Sequencing Batch Reactor Research Articles

First evidence for temperature’s influence on the enrichment, assembly, and activity of polyhydroxyalkanoate-synthesizing mixed microbial communities

Polyhydroxyalkanoates (PHA) are popular biopolymers due to their potential use as biodegradable thermoplastics. In this study, three aerobic sequencing batch reactors were operated identically except for their temperatures, which were set at 15 °C, 35 °C, and 48 °C. The reactors were subjected to a feast–famine feeding regime, where carbon sources are supplied intermittently, to enrich PHA-accumulating microbial consortia. The biomass was sampled for 16S rRNA gene amplicon sequencing of both DNA (during the enrichment phase) and cDNA (during the enrichment and accumulation phases). All temperatures yielded highly enriched PHA-accumulating consortia. Thermophilic communities were significantly less diverse than those at low or mesophilic temperatures. In particular, Thauera was highly adaptable, abundant, and active at all temperatures. Low temperatures resulted in reduced PHA production rates and yields. Analysis of the microbial community revealed a collapse of community diversity during low-temperature PHA accumulation, suggesting that the substrate dosing strategy was unsuccessful at low temperatures. This points to future possibilities for optimizing low-temperature PHA accumulation.

Non-redundant metagenome-assembled genomes of activated sludge reactors at different disturbances and scales

Metagenome-assembled genomes (MAGs) are microbial genomes reconstructed from metagenomic data and can be assigned to known taxa or lead to uncovering novel ones. MAGs can provide insights into how microbes interact with the environment. Here, we performed genome-resolved metagenomics on sequencing data from four studies using sequencing batch reactors at microcosm (~25 mL) and mesocosm (~4 L) scales inoculated with sludge from full-scale wastewater treatment plants. These studies investigated how microbial communities in such plants respond to two environmental disturbances: the presence of toxic 3-chloroaniline and changes in organic loading rate. We report 839 non-redundant MAGs with at least 50% completeness and 10% contamination (MIMAG medium-quality criteria). From these, 399 are of putative high-quality, while sixty-seven meet the MIMAG high-quality criteria. MAGs in this catalogue represent the microbial communities in sixty-eight laboratory-scale reactors used for the disturbance experiments, and in the full-scale wastewater treatment plant which provided the source sludge. This dataset can aid meta-studies aimed at understanding the responses of microbial communities to disturbances, particularly as ecosystems confront rapid environmental changes.

Improving contaminant removal and inhibiting CH4 and H2S emissions from septic tanks: Nitrified human urine as a source of electron acceptor

Septic tanks are widely adopted in decentralized household wastewater treatment systems serving billions of people globally. Due to the lack of effective electron acceptors, insufficient nutrient removal and the emission of harmful gases, e. g. H2S, CH4, etc., are the common drawbacks. In the present work, we attempted to supplement nitrite into septic tanks as an electron acceptor, via nitrifying human urine source-separated from blackwater, to overcome these drawbacks. Partial or complete nitritation of source-separated urine was achieved in a sequencing batch reactor. The addition of nitrified urine into septic tanks improved organic and nitrogen removals in blackwater up to 90 % and 70 %, respectively. The emission of harmful gases from the septic tanks was stably diminished, with more than 75 % of CH4, CO2 and H2S reductions. Nitrite addition significantly reduced the abundance of hydrogenotrophic methanogens in septic tanks. Though the activity of sulfate-reducing bacteria recovered after the initial inhibition upon nitrite addition, the bio-generated H2S was retained in water since the increased wastewater pH after nitrite addition promoted the disassociation of H2S in aqueous solution.

Bibliometric analysis of research trends in biogranulation technology for wastewater treatment.

