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This study elucidates the impact of fluctuating influent conditions and in situ ultrasonic wave exposure on the stability of aerobic granular sludge (AGS) in the treatment of simulated wastewater emanating from rare earth mining operations. During a stable influent period spanning from Day 1 to Day 95, the seed granules underwent an initial disintegration followed by a re-granulation phase. The secondary granulation was achieved on Day 80 and Day 40 for the ultrasonic reactor (R1) and the control reactor (R2), respectively. Notably, granules formed in R1 exhibited a more porous structure compared to those generated in R2. Subsequently, when the ammonia nitrogen in the influent oscillated between 100 and 500 mg/L during Days 96-140, both reactors yielded compact and densely structured granules. Nitrogen removal profiles were comparable between the two reactors: the removal efficiencies for ammonia nitrogen and total inorganic nitrogen escalated from 95% and 80%, respectively, during Days 1-95, to 95% and 90%, respectively, post-Day 140. A suite of performance metrics indicated that steady-state granules from R1 outperformed those from R2 across several parameters. Specifically, the nitrification/denitrification rates, and relative abundance of denitrifying bacteria were all higher in granules from R1. Conversely, the relative abundance of nitrifying bacteria was comparable between granules from both reactors. However, R1 granules demonstrated lower sludge concentration and smaller average particle size than their R2 counterparts. In conclusion, the AGS system demonstrated robust resilience to fluctuating ammonia nitrogen, and the application of ultrasonic waves significantly enhanced granular activity while achieving in situ sludge reduction. [ABSTRACT FROM AUTHOR]

Secondary fiber papermaking wastewater (SPW) has received increasing interest because of its enormous discharge, typical high COD, and low biodegradability. The dense and compact structure of aerobic granular sludge (AGS) results in a high sludge concentration in the sequencing batch biofilter granular reactor (SBBGR), which provides superior conditions for the treatment of highly concentrated wastewater. This study constructed an SBBGR to treat SPW, investigated the changes in the species and structural characteristics of pollutants during wastewater treatment, and analyzed the dominant populations that can degrade pollutants in the SPW. The results showed that SBBGR had a good treatment effect on SPW and the removal rates of COD, TN, TP, SS, and color were 90.3 %, 81.9 %, 85.2 %, 73.1 %, and 75.1 % respectively with the influent organic load of 8.1 kg COD m−3 d−1, which was attributed to its outstanding biodegradability. The types and quantities of aromatic compounds in SPW were significantly reduced, according to the results of FTIR, UV–vis, and GC-MS. Microbial community analysis showed that the presence of Bacteroidetes, Proteobacteria, Macellibacteroides, Chlorobium, and Brachymonas in the SBBGR was responsible for the outstanding biodegradation of pollutants in the SPW. In summary, the treatment of SPW with SBBGR is extremely promising for applications. [ABSTRACT FROM AUTHOR]

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Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluated the efficiency of aerobic granular sludge (AGS) technology in treating wastewater contaminated with tetracycline (TC), a common antibiotic. AGS was cultivated under a TC pressure gradient ranging from 5 mg/L to 15 mg/L and compared with conventional wastewater conditions. The results demonstrated that AGS achieved high removal efficiencies and exhibited robust sedimentation performance, with significant differences in average particle sizes observed under both conditions (618.6 μm in TC conditions vs. 456.4 μm in conventional conditions). Importantly, exposure to TC was found to alter the composition and production of extracellular polymeric substances (EPSs), thereby enhancing the structural integrity and functional stability of the AGS. Additionally, the selective pressure of TC induced shifts in the microbial community composition; Rhodanobacter played a crucial role in EPS production and biological aggregation, enhancing the structural integrity and metabolic stability of AGS, while Candida tropicalis demonstrated remarkable resilience and efficiency in nutrient removal under stressful environmental conditions. These findings underscore the potential of AGS technology as a promising solution for advancing wastewater treatment methods, thus contributing to environmental protection and sustainability amid growing concerns over antibiotic contamination. [ABSTRACT FROM AUTHOR]

Aerobic granular sludge was cultivated as a biological carrier under laboratory conditions, and Chlorella was inoculated to form algal-bacterial granular sludge(ABGS). The effects of different light intensities on pollutant removal efficiency of ABGS system were explored, and the enhancement of Chlorella on the treatment capacity of ABGS system under 5 klx light intensity was emphatically investigated. The results showed that the removal rates of COD, TN and TP by ABGS were 87.01%-95.32%, 53.14%-89.37% and 32.49%-99.40%, respectively, with the SND of 7.70%-83.66%. However, the removal rates of TP and TN in a single Chlorella system were only 20%-30%, while the removal effect of COD was not obvious. Chlorella could increase the concentration of dissolved oxygen in water within a certain light intensity range, and facilitate the degradation of pollutants by promoting the metabolic rate of bacteria in ABGS system. With the increase of light intensity, the removal rates of COD and TP in ABGS system increased, while the removal rates of TN and SND decreased. Too low or too high light intensity would inhibit the photosynthesis and even kill Chlorella, leading to the disintegration of ABGS, system collapse and poor pollutant removal effect. High throughput analysis showed that the addition of algae further expanded the relative abundance of bacteria related to nitrogen and phosphorus metabolism, and enhanced the nitrogen and phosphorus removal effect of the system.

