Growth Of Filamentous Bacteria Research Articles

Filamentous bacteria-induced sludge bulking can alter antibiotic resistance gene profiles and increase potential risks in wastewater treatment systems

Sludge bulking caused by filamentous bacteria is a prevalent issue in wastewater treatment systems. While previous studies have primarily concentrated on controlling sludge bulking, the biological risks associated with it have been overlooked. This study demonstrates that excessive growth of filamentous bacteria during sludge bulking can significantly increase the abundance of antibiotic resistance genes (ARGs) in activated sludge. Through metagenomic analysis, we identified specific ARGs carried by filamentous bacteria, such as Sphaerotilus and Thiothrix, which are responsible for bulking. Additionally, by examining over 1,000 filamentous bacterial genomes, we discovered a diverse array of ARGs across different filamentous bacteria derived from wastewater treatment systems. Our findings indicate that 74.84% of the filamentous bacteria harbor at least one ARG, with the occurrence frequency of ARGs in these bacteria being approximately 1.5 times higher than that in the overall bacterial population in activated sludge. Furthermore, genomic and metagenomic analyses have shown that the ARGs in filamentous bacteria are closely linked to mobile genetic elements and are frequently found in potentially pathogenic bacteria, highlighting potential risks posed by these filamentous bacteria. These insights enhance our understanding of ARGs in activated sludge and underscore the importance of risk management in wastewater treatment systems.

Pathways of inhibition of filamentous sludge bulking by slowly biodegradable organic compounds

The organic compound composition of wastewater, serves as a crucial indicator for the operational performance of activated sludge processes and has a major influence on the development of filamentous bulking in activated sludge. This study focused on the impact of typical soluble and slowly-biodegradable organic compounds, investigating the pathways through which these substrates affect the occurrence of filamentous bulking in systems operated under both high- and low-oxygen conditions. Results showed that slowly-biodegradable organic compounds lead to a concentrated distribution of microorganisms within flocs, with inward growth of filamentous bacteria. Both Tween-80 and granular starch treated systems exhibited a significant increase in protein content. The glucose system, utilizing soluble substrates, exhibited a markedly higher total polysaccharide content. Microbial communities in the Tween-80 and granular starch treated systems were characterized by a higher abundance of bacteria known to enhance sludge flocculation and settling, such as Competibacter, Xanthomonadaceae and Zoogloea. These findings are of high significance for controlling the operational performance and stability of activated sludge systems, deepening our understanding and providing a novel perspective for the improvement of wastewater treatment processes.

Control of Filamentous Bacteria overgrowth by Changing the Hydraulic Flow Distribution of a Step-feed Biological Nitrogen Removal (SFBNR) Process-based WWTP: A Full-scale Study

To facilitate the wastewater recycling process while adhering to environmental and industrial regulations, it becomes imperative to meet stringent standards. This necessitates the effective elimination of organic substances, with particular emphasis on nitrogen-based compounds. To this end, activated sludge methods, particularly the step-feed biological nitrogen removal (SFBNR) process, are employed. Although various operational measures are employed in SFBNR systems, including the elimination of complex substrates, modifications in aeration conditions, the utilization of piston hydraulic flow, and the appropriate distribution of substrates, these systems remain susceptible to the excessive growth of filamentous bacteria. The current study aimed to examine the change in the distribution of the hydraulic flow entering this system on a real scale over a period of five years. It was observed that the quality of sludge settling improved and accordingly the overgrowth of filamentous Microthrix parvicella declined, thereby enhancing the quality of the effluent.

Rapid static feeding combined with Fe2+ addition for improving the formation and stability of aerobic granular sludge in low-strength wastewater

Aerobic granular sludge (AGS) needs a long start-up time and always shows unstable performance when it is used to treat low-strength wastewater. In this study, a rapid static feeding combined with Fe2+ addition as a novel strategy was employed to improve the formation and stability of AGS in treating low-strength wastewater. Fe-AGS was formed within only 7 days and showed favorable pollutant removal capability and settling performance. The ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD) concentration in the effluent were lower than 5 mg/L and 50 mg/L after day 23, respectively. The sludge volume index (SVI) and mixed liquid suspended solids (MLSS) was 37 mL/g and 2.15 g/L on day 50, respectively. Rapid static feeding can accelerate granules formation by promoting the growth of heterotrophic bacteria, but the granules are unstable due to filamentous bacteria overgrowth. Fe2+ addition can inhibit the growth of filamentous bacteria and promote the aggregation of functional bacteria (eg. Nitrosomonas, Nitrolancea, Paracoccus, Diaphorobacter) by enhancing the secretion of extracellular polymeric substances (EPS). This study provides a new way for AGS application in low-strength wastewater treatment.

