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The lab-scale system combined bioelectrochemical and sulfur autotrophic denitrification (CBSAD) was established to evaluate the effects of currents (50-300 mA) on both the performances and microbial communities. Results showed that the nitrate removal rate increased significantly when the current increased from 50 to 200 mA, while it slightly decreased with higher currents. Mass balance results revealed that hydrogen autotrophic denitrification contributed almost three times (70.25-78.62%) to denitrification compared with that of the sulfur part (21.38-29.75%). Illumina MiSeq sequencing showed that the currents changed the bacterial richness and diversity in this system. Phylum Firmicutes and class Clostridia predominated >50% under each condition. And multiple key bacteria capable of denitrification such as Proteiniclasticum, Thauera and Family_XI_uncultured were identified and found in higher proportions when the current was 200 mA. Therefore, this study helps revealing the mechanisms of accelerating nitrate-reduction through applied currents in the CBSAD systems., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Vanadium (V) is a common heavy metal and often co-occurs with nitrate in effluents from mining and metal finishing industry. In the present study, the toxic effects of V(V) were examined in a sulfur and hydrogen based autotrophic denitrification system. This combined system achieved simultaneously microbial denitrification and V(V) reduction. High concentration of V(V) (60 and 100 mg/L) inhibited the denitrification activities, while 30 mg/L V(V) had a very slight effect. V(V) induced increases of lactate dehydrogenase release and reactive oxygen species production, which may inhibit nitrate and nitrite reductases activities and abundances of denitrifying functional genes. Moreover, the extracellular polymeric substance production was also suppressed under V(V) stress, thereby decreasing the amount of biofilm biomass. Microbial community analyses suggesting the genus Bacillus may have higher tolerance to V(V). These findings can provide scientific basis for the optimized design of treatment system to remove nitrate and V(V) simultaneously., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A new operating approach by reducing the aeration time while keeping high intensity was evaluated for enhanced nutrients removal and maintenance of granular stability. Three aerobic granular sequencing batch reactors (SBR) performing simultaneous nitrification, denitrification and phosphorus removal (SNDPR) were run at different aeration time (120, 90, and 60 min). Aerobic granules could remain their integrity and stability over long-term operation under high aeration intensity and different time, and shorter aeration time favored the retention of biomass, better settleability, and more production of extracellular polymeric substances (EPS). Besides, efficient and stable reactor performance for carbon and phosphorus were achieved, especially, enhanced nitrogen removal was obtained due to reduction of aeration time. Further exploration revealed that the aeration time shaped the bacterial community in terms of diversity, composition, as well as the distribution of functional groups involving carbon, nitrogen and phosphorus removal., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A combined bioelectrochemical and sulfur autotrophic denitrification (CBSAD) system was established to treat high concentration nitrate under different pH conditions in this study. The microbial communities and structures were evaluated to deeply reveal the nitrate removal mechanisms in this combined system. When initial pH was adjusted to 6.5, the CBSAD system obtained 66.45% denitrification efficiency. The combined system achieved highest nitrate removal efficiency of 96.84% at pH 7.5. However, nitrate removal efficiency decreased to 87.05% when initial pH increased to 8.5. Microbial analyses demonstrated that pH value slightly influenced the bacterial abundances and bacterial species in this CBSAD system under high nitrate concentration condition. Proteobacteria was the most dominant phylum in this system, which accounted for more than 90% of the total phyla. Epsilonproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the most important classes for denitrification process. Genus Sulfurimonas was primarily responsible for high nitrate removal in this CBSAD system.

Combined bioelectrochemical and sulfur autotrophic denitrification (CBSAD) system had proven to be feasible for nitrate removal at low temperature. This system obtained excellent denitrification efficiency 96.55% at 10 ± 2 °C long term operation. Nitrate removal efficiency presented increased tendency with applied current increased from 50 to 200 mA and then decreased when the applied current was further increased to 300 mA. The CBSAD system owned the most abundant and rich communities at current 200 mA, and the community structures of the microbial samples at different current conditions were clearly different from each other. Phyla Firmicutes, Proteobacteria and classes Epsilonproteobacteria, Gammaproteobacteria, Betaproteobacteria, Clostridia dominated in all the communities in the system. The largest genus at current 50 mA was Arcobacter, whereas Pseudomonas was the most dominant genus at current 100-300 mA condition, suggesting that high current changed the bacterial structure in this CBSAD reactor., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