• A quantitative method was proposed to assess the shear stability of AGS. • Parameter a had a strong positive linear correlation with the wet density of AGS. • LGS represented the equilibrium size for AGS after sheared for a period of time. • LGS was significantly and exponentially related to the parameter a. • The results were validated with the AGS samples from a pilot-scale AGS-MBR. This work established a quantitative method to access the shear stability of aerobic granular sludge (AGS) and validated its feasibility by using the mature AGS from a pilot-scale (50 tons/day) membrane bioreactor (MBR) for treating real municipal wastewater. The results showed that the changing rate (Δ S) of the peak area (S) of granule size distribution (GSD) exhibited an exponential relationship (R 2≥0.76) with the shear time (y = a − b · c x), which was a suitable indicative index to reflect the shear stability of different AGS samples. The limiting granule size (LGS) was defined and proposed to characterize the equilibrium size for AGS after being sheared for a period of time, whose value in terms of Dv50 showed high correlation (R 2=0.92) with the parameter a. The free Ca2+ (28.44–34.21 mg/L) in the influent specifically interacted with polysaccharides (PS) in the granule's extracellular polymeric substance (EPS) as a nucleation site, thereby inducing the formation of Ca precipitation to enhance its Young's modulus, while Ca2+ primarily interacted with PS in soluble metabolic product (SMP) during the initial granulation process. Furthermore, the Young's modulus significantly affected the parameter a related to shear stability (R 2=0.99). Since the parameter a was more closely related (R 2=1.00) to Δ S than that of the parameter b or c , the excellent correlation (R 2=0.99) between the parameter a and the wet density further verified the feasibility of this method. [Display omitted] [ABSTRACT FROM AUTHOR]

The soil surface in the southern Xinjiang region has a high salt content, and flooding water causes salt dissolution and pollutes surface water. Therefore, it is particularly important to study the technology of nitrogen and phosphorus removal in the degradation of high salt wastewater. Activated sludge was inoculated in an SBR system with a height to diameter ratio (RH/D) of 7.5, and synthetic wastewater (containing 0.25 mg/L Ni2+) was used as influent to analyze the changes in sludge morphology, pollutant removal performance, microbial community during the sludge granulation process, as well as the ability of granular sludge to remove pollutants from high salt wastewater under salinity stress. The results showed that the mature granular sludge was yellow in multiple forms, with an average particle size of 357 μm. The average removal rates of COD, TP, and NH4+-N in wastewater were 95%,91.27%,and 94.5%, respectively. The dominant bacterial genera were Zoogloea, Flavobacterium,and Unclassified_f_Comamonadaceae. The influent water quality would change the relative abundance of microorganisms, while there was no significant impact on the microbial community structure. When the salt application rate was 15 g/L, the removal rates of COD, TP, and NH4+-N were 86.7%, 67.2%, and 62.6%, respectively. The sludge maintained good carbon removal ability. When the salt application rate exceeded 15 g/L, the removal rates of all indicators showed a downward trend. The application of low concentrations of heavy metals accelerated the start-up of granular sludge and targeted microorganisms for nitrogen and phosphorus removal, which had reference for the treatment of pollutants in high salt wastewater.

In this study, three sequencing batch biofilter granular reactors (SBBGRs) were employed to treat model lignin wastewater containing different lignin models (2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin). After 40 days of cultivation, uniform-shaped aerobic granular sludge (AGS) was successfully developed through nutrient supplementation with synthetic wastewater. During the acclimation stage, the chemical oxygen demand (COD) reduction efficiencies of the three reactors showed a trend of initial decreasing (5–20%) and then recovering to a high reduction efficiency (exceeding 90%) in a short period of time. During the stable operation stage, all three reactors achieved COD reduction efficiencies exceeding 90%. These findings indicated the cultivated AGS's robust resistance to changes in lignin models in water. UV–Vis spectra analysis confirmed the effective degradation of the three lignin models. Microbiological analysis showed that Proteobacteria and Bacteroidetes were always the dominant phyla. At the genus level, while Acinetobacter (15.46%) dominated in the inoculation sludge, Kapabacteriales (7.93%), SBR1031 (11.77%), and Chlorobium (25.37%) were dominant in the three reactors (for 2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin) after degradation, respectively. These findings demonstrate that AGS cultured with SBBGR effectively degrades lignin models, with different dominant strains observed for various lignin models. HIGHLIGHTS The aerobic granular sludge cultivated in SBBGR was applied to treat lignin models and demonstrated excellent impact resistance.; The high sludge concentration and diverse microbial community enable effective lignin model degradation.; Different strains dominated the cultured AGS in three reactors that degraded 2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin, respectively.;

