Aerobic Granular Sludge Membrane Bioreactor Research Articles

Enhanced performance and mechanism of adsorption pretreatment for alleviating membrane fouling in AGMBR: Impact of structural variations in carbon adsorbents

The structural variances of adsorbents play a crucial role in determining the number of effective adsorption sites and pretreatment performance. However, there is still a gap in comprehending the impact of different carbon structural adsorbents on membrane fouling. Therefore, this study aimed to compare the efficacy of granular activated carbon (GAC), powdered activated carbon (PAC), and activated carbon fiber (ACF) in mitigating membrane fouling during municipal sewage reclamation using an aerobic granular sludge membrane bioreactor (AGMBR). The results demonstrated that the utilization of PAC significantly enhanced the normalized flux and reduced fouling resistance in comparison to GAC and ACF systems. PAC effectively adsorbed low and medium-molecular-weight pollutants present in raw sewage, resulting in an increase in average particle size and a decrease in foulant content on the membrane surface. The Hermia model indicated that adsorption pretreatment minimized standard blocking while promoting the formation of a sparse and porous cake layer. Moreover, according to the extended Derjaguin–Landau–Verwey–Overbeek theory, PAC has been demonstrated as the optimal antifouling system owing to its enhanced repulsion between membrane-foulant and foulant-foulant interactions. Correlation analysis revealed that the exceptional antifouling performance of the PAC system was due to its high removal rates of chemical oxygen demand (~78 %) and suspended solids (~97 %). This research offers valuable insights into the mitigation of membrane fouling through the utilization of adsorbents featuring diverse carbon structures.

Effects of granule disintegration and sludge re-aggregation on fouling behaviors and bio-cake formation in aerobic granular sludge membrane bioreactor (AGMBR)

The contribution of granules to membrane fouling alleviation in aerobic granular sludge-membrane bioreactor (AGMBR) has been increasingly investigated, yet the inoculated granules in MBR are more unstable than those in conventional AGS system and thus in-depth insight into the effects of the mutual transformation between granules and flocs on membrane fouling as well as corresponding bio-cake formation is necessary. Herein, we found that the disintegration of granules was accompanied by the release of soluble microbial products (SMP) and the increase of microbial diversity. The re-granulation phase occurred when granules gradually re-dominated the sludge system with the growth of biomass and the massive secretion of extracellular polymeric substances (EPS), corresponding to the declined microbial diversity and stable pollutants removal (COD: 93.45–98 %, TN: 21.06–36.86 %). Compared with the granule disintegration phase, less flocs deposition and fewer contents of SMP containing high molecular weight (>100 kDa) compounds in bio-cakes in the re-granulation phase resulted in the longer filtration period, as evidenced by lower attractive interaction energies between sludge foulants and membranes according to extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Microbial community analysis demonstrated higher relative abundance of filamentous bacteria (Thiothrix) and lower relative abundance of denitrifiers (e.g, Hydrogenophag, Trichococcus, Arenimonas, Acinetobacter) in bio-cakes in the re-granulation phase. Besides, the genera Thiothrix, norank_f__env.OPS_17 and Aeromonas may be responsible for the organic foulants accumulation on membrane surface. More importantly, stronger positive correlations among microbial populations between bio-cake and suspended sludge in the re-granulation phase indicated the lower propensity of membrane fouling. The systematic insights into the effects of granules disintegration and sludge re-aggregation on fouling layer may have important implications for the future development of membrane fouling control in AGMBR system.

A comparison study of heat-assisted Fe2+/persulfate and powdered activated carbon/persulfate wastewater pre-treatment for membrane fouling alleviation