An aerobic granules simultaneous nitrification, denitrification and phosphorus removal (SNDPR) system was evaluated in terms of the reactor performance and microbial population dynamics with decreasing C/P ratios from 50 to 16. The effects of C/P ratios on organic carbon and nutrients removal were investigated, as well as the alpha diversity of the bacterial community and bacterial compositions by using Illumina MiSeq pyrosequencing technology. Finally, the relative abundances and distribution patterns were identified and assessed given the key functional groups involved in biological nutrients removals to reveal the effects of C/P ratios to aerobic granules in the SNDPR from the molecular level., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The reactor performance, granules characteristics and microbial population dynamics were investigated to assess the chronic responses of aerobic granules to zinc oxide nanoparticles (ZnO NPs) of 0, 5, 10 and 20mg/L for a period of 180days. The results showed that ZnO NPs stimulated COD removal, whereas caused inhibition to both nitrification and denitrification. However, biological phosphorus removal remained effective and stable. Introduction of ZnO NPs sharply decreased the respiration of granules, while did not change the settleability. Both content of extracellular polymeric substances (EPS) and the ratio of protein to polysaccharides (PN/PS) rose significantly. MiSeq pyrosequencing was employed to explore the microbial population dynamics. Results demonstrated that up to 20mg/L reduced the alpha-diversity of bacterial communities. Finally, phylogenetic classification of the dominant functional species involved in biological nutrients removal were identified to assess the effects of ZnO NPs to aerobic granules from the molecular level., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

An aerobic granular sequencing batch reactor (SBR) on an aerobic/oxic/anoxic (AOA) mode was operated for 50days with acetate sodium as the sole carbon source for simultaneous carbon, nitrogen and phosphorus removal. Excellent removal efficiencies for chemical oxygen demand (COD) (94.46±3.59%), nitrogen (96.56±3.44% for ammonia nitrogen (NH4(+)-N) and 93.88±6.78% for total inorganic nitrogen (TIN)) and phosphorus (97.71±3.63%) were obtained over operation. Mechanisms for simultaneous nutrients removal were explored and the results indicated that simultaneous nitrification, denitrification and phosphorus removal (SNDPR) under aerobic conditions was mainly responsible for most of nitrogen and phosphorus removal. Identification and quantification of the granular AOA SBR revealed that higher rates of nutrients removal and more potentials were to be exploited by optimizing the operating conditions including time durations for AOA mode and the feeding compositions., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Bioelectrochemical denitrification system (BEDS) is a promising technology for nitrate removal from wastewaters. The hazards and effects concerning p-nitrophenol (PNP) towards BEDS lack enough investigations and possess great research prospects. This study investigated how PNP affected the nitrate removal efficiency, microbial communities, functional denitrifying genes abundances, nitrate and nitrite reductase activities, diffusible signal factors (DSF) release, and extracellular polymeric substances (EPS) production in the BEDS. Results indicated that nitrate removal efficiency decreased with initial PNP concentration increased from 0 to 100mg/L. Phylum Firmicutes and class Clostridia were the main contributors for denitrification process in this BEDS. The abundances of the denitrifying genes nirS, nirK, napA, and narG all presented decreased trends with increasing PNP. In addition, the concentrations of nitrate reductase (NR), nitrite reductase (NIR), and EPS obviously decreased, while the concentration of DSF increased with increasing PNP, which demonstrated that higher PNP would inhibit the biofilm formation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Influence of pH on the dominant microbial community structure in bioelectrochemical system (BES) for nitrate removal is poorly understood. Here, the dynamics and variations of microbial communities were investigated with pH varied from 6.0 to 9.0 in a novel three-dimensional BES (3D-BES). The maximum nitrate removal efficiencies 97.58 and 96.36 % were obtained at pH 7.0 and 8.0, due to the main contributions of bacterial phylum Firmicutes and class Clostridia. The abundances of dominant phyla and classes tended to decrease under pH 6.0 and 9.0 conditions. Additionally, phylum Proteobacteria and class Gammaproteobacteria preferred acid environment in the BES, while phylum Chloroflexi and class Bacilli and Betaproteobacteria preferred alkaline environment. Furthermore, the excellent nitrate removal ability of the 3D-BES was ascribed to the presences of genera Exiguobacterium, Proteiniclasticum, Pseudomonas, Planococcus, Thauera, Azoarcus, Thiobacillus, etc. These genera facilitated the combined autotrophic denitrification process so that this system achieved excellent nitrate degradation efficiency.

A continuous-upflow biofilter packed with sponge iron was constructed for nitrate removal under an anaerobic atmosphere. Microbacterium sp. W5, a nitrate reducing and Fe(II) oxidizing strain, was added to the biofilter as an inoculum. The best results were achieved when NO3 (-)-N concentration was 30 mg/L and Fe(2+) was 800 mg/L. Nitrite in influent would inhibit nitrate removal and aqueous Fe(2+) resulted in encrustation. Fe(II)EDTA would prevent cells from encrustation and the maximum nitrogen removal efficiency was about 90 % with Fe(II)EDTA level of 1100 mg/L. Nitrate reduction followed first-order reaction kinetics. Characteristics of biofilms were analyzed by X-ray fluorescence spectroscopy.

