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The goal of this study was to unravel the impact of high and low temperatures (T) on glycogen-accumulating microorganisms (GAOs) which were stimulated in an aerobic granular sludge plant fed with industrial wastewater, which is derived from the cleaning of trucks transporting chocolate and beer. Among GAOs, Candidatus Competibacter (Ca. Competibacter) was the most abundant. The long-term impact on (1) anaerobic dissolved organic carbon (DOC) uptake, (2) sludge morphology, and (3) microbial community composition was investigated. In addition, the short-term impact of T changes on the anaerobic uptake rate was evaluated. High T (above 38 °C) and low T (below 11 °C) had a negative impact on the relative read abundance of Ca. Competibacter and the anaerobic DOC uptake. Nevertheless, the carbon removal efficiency and the settleability of the biomass were not affected. Denitrifiers such as Thauera and Zoogloea were promoted over Ca. Competibacter under high T and low T, respectively, indicating their positive contribution to granulation maintenance. HIGHLIGHTS The long-term exposure to high T completely inhibited Ca. Competibacter.; The long-term exposure to low T decreased the Ca. Competibacter population but not at an alarming level.; The short-term exposure of sludge enriched with Ca. Competibacter to high T did not affect the carbon uptake rate.; The short-term exposure of sludge enriched with Ca. Competibacter to low T negatively affected the carbon uptake rate.;

The application of a hybrid-fruit-peel (HFP) coagulant used as an external carbon source (ECS) in both simulated water and real sewage having a low carbon source treated with sequencing batch reactor (SBR) was studied, compared with that of sodium acetate (NaAc). The impact of HFP on sludge properties (such as extracellular polymer substance (EPS), dehydrogenase activity (DHA), charged property, size, microscopic images and bacteria phase) was characterized. The results showed that as an ECS, HFP basically gave similar nitrogen removal to NaAc and also gave a similar developing trend of both dissolved oxygen (DO) and pH. HFP promoted more proliferation of microorganisms and posed higher levels of protein (PN) and polysaccharide (PS) than NaAc, but gave slightly lower DHA than NaAc. After HFP was added as an ECS, the types and quantities of microorganisms increased significantly, the effluent qualities were improved and the sludge size and extensibility became larger, which was conducive to direct contact and remove pollutants. HFP played a similar role to NaAc as ECS and can be used as a quality and slow-releasing ECS for low carbon source wastewaters. HIGHLIGHTS Application of HFP coagulant as an external carbon source (ECS) for low C/N wastewater was studied and gave a similar effect to NaAc.; HFP can be used as a quality and slow-releasing ECS for low C/N wastewater.; HFP produced sludge has a larger size and better extensibility.; HFP promoted more proliferation of microorganisms and gave better effluent qualities.;

The nonaerobic stage is critical for the processes of denitrification and phosphorus release in biological wastewater treatment. A lab-scale sequencing batch reactor (SBR) operating as nonaerobic/aerobic was used to treat synthetic wastewater, and the nutrients removal performance was investigated under different nonaerobic hydraulic retention times (HRTs). The results showed when the nonaerobic HRT changed from 0 to 4 h with constant aerobic HRT of 8 h [dissolved oxygen (DO) 0.50–1.50 mg·L−1 ], the removal efficiencies of PO43−─P and NH4+─N were all above 90.00%, respectively. The nonaerobic HRT could influence carbon utilization between denitrification and phosphorus release, which showed a close relationship with the ratio of consumed chemical oxygen demand (COD)phosphorus release to CODdenitrification (0.94). Specifically, the consumed CODphosphorus release increased with the increase of nonaerobic HRT (0.90), whereas the relationship between consumed CODdenitrification and nonaerobic HRT was limited (−0.60). Furthermore, internal carbon source produced through phosphorus release could promote simultaneous nitrification denitrification. This control strategy could be conveniently applied in intermittent-flow sewage treatment plant through adjusting nonaerobic HRT. [ABSTRACT FROM AUTHOR]

The presence of colonial and solitary ciliated peritrichous protozoa was determined in a Sequencing Batch Reactor system filled with tezontle, a volcanic rock, economic, and abundant material that can be found in some parts of the world, like Mexico. The presence of these protozoa was related to the removal efficiencies of organic matter. Also, two novel staining techniques are proposed for staining both colonial and solitary peritrichous protozoa. The results show that tezontle promotes the growth of solitary and colonial ciliated peritrichous protozoa, which, once identified, could be used as indicators of the efficiency of the wastewater treatment process. Additionally, the staining techniques established in the current study allowed the precise observation of protozoan nuclei. They can represent a useful complementary methodology for identifying protozoan species present in water treatment processes, along with the already existing identification techniques. The number and variety of protozoa found in the system may be considered potential bioindicators of water quality during biological treatments.

In this study, sequencing batch reactor (SBR) using anaerobic/aerobic/anoxic process was coupled to a solar photocatalytic reactor (SPCR) for greywater treatment. The greywater effluent from SBR (operated at the optimal condition: 6.8 h hydraulic retention time (HRT), 0.7 Volumetric exchange ratio (VER) and 7.94 d solids retention time (SRT) with optimal corn cob adsorbent dosage (0.5 g/L)) was fed to the SPCR (operated at optimal conditions: pH – 3, H2O2 dosage – 1 g/L, catalyst dosage – 5 g/L). Chemical oxygen demand (COD) removal of 92.8±0.5% and ∼100% were achieved in SBR and SBR-SPCR, respectively. Similarly, total organic carbon (TOC) removal of 91±0.9% and ∼100% were observed in SBR and SBR-SPCR, respectively. After SBR treatment, average total nitrogen (TN) removal of 84% was found and this TN removal increased to 93% after combined SBR-SPCR treatment. The maximum PO43−_P reduction of 80±1.5% % was achieved with SBR-adsorption system. In addition, a maximum of 87±0.9% of net PO43−_P removal was reached after SBR-SPCR treatment. 58.9±2.3% BP (benzophenone-3) removal was obtained in the SBR while the integration of SBR and SPCR treatment was resulted in 100% BP removal. An effective anionic surfactant (AS) removal rate (80.1±2.2%) was observed in the SBR phase, which further improved to 94.9±1% at the end of 4 h SPCR treatment. HIGHLIGHTS Biological – photochemical system successfully treated greywater.; The coupled system efficiently mineralizes COD, TOC and BP.; Significant removal of TN (93%), PO43−_P (87%) and AS (94.9%) was achieved.; Solar photocatalysis was able to remove emerging contaminants.; Treated SBR-SPCR greywater could meet reuse standards (toilet flushing and others).;