Inadequate management and treatment of wastewater pose significant threats, including environmental pollution, degradation of water quality, depletion of global water resources, and detrimental effects on human well-being. Biogranulation technology has gained increasing traction for treating both domestic and industrial wastewater, garnering interest from researchers and industrial stakeholders alike. However, the literature lacks comprehensive bibliometric analyses that examine and illuminate research hotspots and trends in this field. This study aims to elucidate the global research trajectory of scientific output in biogranulation technology from 1992 to 2022. Utilizing data from the Scopus database, we conducted an extensive analysis, employing VOSviewer and the R-studio package to visualize and map connections and collaborations among authors, countries, and keywords. Our analysis revealed a total of 1703 journal articles published in English. Notably, China emerged as the leading country, Jin Rencun as the foremost author, Bioresource Technology as the dominant journal, and Environmental Science as the prominent subject area, with the Harbin Institute of Technology leading in institutional contributions. The most prominent author keyword identified through VOSviewer analysis was "aerobic granular sludge," with "sequencing batch reactor" emerging as the dominant research term. Furthermore, our examination using R Studio highlighted "wastewater treatment" and "sewage" as notable research terms within the field. These findings underscore a diverse research landscape encompassing fundamental aspects of granule formation, reactor design, and practical applications. This study offers valuable insights into biogranulation potential for efficient wastewater treatment and environmental remediation, contributing to a sustainable and cleaner future.

Impacts of cefalexin on nitrite accumulation, antibiotic degradation, and microbial community structure in nitrification systems

The intensive use of various antibiotics for clinical and agricultural purposes has resulted in their widespread use in wastewater treatment plants. However, little research has been conducted on the effects of antibiotics on nitrite accumulation, antibiotic degradation pathways, or the microbial community structure in nitrification systems. In this study, a laboratory-scale sequencing batch reactor was used to treat wastewater containing cefalexin (CFX) at different doses (5, 10, 15, and 20 mg/L). The results showed that the nitrification performance was gradually inhibited with increasing CFX concentration. Ammonia-oxidizing bacteria (AOB) are more tolerant to CFX than nitrite-oxidizing bacteria (NOB). Under 15 mg/L of CFX, NOB were completely suppressed, whereas AOB were partially inhibited, as evidenced by an ammonium removal efficiency of 60 % and a 90 % of nitrite accumulation ratio. The partial nitritation was achieved. CFX can be degraded into 2-hydroxy-3phenylpyrazine and cyclohexane through bacterial co-metabolism, and CFX degradation gradually diminishes with decreasing nitrification performance. The abundance of Nitrospira gradually decreased with increasing CFX concentration. Ferruginibacter, Hydrogenophaga, Thauera, and Pseudoxanthomonas were detected at relative abundances of 13.2 %, 0.4 %, 0.9 %, and 1.3 %, respectively, indicating their potential roles in antibiotic degradation. These findings provide insight into the interactions between antibiotics and microbial communities, which are beneficial for a better understanding of antibiotic degradation in nitrification systems.

The Influence of Ca2+ Ion Addition on Physical Characteristics of Aerobic Granular Sludge in Sequencing Batch Reactor

The Influence of Ca2+ Ion Addition on Physical Characteristics of Aerobic Granular Sludge in Sequencing Batch Reactor

Winery wastewater treatment by microalgae Chlorella sorokiniana and characterization of the produced biomass for value-added products.

The microalgae Chlorella sorokiniana was used for the treatment of winery wastewater (WWW). Batch experiments were initially conducted to investigate how biomass acclimatization in different media, dilution of wastewater, and addition of ammonium nitrogen (NH4-N) affect the growth of microalgae and the removal of major pollutants. Afterwards, two sequencing batch reactor (SBR) systems were tested applying different configurations and hydraulic retention times. The biomass collected at the end of the experiments was characterized for proteins, lipids, carbohydrates, amino acid profile, and the existence of lutein, β-carotene, chlorophyll a, and tocopherols. Batch experiments showed that Chlorella sorokiniana acclimatization to urban wastewater enhanced the removal of NH4-N and total phosphorus (TP). The operation of a two-stage SBR system achieved COD and NH4-N removal equal to 85 ± 9% and 91 ± 20%, respectively, while the use of a single-stage system feeding with anaerobically pretreated WWW resulted to COD and NH4-N removal of 78 ± 9% and 95 ± 9%, respectively. Analyses of biomass showed higher protein content (up to 58.8%) in batch experiments with NH4-N addition as well as in SBR experiments. The cultivation of microalgae under SBR conditions enhanced the production of pigments and tocopherols. The maximum concentrations of 1075mgkg-1, 45.5mgkg-1, and 131.2mgkg-1 were achieved for lutein, β-carotene, and tocopherols, respectively, in the one-stage system. Our findings suggested that Chlorella sorokiniana cultivation in WWW not only removed nutrients from WWW but also could potentially serve for the production of value-added ingredients used in food industry, cosmetics, and animal feedstock.