Effects of some key factors on hydrogenotrophic denitrification were investigated in lab-scale bioreactors. Results indicated that optimum biomass loading, pH value, temperature, nitrate loading, and C/N ratio in this study were optical density at 600 nm (OD600) of 0.173, 6.0∼7.0, 35 °C, 105 mg L(-1), and 30, respectively. To obtain a better understanding of microbial community in the bioreactors, the 454-pyrosequencing technology was used to characterize the 16S ribosomal RNA (16S rRNA) gene of bacteria in selected samples Y1 and Y2, in which a total of 62,559 effective sequences (36,445 in Y1 and 26,114 in Y2) were obtained. The taxonomic complexities in two samples were compared at phylum/class/genus levels. In total, 41 bacterial phyla, 43 bacterial classes, and 312 genera were detected, where phylum Firmicutes, class Clostridia were most abundant. Genus Proteiniclasticum was predominant among the top 100 genera. This work aims to add some novel insights into hydrogenotrophic denitrification process and its microbial community structures in bioreactors.

A newly aerobic denitrifying bacterial strain, Pseudomonas sp. X31, which was isolated from activated sludge, was added to a newly developed aerobic denitrification bio-ceramsite reactor as an inoculum to treat nitrate-polluted water and the denitrification activities of this system under different air-water ratio, hydraulic loading, and C/N (carbon/nitrogen ratio) conditions were investigated. It demonstrated excellent capability for denitrification in the bio-ceramsite reactor at air-water ratios that varied from 6.5:1 to 8:1. The optimal hydraulic loading for the bio-ceramsite reactor was 0.75 m/h with the optimum denitrification efficiency of 95.18%. The optimal C/N was 4.5:1 with a maximum nitrate removal efficiency of 98.48%. COD could be completely removed under the most appropriate condition (air-water ratio 6.5:1-8:1, hydraulic loading 0.75 m/h, and C/N 4.5:1). The quantity of the biomass in the reactor decreased along with flow, which was in accordance with the variety of the available substrate concentrations in the water. However, the biofilm activity was not proportional to the biomass in the bio-ceramsite reactor, but increased with the quantity of the biomass up to a peak value and then decreased.

An aerobic denitrifier was isolated from activated sludge and the isolate possessed an average nitrate removal efficiency of 95.8% in 24 h, with the maximum nitrite accumulation of 25.6 mg/l. The bacterium could not conduct heterotrophic nitrification. The results of PCR indicated that the strain lacked the gene of amoA. The phylogenetic tree indicated a clear evolutionary divergence that Pseudomonas stutzeri C3 belonged to the group of strains that could not exhibit ammonia oxidation.

In the present study, a novel Pseudomonas sp. W1 was characterized in terms of its ability to perform nitrate removal coupled with anaerobic Fe⁻¹ oxidation under autotrophic growth condition. The effects of operating parameters with respect to the initial solution pH, temperature and initial Fe⁻¹ concentration on nitrate removal were investigated by central composite design. Based on the results of response surface methodology, the maximal nitrate removal efficiency was achieved under the following conditions: pH 7.0, temperature 30 °C and initial Fe⁻¹ concentration 1,100 mg L⁻¹. Under this optimal condition and with an initial NO(3)(-)-N concentration of 55 mg L⁻¹, this strain could remove NO(3)(-)-N with 90% reduction of NO(3)(-)-N, corresponding to oxidizing Fe⁻¹ with 71% oxidation of Fe⁻¹ after 7 days of incubation. The result of kinetic evaluation indicated that this bacterium showed significant substrate affinity to both NO(3)(-)-N and Fe⁻¹.

The effects of the influent nitrate (NO3−-N) concentration on reactor performance and microbial communities of anaerobic methane oxidation coupled to denitrification in a membrane biofilm reactor were emphatically investigated after prolonged storage. The system was run for a period of 185 days including the storage period, reactivating process, and stable operation phase. The influent NO3−-N concentrations varied from 10, 20, and 30 mg/L, and the reactor was continuously operated for 135 days. The denitrification rate in the reactor was activated first and then inhibited, with the average value of NO3−-N consumed of 0.42 mg/L·h−1 at influent NO3−-N of 20 mg/L; there was no obvious nitrite and ammonia–nitrogen accumulation in the whole stage. Illumina MiSeq sequencing results showed that increases in NO3−-N loading could improve the microbial abundance in the system. The highest value for variety and the lowest value for the evenness of the microbial community corresponded to the ideal value of 20 mg/L. It speculated that promoting biofilm bacteria (PBB) became the key functional bacterial group after prolonged storage. Besides, the abundance of methane-oxidizing bacteria was significantly increased in synergy with PBB and denitrifiers to achieve reactivating and stable operation of anaerobic methane oxidation coupled to denitrification. [ABSTRACT FROM AUTHOR]