Heat/Fe2+/persulfate (PS) and heat/powdered activated carbon (PAC)/PS exhibit oxidation, coagulation, and adsorption effects, respectively. However, no studies have been conducted to discuss and compare the synergistic contribution to membrane fouling mitigation under thermal synergy. Herein, heat/Fe2+/PS and heat/PAC/PS systems were used to alleviate membrane fouling during municipal wastewater recycling in an aerobic granular sludge membrane bioreactor (AGMBR), and the effects of oxidation, coagulation, and adsorption on the membrane fouling mitigation were analyzed. The results showed that heat/Fe2+/PS and heat/PAC/PS effectively increased the filtration flux, decreased the fouling resistance, and maintained the membrane surface morphology. Compared to heat/PAC/PS, the heat/Fe2+/PS exhibited better control of membrane fouling owing to the generation of sulfate radicals and Fe3+. The non-radical effect is an important way to mitigate membrane fouling by heat/PAC/PS. Moreover, the pretreatment systems were effective in decomposition and removal of large-particle-size pollutants owing to their excellent oxidation capacity. According to the extended Derjaguin–Landau–Verwey–Overbeek theory, the heat/Fe2+/PS system had the higher energy barrier values of foulant–membrane (155.31 kT) and foulant–foulant (113.75 kT). The cake filtration and intermediate blocking models were the major mechanisms of membrane fouling, and efficient removal of chemical oxygen demand (R2>0.93) and suspended solids (R2>0.92) were beneficial to the membrane fouling mitigation. This study elucidates the differences in the mechanisms of heat/Fe2+/PS and heat/PAC/PS in mitigating AGMBR membrane fouling.

Effect of superficial gas velocity on membrane fouling behavior and evolution during municipal wastewater treatment

Aerobic granular sludge membrane bioreactor (AGMBR) is a promising technology for wastewater reuse and membrane fouling mitigation. Superficial gas velocity (SGV) plays an important role in the efficient and stable operation of AGMBR. However, the effect of SGV on the membrane fouling behavior and evolution of AGMBR has not been reported, which was systematically investigated in this study. AGMBR with various SGVs was used to treat synthetic municipal wastewater, and more than 94.5% and 60.5% of organics and total nitrogen, respectively, were removed at all SGVs. Further, a larger SGV prolonged the AGMBR overall operation. Contents and physiochemical properties of foulants varied with SGV and transmembrane pressure (TMP). Micro-level analyses revealed that the proportion of pore-blocking resistance in total fouling resistance as well as the microbial community diversity in the sludge mixture or on the membrane surface increased with TMP and SGV. The correlation analyses demonstrated that decreasing the polysaccharide content of soluble microbial products, increasing the protein content of tight extracellular polymeric substances in the sludge mixture, and enhancing the relative abundance of Bacteroidia and Gammaproteobacteria were beneficial for mitigating membrane fouling. This study reveals membrane fouling evolution and provides theoretical guidance for the large-scale application of AGMBR in wastewater reuse.

A Review on Development of Aerobic Granular Sludge Membrane Bioreactor for the Industrial Effluent Treatment

The technology of aerobic granular sludge and Membrane Bioreactor (MBR) were combined to develop an Aerobic Granular Sludge Membrane Bioreactor (AGMBR). Biomass content is high, higher the retention time of biomass, and the capacity of phosphorus and nitrogen removal has been shown by aerobic granular sludge; now a day it is a promising option for wastewater treatment. Reclaiming wastewater one of the favourite choices is Membrane technology in removing organic and inorganic impurities they have recognised as moderately operative with biological entities removal from wastewater. Consequently, the wastewater treatment membrane bioreactor and aerobic granular sludge technology are dynamic and new trending cost-efficient technologies. This article aims to review all the potential applications and principles in AGMBR technology.

Pre-coagulation for membrane fouling mitigation in an aerobic granular sludge membrane bioreactor: A comparative study of modified microbial and organic flocculants

Coagulation has become a hotspot for membrane fouling control; however, there is a gap in research regarding the application of modified microbial flocculants (MMFs) to mitigate membrane fouling. Herein, we prepared an MMF and compared it with conventional organic flocculants for their effects on mitigating membrane fouling in an aerobic granular sludge membrane bioreactor (AGMBR). The results showed that electrical neutralization played a dominant role in the flocculation process of polymeric aluminum chloride (PAC)/MMF, which exhibited the optimal performance for the removal of pollutants and membrane fouling control. Moreover, the characteristics of the fouled membrane and the fitting of membrane fouling models indicated that the cake layer formation was the main fouling mechanism underlying membrane fouling, and MMF could mitigate the accumulation of foulants on the membrane surface, forming a loose and porous cake layer. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the largest energy barriers of the membrane-foulant and foulant-foulant interactions were observed in the PAC/MMF-AGMBR hybrid system. Furthermore, correlation analysis revealed that total phosphorus, polysaccharide, zeta potential, and particle size had the greatest correlation with the fouling resistance. Thus, this study shows that MMF pre-coagulation is feasible and provides a new method for membrane fouling mitigation in an AGMBR. • The MMF was used for the first time to mitigate membrane fouling. • The cake layer was the major mechanism of membrane fouling in the MMF-AGMBR system. • The MMF promoted the formation of a loose, porous, and thin cake layer. • The MMF reduced the foulants deposited on the virgin/fouled membranes. • TP, PS, zeta potential, and particle size remarkably affect the fouling resistances.

