Aerobic Biofilm Reactor Research Articles

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

CFD-PBM simulations the effect of aeration rates on hydrodynamics characteristics in a gas-liquid-solid aerobic fluidized bed biofilm reactor

A CFD-PBM coupling model was developed to simulate and calculate multiphase flow parameters, flow morphology, and bubble diameter in the aerobic fluidized bed biofilm reactor (AFBBR) under different aeration rates. The simulated radial solid volume fraction values were generally in agreement (within ±15%) with the experimental values. The gas phase predominantly occupied the central area of the reactor, with three distinct velocity peaks observed in the liquid and solid phases. Higher aeration rates improve the mixing of multiple phases by augmenting fluidization velocity, gas-phase volume fraction, eddies size, and turbulence characteristics, thereby leading to a rise in the average size of bubbles from 1.54 mm to 2.03 mm. However, the proportion of small diameter bubbles (0.27–1.03 mm) decreased from 69.4% to 59.6%. These studies concluded that the multiphase flow parameters under an aeration rate of 5.77 m3/(h·m3) were more favorable for improving oxygen mass transfer efficiency and reducing energy consumption.

Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment.

We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m2-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m2-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.

Insights into the spatial effects of carbon source type on oxygen mass transfer mechanism and microbial community characteristics

The dissolved oxygen (DO) concentrations in wastewater and biofilm under four types of carbon sources were explored to further reveal the mechanism of oxygen mass transfer (OMT). In aerobic fluidized bed biofilm reactor (AFBBR) system, microbial community composition and functional microorganisms were analysed to characterize the influence of OMT on microbial metabolism. The DO concentrations with sodium acetate, sodium propionate, glucose, and starch reached to 6.43 ± 0.36 mg/L, 5.92 ± 0.21 mg/L, 6.91 ± 0.50 mg/L, and 7.20 ± 0.43 mg/L, respectively. Differences in carbon source led to significant differences in wastewater and biofilms OMT efficiency. The oxygen transfer rate (OTR) under four types of carbon sources was in the order starch>glucose>sodium acetate>sodium propionate, but the parameters for diffusion dynamics [Db = (3.68 ± 0.09) × 10−6 cm2/s, Di = (3.26 ± 0.99) × 10−4 cm2/s, ki = (5.94 ± 0.16) × 10−3 cm/s, and LF = (2174 ± 72 μm)] in the biofilms were highest with sodium propionate. With sodium propionate and glucose, Actinobacteria was the dominant bacteria (60.3 % and 78.5 %). However, with sodium acetate and starch, the dominant bacteria was Proteobacteria (88.9 % and 45.0 %). Sodium propionate improved wastewater treatment efficiency by altering microbial community composition and metabolic functions. The average removal of CODcr, NH4+-N, TN, and TP reached to 93.1 %, 86.9 %, 81.3 %, and 57.2 %, respectively.

Performance and bacterial community analysis of multi-stage A/O biofilm system for nitrogen removal of rural domestic sewage

Rural domestic sewage was difficult to collect, and there was a lack of skilled professionals for its treatment. This study constructed a high-efficiency anaerobic- aerobic (A/O) biofilm reactor with multi-stage free combination, simple operation, and low consumption. The nitrogen removal capacity of the system was enhanced by changing the number of A/O stages, influent, and hydraulic retention times (HRT). The most economical system with the required total nitrogen (TN) removal loading is tertiary A/O with a step-feed ratio of 1:1:1 and HRT = 36 h. At this time, the TN removal rate could reach 71.29 %. Realizes high-efficiency nitrogen removal with low consumption and unattended operation. Increasing the influent carbon to nitrogen (C/N) ratio could effectively enhance the nitrogen removal capacity. In addition, chemical oxygen demand (COD) removal was better under various operating conditions. Pseudomonas was the dominant genera in the anaerobic zone, contributing to organic pollutant removal and denitrification. The aerobic zone was enriched with Nitrospira, related to the nitrification and denitrification process. The anoxic zone contained more heterotrophic denitrifying bacteria genera such as Denitratisoma. The system had excellent performance with the synergistic effect of the above microorganisms. The efficient and low-consumption biofilm system developed in this study suits engineering applications in poor rural areas.