Chlorella sorokiniana, the dominant microalgal strain with fast growth rate and high nutrients' adsorption rate, was selected from the mature MBGS system. After adding C6-HSL and 3-oxo-C12-HSL to the MBGS consortia formed by combining it with mature AGS, it could also be found that C6-HSL accelerated the denitrification rate and improved the removal rate of TIN and TP effectively. Besides, the promoting effect of C6-HSL was slightly higher than that of 3-oxo-C12-HSL. By adjusting the concentration of C6-HSL (5 × 10−9, 7.5 × 10−7 and 2.5 × 10−5mol/L), the results revealed that adding 5 × 10−9mol/L C6-HSL significantly improved the efficiency of nitrogen and phosphorus removal in MBGS consortia. However, adding higher concentration of C6-HSL (7.5 × 10−7mol/L) would lead to deterioration of TIN and COD degradation. The content of EPS secreted by bacteria was regulated by different concentrations of AHLs, and the PS/PN value decreased with the increasing trend of C6-HSL concentration. [ABSTRACT FROM AUTHOR]

A long start-up period is one of the main factors limiting the practical application of aerobic granular sludge (AGS). Bioaugmentation could be a good strategy to accelerate aerobic granulation. In this research, four denitrifying strains were isolated from mature AGS. Mycobacterium senegalense X3-1 exhibited the strongest self-aggregation ability and good denitrification ability. Ensifer adhaerens X1 showed the strongest denitrification ability but poor self-aggregation ability. Additionally, strain X3-1 demonstrated the highest extracellular polymeric substances (EPS) contents accompanied by relatively high N-acyl-homoserine lactones (AHLs) concentrations, which could illustrate its predominant aggregation ability—AHLs produced by bacteria regulate EPS secretion to accelerate cell aggregation. Strain X3-1 and X1 were chosen as inoculated bacterium to verify the effects of bioaugmentation on AGS granulation and denitrification. Granulation was achieved in the sequential batch reactors (SBRs) added strain X3-1 10 days earlier than the control group. The particle morphology and TIN removal rate of X3-1 were both superior to the latter. The introduction of strains reduced the richness and diversity of the microbial community, but the key functional bacteria, Candidatus_Competibacter, proliferates in the SBR inoculated with X3-1. Conclusively, it is suggested Mycobacterium senegalense X3-1 could be a prospective strain for enhancing AGS formation and denitrification. [ABSTRACT FROM AUTHOR]

An auto-hydrogenotrophic bioelectrochemical system (BES) was set up to investigate the performance of removing nitrate (NO3−–N) and vanadate (V(V)) simultaneously. In this BES, hydrogen is produced during electrolytic reactions and the microorganisms on cathode biofilm can use it as the electron donor to reduce NO3−–N and V(V). This experiment confirmed that the removal efficiency of nitrate and vanadate could be improved by increasing the electric current and extending the hydraulic retention time (HRT) appropriately. The optimal electric current for the reactor was 200 mA with the optimum denitrification efficiency of 94.12%, vanadate removal efficiency of 77.55%. The optimal HRT was 12 h with the optimum denitrification efficiency of 94.40% and vanadate removal efficiency of 86.71%. However, by increasing the influent concentration of V(V), the removal efficiency of NO3−–N and V(V) were both reduced. These findings may help to reveal the biogeochemical fate of V(V) and nitrate in aquifers and develop technology that can simultaneously remove them from groundwater. [ABSTRACT FROM AUTHOR]

Denitrifying bacterial communities play an important role in nitrogen removal. The diversity, abundance and distribution of denitrifiers can be applied in eutrophication assessment for the bay ecosystems. In this study, the composition and variation of cytochrome cd1-type nitrite reductase gene (nirS)-type denitrifiers in the sediments of Haizhou Bay were investigated by using a PCR-based cloning approach. A total of 156 valid sequences were grouped into 76 OTUs based on 97% sequence similarity. The nirS sequences were identified with their closest-matched sequences from sediments of estuary and eutrophied bay, indicating similarity of the denitrifying bacterial communities in similar coastal environments. Canonical correspondence analysis indicated that nitrogen nutrient and dissolved oxygen were the major contributing parameters for the diversity and spatial distribution of denitrifying bacteria of Haizhou Bay. [ABSTRACT FROM AUTHOR]

