Combined applications of UV and chlorine on antibiotic resistance control: A critical review.

Environmental health problems caused by antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) have become a global concern. ARB and ARGs have been continuously detected in various water environments, which pose a new challenge for water quality safety assurance. Disinfection is a key water treatment process to eliminate pathogenic microorganisms in water, and combined chlorine and UV processes (the UV/Cl2 process, the UV-Cl2 process, and the Cl2-UV process) are considered potential disinfection methods to control antibiotic resistance. This review documented the efficacy and mechanism of combined UV and chlorine processes for the control of antibiotic resistance, as well as the effects of chlorine dose, solution pH, UV wavelength, and water matrix on the effectiveness of the processes. There are knowledge gaps in research on the combined chlorine and UV processes for antibiotic resistance control, in particular the UV-Cl2 process and the Cl2-UV process. In addition, changes in the structure of microbial communities and the distribution of ARGs, which are closely related to the spread of antibiotic resistance in the water, induced by combined processes were also addressed. Whether these changes could lead to the re-transmission of antibiotic resistance and harm human health may need to be further evaluated.

Start-up of glycerol-driven denitrifying phosphorus removal from wastewater: The effects of the microaerobic environment.

Glycerol, an abundant by-product of biodiesel production, represented a promising carbon source for enhancing nutrient removal from low C/N ratio wastewater. This study discovered a novel approach to initiate glycerol-driven denitrifying phosphorus removal (DPR) in situ by creating a short-term microaerobic environment within the aerobic zone. This approach facilitated the in-situ conversion of glycerol, which was subsequently utilized by denitrifying phosphate accumulating organisms (DPAOs) for DPR. The feasibility and stability of glycerol-driven DPR were validated in a continuous-flow pilot-scale reactor. Anaerobic phosphorus release increased from 1.0 mg/L/h to 2.5 mg/L/h, with fermentation bacteria and related functional genes showing significant increases. The stable stage exhibited 92.8% phosphorus removal efficiency and 55.5% DPR percentage. The microaerobic environment enhanced fermentation bacteria enrichment, crucial for glycerol-driven DPR stability. The collaborative interaction between fermentation bacteria and phosphate accumulating organisms (PAOs) played a key role in sustaining glycerol-driven DPR stability. These findings provide a robust theoretical foundation for applying glycerol-driven DPR in established wastewater treatment plants.

Integration of ammonium assimilation with denitrifying phosphorus removal for efficient nutrient management in wastewater treatment.

Nutrient removal from sewage is transitioning to nutrient recovery. However, biological treatment technologies to remove and recover nutrients from domestic sewage are still under investigation. This study delved into the integration of ammonium assimilation with denitrifying phosphorus removal (DPR) as a method for efficient nutrient management in sewage treatment. Results indicated this approach eliminated over 80 % of the nitrogen in the influent, simultaneously recovering over 60 % of the nitrogen as the activated sludge through ammonia assimilation, and glycerol facilitated this process. The nitrification/denitrifying phosphorus removal ensured the stability of both nitrogen and phosphorus removal. The phosphorus removal rate exceeded 96 %, and the DPR rate reached over 90 %. Network analysis highlighted a stable community structure with Proteobacteria and Bacteroidota driving ammonium assimilation. The synergistic effect of fermentation bacteria, denitrifying glycogen-accumulating organisms, and denitrifying phosphorus-accumulating organisms contributed to the stability of nitrogen and phosphorus removal. This approach offers a promising method for sustainable nutrient management in sewage treatment.

Effects of lysed sludge reflux point on ultrasound lysis-cryptic growth in anaerobic/aerobic (A/O) wastewater treatment: Sludge reduction, microbial community, and metabolism.

Ultrasonication allows sludge reduction to be performed in situ during wastewater treatment, and the reflux point of the lysed sludge affects this performance. This study investigated the effects of reflux point (anaerobic stage, carbon/nitrogen (C/N) lowest stage, and aerobic stage) on sludge lysis-cryptic growth in an anaerobic/aerobic reactor and variations in the sludge and microbial community. The best reflux point occurred at the lowest C/N ratio stage, and a 50.96% reduction in excess sludge was achieved. The reflux of the lysed sludge to the aerobic stage reduced nitrogen and phosphorus removal. The reflux of the lysed sludge decreased the average sludge size, reaching 29.2 µm when reflux to the aerobic stage. Scanning electron microscopy showed that the sludge surface was unaffected by the reflux point. The Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy results showed that the most prominent variation in the intensity of the sludge functional groups occurred when the reflux was at the lowest C/N stage. The amount of extracellular polymeric substances decreased the most during reflux to the anaerobic stage. The sludge microbial communities varied with the reflux point, and the dominant phyla during reflux to the anaerobic, lowest C/N, and aerobic stages were Bacteroidetes, Firmicutes, and Bacteroidetes, respectively. Furthermore, the reflux point did not alter the metabolic pathway of sludge microorganisms but increased the number of enzymes in metabolic pathways.