Access the performance of nitrification in an activated sludge reactor for seafood wastewater treatment: Experiment on the SBR model at the lab-scale

Abstract A major challenge in wastewater treatment system design is optimizing the nitrification process in activated sludge reactors, especially in the seafood industry with high concentration of organic matter, fat, oil, and nitrogen. However, in traditional seafood wastewater treatment systems, nitrogen removal is limited by the ratio C:N:P ≈ 100:5:1. With the experiment of the Sequencing Batch Reactor model, the evaluation of biological nitrification reaction is conducted based on the following parameters: organic loading rate, removing efficiency of ammonia - nitrogen, and nitrification rate. By using pre-treatment seafood processing wastewater with a C/N ratio of 5-6, these parameters were determined through an operating biological reactor with F/M from 0.16 to 0.2g BOD5/g MLVSS.d. In terms of the performance of the model, when optimizing the nitrification process, the efficiency removal reaches 78.3-80.0% for BOD5 and 93.9-94.5% for NH4-N. After that, the nitrification process occurred after 30 minutes of reaction phase, reached its maximum rate after 2 hours with nitrification rate from 0.04 to 0.08 g Nox/g MLVSS.d and then maintained for about 1 hour. Moreover, for an optimal nitrification process, the alkaline consumption of the model should be in the range 7.05-7.18 mg CaCO3/mg N.

Design and Life Cycle Assessment (LCA)-based Sustainability Evaluation of a Novel Microbial Fuel Cell (MFC)-Integrated Sequencing Batch Reactor (SBR) System

Although sewage treatment plants form one of the major environmental interventions for eco-friendly and sustainable management of domestic sanitary wastes, yet their own overall sustainability enhancement, rather than process performance assessment are seldom addressed. The sustainability study of a standard sewage treatment plant, namely Sequencing Batch Reactor (SBR) is addressed in the present research work through Life Cycle Assessment (LCA) tools using SimaPro. Following this, an attempt was made herewith to integrate a potential, yet much lesser commercially explored, wastewater management strategy, namely Microbial Fuel Cell (MFC) unto the SBR chamber, with suitable design-modification. The sustainability parameters of the resultant MFC-augment SBR system were also analysed using LCA to compare the effect of this intervention unto the said parameters. The study shows similar normalized trends of overall damage unto sewage as well as sludge, with global warming being the dominant damage cause. Human health was found to be most vulnerable category for both types of SBR’s (namely, with and without MFC), with relatively lower effect in case of MFC-augmented SBR, particularly with regard to infrastructural and short-term domains, in addition to improved water quality and lower water-footprint.

Whatever does not kill them makes them stronger: Using quaternary ammonia antimicrobials to alleviate the inhibition of ammonia oxidation under perfluorooctanoic acid stress