Distribution characteristics of phosphorus-containing substances in a long running aerobic granular sludge-membrane bioreactor with no sludge discharge

This work aimed at revealing the distribution characteristics of phosphorus (P) containing substances in an aerobic granular sludge-membrane bioreactor (AGS-MBR). During the long running period (180 days) with no sludge discharge, AGS was successfully cultivated on day 20, and the system performed well in removing organic pollutants and total nitrogen (TN). However, the removal of total P (TP) showed a fluctuant tendency, and P was found to distribute in all the phases of the system. In the intracellular phase, it occupied the largest ratio all through the period. In AGS, inorganic P (IP) was measured to be about 74.4–77.8% of TP, with non-apatite IP (NAIP) composing 57.5–69.6%, while in organic P (OP), the ratio of monoester and diester phosphate was in the range of 19–26.9% and 12–13.5%, respectively. The presence of highly releasable and bioavailable P (NAIP + OP) in AGS implied that it might be a potential P resource for utilization.

Aerobic Granular Sludge-Membrane BioReactor (AGS-MBR) as a Novel Configuration for Wastewater Treatment and Fouling Mitigation: A Mini-Review.

This mini-review reports the effect of aerobic granular sludge (AGS) on performance and membrane-fouling in combined aerobic granular sludge–membrane bioreactor (AGS–MBR) systems. Membrane-fouling represents a major drawback hampering the wider application of membrane bioreactor (MBR) technology. Fouling can be mitigated by applying aerobic granular sludge technology, a novel kind of biofilm technology characterized by high settleability, strong microbial structure, high resilience to toxic/recalcitrant compounds of industrial wastewater, and the possibility to simultaneously remove organic matter and nutrients. Different schemes can be foreseen for the AGS–MBR process. However, an updated literature review reveals that in the AGS–MBR process, granule breakage represents a critical problem in all configurations, which often causes an increase of pore-blocking. Therefore, to date, the objective of research in this sector has been to develop a stable AGS–MBR through multiple operational strategies, including the cultivation of AGS directly in an AGS–MBR reactor, the occurrence of an anaerobic-feast/aerobic-famine regime in continuous-flow reactors, maintenance of average granule dimensions far from critical values, and proper management of AGS scouring, which has been recently recognized as a crucial factor in membrane-fouling mitigation.

Development of an integrated aerobic granular sludge MBR and reverse osmosis process for municipal wastewater reclamation

The reclamation of municipal wastewater to obtain high-grade product water is a growing need due to the pressing global water shortage. However, the existing municipal wastewater treatment plants (WWTPs) with the conventional activated sludge process as a core is not a sustainable engineering solution towards future water sustainability. To tackle such an emerging water-wastewater nexus, a ferrous-assisted aerobic granular sludge membrane bioreactor and reverse osmosis (AGSMBR-RO) process was developed for municipal wastewater reclamation. Results show that about 99.9%, 99.7% and nearly 100% of dissolved organic carbon (DOC), ammonium-N and total phosphorus (TP), respectively, could be removed in the ferrous-assisted AGSMBR-RO process, while the product water could meet the typical NEWater quality of Singapore with respect to the parameters analysed in this study. Moreover, it was found that an addition of 6 mg/L of ferrous could improve the stability of aerobic granular sludge (AGS) through the coagulation and flocculation of suspended flocs as well as phosphorus removal. These in turn led to reduced membrane fouling in both AGSMBR and RO units. Consequently, the proposed process is a promising alternative for municipal wastewater reclamation.