Strengthen high-loading operation of wastewater treatment plants by composite micron powder carrier: Microscale control of carbon, nitrogen, and sulfur metabolic pathways

The concentration of activated sludge is a crucial factor influencing the capacity and efficiency of sewage wastewater treatment plants (WWTPs). However, high sludge concentrations can lead to sludge loss in the secondary sedimentation tank, resulting in reduced processing capacity, particularly during low-temperature stages and sludge bulking. This study investigated the impact of adding composite micron powder carriers (CMPC) in high-concentration powder carrier biofluidized bed (HPB) technology to the biochemical units of WWTPs on sludge concentration and settling performance. For the traditional activated sludge method (ASM), its hydraulic retention time (HRT) was 8 h, with an average effluent total nitrogen (TN) of 15.14 mg/L. Sludge bulking was prone to occur in low-temperature environments, resulting in a high average sludge volume index (SVI) of 560 mL/g. Conversely, with a CMPC dosage of 4 g/L, the HRT of HPB technology was 4.8 h, and the average effluent TN was 11.40 mg/L, with a removal efficiency of 67.43 %. During operation of HPB technology under high sludge concentration conditions (8 g/L), the average SVI remained at 85 mL/g, indicating excellent settling characteristics. Moreover, in the sequencing batch reactor (SBR), the SVI value of bulking sludge decreased from the original 695 to 111 mL/g by the 9th day of operation with the CMPC dosage of 2 g/L. At the same time, the filamentous bacteria almost disappeared, suggesting that CMPC inhibit the growth of filamentous bacteria. Metagenomic analysis demonstrated that CPMC enhance the utilization of small molecular fatty acids in activated sludge and promote electron transfer between nitrate and nitrite, thereby improving wastewater treatment capacity. Additionally, CMPC enhanced the relative abundance of Saprospiraceae in sludge, which accelerate the degradation of polysaccharides in extracellular polymeric substances, weaken sludge's hydrophilic properties, and improve sludge's settling performance. Overall, these findings suggested that CMPC effectively strengthen the high-loading operation of WWTPs by improving sludge concentration and sedimentation performance.

New insight into soluble extracellular metabolites during sludge bulking process based on excitation-emission matrix spectroscopy and ultrahigh-performance liquid chromatography-mass spectrometry

Soluble extracellular metabolites (SEM) produced by microorganisms might significantly change during sludge bulking, which is a major operational problem caused by the excessive growth of filamentous bacteria. However, knowledge remains limited about the dynamics and potential role of SEM in the bulking of sludge. In this study, filamentous bulking was simulated in a laboratory-scale reactor and changes to SEM characteristics during the bulking process were investigated using excitation-emission matrix spectroscopy and ultrahigh-performance liquid chromatography-mass spectrometry. SEM components changed significantly at different phases of sludge bulking. Changes in SEM were closely correlated with the structure of the bacterial community. Based on the EEM profiles, significant increases in fulvic acid-like and humic acid-like substances in SEM were observed with the development of filamentous bulking. The degree of humification in SEM showed a clear increasing trend. Untargeted extracellular metabolomic analysis showed that the intensity of berberine and isorhamnetin in SEM increased significantly during the bulking phase, which might synergistically facilitate the development of filamentous bulking.

Biotransformation of sulfamethoxazole (SMX) by aerobic granular sludge: Removal performance, degradation mechanism and microbial response