Study on performance and mechanism of enhanced low-concentration ammonia nitrogen removal from low-temperature wastewater by iron-loaded biological activated carbon filter.

In order to strengthen the treatment of low-concentration ammonia nitrogen wastewater at low temperature, iron-loaded activated carbon (Fe-AC) with ultrasonic impregnation method was used as the filter material of biofilter process. The performance and mechanism of ammonia nitrogen removal from simulated secondary wastewater by iron-loaded biological activated carbon filter (Fe-BACF) were studied at 10 °C. The characterization results showed that iron was loaded on the surface of AC in the form of Fe2O3, and the specific surface area, total pore volume, pore size and alkaline functional group content of Fe-AC were obviously increased. After the formation of biofilm on the surface of filter media, the average removal rate of ammonia nitrogen by Fe-BACF (97.9%) was significantly higher than that of conventional BACF (87.8%). The improved surface properties increased the number and metabolic activity of microorganisms, and promoted the secretion of EPS on the surface of Fe-BAC. The results of high-throughput sequencing showed that the existence of Fe optimized the bacterial community structure on the surface of Fe-BAC, with the increase of the abundances of psychrophilic bacteria and ammonia nitrogen removal bacteria. The mechanism of enhanced ammonia nitrogen removal by Fe-BACF was the joint action of many factors, among which the main causal relationship was that modification of iron could optimize the number and category of microorganisms on Fe-BAC surface by improving the surface properties, thus improving the biological nitrogen removal ability. Results of this study provided a practical way for the treatment of low ammonia nitrogen wastewater in cold regions.

Fe-N complex biochar as a superior partner of sodium sulfide for methyl orange decolorization by combination of adsorption and reduction.

To enhance the decolorization of methyl orange (MO), Fe-N complex biochar (Fe-N-BC) was developed as an accelerator in the sodium sulfide (Na2S) reduction system. The decolorization effect and mechanism of MO in the Fe-N-BC/Na2S composite system were studied. Surface pore analysis, Raman spectroscopy, FT-IR, XPS, and electrochemical analysis were used to characterize Fe-N-BC and unmodified biochar (BC). These results demonstrated that Fe-N-BC had better adsorption performance (specific surface area 463.46 m2 g-1) and electron transfer capacity than BC. By adding Fe-N-BC to the Na2S reduction system for MO, it was found that the decolorization of MO was greatly improved (increased by 93%). Besides, the effects of critical factors such as the initial concentration of Na2S, the dosage of Fe-N-BC, pH value, and temperature on the decolorization rate of MO were evaluated. Through the analysis of the action mechanism, the cooperation mode of Fe-N-BC and Na2S was to form an infinite cycle of adsorption-reduction-regeneration, so as to realize the rapid decolorization of MO. On the one hand, Fe-N-BC could adsorb MO and Na2S on its surface to increase the contact opportunity; on the other hand, it could act as a redox mediator to accelerate the electron transfer of the reduction reaction. In addition, the degradation of MO by Na2S was also an in-situ regeneration of Fe-N-BC. These findings may provide a feasible method to decolorize azo dyes quickly by cooperating with chemical reducing agents from a new perspective.

Positive effects of appropriate micro-aeration on landfill stabilization: Mitigating ammonia and VFAs accumulation.

The slow stabilization process of landfill had brought obstacles to urbanization. The paper investigated the efficacy and mechanism of micro-aeration intensity for landfill stabilization. The micro-aeration intensity of 0.05 L/(h·kg) resulted in a significant increase of volatile fatty acids (VFAs) in the hydrolysis stage, and the NH4+-N concentration was reduced by 22.1 %. At the end of landfill, VFAs were rapidly degraded and organic matter was reduced from 36 % to 16 %, which was 55.5 % more efficient than the control group. In addition, the community succession and structure of bacteria and archaea were analyzed. The micro-aeration intensity of 0.05 L/(h·kg) increased the abundance of hydrolyzing functional bacteria such as Pseudomonas and Bacillus, and allowed methanogenic bacteria such as Methanobacterium and Methanothrix to gradually establish oxygen tolerance in the microaerobic environment. The appropriate micro-aeration intensity can accelerate the stabilization process of landfill, which has environmental and economic benefits.

