Effects of antibiotics on enhanced biological phosphorus removal and its mechanisms

Treatment performance of different units in the anaerobic-anoxic-aerobic process of landfill leachate under antibiotic exposure

The effectiveness of three different treatment units (anaerobic, anoxic, and aerobic) in A/A/O reactors when treating landfill leachate that contained varying concentrations of tetracycline (TC) was evaluated. The effluent quality, sludge performance, and removal rates of COD, TN, TP, and NH3-N of the reactors were investigated. The results showed that in the three treatment units (anaerobic, anoxic, and aerobic), when the TC dosage was 10 mg/L, the removal rates of NH3-N continued to decrease to 6.9%, 16.3%, and 32.8%, and the removal rates of COD, TN, and TP in the three treatment units reached their maximum values, which were 37.5%, 57.4%, and 69.6%; 21.1%, 37.1%, and 41.0%; 13.0%, 16.2%, and 27.4%, respectively. During the reactor's operation, the heavy metal content in the treatment units initially increased followed by a decrease, especially for Mn and Zn. This was due to the production of more EPS by microorganisms, resulting in more active sites for heavy metal adsorption. In addition, with the increase of TC concentration, TC removal rate was always positively correlated with PN, COD, TN and heavy metals removal rates, and negatively correlated with NH3-N, TP, pH, and PS. Further analysis revealed that TC was toxic to microorganisms, leading to a decrease in biodiversity and microbial community diversity among the three treatment units in the reactor. This article analyzed the treatment effects of different treatment units in leachate under antibiotic exposure conditions, to explore better external conditions for sewage biological treatment facilities.

Remediation of sulfonamide antibiotic-containing wastewater by constructed wetlands: Importance and action mechanism of plants

Constructed wetlands (CWs) have been proved to be effective in treating sulfonamide antibiotics (SAs) wastewater. Nevertheless, as an essential element in CWs, the significance of plants, continues to be a topic of controversy. In this study, CWs with two different plant species were taken as the research object to investigate their treatment performance, in order to understand the impact of plants on the treatment of SAs wastewater in CWs and to discover the underlying action mechanisms. Experiment results showed that plants played an important role in the CWs, and significantly improved the efficiency of wastewater treatment, with average removal rates for conventional nutrients (COD, NH4+-N, NO3--N and TP) ranging from 73.69 % to 98.92 %, surpassing the non-plant control group (52.16 %-80.70 %). Similarly, for SAs, the removal efficiency in the plant-treated group was 74.15 %-83.67 %, higher than that in the non-plant control group (65.42 %-70.14 %). Although, as time passed, the efficacy of CWs had slightly decreased, but the rate of pollutant removal remained consistently over 60 %. Further analysis showed that plants promoted the removal of SAs through various mechanisms such as plant uptake, microbial degradation and substrate adsorption. Plants had the ability to absorb SAs from wastewater and eliminated them through metabolism or accumulation. Additionally, plants can improve soil enzyme activity to facilitate microbial degradation, indirectly promoting SAs removal. It's worth noting that most SAs can be degraded through plant metabolism after being absorbed by plants, while only a minority of SAs accumulated in plants in the form of parent compounds. Furthermore, the efficacy of CWs in treating wastewater differed between selected plant species. Specifically, Iris pseudacorus showed a higher purifing potential than Scirpus validus. These results revealed the effect of plants on the treatment of SAs wastewater in CWs, and provided a reference for the practical application of antibiotic wastewater removal by CWs.

Deciphering bioprocess responses in organic phosphorus mineralization to different antibiotic stresses: Interaction mechanisms mediated by microbial succession and extracellular polymeric substances and regulatory patterns

Understanding the impacts and mechanisms of different antibiotics on organic phosphorus (OP) mineralization is crucial for promoting the rational utilization of resources and protecting the ecological environment. In this study, the effects of four commonly used antibiotics (sulfadiazine, ciprofloxacin, erythromycin, and ampicillin) on the mineralization of OP were explored using16S rRNA gene sequencing technology. The results showed that ciprofloxacin, erythromycin, and ampicillin negatively affected the mineralization capacity of OP, whereas sulfadiazine positively influenced OP mineralization. The content and composition of extracellular polymeric substances (EPS) and microbial phenotypes (biofilm formation and stress tolerance) were directly correlated with differences in OP mineralization capacity. Microbial diversity, network complexity and stability, and key microorganisms indirectly influenced OP mineralization by regulating EPS content and composition and microbial phenotypes. In summary, this study reveals specific impacts of different antibiotics on OP mineralization, offering valuable insights for addressing "phosphorus limitation" and "phosphorus load" amid various antibiotic stresses.