Simultaneous nitrification, denitrification and phosphorus removal (SNDPR) using aerobic granules is a promising approach in water treatment. The present work investigated the effects of influent carbon to nitrogen (N) ratios (20, 10, and 4) on the SNDPR performance in aerobic granular sequencing batch reactors (AGSBR) under high aeration rate. Results revealed that granules remained long-term stability when the DO concentration was 7–8 mg/L. With the decline of COD/N ratios, the denitrification efficiency was reduced due to the accumulation of nitrate, although the removal of COD and TP remained stable with good efficiency. Rising concentration of ammonia N led to the increase of PN/PS ratio of EPS as well as the protein types according to the results of 3D-EEM fluorescence spectroscopy. MiSeq pyrosequencing technology indicated that the decreasing ratio of COD/N under high DO concentration contributed to accumulation of GAOs and DNPAOs rather than PAOs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Simultaneous denitrification and chromium reduction was achieved in a BES. • The BES could achieve satisfied removal abilities under the selected pH range, and optimum pH was occurred at 7.0. • Key functional groups for denitrification and chromium reduction were identified. • Pseudomonas , Halomonas and Thauera enriched in the BES and facilitated the denitrification and Cr (VI) reduction process. Abstract A novel bioelectrochemical system (BES) was established to investigate the feasibility of simultaneous autotrophic denitrification and chromium removal under different pH conditions in terms of the removal performance and dominant microbial community. Reliable nitrate and hexavalent chromium (Cr (VI)) removal was obtained, and the optimum pH was 7.0 with the highest removal efficiencies of 97.21 and 72.65%, respectively. The bacterial communities exhibited highly selective and concentrated as revealed by the alpha-diversity indices and the Pareto–Lorenz (PL) evenness curves. The highest community richness was achieved under neutral environment, while increasing pH strengthen the species diversity. The predominant phylum Proteobacteria and class Gammaproteobacteria might act as the main contributors, accounting for 95.21–98.47% and 64.49–88.84% of the classified sequences. Key functional groups in terms of the denitrifying bacteria (DNB) and Cr reduction bacteria (CRB) were identified at the genus level. The similar total number of DNB and CRB indicated a good adaptability to pH. The stable removal ability was ascribed to the presences of Pseudomonas , Halomonas and Thauera , which facilitated the combined autohydrogenotrophic denitrification and Cr (VI) reduction process. This study provides a more in-depth understanding of application of BES for simultaneous denitrification and Cr (VI) reduction process. [ABSTRACT FROM AUTHOR]

A bacterial strain (designated as YP1) was isolated from an aerobic granular sequence batch reactor (SBR) performing simultaneous nitrogen and phosphorus removal. Based on the morphological, biochemical characteristics, and phylogenetic analysis of 16S rRNA gene sequence, YP1 was identified as Pseudoxanthomonas sp. strain. Strain YP1 was confirmed to have the ability to conduct denitrifying phosphorus removal (DPR). The optimal conditions for YP1 were pH 8.0, phosphorus (PO43−-P) concentration of 8.0 mg/L, sodium citrate as carbon source, and nitrate nitrogen (NO3−-N) concentration of 30 mg/L. The functional genes including ppk and ppx, narG and narA, nirS and nirK were amplified for understanding the DPR pathways. The results provide more information about denitrifying polyphosphate-accumulating organisms (DPAOs) in aerobic granular sludge (AGS) and lay the foundations for full-scale DPR. [ABSTRACT FROM AUTHOR]

Static experiments were conducted to investigate the effects of environmental factors on nitrate (NO3−-N)-removal efficiency, such as NO3−-N loading, pH value, C/N ratio and temperature in activated sludge using Fe (II) as electron donor. The results demonstrated that the average denitrification rate increased from 1.25 to 2.23 mg NO3−-N/(L·h) with NO3−-N loading increased from 30 to 60 mg/L. When pH increased from 7 to 8, the concentration of NO3−-N and nitrite (NO2−-N) in effluent were all maintained at quite low levels. C/N ratio had little impact on denitrification process, i.e., inorganic carbon (C) source could still be enough for denitrification process with C/N ratio as low as 5. Temperature had a significant effect on the denitrification efficiency, and NO3−-N removal efficiency of 92.03%, 96.77%, 97.67% and 98.23% could be obtained with temperature of 25°C, 30°C, 35°C and 40°C, respectively. SEM, XRD and XRF analysis was used to investigate microscopic surface morphology and chemical composition of the denitrifying activated sludge, and mechanism of the nitrate-dependent anaerobic ferrous oxidation (NAFO) bacterias could be explored with this research. [ABSTRACT FROM PUBLISHER]

Effects of biomass, pH, temperature, nitrate loading, C/N on autohydrogenotrophic denitrification were investigated in a lab-scale bioreactor. Nitrate degradation rate increased as biomass increased. When OD600was 0.173,-N was rapidly reduced down to zero in 3.0 h. The optimum pH for the reactor was 6.0–7.0, high pH values caused accumulated nitrite and decrease of denitrification rate. The average nitrate reduction rate increased from 4.50 to 17.15 mg -N L−1 h−1as temperature increased from 20 to 35°C. However, there was a slight decline in denitrification rate at temperature of 40°C. High nitrate loading of 155 mg-N L−1aroused decrease of denitrification rate. Although C/N value was not directly influence the nitrate reduction rate, it could contribute to increase pH value in order to inhibit the reductase’s activity to hinder the denitrification process. [ABSTRACT FROM PUBLISHER]