A Box‐Behnken design was used for the analysis using a gray wolf optimizer (GWO)‐coupled artificial neural network (ANN) model and response surface methodology (RSM) to analyze the effect of three operating parameters (volumetric exchange ratio [VER], aeration rate [AR], and cycle time [CT]) manipulated during an aerobic granular sludge process (AGS) sequencing batch reactor on modeling the removal of chemical oxygen demand (COD) in mixed wastewater. The most efficient architecture for COD showed the highest efficiency for modeling the AGS. The RSM model and plot results indicate that the CT and AR were the most influential on COD removal efficiency. When compared with models with statistical indices, GWO‐ANN demonstrated higher performance compared to RSM. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of nitrogen loading rates (NLRs) on the stability of aerobic granular sludge (AGS) for treating simulated ionic rare earth mine wastewater with high ammonia nitrogen and extremely low organic content. Mature AGS from a sequencing batch reactor (SBR) was seeded into five identical SBRs (R1, R2, R3, R4 and R5). The five reactors were operated with different NLRs (0.2, 0.4, 0.8, 1.2 and 1.6 kg/m3·d). After 30 days of operation, R1, R2 and R5 were dominated by broken granules, while most of the granules in R3 and R4 still maintained a complete structure. The properties of granules from R1, R2, R3, R4 and R5 deteriorated to varying degrees, while the granules from R3 and R4 showed better stability than that from R1, R2 and R5. In R1, R2, R3 and R4, the steady-state ammonia nitrogen removal efficiencies were all greater than 90%, and the steady-state removal efficiencies of total inorganic nitrogen (TIN) were approximately 30%. In R5, the removal efficiencies of ammonia nitrogen and TIN were both approximately 70%. The dominant nitrifying and denitrifying bacterial genera of the granules from the five reactors were Nitrosomonas and Thauera, respectively, and their relative abundance was much higher in granules from R3 and R4. The results demonstrated that a relative equilibrium between the growth and metabolism of nitrifying/denitrifying bacteria was achieved when NLR was between 0.8 and 1.2 kg/m3·d, which could provide technical support for the stability maintenance of AGS in the treatment of ionic rare earth mine wastewater. [ABSTRACT FROM AUTHOR]

Saline wastewater is regarded as a challenge for wastewater treatment plants because high-salinity conditions negatively affect on traditional biological technologies. Aerobic granular sludge (AGS) has gained attention as a promising technology for saline wastewater treatment because of its compact structure and the ability to withstand toxic loadings. Therefore, this study investigated the salt-resistance performance, sludge properties and microbial community of AGS under low-salinity and high-salinity conditions, with the saline concentrations ranging from 0 to 50 g/L. The results showed that AGS could withstand long-term saline stresses, and the maximum salinity reached 50 g/L within 113 d. Under salinities of 10, 30, and 50 g/L, the chemical oxygen demand (COD) removal efficiencies were 90.3%, 88.0% and 78.0%, respectively. AGS also its maintained strength and aggregation at salinities of 10 and 30 g/L. Overproduction of extracellular polymeric substances (EPS) by non-halophilic bacteria that enhanced sludge aggregation. The compact structure that ensured the microorganisms bioactivity helped to remove organic matters under salinities of 10 and 30 g/L. At a salinity of 50 g/L, moderately halophilic bacteria, including Salinicola, Thioclava, Idiomarina and Albirhodobacter, prevailed in the reactor. The dominant microbial communities shifted to moderately halophilic bacteria, which could maintain aerobic granular stabilization and remove organic matters under 50 g/L salinity. These results in this study provide a further explanation for the long-term operation of AGS for treating saline wastewater at different salinities. It is hoped that this work could bring some clues for the mystery of salt-resistance mechanisms. [ABSTRACT FROM AUTHOR]