Perfluorooctanoic acid (PFOA), benzalkyl dimethylammonium compounds (BAC) and antibiotic resistance genes (ARGs) have negative effects on biological sewage treatment. The performance of nitrification systems under stress of PFOA (0.1–5 mg/L) or/and BAC (0.2–10 mg/L) was explored during 84-day experiments using four sequencing batch reactors, in this study. Low (0.1 mg/L) concentration PFOA had a positive influence on ammonia removal, while medium and high (2 and 5 mg/L) concentrations PFOA caused severe inhibition. Meanwhile, PFOA stress resulted in the enrichment of ARGs in water (w-ARGs). BAC (0–10 mg/L) had no obvious influence on ammonia removal. However, BAC promoted the reduction of ARGs and the bacterial community was the main participator (48.07%) for the spread of ARGs. Interestingly, the joint stress of PFOA and BAC increased the ammonia-oxidizing bacteria (AOB) activity from 5.81 ± 0.19 and 6.05 ± 0.79 mg N/(g MLSS·h) to 7.09 ± 0.87 and 7.23 ± 0.29 mg N/(g MLSS·h) in medium and high concentrations, compared to single stress of PFOA, which was observed for the first time. BAC could reduce bioavailability of PFOA through competitive adsorption and decreasing sludge hydrophobicity by the lower β-Sheet and α-Helix in tightly bound protein. Furthermore, the joint stress of PFOA and BAC was able to intensify the proliferation of w-ARGs and extracellular ARGs in sludge, and developed the most active horizontal gene transfer mediated by intl1 compared to single stress of PFOA or BAC. The batch tests verified the detoxification capacity of BAC on nitrification under 2.5 mg/L PFOA (48 h exposing), and the maximum alleviation of AOB activity was achieved at BAC and PFOA mass ratio of 2:1. In summary, BAC could be used to alleviate the inhibition of PFOA on ammonia oxidation, providing an efficient and sustainable approach in wastewater treatment.

Microbial Selection for the Densification of Activated Sludge Treating Variable and High-Strength Industrial Wastewater

This study investigates the densification/granulation of activated sludge with poor settleability, treating real industrial wastewater from a tank truck cleaning company. The wastewater is low in nutrients, acidic in nature, and high and variable in chemical oxygen demand (COD, ranging from 2770 mg·L−1 to 14,050 mg·L−1). A microbial selection strategy was applied to promote slow-growing glycogen-accumulating microorganisms (GAO) by the implementation of an anaerobic feast/aerobic famine strategy in a sequencing batch reactor (SBR). After 60 to 70 days, the uptake of carbon during the anaerobic phase exceeded 80%, the sludge morphology improved, and the sludge volume index (SVI) dropped below 50 mL·g−1. 16S rRNA gene sequencing showed the enrichment of the GAOs Defluviicoccus and Candidatus Competibacter. Stable sludge densification was maintained when using a constant organic loading rate (OLR) of 0.85 ± 0.05 gCOD·(L·d)−1, but the sludge quality deteriorated when switching to a variable OLR. In view of the integration of densified/granular sludge in a membrane bioreactor configuration, the filtration properties of the densified SBR sludge were compared to the seed sludge from the full-scale plant. The densified sludge showed a significantly lower resistance due to pore blockage and a significantly higher sustainable flux (45 vs. 15 L·(m2·h)−1).

Riboflavin-induced microbial succession for enhanced tellurite reduction in wastewater treatment

Tellurite is a common component of industrial wastewater; thus, its efficient removal is crucial for environmental protection and wastewater treatment. Although the efficiency is low, the activated sludge process (ASP) is frequently used to treat wastewater by reducing tellurite (Te(Ⅳ)) to harmless elemental tellurium (Te(0)). Riboflavin is a biostimulant that when added to ASP can significantly shape the structure of microbial communities and improve the efficiency of treating telluride-containing wastewater. However, the underlying biological mechanism remains unclear. Herein, two groups—control and biostimulation—of sequencing batch reactors (SBRs) were constructed and run under the same conditions. In the control group (CG), only tellurite was added, whereas biostimulation group (BS) was treated with tellurite and riboflavin. After adding riboflavin, chemical oxygen demand, tellurite removal rates, and extracellular polymeric substance generation increased. The 16 S rRNA high-throughput sequencing results revealed that the succession of microbial communities was effectively promoted in the ASP by riboflavin treatments and that telluride-reducing bacteria—such as Sphingopyxis, Shinella, Brevundimonas, and Brucella—were significantly increased. Key topological properties suggested that riboflavin treatments changed the co-occurrence patterns of SBR microbial communities and strengthened microbial interactions, considerably improving the stability and efficiency of the tellurium-containing wastewater treatment system. In summary, we explored the effect of adding riboflavin to the ASP to stimulate the succession of sludge microbial communities for improved tellurite reduction. The findings of this research contribute to our understanding of the mechanism of riboflavin in optimizing wastewater treatment for removing recalcitrant pollutants.