Floccules are another major form of microbial aggregates in aerobic granular sludge systems. Previous studies mainly attributed the persistence of floccules to their relatively faster nutrient uptake and higher growth rate over aerobic granules; however, they failed to unravel the underlying mechanism of the long‐term coexistence of these two aggregates. In this work, the existence and function of the floccules in an aerobic granule‐dominated sequencing batch reactor were investigated from the view of quorum sensing (QS) and quorum quenching (QQ). The results showed that though the floccules were closely associated with the granules in terms of similar community structures (including the QS‐ and QQ‐related ones), they exhibited a relatively higher QQ‐related activity but a lower QS‐related activity. A compatible proportion of floccules might be helpful to maintain the QS‐related activity and keep the granules stable. In addition, the structure difference was demonstrated to diversify the QS‐ and QQ‐related activities of the floccules and the aerobic granules. These findings could broaden our understanding of the interactions between the coexistent floccules and granules in aerobic granule‐dominated systems and would be instructive for the development of the aerobic granular sludge process. [ABSTRACT FROM AUTHOR]

This review explores recent progress in sequencing batch reactors (SBRs) and hybrid systems for wastewater treatment, emphasizing their adaptability and effectiveness in managing diverse wastewater compositions. Through extensive literature analysis from 1985 to 2024, the integration of advanced technologies like photocatalysis within hybrid systems is highlighted, showing promise for improved pollutant removal efficiencies. Insights into operational parameters, reactor design, and microbial communities influencing SBR performance are discussed. Sequencing batch biofilm reactors (SBBRs) demonstrate exceptional efficiency in Chemical Oxygen Demand, nitrogen, and phosphorus removal, while innovative anaerobic-aerobic-anoxic sequencing batch reactors (AOA-SBRs) offer effective nutrient removal strategies. Hybrid systems, particularly photocatalytic sequencing batch reactors (PSBRs), show potential for removing persistent pollutants like antibiotics and phenols, underscoring the significance of advanced oxidation processes. However, research gaps persist, including the need for comparative studies between different SBR types and comprehensive evaluations of long-term performance, environmental variability, and economic viability. Addressing these gaps will be vital for the practical deployment of SBRs and hybrid systems. Further exploration of synergies, economic considerations, and reactor stability will enhance the sustainability and scalability of these technologies for efficient and eco-friendly wastewater treatment. [ABSTRACT FROM AUTHOR]

This article discusses the results of a scientific research work on the use of various types of small wastewater treatment plants for objects of various purposes in conditions of periodic use. The study was carried out on model and real wastewater with subsequent refinement of the characteristics using the calculation methods of the DWA standard.The results of the operation of laboratory facilities operated in the restart mode after a certain time are presented. As a result, the duration of restoration of the operating mode under periodic operating mode was considered for each plant under study and the effectiveness of biological wastewater treatment was determined. More promising technological solutions for small wastewater treatment plants under intermittent use conditions have been identified. According to the sum of the characteristics, the operation of the flooded biofilter system, which is capable of entering the operating mode within 5 days after a long shutdown, is highlighted. These technologies are recommended for use in resort areas and hotels.

ABSTRAK Limbah cair tahu dari industri tahu di Kabupaten Bandung Barat memiliki kandungan senyawa organik yang tinggi. Salah satu sistem pengolahan air limbah yang dapat dilakukan secara efektif adalah Sequencing Batch Reactor (SBR). Tujuan dari penelitian ini adalah untuk mengetahui peforma terbaik SBR dalam meningkatkan efisiensi pengolahan limbah cair tahu. Pada penelitian ini dilakukan pembibitan (seeding), aklimatisasi, dan sistem SBR dengan tahapan variasi kecepatan pengumpanan. Kecepatan pengumpanan SBR pada saat pembibitan (seeding), aklimatisasi, dan running 1 sebesar 200 ml/hari dan sebesar 400 ml/hari pada saat running 2. Hasil penelitian ini memperoleh penurunan konsentrasi COD terbaik dari 8.000 mg/L menjadi 96 mg/L diperoleh pada running 1 dan penurunan konsentrasi COD dari 8.000 mg/L menjadi 160 mg/L diperoleh pada running 2. Efisiensi tertinggi yang dihasilkan adalah 98,8% pada running 1 dan 98% pada running 2. Kata kunci : Limbah cair tahu, Sequencing Batch Reactor (SBR), Kecepatan Pengumpanan ABSTRACT Tofu wastewater collected from the tofu industries in West Bandung Regency has a high organic content. One of the wastewater treatment systems that can be applied effectively is the Sequencing Batch Reactor (SBR) system. The purpose of this study was to find out the best performance of SBR in improving the efficiency of tofu wastewater treatment. This study conducted seeding, acclimatization, and SBR system that varied the feeding rates to find optimum value. The SBR feeding rate at the times of seeding, acclimatization, and running 1 amounted to 200 ml/day and amounted to 400 ml/day at the time of running 2. The results of this study were the best reduction in COD concentration from 8,000 mg/L to 96 mg/L obtained in the first running and reduction in COD concentration from 8,000 mg/L to 160 mg/L obtained in 2nd running. The highest efficiency produced was 98.8% on the first running 1 and 98% obtained from the 2nd running. Keywords: Tofu Wastewater, Sequencing Batch Reactor (SBR), Feeding Rates

The characteristics of the wastewater produced by the tofu industry are high viscosity, slipperiness, and foaming resulting from the continuous fermentation of the tofu bacteria. This made it difficult to reduce the organic content of tofu wastewater, namely biological oxygen demand (BOD5), phosphate (PO4), and Total Nitrogen. A wastewater processor that is designed to handle dense and slippery tofu wastewater is known as a Sequencing Batch Reactor. The impeller is used to create turbulent flow, resulting in more evenly distributed DO, which is difficult to distribute due to the viscous tofu wastewater. The SBR was operated with a hydraulic retention time (HRT) of 24, 36, and 48 hours and an impeller stirring speed of 50, 100, and 150 rpm. The results of the research found that there was an effect on the stirring speed of the impeller and that the low stirring speed of the impeller was not optimal. HRT that was regulated in the SBR cycle has affected the performance of the bacteria. Pseudomonas sp. was found in this study and Bacillus sp., which can degrade up to 90% of phosphate and nitrate. [ABSTRACT FROM AUTHOR]