Aerobic granular sludge (AGS) shows promise in treating piggery wastewater compared to conventional activated sludge methods. However, current AGS research primarily remains confined to the laboratory, with limited practical applications in actual piggery wastewater treatment. Besides, AGS faces challenges such as unstable structure and susceptibility to sludge bulking in practical settings. This study aimed to assess AGS's efficacy in treating actual piggery wastewater and successfully resolved the non-filamentous bulking issue through various measures. AGS formation occurred by the 13th day of operation, demonstrating high pollutant removal rates, with ammonia nitrogen (NH4+-N), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) removal rates reaching 99%, 99%, 90%, and 96%, respectively. However, Zoogloea overgrowth led to increased polysaccharide secretion and subsequent non-filamentous bulking on the 32nd day, which adversely impacted TN, COD, and TP removal efficiency. To address the bulking issue, the influent COD concentration was initially adjusted from 500 ± 50 mg/L to 2000 ± 50 mg/L and then decreased to 700 ± 50 mg/L. Additional measures included lowering water temperature, enhancing hydraulic shear force and selective pressure, and conducting manual screening, resulting in a notable decrease in sludge bulking by the 60th day. Throughout the granulation process, there was a reduction in species diversity and microbial biomass in the sludge, especially noticeable before and after addressing the sludge bulking issue. Initially, Zoogloea dominated the AGS, but following the resolution of the non-filamentous bulking issue, there was a shift to Thauera as the dominant bacterium. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aerobic granular sludge(AGS) technology draw scientific researchers attention, and more and more scientific research focuses on it, due to its superior advantages, such as good settling performance, high biological phase, high toxicity resistance and multiple biological effects. With the rapid development of AGS technology, a considerable amount of residual AGS will be produced, and dehydration is the biggest bottleneck of sludge reduction. This study investigated the dewatering process and method of residual AGS cultured by continuous flow experiment. Experiments were conducted using centrifugal dewatering technology with a dosing scheme to analyze the granular sludge dewatering process, and investigate the release process of EPS component in AGS dewatering. Our results implied the specific resistance of AGS has a very low value ((1.82 ± 0.03) x 109m/kg) and it was not obvious for the conditioning effect of chemical conditioner on AGS dewatering. However, the moisture content can be reduced to 63.5% after dewatering with the presence of inorganic substances. The addition of drinking water treatment plant sludge (Alum sludge) can improve the efficiency of the dewatering of AGS. A possible dewatering process of AGS dewatering was proposed which was divided into two stages: First, a considerable amount of free water in the sludge was quickly removed under the action of gravity without pressure filtration. Second, the bound water release required cooperation between applying centrifugal or pressing force to grind granular cells and separate protein-like substances with the inorganic matter inside the granular sludge. The possible mechanism of AGS dewatering and hypothesis dewatering process are useful to optimize the AGS dewatering process. [ABSTRACT FROM AUTHOR]

The factors affecting the rapid granulation of aerobic granular sludge were reviewed from four aspects: Hydraulic selection pressure, alternating feast-famine periods, inoculated sludge types, and microbial growth substrate. And combined with the above factors, the research progress of aerobic granular sludge culture based on continuous flow reactor is reviewed. The limitations of existing AGS research are introduced and suggestions for future development directions are provided. [ABSTRACT FROM AUTHOR]

Introduction: Microplastics (MPs), identified as emerging contaminants, have been detected across diverse environmental media. Their enduring presence and small size facilitate the adsorption of organic pollutants and heavy metals, leading to combined pollution effects. MPs also accumulate in the food chain thus pose risks to animals, plants, and human health, garnering significant scholarly attention in recent years. Aerobic granular sludge (AGS) technology emerges as an innovative approach to wastewater treatment. However, the impacts of MPs on the operational efficiency and microbial characteristics of AGS systems has been insufficiently explored. Methods: This study investigated the effects of varying concentration (10, 50, and 100 mg/L) of biodegradable MPs (Polylactic Acid, PLA) and nonbiodegradable MPs (Polyethylene Terephthalate, PET) on the properties of AGS and explored the underlying mechanisms. Results and discussions: It was discovered that low and medium concentration of MPs (10 and 50 mg/L) showed no significant effects on COD removal by AGS, but high concentration (100 mg/L) of MPs markedly diminished the ability to remove COD of AGS, by blocking most of the nutrient transport channels of AGS. However, both PLA and PE promoted the nitrogen and phosphorus removal ability of AGS, and significantly increased the removal efficiency of total inorganic nitrogen (TIN) and total phosphorus (TP) at stages II and III (P < 0.05). High concentration of MPs inhibited the growth of sludge. PET noticeably deteriorate the sedimentation performance of AGS, while 50 mg/L PLA proved to be beneficial to sludge sedimentation at stage II. The addition of MPs promoted the abundance of Candidatus_Competibacter and Acinetobacter in AGS, thereby promoting the phosphorus removal capacity of AGS. Both 50 mg/L PET and 100 mg/L PLA caused large amount of white Thiothrix filamentous bacteria forming on the surface of AGS, leading to deterioration of the sludge settling performance and affecting the normal operation of the reactor. Comparing with PET, AGS proved to be more resistant to PLA, so more attention should be paid to the effect of non-biodegradable MPs on AGS in the future. [ABSTRACT FROM AUTHOR]

Salt-tolerant aerobic granular sludge(AGS) was successfully cultivated under the dual stress of tetracycline and 2.5% salinity, resulting in an average particle size of 435.0 ± 0.5 and exhibiting a chemical oxygen demand(COD) removal rate exceeding 80%, as well as excellent sedimentation performance. The analysis of metagenomics technology revealed a significant pattern of succession in the development of AGS. The proportion of Oleiagrimonas, a type of salt-tolerant bacteria, exhibited a gradual increase and reached 38.07% after 42 days, which indicated that an AGS system based on moderate halophilic bacteria was successfully constructed. The expression levels of targeted genes were found to be reduced across the entire AGS process and formation, as evidenced by qPCR analysis. The presence of int1 (7.67 log10 gene copies g−1 in 0 d sludge sample) enabled microbes to horizontally transfer ARGs genes along the AGS formation under the double pressure of TC and 2.5% salinity. These findings will enhance our understanding of ARG profiles and the development in AGS under tetracycline pressure, providing a foundation for guiding the use of AGS to treat hypersaline pharmaceutical wastewater. [ABSTRACT FROM AUTHOR]