Advanced oxidation processes of persulfate coupled with sequencing batch reactor activated sludge process (AOPs-SBR): Biodegradability and toxicity analysis of degradation intermediates

Although carbon-based catalysts are of great significance for potential application in advanced oxidation processes of persulfate, the biotoxicity and biodegradability of degradation intermediates of organic pollutants have been rarely reported. Herein, carbon-based nanofiber materials are prepared by electrospinning energetic metal–organic framework (EMOF) and ferric acetylacetonate, where the puff up of the EMOF creates hierarchical porous structure during high-temperature pyrolysis and provides sufficient space to expose Fe/N active sites. When organic pollutant tetracycline (TTCH) as target contaminant, energetic MOF derived carbon/Fe nanofiber in 900C named ECFe-9, which exhibits larger specific surface area (546.8 m2/g) and higher reaction rate constant k value (0.186 min−1) than that of in 700, 800 and 1000 °C. The biotoxicity of degradation intermediates is investigated by toxicity simulation. The biodegradability is analyzed by using advanced oxidation coupled with sequencing batch reactor activated sludge process (AOPs-SBR). This study provides a new perspective for advanced oxidation processes of persulfate as pretreatment methods for aerobic biochemical degradation of persistent organic pollutants.

Effects of rice husk biochar attachment biofilm with microorganisms on nitrogen removal of digested swine wastewater

Nitrogen in digested swine wastewater is currently difficult to directly degrade by an activated sludge process in a sequencing batch reactor (SBR), with resulting failure of the effluent to meet emission standards. In this study, rice husk biochar was optionally added into SBR to enhance biochemical properties for digested swine wastewater, especially for nitrogen degradation. The relative nitrogen removal mechanism for microbial community was probed by means of high-throughput sequencing. The results indicated that chemical oxygen demand (COD), ammonia (NH4+-N), and total nitrogen (TN) removal efficiency of digested swine wastewater was separately at 85.3%, 81.3%, and 65.2% using rice husk biochar with biofilm, which was 3.5%, 24.4%, and 14.7% higher than that of activated sludge, under influent of 2609 mg·L-1 COD, 337.0 mg·L-1 NH4+-N, 344 mg/L TN, and 7.77 C/N. High-throughput sequencing revealed that rice husk biochar with biofilm contained Proteobacteria, Thauera, Comamonas, Acinetobacter, Pseudomonas, Flavobacterium, and Corynebacterium to enhance nitrogen removal of digested swine wastewater. The results not only provide theoretical support for biochar with biofilm to improve digested piggery wastewater treatment, but also have great significance in resource utilization of agricultural waste and eco-environmental protection.

Enhancing the efficacy of synthesising PHA from nitrogen-limited activated sludge using magnetic field

ABSTRACT Polyhydroxyalkanes (PHA) is a biodegradable biopolyester. In this study, we introduced the biological effects of magnetic field into a sequencing batch reactor (SBR) for PHA production to evaluate the effect of different strength of magnetic field on the efficacy of PHA synthesis by activated sludge and used the magnetic field to enhance the PHA synthesis capacity of nitrogen-limited activated sludge and to optimise the percentage of the content of the two monomers in PHA. The results showed that the magnetic field of appropriate strength was favourable to increase the production of PHA and to increase the percentage of PHV. In addition, microbial community analysis showed that there was an obvious succession of key functional bacteria under different strength of magnetic field. The highest PHA accumulation was achieved after the magnetic field of 16 mT, which reached 57.65% of the dry weight of sludge. In addition, the PHV monomers were more sensitive to the response of the magnetic field, and the magnetic field of 8mT and 16mT positively promoted the synthesis of PHV. It is worth noting that too high a magnetic field would have an inhibitory effect on the synthesis of PHA.