A novel approach has been proposed integrating sludge enrichment with intermittent gradient aeration to achieve partial nitrification (PN). Results indicated that this method suppressed nitrite-oxidizing bacteria (NOB) activity while maintained ammonia-oxidizing bacteria (AOB) activity, achieving an 82.87 % nitrite accumulation rate (NAR) during startup. During stable operation, specific ammonia oxidation rate and specific nitrite oxidation rate reached 18.44 and 2.67 mg N/g MLVSS/h, respectively. Shortening anoxic time from 30 to 20 min enhanced ammonia removal efficiency by 12.5 %, increasing NAR to 89.55 %. Further reduction to 5 min yielded 38.46 % and 91.88 %, respectively. AOB abundance enriched from 0.62 % to 22.28 %, with the AOB-to-NOB ratio jumping from 0.22 to 59.58. This research presented a rapid and effective strategy for achieving PN., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Small scale business / Usaha Skala Kecil (USK) X currently does not have a batik wastewater treatment unit. This condition causes the possibility of contamination to water bodies. USK X wastewater treatment applications' planning needs to be carried out sustainably, namely by reusing water. The process units needed in this planning are the sequencing batch reactor (SBR) and constructed wetlands. The effluent of textile wastewater with this system for parameters BOD, COD, TSS, sulfide, total oil & fat, and color were 0.13 mg/L; 106.5 mg/L; 2.4 mg/L; 0.036 mg/L; 0.07 mg/L; and 90.67 PtCo, respectively. The dimensions of the SBR unit required are 0.75 x 0.6 x 1 m. Modification of the SBR unit uses an ozone generator to produce ozone gas which functions as oxidation of organic pollutants and colors in batik waste. After processing in the SBR unit, it is carried out using a constructed wetland with 2.56 m2.

Aerobic granule in continuous-flow process is drawing increasing global interest in a quest for an efficient and innovative technology in the biological wastewater treatment. This paper presents a review of the literature on the development of extended treatments for complicated pollutants, numerous configurations of continuous flow aerobic granular reactors and enhancements of granule stability in long-term operation. The challenges and prospects of full-scale applications of this process were discussed. The review attempted to shed light on our growing knowledge to this technology, which may accelerate the spread of practical applications. [ABSTRACT FROM AUTHOR]

In this study, the performance of the membrane bioreactor (MBR) and anoxic–aerobic sequencing batch reactor (SBR) are compared in treating municipal wastewater. The aim of the work was to determine the feasibility of these systems for the removal of organics matter and nutriments from the municipal wastewater. The MBR displayed a superior performance with removal efficiencies exceeding 99% for TSS, 94% for chemical oxygen demand (COD) and an improvement on SBR efficiencies was found. In the same way, the MBR produced an effluent with much better quality than SBR in terms of total nitrogen (TN) and total phosphorus (TP) removal efficiencies. Combining membrane separation and biodegradation processes or the membrane bioreactor (MBR) technology improved pollution removal efficiencies significantly. Highlights Municipal wastewater treatment.; Membrane bioreactor process.; SBR process evaluation.; Organic pollution removal.; Reuse in irrigation.;

The main purpose of this study was to investigate the effect of operating conditions on the performance of two methods used for dairy wastewater treatment. First, conventional activated sludge (AS). Second, conventional sequencing batch reactor (SBR). On one side, the study included the comparison between the two basic systems. On the other side, it studied the influence of adding plastic media on both systems. The modified systems are known as biofilm conventional activated sludge (BAS) and biofilm sequencing batch reactor (BSBR). Four pilot-scale bioreactors, were operated in parallel under different conditions of temperature; 20, 35 and 45 °C. Synthetic dairy wastewater was used with characterizations of COD; 5000 mg/l, NH3-N; 250 mg/l and TP; 50 mg/l. The results recorded that the optimum temperature was 35 °C where removal efficiencies for COD were (93.52%, 96.63%, 94.74% and 97.79%), (89.01%, 91.14%, 90.45% and 93.22%) for NH3-N, and the concentration of NO3-N in effluents was (7.56 mg/l, 10.58 mg/l, 8.72 mg/l and 14.12 mg/l) for AS, BAS, SBR and BSBR respectively. At temperature equals to 45 °C; the oxygen consumption recorded the highest level of consumption, it was (1.07 mg/l, 1.64 mg/l, 0.98 mg/l and 1.23 mg/l) for AS, BAS, SBR and BSBR respectively. The results indicated that the sludge settleability was enhanced with the decrease of temperature. Furthermore GPS-X simulator was employed to predicting the performances of the biological systems under high COD concentrating reaching up to 17500 mg/l. GPS-X results indicated that SBR effluent could comply with Egyptian standard NO 2000. An overview, comparing with various treatment systems, it can be concluded that the SBR was the optimum treatment method for dairy wastewater based on the investigated conditions.

This study investigated the individual and synergy effects of tetracycline (TC) and zinc oxide nanoparticles (ZnO-NPs) accumulation on both short-term and long-term nitrogen removal processes in the bench-scale sequencing batch reactors (SBR). During short-term (10 hour) analysis, the removal rates of NH4+-N in 0.1 mg·L−1 ZnO-NPs (98.3%), 5 mg·L−1 TC (97.5%), and the co-addition reactor (96.9%) were significantly higher (P < 0.05) than the control reactor (94.4%) at minimum dosages. Ammonification processes were inhibited by the increasing dosage of ZnO-NPs (≥ 5 mg·L−1) and TC (≥ 15 mg·L−1) due to the cumulative toxic interference. Ultraviolet (UV) radiation with the co-addition of ZnO-NPs and TC promoted NH4+-N removal, and nitrification processes might be enhanced by UV exposure through the produced hydroxyl radicals (·OH) from ZnO-NPs. In the long-term operation, the effect of 0.1 mg·L−1 ZnO-NPs on nitrogen removal was negligible even over 15 days. Although NH4+-N removal rates were initially decreased, they recovered with the prolongation of dosages and operating time due to self-adjustment and the existence of extracellular polymeric substances (EPS) in activated sludge. Fourier transform infrared (FTIR) analysis revealed that the absence of —CH3 may explain the inhibition of NH4+-N removal during TC accumulation. Research results can be served as indications for the understanding of the synergistic effects of ZnO-NPs and TC on the performance of biological treatments used in wastewater systems.