The feasibility of the aerobic granulation of activated sludge was investigated in a continuous-flow anaerobic–anoxic–oxic system under gradient-controlled hydraulic loading on the surface of a cyclone separator. Concentrated domestic sewage was used. After 80 days of operation, 80% of activated sludge in the system was in the form of granular sludge with an average particle size of 373 μm. High removal efficiency was achieved for chemical oxygen demand (94.40%), NH4+-N (99.93%), total nitrogen (89.44%), and total phosphorus (96.92%). A batch study revealed that Pseudomonas (1.34%) and Dechloromonas (1.05%) as the main denitrifying phosphorus-accumulating organisms could efficiently remove phosphorus using nitrate as an electron acceptor, which improved the utilization efficiency of carbon sources and achieved simultaneous denitrification and phosphorus removal. Overall, the study demonstrates the feasibility of enhanced denitrification and phosphorus removal in a continuous-flow granular sludge system. The sludge system enables simultaneous nitrogen and phosphorus removal under low carbon-to-nitrogen ratios. [ABSTRACT FROM AUTHOR]

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study examined the influence of different wastewater treatment processes on the physicochemical properties of Alginate-Like Exopolymers (ALE) extracted from waste sludge. Sludge samples were collected from wastewater treatment plants (WWTPs) processing both combined industrial and domestic wastewater, as well as domestic wastewater alone. Among the processes studied, aerobic granular sludge (AGS) produced the highest ALE yield (352 ± 50 mg/g-VSsludge), significantly exceeding that from membrane bioreactor (170 ± 41 mg/g-VSsludge) and conventional activated sludge (

Palm oil industries have products like Crude Palm Oil (CPO), and 70% of others contain waste. One of the wastes is the liquid waste known as Palm Oil Mill Effluent (POME). The potential of POME to be reprocessed into clean water will be profitable. One of POME's reprocessing methods is the Sequencing Batch Reactor with Aerobic Granulated Sludge (SBR-AGS), which has five main phases: filling, idling, aeration, settling, and discharge, with a cycle time of 360 minutes. The first step in using this reactor is the start-up process, a granule-forming process from some sludge that has already acclimatized. In one complete cycle, the Oxidation-Reduction Potential (ORP) parameter is used to observe the electron transfer process that shows the oxygen supply into the reactor, which enables the condition of each phase in the process to be analyzed. The trend of ORP value is constantly changing in every phase. For the idling phase, the ORP tends to decrease in a value of (-300)-(-400) mV, and for the aeration phase, it will increase in a value of (-100)-100 mV.

The research on recycling has become the focus of the research direction of aerobic granular sludge（AGS） technology，and alginate-like exopolysaccharides（ALE） extracted from AGS is considered to be one of the most valuable recyclable resources in AGS. At present，the technological revolution of sewage treatment plant focuses on the recovery of high value-added products，the recovery and application of ALE has formed a clear path. Based on the formation mechanism and components of aerobic granular sludge，this paper analyzed the unique structure and properties of ALE，summarized the recovery and evaluation methods of ALE at home and abroad，and discussed the effects of factors such as organic load rate，carbon to nitrogen ratio，salinity，particle size and sludge residence time on ALE production. Synchronous recovery of ALE and other value-added products was described. Finally，by discussing the wide application range and actual economic value of ALE，the potential research direction of ALE in the reclamation of AGS was put forward.

Aerobic granular sludge (AGS) in continuous-flow reactors (CFRs) has attracted significant interest, with notable progress in research and application over the past two decades. Cumulative studies have shown that AGS-CFRs exhibit comparable morphology, settleability, and pollutant removal efficiency to AGS cultivated in sequencing batch reactors, despite their smaller particle sizes. Shear force and selection pressure are the primary drivers of granulation. While not mandatory for granulation, feast/famine conditions play a crucial role in ensuring long-term stability and nutrient removal. Additionally, bioaugmentation can facilitate the granulation process. Furthermore, this paper comprehensively assesses the application of AGS-CFRs in full-scale wastewater treatment plants (WWTPs). Currently, AGS-CFRs have been implemented in nine WWTPs, encompassing two distinct processes. Hydrocyclone-based densified activated sludge significantly enhances sludge density, settleability, and biological phosphorus removal efficiency, thus increasing treatment capacity. The microaerobic–aerobic configuration with internal separators can induce granulation, ensuring long-term stability, eliminating the need for external clarifiers, and reducing land and energy requirements. This review demonstrates the high potential of AGS-CFRs for intensifying existing WWTPs with minimal retrofitting needs. However, further research is required in granulation mechanisms, long-term stability, and nutrient removal to promote the widespread adoption of AGS. HIGHLIGHTS Over 100 papers on AGS in CFRs were systematically reviewed.; Full-scale applications of conventional AGS in CFRs were assessed.; Long-term stability, particularly in the cold season, was the primary challenge.; Further research on granulation and nutrient removal mechanisms is required.;