Integrated Anaerobic–Aerobic Moving Bed Biofilm Reactor and Biochar Adsorption for the Efficient Removal of Organic Matter and Nutrients from Brazilian Landfill Leachate

Landfill leachate is a complex and highly polluted wastewater that poses significant environmental challenges worldwide. This study proposes an innovative approach to addressing this challenge by developing an integrated anaerobic–aerobic moving bed biofilm reactor (MBBR) and biochar adsorption method for the efficient removal of organic matter and nutrients from landfill leachate. The MBBR provides a suitable environment for the growth of microorganisms that can degrade organic matter and nutrients, while biochar adsorption removes any remaining pollutants that are not biodegradable. The performance of this integrated system was evaluated under different operating conditions, such as the hydraulic retention time and the organic loading rate, to optimize its efficiency and sustainability. The results showed that the integrated system achieved high removal efficiencies for chemical oxygen demand (COD), ammonium–nitrogen (NH4-N), and total phosphorus (TP), with maximum removal rates of 98.5% (77% after the anaerobic–aerobic MBBR and 85.4% after biochar adsorption), 91.2% (87% after the anaerobic–aerobic MBBR and 95.9% after biochar adsorption), and 99.9% (92% after the anaerobic–aerobic MBBR and 91.7% after biochar adsorption), respectively. The proposed method offers a promising solution for the treatment of landfill leachate, which is a critical environmental issue worldwide. This study also highlights the importance of developing more effective and sustainable methods for treating landfill leachate, which can have significant impacts on public health and the environment.

Antibiotics resistance removal from piggery wastewater by an integrated anaerobic–aerobic biofilm reactor: Efficiency and mechanism

Antibiotic resistance residual in piggery wastewater poses serious threat to environment and human health. Biological treatment process is commonly installed to remove nutrient from piggery wastewater and also effective in removing antibiotics to varying degrees. But the specific pathways and mechanisms involved in the removal of antibiotic resistance are not yet well-understood. An integrated anaerobic–aerobic biofilm reactor (IAOBR) has been demonstrated efficient in removing conventional nutrients. It is here shown that the IAOBR effectively removed 79.0% of Sulfonamides, 55.7% of Tetracyclines and 53.6% of Quinones. Antibiotic resistance bacteria (ARB) were simultaneously inactivated by ~0.5 logs. Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) were decreased by 0.51 logs and 0.42 logs, respectively. The antibiotics were mainly removed through aerobic compartments of the IAOBR. The mass loss of antibiotics in the reactor was achieved by biodegradation and adsorption, accounting for 52.1% and 47.9%, respectively. An obvious accumulation of ARGs was observed in the activated sludge. The potential host of ARGs was analyzed via microbial community and network. Partial least squares-structural equation model and correlation analysis revealed that the enrichment of ARGs was positively affected by MGEs, followed by bacterial community and ARBs, but the effect of antibiotics on ARGs was negative. Outcomes of this study provide valuable insights into the mechanisms of antibiotic resistance removal in biological treatment processes.

Mechanistic insights into 1,2,4-trichlorobenzene removal in flue gas by aerobic denitrifying membrane biofilm reactor