For the first time, high-throughput sequencing was employed to investigate the microbial communities of the biofilm in an autohydrogenotrophic denitrifying bio-ceramsite reactor. 30,418 and 39,178 bacterial 16S rRNA gene sequences were obtained from biofilm Samples C1 and C2 in the reactor under HRT 16 h, pH 7.0 and HRT 48 h, pH 9.0 conditions. Results showed that the mainly reported autohydrogenotrophic denitrifying phyla Proteobacteria , Firmicutes and classes Gammaproteobacteria , Alphaproteobacteria , Bacilli were all detected in the reactor, and their high relative abundances demonstrated they played key roles in the autohydrogenotrophic denitrification process, suggesting that this bio-ceramsite reactor presented better denitrification performance. The heatmap analysis illustrated that the largest genus in Sample C1 was Acinetobacter , while Planomicrobium was the largest genus in Sample C2. In addition, the reported hydrogenotrophic denitrifying genera Ochrobactrum , Paracoccus , Pseudomonas , Hydrogenophaga , and Thauera were always observed in the reactor, suggesting that this bio-ceramsite reactor exhibited autohydrogenotrophic denitrifying capacity to convert nitrate to nitrogen gas. This work might add some new insights into microbial communities in autohydrogenotrophic denitrification process. [ABSTRACT FROM AUTHOR]

Understanding aerobic denitrification has become an important focus of environmental microbiology. Aerobic denitrification can be performed by various genera of microorganisms and describes the use of nitrate (NO) as oxidizing agents under an aerobic atmosphere. Isolation of aerobic denitrifiers, enzymes involved in aerobic denitrifiers, phylogenetic distribution of aerobic denitrifiers, factors affecting the performance of aerobic denitrifiers, attempts of applications and possible future trends are depicted. The periplasmic nitrate reductase is vital for aerobic denitrifiers and NapA gene may be the proof of aerobic denitrification. Phylogenetic analysis revealed that aerobic denitrifiers mainly belong to α-, β- and γ- Proteobacteria. Aerobic denitrifiers tend to work efficiently at 25 ~ 37°C and pH 7 ~ 8, when dissolved oxygen concentration is 3 ~ 5 mg/L and C/N load ratio is 5 ~ 10. In addition, recent progresses and applications on aerobic denitrifiers are described, including single aerobic reactors, sequencing batch reactor and biofilm reactors. The review attempts to shed light on the fundamental understanding in aerobic denitrification. [ABSTRACT FROM AUTHOR]

An aerobic denitrifier was isolated from activated sludge and the isolate possessed an average removal rate of 5.7 mg NO-N l h without accumulation of NO-N (less than 2.1 mg l). The average removal efficiency of nitrate was 93.7 % in 24 h, when the dissolved oxygen (DO) concentrations ranged from 3.2 to 17.5 mg l. The activity of both nap (periplasmic nitrate reductase) and nir (nitrite reductase), whose corresponding genes ( napA and nirS) were amplified by touchdown PCR, could be responsible for the tolerance of DO concentrations. Other three genes relating to narG, norB and nosZ were noted to involve in isolate strain. [ABSTRACT FROM AUTHOR]

• Aerobic granules SNDPR used for hypersaline wastewater treatment. • Reliable nitrogen removal efficiency was achieved at elevated salinity. • EBPR was deteriorated with 2 % (w/v) salinity stress. • Salinity induced changes in granular community structure. • Halophilic and non-halophilic bacteria were recognized. Hypersaline wastewater may pose threats to biological wastewater treatment processes. An aerobic granular sludge-based sequencing batch reactor (SBR) performing simultaneous nitrification, denitrification and phosphorus removal (SNDPR) was evaluated with increased salinity from 1 to 2 % (w/v). Nitrogen removal performance was unaffected by salinity up to 20 g/L in terms of reliable and efficient nitrification and denitrification. Enhanced biological phosphorus removal (EBPR) process was completely deteriorated at salinity up to 2 %, in contrast to excellent phosphorus removal at 1 %. Profiles of phosphorus over one cycle demonstrated that higher salinity not only inhibited anaerobic phosphorus release but also impeded aerobic/anoxic phosphorus uptake. Illumina MiSeq sequencing revealed multiple halophilic and non-halophilic bacteria within aerobic granules with family Anaerolineaceae being the predominant potential salt adapter. Besides, ammonia oxidizing bacteria (AOB), glycogen accumulating organisms (GAOs) were more tolerant to salt than nitrite oxidizing bacteria (NOB) and phosphorus accumulating organisms (PAOs) and denitrifying PAOs (DNPAOs). These results deciphered the resilience of aerobic granular sludge-based biological nitrogen and phosphorus removal processes to hypersaline stress. [ABSTRACT FROM AUTHOR]