Nanoparticles (NPs) are of significant interest due to their unique properties, such as large surface area and high reactivity, which have facilitated advancements in various fields. However, their increased use raises concerns about environmental impacts, including on wastewater treatment processes. This review examines the effects of different nanoparticles on anaerobic, anammox, aerobic, and algal-bacterial granular sludge used in wastewater treatment. CeO2 and Ag NPs demonstrated adverse effects on aerobic granular sludge (AGS), reducing nutrient removal and cellular function, while anaerobic granular sludge (AnGS) and anammox granular sludge (AxGS) showed greater resilience due to their higher extracellular polymeric substance (EPS) content. TiO2 NPs had fewer negative effects on algal-bacterial granular sludge (ABGS) than on AGS, as algae played a crucial role in enhancing EPS production and stabilizing the granules. The addition of Fe3O4 NPs significantly enhanced both aerobic and anammox granulation by reducing granulation time, promoting microbial interactions, improving granule stability, and increasing nitrogen removal efficiency, primarily through increased EPS production and enzyme activity. However, Cu and CuO NPs exhibited strong inhibitory effects on aerobic, anammox, and anaerobic systems, affecting EPS structure, cellular integrity, and microbial viability. ZnO NPs demonstrated dose-dependent toxicity, with higher concentrations inducing oxidative stress and reducing performance in AGS and AnGS, whereas AxGS and ABGS were more tolerant due to enhanced EPS production and algae-mediated protection. The existing knowledge gaps and directions for future research on NPs are identified and discussed.

The use of aerobic granular sludge (AGS) for wastewater treatment has emerged as a promising biotechnology. A sodium alginate nucleus (SAN) incorporated into the AGS system can enhance aerobic granulation. Two important parameters influencing AGS formation and stability are the organic loading rate (OLR) and C/N ratio. In this study, AGS containing the SAN was cultivated under different OLR and C/N ratios. Through morphological analysis, physicochemical properties, and water quality analysis, the effects of the OLR and C/N ratio on the rapid formation and performance of AGS containing the SAN were investigated. The results showed that the most suitable OLR and C/N ratio in the SAN system were 1.4–2.4 kg/(m3∙d) and 10–15, respectively. A recovery experiment of sodium alginate (SA) showed that the group that formed AGS generally had a higher recovery efficiency compared with the group that did not form granular sludge. This work explored the suitable granulation conditions of AGS containing the SAN, and the results provide a theoretical basis for future practical applications. The recycling of SA as presented in this study may broaden the application prospects of SA. [ABSTRACT FROM AUTHOR]

Aerobic granular sludge (AGS) and conventional activated sludge (CAS) are two different biological wastewater treatment processes. AGS consists of self-immobilised microorganisms that are transformed into spherical biofilms, whereas CAS has floccular sludge of lower density. In this study, we investigated the treatment performance and microbiome dynamics of two full-scale AGS reactors and a parallel CAS system at a municipal WWTP in Sweden. Both systems produced low effluent concentrations, with some fluctuations in phosphate and nitrate mainly due to variations in organic substrate availability. The microbial diversity was slightly higher in the AGS, with different dynamics in the microbiome over time. Seasonal periodicity was observed in both sludge types, with a larger shift in the CAS microbiome compared to the AGS. Groups important for reactor function, such as ammonia-oxidising bacteria (AOB), nitrite-oxidising bacteria (NOB), polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs), followed similar trends in both systems, with higher relative abundances of PAOs and GAOs in the AGS. However, microbial composition and dynamics differed between the two systems at the genus level. For instance, among PAOs, Tetrasphaera was more prevalent in the AGS, while Dechloromonas was more common in the CAS. Among NOB, Ca. Nitrotoga had a higher relative abundance in the AGS, while Nitrospira was the main nitrifier in the CAS. Furthermore, network analysis revealed the clustering of the various genera within the guilds to modules with different temporal patterns, suggesting functional redundancy in both AGS and CAS. Key points: • Microbial community succession in parallel full-scale aerobic granular sludge (AGS) and conventional activated sludge (CAS) processes. • Higher periodicity in microbial community structure in CAS compared to in AGS. • Similar functional groups between AGS and CAS but different composition and dynamics at genus level. [ABSTRACT FROM AUTHOR]