1,2,4-Trichlorobenzene (1,2,4-TrClBz) as dioxin indicator in municipal solid waste incineration can increase risk of human health. Aerobic denitrifying membrane biofilm reactor (MBfR) was investigated for 1,2,4-TrClBz removal in flue gas. During the 75 days of operation, 1,2,4-TrClBz removal efficiency achieved 94%. Pseudomonas, Halomonas, Paracoccus, Thauera, Azoarcus, Proteiniphilum, Mesorhizobium, Pelagibacterium, Chelativorans were the core 1,2,4-TrClBz biodegrading-denitrifying bacteria. 1,2,4-TrClBz biodegradation genes and denitrification genes were responsible for the oxidation of 1,2,4-TrClBz and nitrate reduction. 1,2,4-TrClBz was degraded by ring-cleavage before aerobic dechlorination, 1,2,4-TrClBz bio-oxidation was coupled to denitrification formed redox between 1,2,4-TrClBz and nitrate, as shown by metagenomic sequencing and untargeted metabolomic analysis. Therefore, MBfR effectively achieved bioremoval and biodegradation of 1,2,4-TrClBz in flue gas by aerobic denitrification, which may provide a feasible and environment-friendly biotechnique for decontamination of chlorobenzene compounds in flue gas.

Effects of carbon to nitrogen ratio on oxygen mass transfer characteristics in wastewater and biofilms

Systematic elucidation of the oxygen mass transfer (OMT) mechanism is the key to improving aeration and oxygenation efficiency. In this study, an aerobic fluidized bed biofilm reactor (AFBBR) was established to evaluate the OMT in the wastewater phase [macroscopic (reactor) scale] and diffusion kinetic parameters in the biofilm phase (microbiological scale) under different carbon-nitrogen(C:N) ratios. A model relating the oxygen concentration and the aerobic layer thickness of the biofilm was established based on oxygen mass balance theory and Fick's second law. The results showed that the average DO concentration decreased from 7.68 mg/L to 5.85 mg/L with increasing C:N ratio (from 4.79 to 13.94). The oxygen transfer rate (OTR) was consistent with the distribution of the total biomass (total suspended solids, TSS), which was the largest (9.74 ± 0.33 mg/(L·h) and 8178 ± 87 mg/L) under the highest C:N ratio (13.94). Additionally, the α-factor, as a key parameter for evaluating OMT efficiency, had an exponential correlation with chemical oxygen demand (CODcr). The oxygen concentration exhibited in a Gaussian distribution (0.9963 ≤R2 ≤0.9998) relative to the thickness of the aerobic layer. The mass transfer efficiency (ki) and diffusion coefficient (Di) of oxygen in the boundary layer both reached maxima [(8.1 ± 3.2)× 10−5 cm2/s and (2.0 ± 0.1)× 10−3 cm/s] under the condition of C:N = 9.49. However, under the lowest C:N ratio, the biofilm thickness (LF=2422 ± 411 µm) and oxygen diffusion coefficient (Db) both reached maxima. These results have important theoretical significance for improving OMT theory and reducing the energy consumption of the aeration process.

Biodegradation of Aromatic Compounds Under Hypersaline Conditions: Comparing Aerobic Biofilm Reactors with Conventional Activated Sludge

Biodegradation of Aromatic Compounds Under Hypersaline Conditions: Comparing Aerobic Biofilm Reactors with Conventional Activated Sludge

Statistical analysis of treatment of rice mill wastewater using the aerobic inverse fluidized bed biofilm reactor (AIFBBR)

Among the different industries, the ricemill industry is identified as one of the major polluting industries because of the large amounts of effluents generated and variations in the concentration of its constituents. The current experimental study aimed to investigate the treatment of ricemill (simulated) using the aerobic inverse fluidized bed biofilm reactor (AIFBBR). Box–Behnken design (BBD) based statiscal response surface methodology (RSM) was used for the current AIFBBR-ricemill treatment system. For the evaluation of the RSM process through the BBD technique, three input variables: Influent COD (800–3200 mg/L), HRT (12–24 h), and % bed volume (15 − 45), and two output variables: %COD and %TOC removal, were selected. The effect of these chosen variables was verified by conducting 15 experiments in a multivariate system for the AIFBBR-ricemill treatment system. The quadratic polynomial models yielded a regression coefficient (R2) of 0.99 (for both COD and TOC) when the experimental data were fitted to it, which indicates the model's suitability for the process. The precision and efficiency of the model were visualized using the ANOVA and lack of fit test. The system has witnessed the maximum COD (88.95%) and TOC (95.68%) removal at optimum parameters of 2804.27 mg/L of influent COD, 23.79 h of HRT, and at a % bed volume of 44.94. Along with the COD and TOC, parameters such as nutrients (NH4+-N, PO43--P, and NO3--N), phenol, and lignin were also monitored in the present study.