The primary objectives of this study were to identify the effectiveness of hydrazine on partial nitrification in a sequencing batch reactor when treating low-strength ammonia wastewater and to investigate its impact mechanism. Partial nitrification was successfully initiated and maintained by dosing with hydrazine, and the short- and long-term effects of hydrazine on partial nitrification and microbial bioactivity were investigated. The results showed that dosing with a moderate amount of hydrazine improved the nitrite accumulation rate with little effect on the ammonia conversion rate. Both the short- and long-term tests showed the optimum hydrazine dosage was 7.5 mg/L. In the long-term tests, dosing with 7.5 mg/L of hydrazine led to an ammonia conversion rate and nitrite accumulation rate of 99.10% and 93.24%, respectively. The change in the mixed liquid suspended solids (MLSS) and mixed liquid volatile suspended solids (MLVSS) in the long-term tests showed that, although dosing with hydrazine influenced the biochemical activity of the sludge, the MLVSS/MLSS increased after an initial decrease. High-throughput analysis showed that Thauera, Nitrosomonas, and Denitratisoma were the dominant bacteria in the system dosed with 7.5 mg/L of hydrazine, which may explain the high nitrite accumulation. Analysis of the mechanism showed that nitrite-oxidizing bacteria were more inhibited by hydrazine dosing than ammonium-oxidizing bacteria. [ABSTRACT FROM AUTHOR]

A sequencing batch reactor was constructed to realize simultaneous nitrification and denitrification (SND) and denitrifying phosphorus removal (DPR). The influence of different carbon sources (acetate, acetate and propionate, and propionate) was explored. The total nitrogen (TN) removal efficiency reached the highest value of 66.4% with acetate. The total phosphorus (TP) removal efficiency was nearly the same (97.9%–96.1%) with different carbon sources. Propionate facilitates TP removal during the hypoxic stage to weaken glycogen metabolism in phosphorus-accumulating organisms (PAOs) and promote dehydrogenase and phosphorus removal–related enzyme activities. Propionate also facilitates the competitiveness of PAOs against glycogen-accumulating organisms (GAOs). TN removal during the SND process in the hypoxic stage was maintained at 38.2%–40.2%, which is explained by the relative amount of change in nitrifying and denitrifying microorganisms. However, acetate promoted TN (from 9.2% to 17.3%) and TP (from 18.1% to 22.7%) removal during the DPR stage, thus enhancing final TN removal and maintaining TP removal. Consequently, acetate may be a better choice for a SND-DPR–coupled system. [ABSTRACT FROM AUTHOR]

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The effects of three side stream phosphorous recovery volume on the performance and microbial structure of biological phosphorous removal system were investigated. Results showed that the removal of COD and nitrogen had no significant impacts by side stream operation, but the removal of phosphorous were gradually enhanced with the increase in side stream volume (SSV). The secretion of extracellular polymeric substance (EPS) were variously promoted at the stripping period. However, with the increase in SSV, the inhibition on EPS and phosphorus-accumulating organisms (PAOs) phosphorous absorption were severe and the restoration were tougher. The high throughout 16S rRNA gene sequencing revealed the succession of microbial population were significantly effected by side stream operation. The relative abundances of PAOs reduced to 0.17%, 0.09% and 0.07% with 30%, 60% and 90% side stream operations, respectively. At the restoration period, the relative abundance could restore to 95.4%, 65% and 38% initial values, respectively. The relative abundances of glycogen-accumulating organisms were variously enhanced under various SSV conditions. In conclusion, at SSV of 60%, more abundant recovered phosphorous could be obtained and had slighter and reversible effects on activated sludges. The SSV of 60% was the applicable SSV for phosphorous recovery from the biological phosphorus removal system. [ABSTRACT FROM AUTHOR]

In this paper, the performance of the fungal treatment system with various hydraulic retention time (HRT) conditions for improving the biodegradability of tapioca starch wastewater was objectively evaluated. Wastewater used in the study was synthesized using tapioca starch. The experimental process was carried out in Sequencing Batch Reactors (SBR) operated with HRT of 6-48 h, mixed by a diffused aeration system, and adjusted to the optimum pH of 3.0±0.2. The fungal SBR system produced the effluent with COD, SCOD, and BOD in the ranges of 164-265 mg/L, 36-55 mg/l, and 21-45 mg/L, respectively. This corresponded to the removal efficiency of 83.79-90.31% for COD. The optimal condition for removing organic matter was found to be with the 24hrs HRT. After the fungal treatment, the readily biodegradable (SS) increased to about 13.10% of TCOD for HRT of 24 h. Furthermore, the BOD/COD ratio in the effluent was 0.275, which is about 1.53 times higher than that in the influent, indicating that the fungi utilization can improve the biodegradable fraction in the wastewater. Applicably, the effluent can be used for agricultural irrigation or discharged into a fishpond. [ABSTRACT FROM AUTHOR]

The formation and characteristics of aerobic granular sludge (AGS) under different operational conditions in a sequencing batch reactor (SBR), designed to treat Mustard tuber wastewater (MTW, characterized as saline wastewater), had been investigated in this study. Morphology and structure during granulation were determined using a microscope with digital camera and scanning electron microscope (SEM). Granules formed in the reactors could be classified as zoogloea granules with a clear boundary outline and filamentous granules with mycelia bestrewing boundary. Zoogloea granules, cultivated in reactor R1 and R2, were with higher density than filamentous granules, cultivated in reactor R3, and consequently had a higher settling velocity. Results showed that divalent metal ions such as Ca2+ and Mg2+ with phosphate in inflow could transform into precipitates, serving as crystal nucleus and carriers for granulation. Moreover, appropriate organic loading, hydrodynamic