Recently, one of the main purposes of wastewater treatment plants is to achieve a neutral or positive energy balance while meeting the discharge criteria. Aerobic granular sludge (AGS) technology is a promising technology that has low energy and footprint requirements as well as high treatment performance. The effect of co-treatment of municipal wastewater and food waste (FW) on the treatment performance, granule morphology, and settling behavior of the granules was investigated in the study. A biochemical methane potential (BMP) test was also performed to assess the methane potential of mono- and co-digestion of the excess sludge from the AGS process. The addition of FW into wastewater enhanced the nutrient treatment efficiency in the AGS process. BMP of the excess sludge from the AGS process fed with the mixture of wastewater and FW (195 ± 17 mL CH4/g VS) was slightly higher than BMP of excess sludge from the AGS process fed with solely wastewater (173 ± 16 mL CH4/g VS). The highest methane yield was observed for co-digestion of excess sludge from the AGS process and FW, which was 312 ± 8 mL CH4/g VS. Integration of FW as a co-substrate in the AGS process would potentially enhance energy recovery and the quality of effluent in municipal wastewater treatment. [ABSTRACT FROM AUTHOR]

Currently, there is a growing interest in transforming wastewater treatment plants (WWTPs) into resource recovery plants. Microorganisms in aerobic granular sludge produce extracellular polymeric substances (EPS), which are considered sustainable resources to be extracted and can be used in diverse applications. Exploring applications in other high-value materials, such as adhesives, will not only enhance the valorization potential of the EPS but also promote resource recovery. This study aimed to characterize a water-soluble fraction extracted from the EPS collected at the demonstration plant in the Netherlands based on its chemical composition (amino acids, sugar, and fatty acids) and propose a proof-of-concept for its use as an adhesive. This fraction comprises a mixture of biomolecules, such as proteins (26.6 ± 0.3%), sugars (21.8 ± 0.2%), and fatty acids (0.9%). The water-soluble fraction exhibited shear strength reaching 36-51 kPa across a pH range of 2-10 without additional chemical treatment, suggesting a potential application as an adhesive. The findings from this study provide insights into the concept of resource recovery and the valorization of excess sludge at WWTPs. [ABSTRACT FROM AUTHOR]

Nowadays, the discharge of wastewater is a global concern due to the damage caused to human and environmental health. Wastewater treatment has progressed to provide environmentally and economically sustainable technologies. The biological treatment of wastewater is one of the fundamental bases of this field, and the employment of new technologies based on granular biofilm systems is demonstrating success in tackling the environmental issues derived from the discharge of wastewater. The granular-conforming microorganisms must be evaluated as functional entities because their activities and functions for removing pollutants are interconnected with the surrounding microbiota. The deep knowledge of microbial communities allows for the improvement in system operation, as the proliferation of microorganisms in charge of metabolic roles could be modified by adjustments to operational conditions. This is why engineering must consider the intrinsic microbiological aspects of biological wastewater treatment systems to obtain the most effective performance. This review provides an extensive view of the microbial ecology of biological wastewater treatment technologies based on granular biofilms for mitigating water pollution. [ABSTRACT FROM AUTHOR]

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Aerobic granular sludge (AGS) biotechnology has recently obtained considerable interest as a viable alternative to the activated sludge process (ASP) technique. This is because AGS can improve the performance of wastewater treatment and its significant capability for attaining sustainable growth. One of the main challenging issues for the aerobic granular sludge is the long startup time in wastewater treatment. This review presents a comprehensive analysis of AGS biotechnology, aiming specifically at its global adoption, startup duration, and granule stability. Aerobic granular sludge (AGS) is becoming more widespread globally. To ensure the successful implementation of AGS biotechnology, it is crucial to thoroughly identify the development of dense and stable granules, which is vital for the proper operation of wastewater treatment plants (WWTPs). Additionally, it offers a comprehensive summary of the latest advancements in the inoculum and polymer additives and their respective contributions to accelerate various processes through distinct mechanisms. In addition, this paper reviews the prevailing research patterns in the prompt initiation of rapid startup of AGS technology and outlines specific issues for future investigations.

This study evaluated the efficiency of aerobic granular sludge (AGS) technology in treating wastewater contaminated with tetracycline (TC), a common antibiotic. AGS was cultivated under a TC pressure gradient ranging from 5 mg/L to 15 mg/L and compared with conventional wastewater conditions. The results demonstrated that AGS achieved high removal efficiencies and exhibited robust sedimentation performance, with significant differences in average particle sizes observed under both conditions (618.6 μm in TC conditions vs. 456.4 μm in conventional conditions). Importantly, exposure to TC was found to alter the composition and production of extracellular polymeric substances (EPSs), thereby enhancing the structural integrity and functional stability of the AGS. Additionally, the selective pressure of TC induced shifts in the microbial community composition; Rhodanobacter played a crucial role in EPS production and biological aggregation, enhancing the structural integrity and metabolic stability of AGS, while Candida tropicalis demonstrated remarkable resilience and efficiency in nutrient removal under stressful environmental conditions. These findings underscore the potential of AGS technology as a promising solution for advancing wastewater treatment methods, thus contributing to environmental protection and sustainability amid growing concerns over antibiotic contamination.