Mechanism of trehalose-enhanced metabolism of heterotrophic nitrification-aerobic denitrification community under high-salt stress

Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria are aerobic microorganisms that can remove nitrogen under high-salt conditions, but their performance in practical applications are not satisfactory. As a compatible solute, trehalose helps microorganisms to cope with high salt stress by participating in the regulation of cellular osmotic pressure, and plays an important role in promoting the nitrogen removal efficiency of microbial populations in the high-salt environment. We investigated the mechanism of exogenous-trehalose-enhanced metabolism of HN-AD community under high-salt stress by starting up a membrane aerobic biofilm reactor (MABR) to enrich HN-AD bacteria, and designed a C150 experimental group with 150 μmol/L trehalose addition and a C0 control group without trehalose. The reactor performance and the community structure showed that NH4+-N, total nitrogen (TN) and chemical oxygen demand (COD) removal efficiency were increased by 29.7%, 28.0% and 29.1%, respectively. The total relative abundance of salt-tolerant HN-AD bacteria (with Acinetobacter and Pseudofulvimonas as the dominant genus) in the C150 group reached 66.8%, an 18.2% increase compared with that of the C0 group. This demonstrated that trehalose addition promoted the enrichment of salt-tolerant HN-AD bacteria in the high-salt environment to enhance the nitrogen removal performance of the system. In-depth metabolomics analysis showed that the exogenous trehalose was utilized by microorganisms to improve proline synthesis to increase resistance to high-salt stress. By regulating the activity of cell proliferation signaling pathways (cGMP-PKG, PI3K-Akt), phospholipid metabolism pathway and aminoacyl-tRNA synthesis pathway, the abundances of phosphoethanolamine, which was one of the glycerophospholipid metabolites, and purine and pyrimidine were up-regulated to stimulate bacterial aggregation and cell proliferation to promote the growth of HN-AD bacteria in the high-salt environment. Meanwhile, the addition of trehalose accelerated the tricarboxylic acid (TCA) cycle, which might provide more electron donors and energy to the carbon and nitrogen metabolisms of HN-AD bacteria and promote the nitrogen removal performance of the system. These results may facilitate using HN-AD bacteria in the treatment of high-salt and high-nitrogen wastewater.

Impact of gradually-achieved high phenol loads on the nitrification and COD removal performance of an MBBR fed with synthetic wastewater

ABSTRACT Phenol is a noteworthy pollutant, found in effluents of many industrial processes, like oil refining and drugs production, which can impair the treatment efficiency of bioreactors. This study evaluated the performance of phenol, COD, and nitrogen removal of an aerobic bench-scale Moving Bed Biofilm Reactor (MBBR) exposed to gradually increasing phenol content over 233 days. The reactor had Hydraulic Retention Time (HRT) set at 3 h and 40% filling degree (K1 media), and was fed with synthetic wastewater containing phenol (10, 20, 50, 100, 250 and 400 mg/L), glucose (400 mgCOD/L), and 40 mgN-NH3/L. Phenol, COD, and ammoniacal nitrogen removal averages were high – above 88%, 81%, and 82%, respectively –, even when the MBBR was exposed to the greatest phenol loads, indicating that the biofilm was able to acclimate and resist high phenol concentrations. However, the intense EPS production revealed the impact caused by phenol to the biofilm from the concentration of 250 mg/L onwards. Even though, at this concentration, the average removals of COD and phenol were 87.2% and 89.7%. The removal of ammoniacal nitrogen by nitrification was compromised, being 91.6% of the ammoniacal nitrogen removed by assimilation and only 0.35% removed by nitrification. At 400 mg phenol/L, the reactor provided COD and phenol average removals equal 88.6% and 80.9%, respectively. On the last day of operation, the removal of COD dropped to 55.4% and phenol removal was equal 49.0%. Novel microscopical evaluation of the MBBR’s biofilm revealed some negative effects of the phenol on the microbiota composition.