The main purpose of this study was to investigate the effect of operating conditions on the performance of two methods used for dairy wastewater treatment. First, conventional activated sludge (AS). Second, conventional sequencing batch reactor (SBR). On one side, the study included the comparison between the two basic systems. On the other side, it studied the influence of adding plastic media on both systems. The modified systems are known as biofilm conventional activated sludge (BAS) and biofilm sequencing batch reactor (BSBR). Four pilot-scale bioreactors, were operated in parallel under different conditions of temperature; 20, 35 and 45 °C. Synthetic dairy wastewater was used with characterizations of COD; 5000 mg/l, NH 3 -N; 250 mg/l and TP; 50 mg/l. The results recorded that the optimum temperature was 35 °C where removal efficiencies for COD were (93.52%, 96.63%, 94.74% and 97.79%), (89.01%, 91.14%, 90.45% and 93.22%) for NH 3 -N, and the concentration of NO 3 -N in effluents was (7.56 mg/l, 10.58 mg/l, 8.72 mg/l and 14.12 mg/l) for AS, BAS, SBR and BSBR respectively. At temperature equals to 45 °C; the oxygen consumption recorded the highest level of consumption, it was (1.07 mg/l, 1.64 mg/l, 0.98 mg/l and 1.23 mg/l) for AS, BAS, SBR and BSBR respectively. The results indicated that the sludge settleability was enhanced with the decrease of temperature. Furthermore GPS-X simulator was employed to predicting the performances of the biological systems under high COD concentrating reaching up to 17500 mg/l. GPS-X results indicated that SBR effluent could comply with Egyptian standard NO 2000. An overview, comparing with various treatment systems, it can be concluded that the SBR was the optimum treatment method for dairy wastewater based on the investigated conditions. [ABSTRACT FROM AUTHOR]

This study evaluated the properties and pollutant removal ability of sludge from low-strength synthetic wastewater during the formation of aerobic granules at low dissolved oxygen (DO) (1.0 ± 0.2 mg L–1). After 141 d operations, the aerobic granules were successfully cultivated. The removal efficiencies of chemical oxygen demand, NH4 +, total nitrogen and total phosphorus were 91.0%, 98.6%, 77.6% and 92.5%, respectively. The morphology of the mature granules was almost spherical, with an average granule size of 436.5 ± 12 μm. Filamentous bacteria on the surface were embedded in extracellular polymeric substances. The protein amount (190.4 mg g–1 VSS) was greater than that of polysaccharide (30.0 mg g–1 VSS). Aerobic granule at low DO (1.0 ± 0.2 mg L–1) consumed a 27.9% less aeration rate compared with conventional biological treatment methods. The good removal performance of aerobic granule at low DO could be suitably applied in wastewater treatment with low energy consumption. [ABSTRACT FROM AUTHOR]

In this work, the performance of a sequencing batch reactor (SBR) was studied for treating sanitary wastewater of Yazd power plant, Iran. For this purpose, at the first, a pilot system was designed, installed, and started up. Then the effects of retention time, pH, temperature, influent chemical oxygen demand (COD) concentration, and air flow rate were investigated on the effluent concentration of COD. In SBR reactor used in the Yazd power plant, the microalga was not used for the wastewater treatment. In this case, the COD effluent output was, at the best conditions, approximately 92 mg/L. In the studied SBR system, we used the Chlorella vulgaris microalgae and microorganisms, simultaneously. In this case, the COD level reached 34 mg/L. An artificial neural network (ANN) was developed by applying Levenberg‐Marquardt training algorithm to predict the effluent concentration of COD. The optimum conditions were obtained at pH = 8, temperature of 30°C, influent COD concentration of 600 mg/L, and air flow rate of 50 L/min. ANN predicted results were in good agreement with the experimental data with a validation coefficient of determination (R2) and validation mean square error of 0.962 and 0.0015, respectively. [ABSTRACT FROM AUTHOR]

An anaerobic/aerobic sequencing batch reactor was used to test enhanced biological phosphorus removal (EBPR) in wastewater. In the present study, after 6 weeks of operation, the phosphorous and TOC removal efficiency reached to 97.8 and 97.5%, respectively. Our results suggest that phosphate‐accumulating organisms (PAOs) play a key role in the phosphorus removal in the EBPR system. Qualitative and quantitative measurements indicate the appear and changing trend of characteristic particles in activated sludge, which further illustrates the metabolic activity and mechanism of PAOs. Fluorescence in situ hybridization (FISH) images showed that PAOs gradually became the predominant bacteria in the EBPR system, aligning with the results of phosphorus removal rate. PCR‐DGGE profile demonstrated that with the operation of EBPR process, the composition of microorganisms became more and more abundant in the EBPR system over time. Further sequencing analysis indicated that these microbial populations belonged to α‐Proteobacteria, β‐Proteobacteria, γ‐proteobacteria, Rhodococcus sp. and Pseudomonas sp. [ABSTRACT FROM AUTHOR]

This study investigated the biological treatment of high-salinity wastewater using aerobic granular sludge (AGS). The removal performance, AGS characteristics, and microbial community were examined under salinity conditions ranging from 0.5 to 3.0 wt.%. When the salinity was increased, the removal efficiency of the chemical oxygen demand did not change substantially. The mean removal efficiency of NH4 +-N ranged from 43.7 to 72.6% during the operation period. As for the concentration of extracellular polymeric substances (EPS), the polysaccharide/protein (PS/PN) ratio increased from 0.37 to 0.57. The concentrations of the mixed liquor suspended solid (MLSS) and mixed liquor volatile suspended solid (MLVSS) were 4,560 and 3,170 mg/L, respectively, in the end phase, and the MLVSS/MLSS ratio decreased from 0.81 to 0.69. The sludge volume index (SVI30) decreased linearly from 88 to 58 mL/g. In the microbial community analysis, Nitrosomonas species accounted for 22.9% of the total bacteria in the initial phase, whereas Halomonas accounted for 43.2% in the end phase. Hence, the gradually increased salinity appears to facilitate the dominance of halophilic microorganisms in the long-term operation of an AGS-based biological treatment system and the stable retention of AGS. [ABSTRACT FROM AUTHOR]