Evaluation of various carbon sources on ammonium assimilation and denitrifying phosphorus removal in a modified anaerobic-anoxic-oxic process from low-strength wastewater.

A pilot-scale continuous-flow modified anaerobic-anoxic-oxic (MAAO) process examined the impact of external carbon sources (acetate, glucose, acetate/propionate) on ammonium assimilation, denitrifying phosphorus removal (DPR), and microbial community. Acetate exhibited superior efficacy in promoting the combined process of ammonia assimilation and DPR, enhancing both to 50.0 % and 60.0 %, respectively. Proteobacteria and Bacteroidota facilitated ammonium assimilation, while denitrifying phosphorus-accumulating organisms (DPAOs) played a key role in nitrogen (N) and phosphorus (P) removal. Denitrifying glycogen-accumulating organisms (DGAOs) aided N removal in the anoxic zone, ensuring stable N and P removal and recovery. Acetate/propionate significantly enhanced DPR (77.7 %) and endogenous denitrification (37.9 %). Glucose favored heterotrophic denitrification (29.6 %) but had minimal impact on ammonium assimilation. These findings provide valuable insights for wastewater treatment plants (WWTPs) seeking efficient N and P removal and recovery from low-strength wastewater.

Effect of magnetic field coupled magnetic biochar on membrane bioreactor efficiency, membrane fouling mitigation and microbial communities.

The excitation by magnetic field was established to mitigate the membrane fouling of magnetic biochar (MB)-supplemented membrane bioreactor (MBR) in this study. The results showed that the transmembrane pressure (TMP) increase rates decreased by about 8 % after introducing the magnetic field compared with the magnetic biochar-MBR (MB-MBR). Membrane characterization suggested that the flocs in the magnetic field-magnetic biochar-MBR (MF-MB-MBR) formed a highly permeable developed cake layer, and a fluffier and more porous deposited layer on membrane surface, which minimized fouling clogging of the membrane pores. Further mechanistic investigation revealed that the decrease in contact angle of fouled membrane surface in MF-MB-MBR, i.e. an enhanced membrane hydrophilicity, is considered important for forming highly permeable layers. Additionally, the magnetic field was demonstrated to have a positive effect on the improvement of the magneto-biological effect, the enhancement of charge neutralization and adsorption bridging between sludge and magnetic biochar, and the reduction of formation of extracellular polymeric substances (EPSs), which all yielded sludge flocs with a large pore structure conducive to form a fluffy and porous deposited layer in the membrane surface. Furthermore, high-throughput sequencing analysis revealed that the magnetic field also led to a reduction in microbial diversity, and that it promoted the enrichment of specific functional microbial communities (e.g. Bacteroidetes and Firmicutes) playing an important role in mitigating membrane fouling. Taken together, this study of magnetic field-enhanced magnetic biochar for MBR membrane fouling mitigation provides insights important new ideas for more effective and sustainable operation strategies.

Synergistic enhancement of microbes-to-pollutants and inter-microbes electron transfer by Fe, N modified ordered mesoporous biochar in anaerobic digestion.

Extracellular electron transfer was essential for degrading recalcitrant pollutants by anaerobic digestion (AD). Therefore, existing studies improved AD efficiency by enhancing the electron transfer from microbes-to-pollutants or inter-microbes. This study synthesized a novel Fe, N co-doped biochar (Fe, N-BC), which could enhance both the microbes-to-pollutants and inter-microbes electron transfer in AD. Detailed characterization data indicated that Fe, N-BC has an ordered mesoporous structure, high specific surface area (463.46 m2/g), and abundant redox functional groups (Fe2+/Fe3+, pyrrolic-N), which translate into excellent biocompatibility and electrochemical properties of Fe, N-BC. By adding Fe, N-BC, the stability and efficiency of the medium-temperature AD system in the treatment of methyl orange (MO) wastewater were improved: obtained a high degradation efficiency of MO (96.8 %) and enhanced the methane (CH4) production by 65 % compared to the control group. Meanwhile, Fe, N-BC reduced the accumulation of volatile fatty acids in the AD system, and the activity of anaerobic granular sludge electron transport system and coenzyme F420 was enhanced. In addition, Fe, N-BC showed positive enrichment of azo dyes decolorization bacteria (Georgenia) and direct interspecies electron transfer (DIET) synergistic partners (Syntrophobacter, Methanosarcina). Overall, the rapid degradation of MO and enhanced CH4 production in AD systems by Fe, N-BC is associated with enhancing two electronic pathways, i.e., microbes to MO and DIET between syntrophic bacteria and methanogenic archaea. This study introduced an enhanced "two-pathways of electron transfer" theory, realized by Fe, N-BC. These findings provided new insights into the interactions within AD systems and offer strategies for enhancing their performance with recalcitrant pollutants.