Kinetic Study for Startup of Aerobic Moving Bed Biofilm Reactor in Treatment of Textile Dye Wastewater.

Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24h. The biofilm on the media was developed in 63days duration and the reactor attained pseudo-steady state (PSS) in 185days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monodgrowth kinetics. The values of bio-kinetic coefficients of yieldof heterotrophic biomass (Y) and endogenousdecay coefficient for heterotrophic biomass (Kd) recorded are 0.394 mgVSS/mgCOD.d and 0.087day-1, respectively. The values of specific substrate removal rate (k), Monodhalf saturation constant (Ks), and maximumspecific growth rate for heterotrophic biomass (µmax) are 0.024 mgCOD/mgVSS.d, 53.203mg/L, and 0.0095day-1, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.

ORGANIC REMOVAL IN DOMESTIC WASTEWATER USING ANAEROBIC TREATMENT SYSTEM-MBBR WITH FLOW RECIRCULATION RATIO AND INTERMITTENT AERATION

Aim: The modified Small-scale Domestic Sewage Treatment Plant (SDSTP) reactor with anaerobic fixed bed- aerobic Moving Bed Biofilm Reactor (MBBR) is implemented to find the optimum condition for organic degradation related to recirculation and intermittent aeration practices with the purpose to comply with the governmental regulation standard. Methodology and Results: This research have been done with the artificial wastewater with characteristic similar to the sewage treatment plant (STP) of Telkom company with ratio C:N:P of characterized domestic wastewater is 252.40:85.42:3.01 that consists of glucose, NH4Cl, potassium dihydrogen phosphate, potassium nitrate, and sodium nitrite (NaNO2). Reactor design related with attached biomass in media until 2478.56 mg MLVSS.L-1 with the growth kinetics rate (μ) of 0.4691 day—1. The artificial wastewater is applied the determine the optimum variation of flow recirculation and periodic aeration in specific Hydraulics Retention Time (HRT) and Organic Loading Rate (OLR). In this research, the optimum recirculation ratio for organic degradation is 26.40 L.h-1 and the optimum aeration frequency variation is 12 hours in intermittent frequency with the maximum efficiency of organic degradation of 76.10% with the degradation efficiency real domestic wastewater application from STP Telkom company is 83.09%. Conclusion, significance and impact study: Stover-Kincannon model is the best model with highest accuracy rate to model the degradation performance of organic compounds by the anaerobic fixed bed- aerobic MBBR SDSTP with determination coefficient 0.8623 and also degradation coefficient 38.121 day-1 compared with other models studied in this research.

Evaluation of the nitrogen removal mechanism by analysing the kinetic characteristics, microbial compositions and functional genes in an aerobic fluidized bed biofilm reactor at different carbon to nitrogen (C:N) ratios

The nitrogen removal mechanism in an aerobic fluidized bed biofilm reactor (AFBBR) was explored by analysing the nitrogen removal efficiencies, pollutant degradation kinetics, microbial characteristics, and functional gene abundances. The carbon to nitrogen (C:N) ratios significantly changed the treatment efficiencies for the chemical oxygen demand (CODcr), total nitrogen (TN), and ammonia nitrogen (NH4+-N). Moreover, the average removal rates of NH4+-N (73.2%) and TN (72.7%) under the C:N = 13.94 condition were higher than those under the other conditions. High C:N ratios improved the simultaneous nitrification and denitrification (SND) rate (98.8%) in the AFBBR system. The pollutant degradation kinetics conformed to the Haldane fictitious kinetic model. Actinobacteria and Protrobacteria were the dominant bacteria in the AFBBR system. Additionally, low C:N ratios increased the relative Protrobacteria (43.5%) abundance. The real-time quantitative polymerase chain reaction (qPCR) results indicated that high C:N ratios increased the SND through enhancing the nirS, nirK, and amx-16S gene abundances. These findings showed that high C:N ratios increased the nitrogen removal rates by improving the functional gene abundances of denitrification and anaerobic ammonia oxidation (ANAMMOX).