This study was conducted to determine alkaline pre-chlorination effects on chemical oxygen demand (COD) removal and poly-β-hydroxybutyrate (PHB) production in tapioca wastewater treatment. The alkaline pre-chlorination effect was evaluated by applying various chlorine (Cl2) dosages (0, 2, 4, 6, and 8 mg/L) to the wastewater with a pH of 8 before being treated in a sequencing batch reactor (SBR). The cycle time of the SBR consisted of 1 h of filling and 8 h of aeration. COD and mixed liquor suspended solids (MLSS) of the effluent were measured at 2 h intervals during the aeration period. Both parameters were to estimate the optimum Cl2 dosage corresponding to the organic removal kinetics, the maximum specific growth rate, and the relationship between substrate utilization and microorganism's growth rate. The effluent of tapioca wastewater pre-chlorination under optimum Cl2 dosage was treated using the SBR with the cycle period: filling (1 h), aeration (8 h), and settling (8 h). PHB, COD, and MLSS of effluent were measured at 2 h intervals of aeration and settling period for estimating PHB formation kinetics parameter values. For the Cl2 dosage of 6 mg/L, SBR shows the best performance in terms of COD removal rate constant (k) and maximum specific growth rate (μmax) with values of 0.327 and 2.681 h-1, respectively. First-order kinetics, Contois equation, substrate utilization rate based on Monod equation considers cell death, and non-growth associated product formation was being appropriate models to describe organic removal rate, specific growth rate, kinetic of COD conversion to PHB, and PHB production rate, respectively. Another result showed excessive aeration time and settling time application decreased the level of microbial conversion of COD to PHB and PHB production rate per cell mass formed. Maximum yield coefficient of COD to PHB (YP/S) of 0.01 mg PHB/mg COD and non-growth associated PHB yield coefficient (β) of 9.07 × 10-4 mg PHB/mg MLSS/h was achieved when the aeration time was about 6 h. These results suggest that the alkaline pre-chlorination can effectively enhance the performance of the SBR system, especially treating the tapioca wastewater. The optimum process of this treatment is when SBR operated with a cycle consisted of 1 h of filling, 6 h of aeration, and 0.5 h of settling with a Cl2 dosage of 6 mg/L (pH 8) as wastewater pretreatment. [ABSTRACT FROM AUTHOR]

• Uncoupled carbon and nitrogen feeding enhances the biomass PHA storage response. • The OLR has a strong impact on storage response and PHA volumetric productivity. • The MMC selected with uncoupled feeding reached more than 70 % g PHA/g VSS. • High OLR and uncoupled C-N feeding make the accumulation stage unnecessary. • Polymer composition is strongly affected by the OLR applied. The selection and enrichment of a mixed microbial culture (MMC) for polyhydroxyalkanoates (PHA) production is a well-known technology, typically carried out in sequencing batch reactors (SBR) operated under a feast-famine regime. With a nitrogen-deficient carbon source to be used as feedstock for PHA synthesis, a nutrient supply in the SBR is required for efficient microbial growth. In this study, an uncoupled carbon (C) and nitrogen (N) feeding strategy was adopted by dosing the C-source at the beginning of the feast and the N-source at the beginning of the famine, at a fixed C/N ratio of 33.4 g COD/g N and 12 h cycle length. The applied organic loading rate (OLR) was increased from 4.25 to 8.5 and finally to 12.725 g COD/L d. A more efficient selective pressure was maintained at lower and intermediate OLR, where the feast phase length was shorter (around 20 % of the whole cycle length). However, at the higher OLR investigated, the PHA content in the biomass reached a value of 0.53 g PHA/g VSS at the end of the feast phase, as a consequence of the increased C-source loaded per cycle. Moreover, 2nd stage PHA productivity was 2.4 g PHA/L d, 1.5 and 3.0-fold higher than those obtained at lower OLR. The results highlight the possibility of simplifying the process by withdrawing the biomass at the end of the feast phase directly to downstream processing, without a need for the intermediate accumulation step. [ABSTRACT FROM AUTHOR]

• Enrichment of comammox Nitrospira in a mainstream SBR in the step-feeding mode. • Candidatus Nitrospira nitrosa was the dominant (∼95 %) comammox species enriched. • Identification of K NH4 -N and K O2 for enriched comammox bacteria-dominant sludge. • Floccular sludge enriched with comammox Nitrospira possessed low N 2 O and NO yields. The discovery of complete ammonium oxidation (comammox) has subverted the traditional perception of two-step nitrification, which plays a key role in achieving biological nitrogen removal from wastewater. Floccular sludge-based treatment technologies are being applied at the majority of wastewater treatment plants in service where detection of various abundances and activities of comammox bacteria have been reported. However, limited efforts have been made to enrich and subsequently characterize comammox bacteria in floccular sludge. To this end, a lab-scale sequencing batch reactor (SBR) in the step-feeding mode was applied in this work to enrich comammox bacteria through controlling appropriate operational conditions (dissolved oxygen of 0.5 ± 0.1 g-O 2 /m3, influent ammonium of 40 g-N/m3 and uncontrolled longer sludge retention time). After 215-d operation, comammox bacteria gradually gained competitive advantages over counterparts in the SBR with a stable nitrification efficiency of 92.2 ± 2.2 %: the relative abundance of Nitrospira reached 42.9 ± 1.3 %, which was 13 times higher than that of Nitrosomonas , and the amoA gene level of comammox bacteria increased to 7.7 ± 2.1 × 106 copies/g-biomass, nearly 50 times higher than that of conventional ammonium-oxidizing bacteria. The enrichment of comammox bacteria, especially Clade A Candidatus Nitrospira nitrosa , in the floccular sludge led to (i) apparent affinity constants for ammonium and oxygen of 3.296 ± 0.989 g-N/m3 and 0.110 ± 0.004 g-O 2 /m3, respectively, and (ii) significantly low N 2 O and NO production, with emission factors being 0.136 ± 0.026 % and 0.023 ± 0.013 %, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Sequencing batch reactor (SBR) technology has found many applications in industrial wastewater treatment in recent years. The aim of this study was to determine the optimal time for a cycle of the sequencing batch reactor (SBR) and evaluate the performance of a SBR for petrochemical wastewater treatment in that cycle time. The reactor was operated with a suspended biomass configuration under aerobic conditions. Carbon removal and operating parameters such as pH, temperature and dissolved oxygen (DO) were monitored during the wastewater treatment. The SBR was run at different cycle times and amongst the cycle times tested, the best performance was obtained with a 7 h cycle time composed of a fill time of 15min, reaction of 6 h, settling of 30 min, and withdrawal of 15 min. The SBR with the determined cycle time was used to study the treatment of wastewater with various organic loading rates (12.88 gr COD/L.d, 18.02 gr COD/L.d and 31.39 gr COD/L.d). The SBR performance was evaluated by chemical oxygen demand (COD), total solids (TS) total suspended solids (TSS) removal efficiencies. During the shock loading tests, the maximum COD, TS and TSS removal efficiencies were 84%, 67% and 92%, respectively.

Comparing the problems in Romania and Senegal, regarding wastewater treatment, the present paper aims to identify the best methods and techniques to treat the municipal wastewater in small treatment plants with sequential operation. This paper examines the possibility of using Sequencing Batch Reactor (SBR) process to treat the municipal wastewater characterized by low flow. This paper also presents a comparative analysis of the degree of purification achieved in a SBR wastewater treatment plant, as well as legislative regulations in Romania and Senegal. Finally, the paper identifies the possible uses of the treated wastewater in different household activities.