Aerobic granular sludge (AGS) is a promising biotechnology for the treatment of antibiotic−rich wastewater. However, little is known about the antibiotics degradation mechanism and microbial response in a sulfamethoxazole (SMX)-loaded AGS system. Herein, the results of a continuous 240 days test suggested that 0.5–5 mg/L of SMX could be thoroughly removed by AGS via adsorption and degradation. The degradation pathway of SMX involved the hydrolysis of the sulfonamide bond and cleavage of NS or CS bonds, subsequently leading to the production of small molecular substances (e.g. benzene and 5-methyl-isoxazole). In terms of the AGS system, it exhibited a strong resistance to 0.5 mg/L of SMX, while 1 and 5 mg/L of SMX significantly inhibited the microbial growth, declined the nitrification efficiency, weakened the sludge settleability, and triggered the excessive growth of filamentous bacteria. Besides, the secretion of extracellular polymer substances was suppressed by 57.3% when increasing the SMX concentration from 0.5 to 5 mg/L, which was not conducive to the system stability. The long−term presence of SMX enhanced the proliferation of antibiotics resistance genes (sul1and sul2) and exerted a strong selection pressure on the microbial community, especially with Thiothrix being the dominating genus. Overall, this study elucidated that AGS qualified promising application prospects in the removal of SMX present in wastewater, but SMX at high concentrations posed great adverse impacts on the performance of the AGS system, which causes concern when treating SMX rich wastewaters.

Prediction of sludge settleability through artificial neural networks with optimized input variables

AbstractSludge bulking is a major problem in activated sludge processes. It is of great practically useful to predict the sludge settleability through water quality (influent and effluent) and the operation patterns. In this study, the artificial neural network (ANN) to predict the variation of sludge settleability was established with MLSS, organic loading rate and NH4+‐N loading rate as basic input variables. Additional input variables were optimized through comparing the performance of multilayer perceptron artificial neural network (MLPANN) with different combinations. The results showed that excellent nitrification will improve sludge settleability, and the famine phase would promote the growth of filamentous bacteria. Furthermore, the model performance of MLPANN and long short‐term memory networks (LSTM) were compared by using optimized input variables. The results indicated the MLPANN performed better than LSTM with optimized inputs. This study provided a reference of optimizing variables to predict the variation of sludge settleability in activated sludge process. This study will provide a reference for selecting appropriate variables to predict sludge settleability in activated sludge processes.

Distinct responses of aerobic granular sludge sequencing batch reactors to nitrogen and phosphorus deficient conditions

The nutrients availability determines efficiency of biological treatment systems, along with the structure and metabolism of microbiota. Herein nutrients deficiencies on aerobic granular sludge were comparatively evaluated, treating wastewater with mass ratios of chemical oxygen demand : nitrogen : phosphorus being 200:20:4, 200:2:4, and 200:20:0.4 (deemed as nutrient-balanced, nitrogen-deficient, and phosphorus-deficient), respectively. Results revealed that both nitrogen and phosphorus deficiencies significantly raised the effluent qualities especially nitrogen removal. However, nitrogen deficiency aroused considerable growth of filamentous bacteria, while granules kept compact structure under phosphorus deficient condition. Extracellular polymeric substances (EPS) also varied in contents and structures in response to different wastewaters. Microbial community structure analysis demonstrated that nitrogen deficiency led to lower richness and higher diversity, while the reverse was observed under phosphorus deficient condition. Nitrogen deficiency mainly induced decrease of nitrifying bacteria, while similarly phosphorus deficiency led to loss of phosphorus accumulating organisms. Dramatic enrichment Candidatus_Competibacter and filamentous Thiothrix were found under nutrients deficiencies, in which the latter explained and indicated filamentous bulking potential especially under nitrogen limited condition. Bacterial metabolism patterns verified the functions of microbial community responding to nutrients via PICRUSt2 prediction mainly by up-regulating cell motility, and cellular processes and signaling. This study could aid understanding of long-term stability of aerobic granular sludge for low-strength wastewater treatment.

Linking endogenous decay and sludge bulking in the microbial community to membrane fouling at sub-critical flux

This study examined membrane fouling and associated microbial taxa in a membrane bioreactor operating at a sub-critical flux condition using next-generation amplicon sequencing. The membrane was operated at a sub-critical flux, thus, fouling was not observed until endogenous decay. The observed fouling could be attributed to endogenous decay which was driven by nutrient deficiency at high sludge age and low food-to-microorganisms ratio (decreasing from 0.15 to 0.09 gBOD/gMLVSS.d). Endogenous decay resulted in a sharp decrease of the number of species and evenness between different species (49.7 and 58.9% compared to the inoculum, respectively). The release of dissolved organic matters and cell debris from endogenous decay as well as the excessive growth of filamentous bacteria, e.g. Thiotrichales were the main contributors to membrane fouling. The relative abundance of Thiotrichales significantly correlated with TMP (Pearson R = 0.996, p-value <0.001), indicating this order's contribution to membrane fouling. Other dominant orders in the mixed liquor after endogenous decay such as Rhizobiales, Burkholderiales, Rhodospirillales and Myxococcales, Flavobacteriales can produce extracellular polymeric substances and aggravating membrane fouling. Fouling layers possess highly similar microbial composition with the mixed liquor, with some filamentous microbial orders, e.g. Corynebacteriales and Oligoflexales showing increased relative abundance by 6.83 and 5.64 folds, respectively.