An assessment of the purification performance and resilience of sponge-based aerobic biofilm reactors for treating polluted urban surface waters.

Pollutants are continuously released into surface waters, which decrease the dissolved oxygen (DO) concentration and leads to the formation of black-odorous water, especially in slow-flowing urban lakes and enclosed small ponds. In situ treatment by artificial aeration or water cycling, coupled with biofilm, can address this problem without occupying large amounts of land. In this study, we designed a novel sponge-based aerobic biofilm reactor (SABR) and evaluated its performance in purifying urban surface water under different conditions. In the urban lake water treatment, the continuous inflow results revealed that the NH4+-N and NO2--N concentrations in the effluent were stable and remained lower than 0.10mg/L and 0.05mg/L, respectively. Abrupt increases in the NH4+-N and NO2--N concentrations in the influent and sudden increases in the NH4+-N and NO2--N concentrations in the effluent were observed, and only 4 to 8days were required for the concentrations to decline below 0.10mg/L and 0.05mg/L, respectively. Increases in the polyurethane sponge filling ratios in the SABRs can reduce the DO concentration but do not affect NH4+-N removal. When no biodegradable organic matter was present in the enclosed surface water, the degradation time of NH4+-N from 14.22 to 0.10mg/L was only 9days when SABRs were combined with water cycling, which was shorter than the time needed by water cycling alone (16days), and most of the NH4+-N was converted to NO3--N. When massive amounts of biodegradable organic matter were present in the enclosed surface water, 22days were required to remove the NH4+-N when SABRs were combined with water cycling. Our results indicated that organic matter could be used as a carbon source to eliminate the produced NO3--N in SABRs. Therefore, the newly developed bioreactor provides an effective approach for treating N-polluted urban surface waters.

A Comparative Study on the Microbial Communities Developed in Two Pilot-Scale Aerobic Moving Bed Biofilm Reactor Systems Treating High Strength Saline Bilge Wastewater

A Comparative Study on the Microbial Communities Developed in Two Pilot-Scale Aerobic Moving Bed Biofilm Reactor Systems Treating High Strength Saline Bilge Wastewater

Relationship of Phosphorus Removal, Extracellular Polymeric Substances Characteristics, and Microbial Community Diversity in an Aerobic Moving Bed Biofilm Reactor: Effect of Carbon Sources

Relationship of Phosphorus Removal, Extracellular Polymeric Substances Characteristics, and Microbial Community Diversity in an Aerobic Moving Bed Biofilm Reactor: Effect of Carbon Sources

Effects of various antibiotics on aerobic nitrogen removal and antibiotic degradation performance: Mechanism, degradation pathways, and microbial community evolution

Little information about the selective stress of various antibiotics and how they influence different stages of aerobic nitrogen removal is available. A long-term aerobic nitrogen removal-moving bed biofilm reactor was established by the inoculation of Achromobacter sp. JL9, capable of heterotrophic nitrification and aerobic denitrification, and aerobic activated sludge. The nitrogen removal and antibiotic degradation performances of various antibiotics were then measured. High total nitrogen (91.83% and 91.51%) removal efficiencies were achieved with sulfamethoxazole or no antibiotics, and lower efficiencies were observed with other antibiotics (trimethoprim, teicoplanin, and ciprofloxacin). These results suggest that various antibiotics have different selective inhibitory effects on aerobic nitrogen removal. Additionally, all antibiotics were partly degraded; proposed degradation pathways according to the detected intermediates included ring-opening, S-N bond cleavage, amination, hydroxylation, and methylation. High-throughput sequencing indicated that aerobic denitrifying, recalcitrant pollutant degrading, and antibiotic-resistant bacteria dominate during the community evolution process.