In this work, the parametric optimization of real domestic wastewater treated in an activated sludge sequencing batch reactor (SBR) was performed by means of the response surface methodology (RSM). The influences of influent organic matter concentration as chemical oxygen demand (CODinf), biomass concentration (Xs) and aeration time (t) on the COD, organic matter removal efficiency as COD (η) and sludge volume index (SVI) were determined to evaluate the performance of activated sludge SBR. The results showed that organic matter efficiency and maximum SVI were obtained at a t of 12 h, 300 mg L−1 of CODinf and 2000 mg L−1 of Xs. The SBR-activated sludge exhibited a η of 73% and an SVI of 119 mL g−1. Both values indicated a very good performance. Furthermore, the COD of the effluent under these conditions complied with Mexican regulations for wastewater discharged into water bodies. [ABSTRACT FROM AUTHOR]

Advanced nitrogen removal without the addition of external carbon source is challenging in the conventional biological nitrogen removal processes. This study presented a novel anaerobic/aerobic/anoxic sequencing batch reactor (A/O/A SBR) based on endogenous nitrate (NO3−–N) respiration to enhance nitrogen removal. The mean effluent total nitrogen (TN) in the A/O/A SBR could be reduced to as low as 3.5 mg/L, when the average influent TN and chemical oxygen demand (COD) were 52.7 and 235.4 mg/L, respectively. This advanced nitrogen removal was attributed to the post-denitrification, since 82.7% of TN removal was achieved in the post-anoxic stage. The post-denitrification rate with nitrite (NO2−–N, 0.59 mg NO2−–N/gMLVSS/h) was higher than that with NO3−–N (0.35 mg NO3−–N/gMLVSS/h). Therefore, the post-anoxic time could be further optimized by achieving denitrification via NO2−–N. The A/O/A SBR has good potential in achieving advanced nitrogen removal, especially in nitrogen-sensitive rural areas. [ABSTRACT FROM AUTHOR]

The adaptation mechanisms of bacterial community for nitrogen removal performance exposed to fluctuated levels of levofloxacin (LVX) during wastewater treatment in SBRs were investigated. Although LVX is completely synthetic, the results of minimum inhibitory concentration (MIC, 32 mg-LVX/L) and minimum bactericidal concentration (MBC, 512 mg-LVX/L) of the sampled sludge showed that the LVX resistance/tolerance for bacterial growth has already existed in the actual wastewater treatment plants (WWTPs). The key bacteria, i.e. Nitrosomonas sp. (ammonia-oxidizing bacteria), Nitrospira sp. (nitrite-oxidizing bacteria) and Thauera sp. (the predominant denitrifiers), decreased with LVX exposure, and the recovery of biological process in the reactor was disturbed due to LVX exposure. However, after stopping exposure their population was quickly increased and thus the performance was recovered. The results of the non-metric multidimensional scaling and microbial community by sequencing showed the LVX concentration was a crucial factor to the change of bacterial communities and controlled the quantitative evolution of the communities in our systems. This effect was more pronounced as the LVX concentration was higher. The results suggested the removal of residual antibiotics to accomplish under no effect concentration before biological treatment is important to suppress emerging and increasing of the antibiotic resistant bacteria in WWTPs. Unlabelled Image • LVX resistance/tolerance bacteria have lived in the sludge of actual WWTPs. • At least 50% of the influent LVX still remained in the effluent. • Bacteria related to N removal were affected by LVX exposure thus deteriorated. • AOB recovery led to better NH 4 -N oxidation efficiencies at the end of exposure. • Acinetobacter sp. and Chryseobacterium sp. could be one of the sources for ARB. [ABSTRACT FROM AUTHOR]

The formation and characteristics of aerobic granular sludge (AGS) under different operational conditions in a sequencing batch reactor (SBR), designed to treat Mustard tuber wastewater (MTW, characterized as saline wastewater), had been investigated in this study. Morphology and structure during granulation were determined using a microscope with a digital camera and scanning electron microscope (SEM). Granules formed in the reactors could be classified as zoogloea granules with a clear boundary outline and filamentous granules with mycelia bestrewing boundary. Zoogloea granules, cultivated in reactor R1 and R2, was with higher density than filamentous granules, cultivated in reactor R3, and consequently had a higher settling velocity. Results showed that divalent metal ions such as Ca2+ and Mg2+ with phosphate in inflow could transform into precipitates, serving as crystal nucleus and carriers for granulation. Moreover, appropriate organic loading, hydrodynamic shear and salt-stress selection can induce moderate growth of filamentous bacteria to act as granulation backbone and consequently granulation process under salt stress was a result together with crystal nucleus, filamentous bacteria, and extracellular polymeric substances (EPS), which could be affected by salinity-shifting strategies and dosage of aluminum salt coagulant. [ABSTRACT FROM AUTHOR]

The shortcut biological nitrogen removal (SBNR) process requires less aeration and external carbon due to the oxidization of ammonia into nitrite and its direct denitrification to nitrogen gas during the biological nitrogen removal process. However, this process produces a poor effluent containing NH4+, since the system has to maintain a high free ammonia (FA, NH3) concentration. To overcome this drawback, in this study, the solid retention time (SRT) and the dissolved oxygen (DO) concentration were controlled to achieve both a high ammonia removal rate and nitrite accumulation in the sequencing batch reactor (SBR) process, which can remove nitrogen from wastewater to the desired concentration and provide high free ammonia inhibition and continuous shock loading. When sufficient DO was supplied, nitrite did not accumulate with a 20-day SRT, but the wash-out of nitrite oxidizers in a shorter SRT resulted in a high nitrite accumulation. When DO acted as a limitation, nitrite accumulated at all SRTs. This indicates that nitrite accumulation is more highly influenced by SRT and DO concentration than by FA inhibition. Also, as nitrite accumulated over a 10-day SRT regardless of DO concentration, the accumulation was more highly influenced by SRT than by DO concentration. [ABSTRACT FROM AUTHOR]