Treatment of municipal wastewater with aerobic granular sludge membrane bioreactor (AGMBR): Performance and membrane fouling

Aerobic granular sludge membrane bioreactor (AGMBR) has been widely studied in recent years owing to its excellent wastewater treatment performance and antifouling property. However, the mechanisms of membrane fouling are lack of systematic and comprehensive elaboration. Here, the mechanisms of and distinctions between fouling of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) membranes in an AGMBR were investigated. The nutrient-removal performances were excellent in both cases. Compared with the PVDF membrane, the PTFE membrane exhibited a better antifouling property, with a lower transmembrane-pressure growth rate (0.407 kPa/d). Moreover, the PTFE membrane had lower contents of extracellular polymeric substances (EPS) and soluble microbial products, probably owing to the lower relative abundance of the class Gammaproteobacteria, which is the producer of EPS. Additionally, a thermomechanical analysis revealed that the energy barrier of the PTFE membrane–foulant (71.20 kT) was higher than that of the PVDF membrane–foulant (51.77 kT), confirming that the PTFE membrane had better antifouling performance. Overall, this study enhances the understanding of mechanisms of membrane fouling in an AGMBR and is conducive motivate large-scale applications of AGMBR technology.

Submerged aerobic granular sludge membrane bioreactor (AGMBR): Organics and nutrients (nitrogen and phosphorus) removal

The capability of submerged aerobic granular sludge membrane bioreactor (AGMBR) to remove organics and nutrients was studied in a 2 × 2 factorial experimental design. The hydraulic retention time (HRT) - 6, 8 and 10 h - and chemical oxygen demand (COD) - 298 ± 32, 543 ± 14, and 790 ± 33 mg/L - were the independent variables. AGMBR achieved >96%, 97%, 50%, and 35% removal for COD, NH3-N, total nitrogen, and PO4-P, respectively. Meganema and Thauera, responsible for organics degradation, were present during all the runs. Nitrosomonas and Nitrospira allowed for complete nitrification. The presence of Azoarcus and Thauera points to anoxic conditions in the granules, indicating partial denitrification. Negligible PAOs were detected; hence, low PO4-P removal (~35%) mainly via the consumption and biologically induced precipitation pathways. Overall, two runs - 298 ± 32 mg/L COD at 6 h HRT and 790 ± 33 mg/L COD at 6 h HRT - performed best in terms of organics and nutrients removal.

Aerobic granular sludge membrane bioreactor (AGMBR): Extracellular polymeric substances (EPS) analysis

Aerobic granular sludge membrane bioreactor (AGMBR) has emerged with strong potential to overcome membrane fouling. There have been no extensive studies on extracellular polymeric substances (EPS) in AGMBR. The present work aimed at conducting an in-depth study of EPS and monitoring fouling development in AGMBR using a 22 factorial design having hydraulic retention time (HRT) and total organic carbon (TOC) as independent variables. HRT was tested at three levels of 6, 8 and 10 h while the TOC levels were 104 ± 13, 189 ± 17, and 266 ± 27 mg/L. AGMBR exhibited high proteins (PN) in the tightly-bound EPS (TB-EPS) resulting in high proteins/polysaccharides (PN/PS) ratios of 2–16. The PN in the LB-EPS was low, ranging from 0.01 to 1.92 mg/g MLVSS, but the range of PN/PS ratio was also of 2–16. Despite the high PN/PS ratio, TMP rise was low. Water jet easily sloughed off the developed membrane cake layer. The elimination of chemicals for membrane cleaning has significant cost savings. TOC had a significant main effect on both the PN and PS components of TB-EPS at α < 0.05. TB-EPS PN increased with increase in TOC. TB-EPS PN decreased as HRT increased from 6 h to 10 h at 104 ± 13 mg/L TOC but the change of HRT from 10 h to 6 h at 266 ± 27 mg/L TOC did not affect TB-EPS PN. The TMP increased with increasing HRT at 104 ± 13 and 266 ± 27 mg/L TOC. An increase in sEPS PN correlated well with increase in membrane fouling (r = 0.581). Three runs performed best: 266 ± 27 mg/L TOC and 10 h HRT; 104 ± 13 mg/L TOC and 6 h HRT; and 266 ± 27 mg/L TOC and 6 h HRT as TMP was below the 50 kPa threshold. AGMBR achieved 98 ± 1%, 99 ± 1%, 52 ± 33% organics degradation, NH3-N removal, total nitrogen removal, respectively.