Unraveling the effects and mechanisms of antibiotics on aerobic simultaneous nitrogen and phosphorus removal by Acinetobacter indicus CZH-5

The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1-1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE, aarA, and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.

Vital role of CYP450 in the biodegradation of antidiabetic drugs in the aerobic activated sludge system and the mechanisms

The extensive use of antidiabetic drugs (ADDs) and their detection in high concentrations in the environment have been extensively documented. However, the mechanism of ADDs dissipation in aquatic environments is still not well understood. This study thoroughly investigates the dissipation behavior of ADDs and the underlying mechanisms in the aerobic activated sludge system. The results indicate that the removal efficiencies of ADDs range from 3.98% to 100% within 48 h, largely due to the biodegradation process. Additionally, the gene expression of cytochrome P450 (CYP450) is shown to be significantly upregulated in most ADDs-polluted samples (P < 0.05), indicating the vital role of CYP450 enzymes in the biodegradation of ADDs. Enzyme inhibition experiments validated this hypothesis. Moreover, molecular docking and simulation results indicate that a strong correlation between the biodegradation of ADDs and the interactions between ADDs and CYP450 (Ebinding). The differences in dissipation behavior among the tested ADDs are possibly due to their electrophilic characteristics. Overall, this study makes the initial contribution to a more profound comprehension of the crucial function of CYP450 enzymes in the dissipation behavior of ADDs in a typical aquatic environment.

Sulfamethoxazole removal from wastewater via anoxic/oxic moving bed biofilm reactor: Degradation pathways and toxicity assessment

The effects of sulfamethoxazole (SMZ), an antibiotic commonly detected in the water environment, on the performance of a single staged anoxic/oxic moving bed biofilm reactor (A/O MBBR), was investigated. The anoxic zone played a key role in the removal of SMZ with a percentage of contribution accounting for around 85% in the overall removal. Denitrifying heterotrophic microbes present in the anoxic zone showed relatively more resistance to higher SMZ loads. It was found that in extracellular polymeric substances, protein content was increased consistently with the increase in SMZ concentration. Based on the detected biotransformation products, four degradation pathways were proposed and the toxicity was evaluated. Metagenomic analysis revealed that at higher SMZ load the activity of genera, such as Proteobacteria and Actinobacteria was significantly affected. In summary, proper design and operation of staged A/O MBBR can offer a resilient and robust treatment towards SMZ removal from wastewater.

Exploring the Application Potential of Aquaculture Sewage Treatment of Pseudomonas chengduensis Strain WD211 Based on Its Complete Genome

Pseudomonas chengduensis is a new species of Pseudomonas discovered in 2014, and currently, there is a scarcity of research on this bacterium. The P. chengduensis strain WD211 was isolated from a fish pond. This study investigated the purification capability and environmental adaptability of strain WD211 in wastewater and described the basic features and functional genes of its complete genome. According to the results, the sewage treated with strain WD211 showed a decrease in concentration of 18.12% in total nitrogen, 89.39% in NH4+, 62.16% in NO3-, 79.97% in total phosphorus, and 71.41% in COD after 24 h. Strain WD211 is able to survive in a pH range of 6-11. It shows resistance to 7% sodium chloride and different types of antibiotics. Genomic analysis showed that strain WD211 may remove nitrogen and phosphorus through the metabolic pathway of nitrogen assimilation and phosphorus accumulation, and that it can promote organic decomposition through oxygenase. Strain WD211 possesses genes for producing betaine, trehalose, and sodium ion transport, which provide it with salt tolerance. It also has genes for antibiotic efflux and multiple oxidases, which give it antibiotic resistance. This study contributes to the understanding of the sewage treatment ability and potential applications of P. chengduensis.