The characteristics of excess aerobic granular sludge, related to its structure and chemical composition, limit the efficiency of anaerobic digestion. For this reason, pre-treatment methods and compositions with other organic substrates are used. In earlier work, no attempt was made to intensify the methane fermentation of the excess aerobic granular sludge by adding fatty waste materials. The aim of the research was to determine the effects of co-digestion of pre-hydrodynamically cavitated aerobic granular sludge with waste fats on the efficiency of methane fermentation under mesophilic and thermophilic conditions. The addition of waste fats improved the C/N ratio and increased its value to 19. Under mesophilic conditions, the highest effects were observed when the proportion of volatile solids from waste fats was 25%. The amount of biogas produced increased by 17.85% and CH4 by 19.85% compared to the control. The greatest effects were observed in thermophilic anaerobic digestion at 55 °C, where a 15% waste fat content in volatile solids was ensured. This resulted in the production of 1278.2 ± 40.2 mL/gVS biogas and 889.4 ± 29.7 mL/gVS CH4. The CH4 content of the biogas was 69.6 ± 1.3%. The increase in biogas and CH4 yield compared to pure aerobic granular sludge anaerobic digestion was 34.4% and 40.1%, respectively. An increase in the proportion of waste fats in the substrate had no significant effect on the efficiency of methane fermentation. Strong positive correlations (R2 > 0.9) were observed between biogas and CH4 production and the C/N ratio and VS concentration. [ABSTRACT FROM AUTHOR]

Complex heavy metal (HM)-containing wastewater discharges pose substantial risks to global water ecosystems and human health. Aerobic granular sludge (AGS) has attracted increased attention as an efficient and low-cost adsorbent in HM-containing wastewater treatment. Therefore, this study systematically evaluates the effect of Cu(II), Ni(II), and Cr(III) addition on the characteristics, performance and mechanism of AGS in complex HM-containing wastewater treatment process by means of fourier transform infrared spectroscopy, inductively coupled plasma spectrocopcy, confocal laser scanning microscopy, extracellular polymeric substances (EPS) fractions detection and scanning electron microscope-energy dispersive X-ray. The results showed that AGS efficiently eliminated Cu(II), Ni(II), and Cr(III) by the orchestrated mechanisms of ion exchange, three-layer EPS adsorption [soluble microbial products EPS (SMP-EPS), loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS)], and inner-sphere adsorption; notably, almost 100% of Ni(II) was removed. Threelayer EPS adsorption was the dominant mechanism through which the HM were removed, followed by ion exchange and inner-sphere adsorption. SMPEPS and TB-EPS were identified as the key EPS fractions for adsorbing Cr(III) and Cu(II), respectively, while Ni(II) was adsorbed evenly on SMP-EPS, TB-EPS, and LB-EPS. Moreover, the rates at which the complex HM penetrated into the granule interior and their affinity for EPS followed the order Cu(II) > Ni(II) > Cr(III). Ultimately, addition of complex HM stimulated microorganisms to excrete massive phosphodiesterases (PDEs), leading to a pronounced decrease in cyclic diguanylate (c-di-GMP) levels, which subsequently suppressed EPS secretion due to the direct linkage between c-di-GMP and EPS. This study unveils the adaptability and removal mechanism of AGS in the treatment of complex HM-containing wastewater, which is expected to provide novel insights for addressing the challenges posed by intricate real wastewater scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a strategy for the establishment of an aerobic granular sludge (AGS) system for simultaneous nitrogen and Pb(II) removal from inorganic wastewater. AGS was stored in lead nitrate solution to select functional bacteria resistant to lead poison, and then an AGS system for ammonia nitrogen (180-270 mg/L) and Pb(II) (15-30 mg/L) removal was established based on carbon dosing and a two-stage oxic/anoxic operational mode. After storage for 40 days, the stability of AGS decreased because specific oxygen uptake rate, nitrification rate and abundance of Nitrosomonas decreased to different degrees compared with those before storage. During the first 70 days of the recovery process, AGS in R1 (the blank reactor) and R2 (the control reactor) both experienced a first breakage and then regranulation process. The main properties of AGS in reactors R1 and R2 tended to be stable after days 106 and 117, respectively, but the structure of steady-state AGS in R2 was more compact. The total inorganic nitrogen (TIN) in effluent from R1 and R2 basically remained below 25 mg/L after days 98 and 90, respectively. The Pb(II) concentration in effluent from R2 was always below 0.3 mg/L. On day 140, the relative abundance of Nitrosomonas in R2 (6.17%) was significantly lower than that in R1 (12.15%), whereas the relative abundance of denitrifying bacteria was significantly higher than that in R1 (62.44% and 46.79%). The system removed 1 kg of influent TIN only consuming approximately 1.85 kg of carbon source, demonstrating clear advantages in energy savings. [ABSTRACT FROM AUTHOR]