• Aerobic granulation was achieved in continuous-flow mode treating low-strength sewage. • An obvious three-stages sludge granulation process was observed in this work. • Metabolic and hydraulic selection pressure contributed to the aerobic granulation. • A low sludge yield of 0.1 gMLSS/gCOD was obtained for dramatic in situ sludge reduction. • Existing infrastructure can achieve granulation with minor retrofitting. The culture of aerobic granular sludge (AGS) in continuous-flow system for treating low-strength municipal wastewater is still a challenge for its widespread application. This study developed a continuous-flow reactor based on metabolic and hydraulic selection pressure to explore the feasibility of culturing AGS in conventional continuous-flow mode. The results showed that aerobic granulation was successfully achieved with a mean particle size of 373 μm and almost all granules (95.6 %) were larger than 200 μm. An obvious three-stages granulation process comprised of initial adhesion, the formation of early aggregates that acted as nuclei of granules, and the final AGS maturation, was observed in this work. The selective enrichment of slow-growing bacteria in alternating feast/famine condition played a critical role in the aerobic granulation. The analysis results of extracellular polymeric substances revealed that β-polysaccharides and proteins distributed uniformly within the mature granules, while α-polysaccharides were found mainly concentrated around the granules, which was believed to enhance the mechanical strength of granules. The continuous-flow AGS system exhibited an excellent simultaneous carbon, nitrogen, and phosphorus removal performance with high removal efficiencies of NH 4 +-N (97.6 %), TIN (91.0 %), COD (93.7 %), and TP (94.8 %). Moreover, a low sludge yield of 0.1 gMLSS/gCOD was obtained for dramatic in situ sludge reduction. Illumina MiSeq sequencing results confirmed the outstanding accumulation of GAOs (Candidatus_Competibacter) and PAOs (Rhodocyclaceae) in the system, which were responsible for simultaneous C, N, P removal and sludge reduction. Overall, this study demonstrated the feasibility of aerobic granulation in conventional continuous-flow mode and offered insights into the granulation mechanism, providing implications and references for the application of AGS technology in existing wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Abstract In this work, aerobic granules were cultivated in two reactors which were denoted as R L and R H under 0.6 and 1.8 kg m−3 d−1 of aniline loading rates, respectively. The aerobic granular sludge (AGS) in the two sequential batch reactors for treating aniline-rich wastewater was compared. The results showed that the AGS could be rapidly formed with sludge volume index below 30 mL g−1. The AGS in R L had more filamentous bacteria than that in R H by microstructural observations while the secretion of protein in extracellular polymeric substances was improved in R H and in turn increased relative hydrophobicity of AGS. Within 4-h cycle, the excellent removal of aniline and chemical oxygen demand (COD) were achieved in the two reactors. The removal efficiencies of aniline and COD were consistently over 99.7%, 89.6%, respectively in R L and 98.6%, 86.6%, respectively in R H. As for nitrogen removal, NH 4 +-N released from aniline biodegradation could also be reduced efficiently via nitrification and no nitrite accumulation occurred in both the reactors. Total nitrogen removal performance in R H was better, due to a more compact structure of AGS. The investigation of microbial community succession by pyrosequencing showed that the diversity of microorganisms decreased when AGS was developed. Proteobacteria especially Gammaproteobacteria significantly increased during aerobic granulation in both reactors. It was also found that the relative abundance of Actinobacteria was higher in R H than that in R L. Furthermore, the strains responsible for aniline biodegradation, nitrification, denitrification, and phosphorous accumulation were detected in the systems. Graphical abstract Unlabelled Image Highlights • AGS was rapidly developed with different aniline loading rates (ALRs). • High removal efficiencies of aniline, COD, and NH 4 +-N were achieved in the reactors. • TN removal performance was better with higher concentration of aniline. • Proteobacteria was dominant and Actinobacteria was enriched with higher ALRs. • Pseudomonas plays a crucial role in aniline degradation as well as denitrification. [ABSTRACT FROM AUTHOR]

An aerobic granular simultaneous nitrification, endogenous denitrification and phosphorus removal (SNDPR) system was configured for simultaneous carbon and nutrients removal fed with low-strength synthetic wastewater (0.3 kg COD/(m 3 ·d)). The SNDPR system was operated on an anaerobic/oxic/anoxic (AOA) mode with a gradually dropping superficial gas velocity (SGV) from 0.17, 0.11 to 0.04 cm/s. Long term operation over 120 days revealed decreasing SGV resulted in poorer settleability and microbial activity as well as larger particle sizes, which were in great linear correlations with the sharp decrease of protein/polysaccharides (PN/PS). Excellent removal of chemical oxygen demand (COD) and phosphorus were achieved during the whole process, while enhanced nitrogen removal was observed by dropping the SGV. Both simultaneous nitrification and denitrification rate (SND) and nitrite accumulation rate (NUR) increased significantly, as with the removal efficiency for nitrogen. Illumina MiSeq pyrosequencing displayed glycogen-accumulating organisms (GAOs) Candidatus_Competibacter predominated the SDNPR system, while the PAOs Candidatus_Accumulibacter grew notably with decreased SGV. Lower SGVs favored the enrichment of ammonia-oxidizing bacteria (AOB) while suppressed the accumulation of nitrite-oxidizing bacteria (NOB). This study might contribute to the application of SNDPR system for simultaneous carbon, nitrogen and phosphorus removal. [ABSTRACT FROM AUTHOR]