Cu2(OH)3NO3/γ-Al2O3 catalyzes Fenton-like oxidation for the advanced treatment of effluent organic matter (EfOM) in fermentation pharmaceutical wastewater: The synergy of Cu2(OH)3NO3 and γ-Al2O3.

The secondary effluent of fermentation pharmaceutical wastewater exhibits high chromaticity, elevated salinity, and abundant refractory effluent organic matter (EfOM), presenting significant treatment challenges and environmental threats. Herein, Cu2(OH)3NO3/γ-Al2O3 was fabricated through ultrasound-assisted impregnation and calcination to catalyze the Fenton-like oxidation for degrading organic pollutants in this secondary effluent. Under neutral conditions, with 400.00 mg/L H2O2, 8 g/L catalyst, and at 30 ℃, the EfOM and CODCr removal efficiencies can reach 96.90 % and 51.56 %, respectively. The Cu2(OH)3NO3/γ-Al2O3 catalyst possesses ideal reusability, maintaining CODCr, chromaticity, and EfOM removal efficiencies at 44.44 %-64.59 %, 85.45 %-93.45 %, and 61.00 %-95.00 % over 220 h in a continuous-flow catalytic oxidation system operated at room temperatures (15-25 ℃). Electron paramagnetic resonance results and density functional theory calculations indicate that •OOH may be the predominant reactive oxygen species, facilitated by the easier elongation of the OH bond in H2O2 compared to the OO bond. The adjusted electronic structure endows Cu2(OH)3NO3/γ-Al2O3 composite sites with superior catalytic selectivity for H2O2 activation compared to Cu2(OH)3NO3 single crystal sites, with γ-Al2O3 additionally facilitating H2O2 activation through electron donation. This research highlights the efficacy of Cu2(OH)3NO3/γ-Al2O3 in the advanced treatment of complex industrial wastewater, elucidating its catalytic mechanisms and potential applications.

Synchronous reinforcement azo dyes decolorization and anaerobic granular sludge stability by Fe, N co-modified biochar: Enhancement based on extracellular electron transfer.

Anaerobic digestion (AD) treatment of azo dyes wastewater often suffers from low decolorization efficiency and poor stability of anaerobic granular sludge (AnGS). In this study, iron and nitrogen co-modified biochar (FNC) was synthesized based on the secondary calcination method, and the feasibility of this material for enhanced AD treatment of azo dye wastewater and its mechanism were investigated. FNC not only formed richer conducting functional groups, but also generated Fe2+/Fe3+ redox pairs. The decolorization efficiency of Congo red and AD properties (e.g., methane production) were enhanced by FNC. After adding FNC, the content of extracellular polymeric substances (EPS) and the ratio of proteins remained stable under the impact of Congo red, which greatly protected the internal microbial community. This was mainly contributed to the excellent electrochemical properties of FNC, which strengthened the microbial extracellular electron transfer and realized the coupled mechanism of action: On the one hand, an electron transfer bridge between decolorizing bacteria and dyes was constructed to achieve rapid decolorization of azo dyes and mitigate the impact on methanogenic bacteria; On the other hand, the stability of AnGS was enhanced based on enhanced extracellular polymeric substances secretion, microbial community and direct interspecies electron transfer (DIET) process. This study provides a new idea for enhanced AD treatment of azo dyes wastewater.

Recent advances in methane and hydrogen production from lignocellulosic degradation with anaerobic fungi.

Anaerobic fungi (AF) efficiently degrade lignocellulosic biomass with unique pseudoroot system and enzymatic properties that can remove polysaccharides and some lignified components from plant cell walls, further releasing acetate, lactate, ethanol, hydrogen (H2), etc. As research on AF for bioengineering has become a hot topic, a review of lignocellulosic conversion with AF for methane (CH4) and H2 production is needed. Efficient degradation of lignocellulose with AF mainly relies on multiple free carbohydrate-active enzymes and cellulosomes in the free and bound state. Meanwhile, co-cultivation of AF and methanogens significantly improves the lignocellulose degradation and CH4 production, and the maximum CH4 yield reached 315 mL/g. Bioaugmentation of AF in anaerobic digestion increases the maximum CH4 yield by 330 %. Also, AF show H2 production potential, however, H2 yield from anaerobic fungal fermentation of lignocellulose remains low. Therefore, anaerobic fungi have great potential in the conversion of lignocellulosic biomass to CH4 and H2.