• Drawbacks of leachate recirculation in fresh refuse landfill were NH 4 + accumulation. • Combined leachate recirculation and ex-situ SBR was effective to remove nitrogen. • Methanogenesis occurred easily in combined leachate recirculation and ex-situ SBR. We determined the effects of ex situ biological wastewater treatment on landfill stabilization under continuous circulation of leachate. Specifically, the waste composition and nitrogen in the leachate during leachate circulation (LC) alone was compared with that in a nitrified leachate circulation (NLC) system. An ex situ sequencing batch reactor (SBR) was applied in the NLC system to oxidize the ammonium to nitrite or nitrate, which was then circulated to landfill for denitrification to nitrogen gas. The chemical oxygen demand (COD) concentration in the leachate was low by NLC versus LC, because in the NLC system, ammonium was oxidized to nitrite/nitrate in the ex situ SBR, and aerobic decomposition and denitrification occurred simultaneously in the landfill, suggesting that the NLC system significantly improves the waste decomposition rate and accelerates landfill stabilization. Because denitrification in the landfill was activated in the NLC system and nitrite/nitrate was reduced to nitrogen gas, the proportion of nitrogen in the gas was higher compared with LC. LC, combined with an SBR, might have value in removing the nitrogen that is discharged from the leachate and in accelerating landfill stabilization, because landfill waste was used as the carbon source for denitrification. [ABSTRACT FROM AUTHOR]

This study investigated the characteristic of aerobic granular sludge (AGS) process to treat the sewage having low carbon/nitrogen ratio (Biochemical oxygen demand (BOD5):Total nitrogen (T-N), 4.5:1) in sequencing batch reactor (SBR). The removal efficiency of BOD5, suspended solid (SS), T-N and phosphorus (PO43--P) were 92.6%, 64.3% and 90.1%. Concentration and size of AGS were changed in proportion to the organic matters and nitrogen concentration of the influent (Concentration and size of AGS: 1,700-3,000 mg/L, 0.5-1.0 mm). Mixed liquor suspended solid (MLSS) also changed with the concentration of AGS (MLSS: 2,000-3,500 mg/L). When the settling time was shortened from 15 min to 10 min, size and shape of AGS were maintained (Size of AGS: 1.0-1.5 mm). In addition, the concentration of AGS and MLSS increased (Concentration of AGS: 3,500 mg/L, MLSS: 4,000 mg/L). Concentration, size and shape of AGS were affected the settling time of the reactor more than the concentration of organic matter and nitrogen in the influent. In the results of removal efficiency and changes in AGS, we confirmed that the SBR process using AGS can be used to treat the sewage having low carbon/nitrogen ratio by applying short settling time. [ABSTRACT FROM AUTHOR]

Nitrification in biological wastewater treatment is a two-step process: first from ammonium to nitrite and then from nitrite to nitrate. This two-step nitrification process has been incorporated into different versions of International Water Association (IWA) activated sludge models (ASM), but numerical simulation on the combined inhibitory effect from organic carbon and nitrogen on the two-step nitrification process still seem not thoroughly enough, especially from process operation standpoint. In this study, the combined inhibitory effect from organic carbon and ammonium on two-step nitrification is simulated within a modified ASM1-based two-step nitrification framework. Specifically, the combined inhibitory effects from organic carbon and ammonium are comparably presented in two different mathematic forms: a traditional Monod type and a Logistic type. The two types of modified models are evaluated under two different SBR scenarios. The simulation results proved that both of the two mathematical forms show improvements in model prediction, with the Logistic-type inhibition form offers an even better model performance. This outcome suggests it is necessary to use appropriate model forms to reflect the combined inhibitory effects from organic carbon and ammonium on two-step nitrification modeling. However, the results of this study should not be interpreted as a holistic modeling approach, but an attempt to attract more in-depth studies on the two-step nitrification process from both mechanical and numerical perspectives so as to offer more accurate predictions and controls on nitrogen removals for the wastewater industry. [ABSTRACT FROM AUTHOR]

Abstract Phosphorus recovery is usually based on the chemical precipitation of struvite from the supernatant comming from anaerobic digestion of surplus sludge of wastewater treatment plants. However, the recovery of phosphorus from the mainstream would be very beneficial to the operation of the plant. This work represents a step forward in this challenge. The configuration of a sequencing batch reactor performing Enhanced Biological Phosphorus Removal (EBPR) was modified to include the extraction of a P-rich supernatant after a settling period. The liquid extracted after the anaerobic phase has the highest phosphorus concentration in all the reactor cycle and is therefore suitable for implementing P-recovery strategies. This is the first experimental system operated under this configuration and in a long-term basis (more than one year) under different influent COD/P ratios with good performance and stability. This work shows experimentally that up to 60% of the P could be extracted without a deleterious effect on EBPR. The system could even operate at high COD/P ratio (7.5) with high activity. Finally, anaerobic supernatant extraction was linked to anaerobic sludge purging and it was demonstrated that higher methane production (24.3%) was obtained compared to the default case with the sludge purged at the end of the aerobic phase. Highlights • Long-term assessment of the EBPR2 configuration for P-recovery from mainstream line. • 60% P-recovery with anaerobic supernatant extraction without adverse effect on EBPR. • Long-term good performance under low influent COD/P ratio with high EBPR activity. • 24.3% higher methane production with sludge purged at anaerobic phase vs aerobic. [ABSTRACT FROM AUTHOR]

A modified sequencing batch reactor, which adds a pre-anoxic phase before the aeration phase, was used to treat toxic landfill leachate, and high-throughput sequencing technology used to study how the classification, distribution and abundance of functional bacterial communities varies during system operation. The system operation results are as follows: in the full load steady operation period (II), influent/effluent chemical oxygen demand (COD) and total nitrogen (TN) concentrations were approximately 6,421/645 and 1,210/19 mg/L, respectively; TN and COD removal rates of the system were above 93% and 87%, respectively. The bacterial community structure of the system is as follows: when compared with the bacterial community structure of the inoculation sludge, the final dominant phyla of the system were Proteobacteria (49.4%) and Bacteroidetes (36.5%), while β-Proteobacteria (30.05%) and α-Proteobacteria (16.4%) under Proteobacteria were the two dominant classes in the full load steady operation period (II). Nitrosomonas (22.56%) was the main ammonia-oxidizing bacteria within β-Proteobacteria. The bacterial community associated with endogenous denitrification included Paracoccus (α-Proteobacteria, 19.15%), Thauera (β-Proteobacteria, 8.36%), and Truepera (4.96%). Paracoccus and Thauera were endogenous denitrifying bacteria that could transform organic matter into polyhydroxyalkanoates (PHA) and use PHA to remove nitrogen under anaerobic conditions, and Truepera could resist leachate toxicity. [ABSTRACT FROM AUTHOR]