Integration of aerobic granular sludge and membrane filtration for tapioca processing wastewater treatment: fouling mechanism and granular stability

In this study, a novel aerobic granular sludge membrane bioreactor (AGMBR) was developed and its performance was compared with that of a traditional membrane bioreactor (MBR). The findings of membrane filtration at the flux of 12 L/m2 h showed that the fouling rate of the AGMBR was 0.490 kPa/day, half that of the MBR. Resistance analysis implied that the cake resistance was the major fouling factor in the MBR, up to 67.2% of total resistance, while pore blocking was the key fouling factor in the AGMBR, accounting for 50.3%. Aerobic granules maintained stability in the AGMBR with a size of 1.2–1.5 mm and a sludge volume index (SVI) of 60–70 mg/L. It was therefore possible to reduce cake resistance and fouling rate. In addition, the concentration of soluble extracellular polymeric substances (sEPS) in the AGMBR was 33.1 mg/L, three times lower than that of the MBR, which resulted in a reduction in membrane fouling for the AGMBR compared with the MBR.

Simultaneous organics and nutrients removal in side-stream aerobic granular sludge membrane bioreactor (AGMBR)

Membrane fouling mitigation has been variously reported in aerobic granular sludge membrane bioreactor (AGMBR). AGMBR has also achieved, to varying degrees, the removal of organics and nitrogen-based compounds from wastewater. However, scanty information is available in the literature on phosphorus removal in AGMBR. Thus, the present study focused on simultaneous removal of organics and both nutrients (nitrogen and phosphorus) in AGMBR at semi-pilot-scale. Aerobic granules were cultivated in a cylindrical reactor with a working volume of 19 L, diameter of 15 cm, and height-to-diameter (H/D) ratio of 8. The effluent from the granular reactor was discharged into a side-stream membrane module. At steady state, the granule mean size, 5-min sludge volume index (SVI5), SVI30, and MLSS were 576 μm, 40 mL/g, 37 mL/g, and 9200 mg/L, respectively. Results show that the system achieved 98% chemical oxygen demand (COD) degradation, 96–99% total nitrogen (TN) removal, and ≥95% removal of PO4-P. The outstanding removal of both organics and nutrients in the AGMBR is attributed to the coexistence of aerobic and anaerobic layers within the granule as well as the anaerobic feeding adopted. These findings demonstrate the potential of AGMBR to simultaneously remove organics and nutrients (nitrogen and phosphate)

Utilization of aerobic granulation to mitigate membrane fouling in MBRs

Membrane bioreactor (MBR) is a compact and efficient wastewater treatment and reclamation technology; but, it is limited by membrane fouling. The control of membrane fouling significantly increases operational and maintenance costs. Bacteria and their byproducts - extracellular polymeric substances (EPS) - are major contributors to membrane fouling in MBRs. A recent attempt at fouling mitigation is the development of aerobic granular sludge membrane bioreactor (AGMBR) through the integration of a novel biotechnology - aerobic granulation - and MBR. This paper provides an overview on the development of AGMBR to mitigate membrane fouling caused by bacteria and EPS. In AGMBR, EPS are used up in granule formation; and, the rigid structure of granules provides a surface for bacteria to attach to rather than the membrane surface. Preliminary research on AGMBR using synthetic wastewater show remarkable membrane fouling reduction compared to conventional MBR, thus improved membrane filtration. Enhanced performance in AGMBR using actual municipal wastewater at pilot-scale has also been reported. Therefore, further research is needed to determine AGMBR optimal operational conditions to enhance granule stability in long-term operations and in full-scale applications.

Reactor performance and membrane fouling of a novel submerged aerobic granular sludge membrane bioreactor during long-term operation

Abstract The aerobic granular sludge membrane bioreactor (AGS-MBR) has the potential for simultaneous carbon/nitrogen removal and membrane fouling mitigation. Most studies have focused on comparison of granular sludge MBR and flocculent sludge MBR in short-term tests using synthetic wastewater. In this study, two identical AGS-MBRs were developed, and the reactor performance and membrane fouling were examined systemically over 120 days for synthetic wastewater and municipal sewage treatment, respectively. Results showed that regular granules with good settling ability were developed and maintained throughout the experimental period. Regardless of the substrate type, AGS-MBR demonstrated a stable removal of carbon (85–95%) and nitrogen (50–55%) in long-term operation. In addition, the membrane fouling propensity is apparently lower in AGS-MBRs with no membrane cleaning for 4 months at a flux of 20 L m−2h−1. The filtration resistance analysis indicates that the main membrane resistance was caused by irreversible fouling in both of the reactors. Membrane foulant analysis indicates that proteins in extracellular polymeric substances are more prone to be attached by the membrane of AGS-MBRs because of their hydrophobic nature. This study shows that AGS-MBR is effective and stable for municipal sewage treatment and reuse during long-term operation.