Unraveling the Role of Microalgae in Mitigating Antibiotics and Antibiotic Resistance Genes in Photogranules Treating Antibiotic Wastewater

Harnessing the potential of specific antibiotic-degrading microalgal strains to optimize microalgal-bacterial granular sludge (MBGS) technology for sustainable antibiotic wastewater treatment and antibiotic resistance genes (ARGs) mitigation is currently limited. This article examined the performance of bacterial granular sludge (BGS) and MBGS (of Haematococcus pluvialis, an antibiotic-degrading microalga) systems in terms of stability, nutrient and antibiotic removal, and fate of ARGs and mobile genetic elements (MGEs) under multiclass antibiotic loads. The systems exhibited excellent performance under none and 50 μg/L mixed antibiotics and a decrease in performance at a higher concentration. The MBGS showed superior potential, higher nutrient removal, 53.9 mg/L/day higher chemical oxygen demand (COD) removal, and 5.2-8.2% improved antibiotic removal, notably for refractory antibiotics, and the system removal capacity was predicted. Metagenomic analysis revealed lower levels of ARGs and MGEs in effluent and biomass of MBGS compared to the BGS bioreactor. Particle association niche and projection pursuit regression models indicated that microalgae in MBGS may limit gene transfers among biomass and effluent, impeding ARG dissemination. Moreover, a discrepancy was found in the bacterial antibiotic-degrading biomarkers of BGS and MBGS systems due to the microalgal effect on the microcommunity. Altogether, these findings deepened our understanding of the microalgae's value in the MBGS system for antibiotic remediation and ARG propagation control.

Impact of emerging pollutant florfenicol on enhanced biological phosphorus removal process: Focus on reactor performance and related mechanisms

Florfenicol (FF), an emerging pollutant antibiotic that is difficult to biodegrade, inevitably enters sewage treatment facilities with high level. To date, however, the performance and related mechanism of FF on enhanced biological phosphorus removal (EBPR) have not been reported. In order to fill this gap, this work investigated the potential impacts of FF on EBPR and revealed the relevant mechanisms. The effect of FF on EBPR was dose-dependent, that was, low dose had no effect on EBPR, while high FF concentration inhibited EBPR. Mechanism investigation showed that FF had no effect on anaerobic phosphate release, but reduced oxic phosphorus uptake. Three-dimensional Excitation-emission Matrix fluorescence spectroscopy and X-ray photoelectron spectroscopy analysis showed that FF affected the structure and components of activated sludge extracellular polymers (EPS). High content of FF stimulated sludge to secrete more EPS. High level of FF reduced the relative abundance of microorganisms responsible for biological phosphorus removal. Microbiological community structure analysis indicated 2.0 mg FF/L increased the relative abundance of Candidatus_Competibacter and Terrimonas from 9.22 % and 12.49 % to 19.00 % and 16.28 %, respectively, but significantly reduced the relative abundance of Chinophagaceae from 11.32 % to 0.38 %, compared with the blank.

Co-existence effect of copper oxide nanoparticles and ciprofloxacin on simultaneous nitrification, endogenous denitrification, and phosphorus removal by aerobic granular sludge

Nanoparticles and antibiotics are toxic to humans and ecosystems, and they inevitably coexist in the wastewater treatment plants. Hence, the co-existence effects and stress mechanism of copper (II) oxide nanoparticles (CuO NPs) and ciprofloxacin (CIP) on simultaneous nitrification, endogenous denitrification and phosphorus removal (SNEDPR) by aerobic granular sludge (AGS) were investigated here. The co-existence stress of 5 mg/L CuO NPs and 5 mg/L CIP resulted in the synergistic inhibitory effect on nutrient removal. Transformation inhibition mechanisms of carbon (C), nitrogen (N) and phosphorus (P) with CuO NPs and CIP addition were time-dependent. Furthermore, the long-term stress mainly inhibited PO₄^3--P removal by inhibiting phosphorus release process, while short-term stress mainly inhibited phosphorus uptake process. The synergistic inhibitory effect of CuO NPs and CIP may be due to the changes of physicochemical characteristics under the co-existence of CuO NPs and CIP. This further altered the sludge characteristics, microbial community structure and functional metabolic pathways under the long-term stress. Resistance genes analysis exhibited that the co-existence stress of CuO NPs and CIP induced the amplification of qnrA (2.38 folds), qnrB (4.70 folds) and intI1 (3.41 folds) compared with the control group.

