treat wastewater containing multiple antibiotics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The anaerobic ammonium oxidation (anammox) process has been recognized as an efficient nitrogen removal technology. However, anammox bacteria are susceptible to surrounding environments and different pollutants, which limits the extensive application of the anammox process worldwide. Numerous researchers investigate the effects of various pollutants on the anammox process or bacteria, and related findings have also been reviewed with the focused on their inhibitory effects on process performance and microbial community. This review systemically summarized the recent advances in the inhibition, mechanism and recovery process of traditional and emerging pollutants on the anammox process over a decade, such as organics, metals, antibiotics, nanoparticles, etc. Generally, low-concentration pollutants exhibited a promotion on the anammox activity, while high-concentration pollutants showed inhibitory effects. The inhibitory threshold concentration of different pollutants varied. The combined effects of multipollutant also attracts more attentions, including synergistic, antagonistic and independent effects. Additionally, remaining problems and research needs are further proposed. This review provides a foundation for future research on the inhibition in anammox process, and promotes the proper operation of anammox processes treating different types of wastewaters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The preservation of anammox granules is of great significance for the rapid start-up of the anammox process and improvement of performance stability. Therefore, it is necessary to explore an economical and stable preservation strategy. Exogenous extracellular polymeric substances (EPS) were used as protective agents for the preservation of anammox granules in this study. In brief, EPS from anammox sludge (A-EPS) and denitrifying sludge (D-EPS) were added to preserve anammox sludge at 4 °C and room temperature (15-20 °C). The results showed that A-EPS addition at 4 °C was the optimal condition for the preservation of anammox granules. After 90 days of preservation, the specific anammox activity (SAA) of the anammox granules remained at 92.7 ± 2.2 mg N g -1  VSS day -1 (remaining ratio of 33.4%), while that of the sludge with D-EPS addition at the same temperature was only 77.1 ± 3.2 mg N g -1  VSS day -1 (remaining ratio of 27.8%). The nitrogen removal efficiency of the experimental group with D-EPS at room temperature was 85.9%, and that of the A-EPS group reached 90.6% under the same temperature conditions. The abundance of the functional genes hzsA, hdh and nirS of the sludge (4 °C; A-EPS addition) after recovery were 138.5%, 317.1%, and 375.9%, respectively, of those of sludge from the D-EPS-added group at the same temperature. RDA revealed the contribution of proteins to the preservation process. Overall, this study provides an economical and robust strategy for the preservation of anammox granules., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Anaerobic ammonium oxidation (anammox) bacteria are sensitive and susceptible to operating condition fluctuations that can lead to the instability of a bioreactor. Through multivariate spectral analysis, the dynamic changes of intracellular and extracellular metabolites of anammox sludge under the declined temperature stress were characterized. It was found that effluent fluorescence components were positively related to the bacterial activity, and the response of the protein-like substances to the temperature change was more sensitive than that of humic substances. Under the transient disturbance during temperature change from 35 to 15 °C, anammox system tended to considerably excrete extracellular polymeric substances to resist the low temperature inhibition. However, the long-term exposure of the sludge at 10 °C resulted in the considerably inhibition of sludge activity, granular disintegration and heterotrophic denitrification bacteria increase. The two-dimensional correlation analysis further revealed that the humic acid in extracellular polymeric substances was preferentially responded to the temperature change than protein. Anammox bacteria tended to increase the intracellular protein and electron transfer-related reactive substance excretion to counteract the low temperature inhibition. Herein, both the intra- and extra-cellular response characteristics of anammox sludge to temperature variation were successfully resolved via the combined spectra. This work provides a comprehensive understanding on the mechanism of anammox sludge to temperature variation and may be valuable for the development of bioreactor monitoring techniques., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The sustainable management and recirculation of phosphorus resources are essential to our human lives. In this work, phosphorus removal and recovery from secondary effluent were achieved using municipal wastewater-derived materials as adsorbents. Through modification with 0.5 M NaOH for 30 min, iron containing sludge that originated from the coagulation pretreatment of municipal wastewater was successfully converted to phosphorus adsorbent. The maximal adsorption capacity of the prepared adsorbent was estimated to be 22 mg-P/g, and the adsorption performance remained stable in the pH range of 5-8. FeO(OH) was