Influence of Influent Quality and Operational Modes on the Excessive Growth of Filamentous Bacteria in Kuwait’s Activated Sludge Systems

Kuwait’s wastewater treatment plants experience severe sludge bulking and foaming problems during the winter months. In an effort to identify the possible causes of these problems, sample of wastewater and sludge was collected from Um-Al-Haiman and Riqqa activated sludge systems each week for 32 weeks. The quality of wastewater was determined following standard methods of water analysis, while the dominant filamentous bacteria were identified and quantified using a molecular method called Vermicon Identification Technology (VIT). Multivariate statistical analysis (namely, Pearson’s correlation analysis and principal component analysis) was then carried out on the obtained datasets of results. Pearson’s correlation analysis revealed several significant associations between filamentous bacteria growth and influent quality and operational modes for the systems. The principal component analysis revealed six components that accounted for more than 70% of the total datasets’ information. The techniques used in this study can also be used to assess the relationship between filamentous bacteria growth and the operating conditions of other activated sludge systems.

Leptothrix cholodnii Response to Nutrient Limitation.

Microorganisms are widely utilized for the treatment of wastewater in activated sludge systems. However, the uncontrolled growth of filamentous bacteria leads to bulking and adversely affects wastewater treatment efficiency. To clarify the nutrient requirements for filament formation, we track the growth of a filamentous bacterium, Leptothrix cholodnii SP-6 in different nutrient-limited conditions using a high aspect-ratio microfluidic chamber to follow cell-chain elongation and sheath formation. We find that limitations in Na+, K+, and Fe2+ yield no observable changes in the elongation of cell chains and sheath formation, whereas limitations of C, N, P, or vitamins lead to more pronounced changes in filament morphology; here we observe the appearance of partially empty filaments with wide intercellular gaps. We observe more dramatic differences when SP-6 cells are transferred to media lacking Mg2+ and Ca2+. Loss of Mg2+ results in cell autolysis, while removal of Ca2+ results in the catastrophic disintegration of the filaments. By simultaneously limiting both carbon and Ca2+ sources, we are able to stimulate planktonic cell generation. These findings paint a detailed picture of the ecophysiology of Leptothrix, which may lead to improved control over the unchecked growth of deleterious filamentous bacteria in water purification systems.

Intermittent aeration improving activated granular sludge granulation for nitrogen and phosphorus removal from domestic wastewater

Given the large quantity discharge of nutrients in sewage, nitrogen and phosphorus is getting a worldwide concern. This manuscript assigned two different aeration modes of intermittent aeration/anoxia aeration and continuous aeration to study dissolved oxygen (DO) affecting contaminant removal, AGS granulation and microbial community diversity. The results demonstrated that intermittent aeration contributed to higher removal efficiencies of organics, nitrogen and phosphorus and faster granulation process, larger particle size, and more microbial communities than continuous aeration. The temporal lack of DO for intermittent aeration module did not only save approximately 40% energy but also change microbial communities. The intermittent aeration had no growth of filamentous bacteria and more microbial communities consist of Paracoccus, Delftia, Flavobacterium, Brevundimonas, Roseobacter_clade_CHAB-I-5_lineage, which accelerated AGS granulation, and Nitrosopumilus, Nitrospina, Facultative anaerobes, Pelagibacter and UKL 13-1 bacteria, which played crucial roles in N and P removal.

Effect of Magnetic Fields on the Sludge Properties in the Aeration Basin of the Activated Sludge Treatment Process

Purpose: Sludge management is one of the most important problems in wastewater treatment plants (WWTPs) and an activated sludge treatment process. Excessive growth of filamentous bacteria may cause, less dense floc structure, poor sludge compaction, slow settling, and wash-out solids from the final clarifiers. Sludge volume index (SVI) is an unknown method and the most appropriate parameter to express and estimate the settling characteristics of the sludge. The use of chemical materials to increase the volume of sludge is custom, but these methods are expensive and are not a green process. In recent years, the use of integrated treatment methods such as the use of magnetic fields (MFs) with biological methods, to accelerate the growth of microorganisms has become common. Methods: In this case and control study use of MFs (from 0.19 to 3.21mT) to decrease SVI (30 minutes time to settling) or enhancement of sludge, considered. Results: Based on the result of this study by increased the intensity of MFs, a decrease in SVI (0.03 to 53 percent) happened statistically. Conclusion: One of the main, physical, and practical methods to reduce the huge volume of sludge by decrease SVI in WWTPs can be used by applying MFs.