Toxic waste sludge derived hierarchical porous adsorbent for efficient phosphate removal

Global effective treatment of phosphorus crisis and toxic waste sludge in one way is urgently needed but still insufficient due to single function, environmental damage, and complicated fabrication process. Herein, we proposed a facile, low-cost, and sustainable strategy to fabricate NiAl layered double oxides/nickel-containing sludge (LDOs/NCS) adsorbent using toxic NCS as raw material via two-step method including hydrothermal process and calcination. The as-designed hierarchical porous adsorbent with large specific surface area and pore volume exhibited excellent adsorption properties towards phosphate. Langmuir adsorption model exhibited the best fit to the experimental data, which illustrated that the adsorption process was dominated by monolayer adsorption. Moreover, even in various double anions systems or in a wide pH range environment (2-12), the as-designed LDOs/NCS still maintained relatively stable adsorption capacity. A possible adsorption mechanism involving surface complexation and electrostatic interactions was investigated. Besides, the LDOs/NCS also displayed admirable durability and reusability. Therefore, this waste-control-waste strategy not only simultaneously addresses phosphorus crisis treatment and toxic NCS management, but also could be potentially extended towards rational design of other metals-containing sludge derived functional materials.

Enhanced biological phosphorus removal from wastewater by current stimulation coupled with anaerobic digestion

The integrated wastewater discharge standard for phosphorus has become increasingly strict. In this study, a synergetic current stimulation system coupled with anaerobic digestion was used to enhance phosphorus removal from wastewater. The effects of current intensity, pH, and methane (CH₄) synthesis on phosphorus removal were investigated. As direct current was supplied to an anaerobic bioreactor, the removal of sewage total phosphorus was significantly enhanced. The conditions of weak acid and low negative oxidation-reduction potential facilitated the phosphorus removal from wastewater. The optimal parameters for the dephosphorisation process were a current intensity of 100 mA and a pH of 6.0. When the anaerobic digestion process was inhibited by the reagent 2-bromoethanesulphonic acid sodium (BES), abundant metabolic intermediates accumulated and methanogenesis clearly decreased. Affected by the current stimulation and the inhibition of CH₄ synthesis, the formation of gaseous phosphine (PH₃) was greatly improved, and then PH₃ escaped from the digestion mixture after it was absorbed by microbial cells. The maximum PH₃ content of the digestion gas was 41.8 mg m^-3 in the reactor supplied with a current of 100 mA and BES addition of 10 mmol L^-1, and the phosphorus removal in this digestion system reached 55.2% at 6 d; however, the removal in the conventional anaerobic digestion system was only 17.7% after the same amount of time. Finally, a pathway of enhanced anaerobic biological phosphorus removal was proposed to better understand the inherent synergistic mechanism.

Changes of antibiotic resistance genes and bacterial communities in the advanced biological wastewater treatment system under low selective pressure of tetracycline

Effluents of conventional wastewater treatment systems contain antibiotic residues at concentrations below the minimal inhibitory concentrations (MIC), which nevertheless could still select for antibiotic-resistant bacteria. This work focuses on evaluating the changes of antibiotic resistance genes (ARGs) and bacterial communities in a planted advanced biological wastewater treatment system (ABWWTS) under long-term exposure to sub-MIC tetracycline. In the ABWWTS, the removal rates of tetracycline ranged from 97.9% to 99.9%, and a 17.2% decrease in the average removal rates of NH₄⁺-N was observed after the addition of tetracycline. Although the background of ABWWTS contributed to the ARGs in effluents, the concentration of 283 targeted ARGs (ΣARGs) was 83.5% lower in effluents than in influents after sub-MIC tetracycline exposure, and the concentrations of ΣARGs in the ABWWTS were, on average, 30.0% lower than those in an unplanted biological wastewater treatment system (UBWWTS) after a performance of 130 days. The relative abundance of tetracycline resistance genes increased within ABWWTS and UBWWTS under tetracycline exposure. After tetracycline exposure, bacterial diversity in ABWWTS and UBWWTS increased on average by 36.2% and 42.7%, respectively, and the abundances of Nitrosomonas and Nitrospira in the aerobic zone were more than 10-times higher in the ABWWTS than in the UBWWTS. Sub-MIC tetracycline concentrations were linearly correlated with the relative abundance of tetracycline resistance genes in Escherichia coli (E. coli). Long-term exposure to tetracycline at the same concentration increased abundances of the same ARGs (i.e., tetR-02 and tetM-01) in E. coli and the microflora of the ABWWTS, revealing that sub-MIC tetracycline could increase the abundance of ARGs in the ABWWTS by facilitating the vertical transfer of tetracycline resistance genes. These findings demonstrated that planted ABWWTS played a positive role in removing ARGs under low antibiotic selective pressure, which was in accompany with increasing levels of corresponding ARGs within the system.