Effects of aeration control strategies on nitrous oxide emissions in alternating anoxic–oxic sequencing batch reactor systems

Reducing N2O emissions is key to controlling greenhouse gases (GHG) in wastewater treatment plants (WWTPs). Although studies have examined the effects of dissolved oxygen (DO) on N2O emissions during nitrogen removal, the precise effects of aeration rate remain unclear. This study aimed to fill this research gap by investigating the influence of dynamic aeration rates on N2O emissions in an alternating anoxic–oxic sequencing batch reactor system. The emergence of DO breakthrough points indicated that the conversion of ammonia nitrogen to nitrite and the release of N2O were nearly complete. Approximately 91.73 ± 3.35% of N2O was released between the start of aeration and the DO breakthrough point. Compared to a fixed aeration rate, dynamically adjusting the aeration rates could reduce N2O production by up to 48.6%. Structural equation modeling revealed that aeration rate and total nitrogen directly or indirectly had significant effects on the N2O production. A novel regression model was developed to estimate N2O production based on energy consumption (aeration flux), water quality (total nitrogen), and GHG emissions (N2O). This study emphasizes the potential of optimizing aeration strategies in WWTPs to significantly reduce GHG and improve environmental sustainability.

Characterization and Comparison of Anammox Immobilization in Polyvinyl Alcohol, Polyethylene Glycol and Water-Borne Polyurethane

Anammox bacteria were embedded with different mass fractions of polyvinyl alcohol (PVA), polyethylene glycol (PEG) and water-based polyurethane (WPU) materials. The embedded immobilized pellets with different particle sizes of about 2.8–3.2 mm were prepared. The effects of the mass fraction of the embedding material (PVA 6–12%, PEG 6–9%, WPU 10%) and the concentration of activated carbon added in the embedding process (0–4%) on the pellet was investigated. The performance of pellet formation, sedimentation rate, mechanical strength, expansion coefficient, and elasticity were compared and analyzed under different immobilization conditions, and the parameters of each embedding step were optimized. Anammox immobilized pellets prepared with 10% polyvinyl alcohol (PVA), 2% sodium alginate (SA), and 2% powdered activated carbon were proposed. The effects of salinity on anammox were investigated through a batch test, and the optimal reaction conditions were selected to carry out the operation test. The functional groups of embedded and unembedded anammox sludge were detected using the infrared spectrum. A continuous flow sequencing batch reactor (SBR) demonstrated stable operation with immobilized anammox. Scanning electron microscopy revealed that the immobilized anammox pellets appeared as irregular particles, with each micro-unit predominantly being spherical. Additionally, a minor presence of rod-shaped bacteria was also noted. After 30 days of stable operation of the reactor, the ammonia nitrogen removal rate reached 84.7%.

A dynamic compartmental model of a sequencing batch reactor (SBR) for biological phosphorus removal

ABSTRACT Bioreactors are usually modelled as continuous stirred tank reactors (CSTRs) or CSTRs connected in series (Tanks-In-Series configuration). In large systems with non-ideal mixing, such approaches do not sufficiently capture the complex hydrodynamics, leading to model inaccuracies due to the lumping of spatial gradients. Highly detailed computational fluid dynamics (CFD) models provide insight into complex hydrodynamics but are computationally too expensive for flow-sheet models and digital twin applications. A compartmental model (CM) can be a middle-ground by providing a more realistic representation of the hydrodynamics and still being computationally affordable. However, the hydrodynamics of a plant can be very different under varying flow conditions. Dynamic CMs can capture these changes in an elegant way. So far, the application of CMs has been limited mostly to continuous flow systems. In this study, a dynamic CM of a sequencing batch reactor (SBR) is developed for a bio-P removal process. The SBR comes with challenges for CM development due to its distinct operational stages. The dynamic CM shows significant improvements over the CSTR model (using the same biokinetic parameters) for dissolved oxygen and phosphate predictions reducing the need for model recalibration that can lead to over-fitting and limited extrapolation capability of the model.