ВЛИЯНИЕ ЗАГРЯЗНЕНИЙ СТОЧНЫХ ВОД НА БИОЦЕНОЗ АКТИВНОГО ИЛА

Wastewater from agro-industrial complexes is rich in organic components. Biological method is considered to be the most universal for their purification. It provides a high rate of biodegradation of pollution. But due to the high concentration of incoming pollutants, activated sludge microbiome can reduce its cleaning ability. High aeration rate is required for the effective decomposition of such compounds, since aerobic microorganisms predominate in the activated sludge. Under real conditions, the time for the oxidation of these substances by microbial communities is often insufficient. This imbalance between incoming organic matter and oxidized activated sludge microbiota leads to the growth of filamentous bacteria, which is one of the reasons of activated sludge swelling. The influence of high concentrations of pollutants in wastewater on a consortium of microorganisms of activated sludge was investigated to eliminate this negative factor. Physical and chemical composition of the wastewater was carried out according to standard methods. The composition of the activated sludge bacteriocenosis and pig intestine microbiome were determined by standard methods of inoculation in liquid and solid nutrient media. A correlation between the decrease in the concentration of pollutants and regeneration of activated sludge biocenosis has been established. A 59.8% decrease in the overall level of COD contamination of source effluents led to an increase in the number of flocculating microorganisms by 41.7%. Deep destruction of amine nitrogen (99%) and phosphorus (71.4%) was observed due to the activation of heterotrophic microorganisms.

An evaluation of the oilfield-produced water treatment by the membrane bioreactor

Detailed understanding of the membrane application is essential for the treatment of wastewater to remove organic and inorganic pollutants. Even though the membrane bioreactor (MBR) has been widely used for the removal of oil and grease (O&G) and chemical oxygen demand (COD) from wastewater, the use of MBR to remove the organic and inorganic pollutants from oilfield-produced water (OPW) needs to be verified. This study used two submerged MBRs to remove the COD, O&G, NH3 and PO43- pollutants from OPW by considering two variables of NaCl content and C/N/P ratio in the analysis of experimental data. The results show the use of the MBR system to remove COD, O&G and NH3 reaching at an efficiency of higher than 90%. The efficiency of the MBR system to remove PO43- increases by 14.95% for the treatment of OPW with salt content of 10 gNaCl L-1 and by 15.71% for that with salt content of 17.5 gNaCl L-1. Despite of the change in C/N/P ratio from 100/10/1 to 100/2/1 shows a decrease in the sludge volume index by 61.27% for the treatment of OPW with salt content of 10 gNaCl L-1 and by 61.43% for that with salt content of 17.5 gNaCl L-1, the occurrence of membrane fouling could be due to the growth of filamentous bacteria in OPW when conditioned with 17.5 gNaCl L-1. A valuable insight into the practical design of MBR technology can be obtained from this study to contribute to the future development of OPW treatment process.

Stable granulation of seawater-adapted aerobic granular sludge with filamentous Thiothrix bacteria

Many sources of wastewater contain sulfides, which can cause excessive growth of filamentous bacteria such as Thiothrix sp. resulting in bulking sludge in conventional activated sludge systems. Granular sludge systems could potentially also suffer from the growth of filamentous bacteria. Uptake of easily degradable COD by the relatively slow growing Ca. Accumulibacter phosphatis bacteria and the absence of strong diffusion gradients due to plug flow feeding through the settled granular sludge bed are assumed to be the dominant factors for successful granulation. Sulfides will remain after this anaerobic phase and cause growth of sulfide-consuming bacteria such as Thiothrix sp. Here we observed the impact of growth of Thiothrix sp bacteria in a laboratory aerobic granular sludge reactor by feeding a mixture of acetate and thiosulfate in the influent. Thiothrix sp, proliferated when 18% of the influent COD was due to thiosulfate, forming 51.4 ± 8.3% of the total granular biomass. Despite the strong presence of these filamentous bacteria a well settling sludge was maintained (SVI10 equal to 13.3 mL/g). These results confirm that sludge morphology is not necessarily a reflection of the cell morphology of the bacteria, but is highly influence by reactor operation. It also reiterates the fact that compact biofilms are formed when the substrate consumption rate is lower than the substrate transport rate.