Removal of pharmaceuticals from synthetic wastewater in an aerobic granular sludge membrane bioreactor and determination of the bioreactor microbial diversity

Five types of pharmaceuticals and personal care products (PPCPs) substances were selected as pollutants in this study. The effects of the removal of these pollutants and the microbial succession process in a granular sludge membrane bioreactor (GMBR) were investigated. Results showed that wastewater containing PPCPs influenced the performance of granular sludge. The removal of the five PPCPs from the GMBR had different effects. The removal rates of prednisolone, norfloxacin and naproxen reached 98.5, 87.8 and 84%, respectively. The degradation effect in the GMBR system was relatively lower for sulphamethoxazole and ibuprofen, with removal efficiency rates of 79.8 and 63.3%, respectively. Furthermore, the microbial community structure and diversity variation of the GMBR were analysed via high-throughput sequencing technology. The results indicated the structural and functional succession of the microbial community based on the GMBR process. The results indicate the key features of bacteria with an important role in drug degradation.

PPCPs removal by aerobic granular sludge membrane bioreactor.

An aerobic granular sludge membrane bioreactor (GMBR) was applied to the treatment of pharmaceutical and personal care products (PPCPs) wastewater. The influence of granular sludge on five antibiotic and antiphlogistic PPCPs wastewater and the removal effect of methyl alcohol and conventional organic matter were investigated while constantly reducing the density of inflow organic matter. The results showed that the sludge granulation process in the system was rapid but unstable, and that the system exhibits a dissolution-reunion dynamic equilibrium. The reactor demonstrated varying removal effects of PPCPs on different objects. The use of a GMBR was more effective for the removal of prednisolone, naproxen, and ibuprofen; the first two drugs were lower the average removal rate of which reached 98.46 and 84.02 %, respectively; whereas the average removal rate of ibuprofen was 63.32 %. By contrast, the GMBR has an insignificant degradation effect on antibiotics such as amoxicillin, indicating that such antibiotic medicine is not easily degraded by microorganisms, which plays different roles in system operation. Because of the different chemical structures and characteristics of drugs that result in various degradation behavior. During the GMBR granulation process, the value of mixed liquor volatility suspended solids (MLVSS) gradually increases from 1.5 to 4.1 g/L during the GMBR granulation process, and the removal rate of CODCr reaches up to 87.98 %. After reducing the density of organic matter is reduced, the removal rates of NH3-N and TP both reach more than 90 %, respectively. Moreover, the proposed technique is considerably effective in the removal of methanol.

Treatment of high concentration ammonium nitrogen wastewater by aerobic granular sludge membrane bioreactor

Treatment of high concentration ammonium nitrogen wastewater by aerobic granular sludge membrane bioreactor

Organics and nitrogen removal and sludge stability in aerobic granular sludge membrane bioreactor

Novel aerobic granular sludge membrane bioreactor (GMBR) was established by combining aerobic granular sludge technology with membrane bioreactor (MBR). GMBR showed good organics removal and simultaneous nitrification and denitrification (SND) performances for synthesized wastewater. When influent total organic carbon (TOC) was 56.8-132.6 mg/L, the TOC removal of GMBR was 84.7-91.9%. When influent ammonia nitrogen was 28.1-38.4 mg/L, the ammonia nitrogen removal was 85.4-99.7%, and the total nitrogen removal was 41.7-78.4%. Moreover, batch experiments of sludge with different particle size demonstrated that: (1) flocculent sludge under aerobic condition almost have no denitrification capacity, (2) SND capacity was caused by the granular sludge, and (3) the denitrification rate and total nitrogen removal efficiency were enhanced with the increased particle size. In addition, study on the sludge morphology stability in GMBR showed that, although some granular sludge larger than 0.9 mm disaggregated at the beginning of operation, the granular sludge was able to maintain the stability of its granular morphology, and at the end of operation, the amount of granular sludge (larger than 0.18 mm) stabilized in GMBR was more than 56-62% of the total sludge concentration. The partial disaggregation of large granules is closely associated with the change of operating mode from sequencing batch reactor (SBR) system to MBR system.