Regulation of extracellular polymers based on quorum sensing in wastewater biological treatment from mechanisms to applications: A critical review.

Extracellular polymeric substances (EPS) regulated by quorum sensing (QS) could directly mediate adhesion between microorganisms and form tight microbial aggregates. Besides, EPS have redox properties, which can facilitate electron transfer for promoting electroactive bacteria. Currently, the applications research on improving wastewater biological treatment performance based on QS regulated EPS have been widely reported, but reviews on the level of QS regulated EPS to enhance EPS function in microbial systems are still lacking. This work proposes the potential mechanisms of EPS synthesis by QS regulation from the viewpoint of material metabolism and energy metabolism, and summarizes the effects of QS on EPS synthesis. By synthesizing the role of QS in EPS regulation, we further point out the applications of QS-regulated EPS in wastewater biological treatment, which involve a series of aspects such as strengthening microbial colonization, mitigating membrane biofouling, improving the shock resistance of microbial metabolic systems, and strengthening the electron transfer capacity of microbial metabolic systems. According to this comprehensive review, future research on QS-regulated EPS should focus on the exploration of the micro-mechanisms, and economic regulation strategies for QS-regulated EPS should be developed, while the stability of QS-regulated EPS in long-term production experimental research should be further demonstrated.

A new strategy for accelerating recovery of anaerobic granular sludge after low-temperature shock: In situ regulation of quorum sensing microorganisms embedded in polyvinyl alcohol sodium alginate.

Low-temperature could inhibit the performance of anaerobic granular sludge (AnGS). Quorum sensing (QS), as a communication mode between microorganisms, can effectively regulate AnGS. In this study, a kind of embedded particles (PVA/SA@Serratia) based on signal molecule secreting bacteria was prepared by microbial immobilization technology based on polyvinyl alcohol and sodium alginate to accelerate the recovery of AnGS system after low temperature. Low-temperature shock experiment verified the positive effect of PVA/SA@Serratia on restoring the COD removal rate and methanogenesis capacity of AnGS. Further analysis by metagenomics analysis showed that PVA/SA@Serratia stimulated higher QS activity and promoted the secretion of extracellular polymeric substance (EPS) in AnGS. The rapid construction of EPS protective layer effectively accelerated the establishment of a robust microbial community structure. PVA/SA@Serratia also enhanced multiple methanogenic pathways, including direct interspecies electron transfer. In conclusion, this study demonstrated that PVA/SA@Serratia could effectively strengthen AnGS after low-temperature shock.

Comprehensive carbon footprint analysis of wastewater treatment: A case study of modified cyclic activated sludge technology for low carbon source urban wastewater treatment.

To reduce pollution and carbon emissions, a quantitative evaluation of the carbon footprint of the wastewater treatment processes is crucial. However, micro carbon element flow analysis is rarely focused considering treatment efficiency of different technology. In this research, a comprehensive carbon footprint analysis is established under the micro carbon element flow analysis and macro carbon footprint analysis based on life cycle assessment (LCA). Three wastewater treatment processes (i.e., anaerobic anoxic oxic, A2O; cyclic activated sludge technology, CAST; modified cyclic activated sludge technology, M-CAST) for low carbon source urban wastewater are selected. The micro key element flow analysis illustrated that carbon source mainly flows to the assimilation function to promote microorganism growth. The carbon footprint analysis illustrated that M-CAST as the optimal wastewater treatment process had the lowest global warming potential (GWP). The key to reduce carbon emissions is to limit electricity consumption in wastewater treatment processes. Under the comprehensive carbon footprint analysis, M-CAST has the lowest environmental impact with low carbon emissions. The sensitivity analysis results revealed that biotreatment section variables considerably reduced the environmental impact on the LCA and the GWP, followed by the sludge disposal section. With this research, the optimization scheme can guide wastewater treatment plants to optimize relevant treatment sections and reduce pollution and carbon emissions.

Performance and mechanism of modified biological nutrient removal process in treating low carbon-to-nitrogen ratio wastewater.