identified as the key adsorption site, and the ligand exchange mediated chemical adsorption was the main mechanism for phosphorus removal by the prepared material. Moreover, a laboratory-scale continuous-flow adsorption column experiment showed that the surplus phosphorus in secondary effluent could be readily reduced to <0.1 mg/L. By pyrolysis of P-laden alkali-treated iron sludge under oxygen limited conditions, the phosphorus was recovered and successfully applied to support wheat growth. This work provides valuable information for both the sustainable management of phosphorus streams in wastewater and cyclic utilization of waste sludge., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Anammox and autotrophic desulfurization-denitrification (AADD) process is feasible for the nitrogen and sulfide removal in the same reactor, and the influence of excess nitrate produced by anammox could also be alleviated simultaneously. This study firstly proposed a novel strategy with inoculating single anammox sludge to start up the AADD process. Results demonstrated that the 90% nitrogen removal efficiency (NRE), 2.55kgm -3 d -1 nitrogen removal rate (NRR), and 95% sulfide removal efficiency (SRE) were obtained at the influent total nitrogen of 280mgL -1 and sulfide of 221.5mgL -1 , and the final effluent nitrate concentration was as low as 8mgL -1 under the appropriate operation conditions. Tryptophan-like and protein-like substances were characterized as the main components in bound EPS. Thiobacillus (35.68%) and Pseudoxanthomonas (11.61%) were identified as the predominant genera. This study will pave a potential avenue to promote the treatment of high concentration nitrogen and sulfide in wastewater in the future., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Both nickel and salinity are often detected in the environment. Especially electroplating wastewater contains some salt and nickel, which affects microbial activity in biological wastewater treatment process. In this study, the effects of sustaining addition of a high-concentration salinity and Ni(II) on the anaerobic ammonium oxidation (anammox) process were examined. The results indicated that the anammox system had an acclimation ability to <0.2 mg L -1 Ni(II) and 20 g L -1 NaCl. After a recovery phase of approximately 70 days, the nitrogen removal efficiency and rate reached at 77.1% and 1.18 kg N m -3  d -1 , respectively. The three-dimensional excitation-emission matrix fluorescence and Fourier transform infrared spectra results showed that the introduction of NaCl and Ni(II) caused a substantial variation in the quantity and composition of the bound EPS in the surface of anammox granules. The present study is the first to document the long-term effect of co-existence of salinity and Ni(II) on the performance of the freshwater-derived anammox bacteria in the upflow anaerobic sludge blanket reactor and to provide a reference for the stable operation of anammox bioreactors for the treatment of sulfonamide-containing wastewater., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The short- and long-term influence of quinoline on the properties of anaerobic ammonium oxidation (anammox) biogranules was evaluated. During batch tests, the bioactivity of anammox granules in the presence of different quinoline concentrations was monitored, and the IC 50 of quinoline was calculated to be 13.1 mg L -1 using a non-competitive inhibition model. The response of anammox granules to pre-exposure to quinoline was dependent on metabolic status, and the presence of both quinoline and NO 2 - -N had a rapid detrimental effect, resulting in a 64.5% decrease within 12 h. During continuous-flow experiments, the nitrogen removal rate (NRR) of the reactor decreased sharply within 3 days in the presence of 10 mg L -1 quinoline and then was restored to 2.6 kg N m -3  d -1 . In the presence of quinoline-induced stress, the specific anammox activity and levels of extracellular polymeric substance and heme c were decreased, while settling velocity persistently increased. After cultivation and acclimation obtained by adding a medium level of quinoline to the influent, the anammox granule sludge was able to tolerate 10 mg L -1 quinoline in 178 days., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Given the increasing applications of NiO nanoparticles (NPs) in battery products, the potential effects of NiO NPs on anaerobic ammonium oxidation (anammox) systems were studied for the first time. The results showed that the anammox system performance obviously differed under the stresses of different NiO NPs concentrations. After the withdrawal of NiO NPs, the nitrogen removal performance of the anammox reactor returned to nearly that of the initial phase within 35 days. Compared with 0 mg L -1 NiO NPs, the specific anammox activity first increased and then decreased to the minimum value of 116.8 ± 13.8 mg TN g -1  VSS d -1 at 60 mg L -1 NiO NPs. The variations in the heme c contents and extracellular polymeric substance amounts were similar to the variations in the specific anammox activity throughout the whole experiment. Additionally, the relative abundance of the dominant bacteria (Candidatus kuenenia) increased from 20.44% at 60 mg L -1 NiO NPs to 23.14% at the end of the last phase. Thus, the potential effects of NiO NPs on anammox systems should be a cause for great concern., (Copyright © 2018. Published by Elsevier B.V.)