Seasonal variation pattern of physicochemical and microbial parameters in a wastewater treatment plant

According to the statistical analysis results of the samples from the Kabd WWTP obtained over four years from January 2013 to December 2016 and four seasons (winter, spring, summer and fall), the following conclusions are obtained in this study. 1. Variations in the water temperature affect the treatment system, especially the biological treatment system and microorganism population. The sudden temperature rise in summer causes problems for aerobic digestion and nitrification. In addition, the DO of warm water is usually less than that of cold water, and if the temperature suddenly drops during winter, then the bacterial population will be affected. 2. Seasonal variations are observed in the physicochemical parameters. A small variation in pH occurs during all seasons. pH affects the microbial activity in the biological treatment, and an extreme value indicates the presence of toxic material in the wastewater. The electrical conductivity increased as the temperature increased. The maximum average removal of suspended solids, including VSS, depends primarily on the treatment quality process during fall and winter but also depends on the temperature. The removal efficiency is better during fall than that during summer because high temperatures improve the reproduction of nitrifying bacteria and the production of nitrogen in sludge in the final effluent. The SVI in the aeration tanks increased as the temperature increased; however, a value of <150 mg/L indicates filamentous bacteria growth and sudden reproduction. The maximum average removal of BOD5 is equivalent in winter, spring and fall, and these values are higher than that in summer, and the maximum removal of COD is observed in fall. The values of the BOD5 and COD indicate high organic pollution and a large concentration of microorganisms. However, organic substances may present more rapid chemical oxidation than does biological oxidation, and certain organic substances can be toxic to the microorganisms that were used for the 50 BOD5 test. Oxides contributed by dichromate in inorganic substances enhance the organic content and lead to higher COD than BOD values. The maximum average removal of O&G, which is related to the fat and oil content of wastewater, in the secondary treatment level occurs in summer. The fat and oil content related to the food consumed in Kuwait, which usually includes high quantities of butter, meats, nuts, margarine and vegetable fats and oils. 3. Seasonal variations in microbial parameters were observed. The highest average concentrations of coliform count in the raw wastewater were observed in spring, although in the tertiary treatment level, coliform survive better than they do in winter. Salmonella, streptococci and fungi resist and survive better in spring in the inflow wastewater and effluent, and F. coli survives better in the influent and tertiary treatment level in spring. 4. The efficiency of the plant was very good, and it presented a removal efficiency >95% for BOD, COD, TSS, VSS, O&G and % 72 < for NH3-N and PO4-3. 5. The Kabd WWTP followed the KEPA and project contract water standards for irrigation use. All the parameters meet the KEPA and project contract standards, with F. coli and salmonella exceeding the project contract standards.

Seasonal variations of the growth of filamentous bacteria in Kuwait’s wastewater treatment plants

Seasonal variations of the growth of filamentous bacteria in Kuwait’s wastewater treatment plants

Start-up of aerobic granular biofilm at low temperature: Performance and microbial community dynamics

Low temperature is a great challenge for the biological treatment of wastewater. In this study, the rapid start-up of aerobic granular biofilm (AGF) reactor was realized by adding micro-sized polyurethane (PU) sponges as matrices at 10 °C. The results showed that the granulation process of AGF was different from that of traditional aerobic granular sludge and biofilms, which was formed by using the sludge intercepted in PU matrix instead of sponge skeletons as granulation carriers. During the 5-month operation period, stable pollutants removal performance was achieved within 70 days, besides, the corresponding ammonium, total nitrogen, and total phosphorus removal efficiencies were 98%, 70%, and 95%, respectively. The addition of PU matrices inhibited the growth of filamentous bacteria and provided support for high structural stability of AGF. With the operation of the reactor, the relative abundance of traditional denitrifying bacteria (genera Thauera and Acidovorax, etc.) decreased gradually, and the putative denitrifying phosphorus accumulating genus, Dechloromonas, occupied a dominant position in the system. This experiment showed that AGF system could be successfully started-up and operated with efficient pollutants removal performance under low temperature when using micro-sized PU sponges as matrices.