For solving the challenge of difficult nutrient removal, high running cost and CO2 emission at low carbon-to-nitrogen (C:N) ratio, Bi-Bio-Selector for nitrogen and phosphorus removal (BBSNP) process was developed. Under parallel operation conditions, full-scale BBSNP was less influence by low C:N ratio (3.5-2) than Anaerobic-anoxic-aerobic (AAO) and achieved better nitrogen removal performance. The mechanism of performance advantage in BBSNP was analyzed by mass balance and high throughout sequencing. It demonstrated BBSNP developed unique microbial community at C:N ratio of 2. Higher abundance of Saccharibacteria, Ferruginibacter, Ottowia, Dokdonella, Candidatus_Nitrotoga and Nitrospira in BBSNP was responsible for better chemical oxygen demand (COD) utilization efficiency, denitrification, denitrifying phosphorus removal and nitrification. Meanwhile, under low C:N ratio, BBSNP could save 10% organic carbon and 15% oxygen requirement, reduce 53% running cost and 21% CO2 emission, which had practical value in relieving energy crisis and carbon emission of wastewater treatment plants (WWTPs).

Roles and regulation of quorum sensing in anaerobic granular sludge: Research status, challenges, and perspectives.

Anaerobic granular sludge (AnGS) has a complex and important internal microbial communication system due to its unique microbial layered structure. As a concentration-dependent communication system between bacterial cells through signal molecules, QS (quorum sensing) is widespread in AnGS and exhibits great potential to regulate microbial behaviors. Therefore, the universal functions of QS in AnGS have been systematically summarized in this paper, including the influence on the metabolic activity, physicochemical properties, and microbial community of AnGS. Subsequently, the common QS-based AnGS regulation approaches are reviewed and analyzed comprehensively. The regulation mechanism of QS in AnGS is analyzed from two systems of single bacterium and mixed bacteria. This review can provide a comprehensive understanding of QS functions in AnGS systems, and promote the practical application of QS-based strategies in optimization of AnGS treatment process.

Micro-aeration and leachate recirculation for the acceleration of landfill stabilization: Enhanced hydrolytic acidification by facultative bacteria.

The long duration of landfill stabilization is one of the challenges faced by municipalities. In this paper, a combination of micro-aeration and leachate recirculation is used to achieve rapid degradation of organic matter in landfill waste. The results showed that the content of volatile fatty acids (VFAs) in the hydrolysis phase increased significantly and could enter the methanogenic phase quickly. Until the end of the landfill, the removal rates of chemical oxygen demand (COD), total phosphorus (TP) and ammonia nitrogen (NH4+-N) by micro-aeration and leachate recirculation reached 80.17 %, 48.30 % and 48.56 %, respectively, and the organic matter degradation rate reached 50 %. Micro-aeration and leachate recirculation enhanced the abundance of facultative hydrolytic bacteria such as Rummeliibacillus and Bacillus and the oxygen tolerance of Methanobrevibacter and Methanoculleus. Micro-aeration and leachate recirculation improved the organic matter degradation efficiency of landfill waste by promoting the growth of functional microorganisms.

Adsorption-desorption behaviors of ciprofloxacin onto aged polystyrene fragments in aquatic environments.

As two emerging pollutants of great concern, microplastics (MPs) and antibiotics inevitably cooccur in various aquatic environments and interact with each other, impacting the fate and ecological risks. Aging obviously complicates their interaction and deserves further study. Therefore, the adsorption-desorption behaviors of ciprofloxacin (CIP) onto polystyrene (PS) fragments with various aging extent were investigated, and the key physiochemical properties influencing the interaction and the interaction mechanisms were clarified by redundancy analysis, FTIR and XPS spectra. The physicochemical properties of PS MPs were significantly changed with aging time, and the morphological and chemical changes seemed to occur asynchronously. The adsorption of CIP onto the pristine PS MPs relied on physisorption, especially the ion-involving electrostatic and cation-π interaction. Due to the hydrogen bonding formed by the C-OH, CO, and O-CO groups of PS and CIP, the adsorption capacities of the aged PS MPs were greatly increased. The desorption efficiency of CIP from MPs in the gastric fluid was closely related to the solution ionic strengths, C-OH and CO groups of MPs, while that in the intestinal fluid was associated with O-CO groups of MPs. The different impact factors could be well described by the differences in the chemical components and pHs of the simulated gastric and intestinal fluids. This study gives a comprehensive understanding of the adsorption-desorption behaviors of antibiotics onto MPs at a molecular level and indicates that MPs could act as Trojan horses to transport antibiotics into aquatic organisms.