Mechanisms of denitrifying granular sludge disintegration and calcium ion-enhanced re-granulation in acidic wastewater treatment

Granular sludge is an alternative technology for the direct treatment of acidic nitrate-containing wastewater. Rapid remediation of disintegrated granules is essential to achieve efficient nitrogen removal. In this study, denitrifying granules were inactivated and disintegrated when the influent nitrate-nitrogen concentration was elevated from 240 to 360 mg L−1 in acidic wastewater (pH = 4.1) in a sequencing batch reactor. Tightly bound extracellular polymeric substances (TB-EPS) decreased by 60%, and extracellular protein (PN) was the main component of the reduced EPS. The three-dimensional excitation emission matrices (3D-EEM) results confirmed that the PNs that decreased were mainly tryptophan-like, tyrosine-like, and aromatic. This study further confirmed that the decrease in PN was mainly from the destruction of C=O (amide I) and N–H functional groups. Overloading of nitrogen-inhibited denitrifying activity and the destruction and dissolution of TB-EPS by acidic pH were responsible for granule disintegration, with PNs playing a major role in maintaining granule stability. Based on this, new granules with an average particle size of 454.4 μm were formed after calcium chloride addition; EPS nearly doubled during granule formation with PN as the dominant component, accounting for 64.7–78.4% of the EPS. Atomic force microscopy (AFM) revealed that PN-PN adhesion increased by 1.6–4.9 times in the presence of calcium ions, accelerating the re-granulation of disintegrated particles. This study provides new insights into the disintegration and remediation of granular sludge under acidic conditions.

N2O Emission Factors from Wastewater Treatment Plants Based on Literature Statistics and Model Fitting

The emission of nitrous oxide （N2O） during wastewater treatment cannot be ignored. The analysis of statistical data from literature based on 126 empirical studies revealed that the geographical factors of wastewater treatment plants （WWTPs） had a significant impact on N2O emission factors. However, the N2O emission factors of WWTPs in all regions of the world were generally lower than the Intergovernmental Panel on Climate Change （IPCC） recommended values. In China, the N2O emission factors （in N2O-N/Ninfluent） of WWTPs were approximately 0.000 35-0.065 20 kg·kg-1. Meanwhile, the N2O emission factors of different wastewater treatment processes were also significantly different, especially since the sequencing batch reactor （SBR） process had higher emissions. The use of uniform default emission factors for accounting was prone to overestimate N2O emissions, and it is recommended that countries conduct actual monitoring or modeling studies to develop categorical emission factors suitable for local conditions. In addition, the N2O emission factor based on total nitrogen （TN） removal was weakly negatively correlated with TN removal in 126 empirical data, which was more in line with bioprocessing stoichiometry and could provide an accurate accounting method for N2O. To this end, a digital twin model was developed to dynamically simulate a case anaerobic-anoxic-aerobic （AAO） WWTP to comprehensively quantify the dynamic emission behavior of N2O, which demonstrated that N2O emissions had significant seasonal and daily variability and were only equivalent to 11% of the calculated value of the emission factor based on the IPCC recommendation. Comparing the scatter linear fitting and categorical mean exponential fitting methods, it was found that the latter could more accurately reflect the negative correlation between the N2O emission factors and the TN removal rate, and an exponential regression equation between the average N2O emission factor based on the amount of TN removed and the TN removal rate was further developed to predict the N2O emission. The dynamic simulation and categorical index fitting methods provided in this study are important references for the accurate accounting of N2O emissions in similar WWTPs and provide help for understanding and responding to the N2O emission problems.