In this study, a three dimensional bioelectrochemical denitrification system (3D-BEDS) was operated under long-term graphene oxide (GO) condition to treat high nitrate polluted water. When GO concentration increased from 0 to 100 mg L −1 , nitrate removal efficiency slightly decreased from 99.52% to 94.81%. However, when GO concentration was further increased to 150 mg L −1 , the denitrification efficiency dramatically decreased to 74.95%. Increasing GO concentration in this BEDS resulted in decreased community richness, and the abundances of the dominant bacterial communities presented obvious shift. The abundances of denitrifying genes napA , nirS , and nirK showed no obvious changes with GO concentration lower than 50 mg L −1 . However, the abundances of the three genes decreased when GO concentration was further increased to higher than 100 mg L −1 . The increased lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) production demonstrated that long-term presence of GO caused chronic impacts onto microorganisms in this BEDS. [ABSTRACT FROM AUTHOR]

• Effects and removal of OTC by different granulated sludge were assessed. • Low-granulated sludge showed better denitrification performance and resistance. • OTC removal via rapid adsorption and slow degradation. • TB-EPS was conductive to OTC adsorption. • Granulation grade and OTC concentration shaped microbial community. Aerobic granular sludge as a promising technology showed great resistance to adverse conditions. However, the interaction between oxytetracycline (OTC) and granular sludge was not studied sufficiently. This study therefore investigated OTC-tolerance ability of incomplete and complete granulation sludge from aspects of simultaneous nutrients removal, sludge characteristics, microbial activity, community changes, and vice versa OTC removal performance. Incomplete granulation sludge showed better denitrification performance and resistance. Whereas, denitrification and phosphorus removal of complete granulation sludge suffered a permanent collapse under 5 mg/L OTC. OTC could be removed by rapid adsorption and slow biodegradation via granular sludge. The EPS, especially TB-PS, played a significant role during the operational period subjected to OTC. The major genera of Lysobacter and Candidatus_Competibacter laid the biological basis for stability and functionality of granules, which acted as the putative contributors for resisting and removing OTC. This study showed that incomplete-granulated sludge qualified more promising application prospect. [ABSTRACT FROM AUTHOR]

• A bioaugmented SBR with high-efficiency degradation of aniline was start-up. • Thauera contributed the most to aniline degradation and nitrogen metabolism. • 600 mg/L aniline has a negative effect on the abundance of nitrogen removal genes. • Aniline biodegradation and nitrogen metabolism mechanism was elucidated. An enhanced sequencing batch reactor (SBR) system was developed to treat synthetic wastewater rich in 600 mg/L aniline. The aniline degradation efficiency was almost 100%, and the total nitrogen (TN) removal rate was more than 50%. Metagenomics technology revealed the community structure, functional genes and metabolic mechanism during the start-up of the enhanced reactor. Sequencing results showed that Proteobacteria, Bacteroidetes, Chloroflexi and Actinobacteria were dominant phylum. The proportion of degradation of aromatic compounds function increased gradually, but the proportion of nitrogen metabolism function changed little. Functional genes involved in aniline degradation including benA-xylX and dmpB/xylE were detected. The functional genes of nitrogen metabolism were involved in complete nitrification, traditional denitrification, assimilation nitrate reduction and dissimilation nitrate reduction. The functional contribution analysis and network analysis showed that the cooperation and competition of Thauera , Delftia , Diaphorobacter , Micavibrio and Azoarcus ensured the effective removal of aniline and nitrogen. [ABSTRACT FROM AUTHOR]

• Mixed carbon source of sodium succinate and acetate was utilized. • Robust removal performance kept at varying mixed carbon source ratios. • Amount and function of EPS were revealed in terms of the chemical compositions. • Mixture of sodium succinate and acetate balanced competition of PAOs and GAOs. Aerobic granular sludge-based simultaneous nitrification, denitrification and phosphorus removal (SNDPR) systems were configured for the treatment of low-strength municipal wastewater. Granular characteristics, process performance, and the corresponding microbial ecology dynamics were comprehensively explored with sodium acetate and succinate as mixed carbon source. Results revealed that aerobic granules kept structural and functional resilience, while mixed carbon source largely altered and balanced the growth and competition of phosphorus/glycogen accumulating organisms (PAOs/GAOs). Appropriate ratio of mixed carbon source was vital for superb physiochemical behaviors and reliable removal performance by aerobic granules. Therefore, the aerobic granular SNDPR system could achieve deep-level nutrients removal through enhancing the anaerobic carbon uptake rate and strengthening the carbon usage efficiency. The present work could add some guiding sight into the application of aerobic granular SNDPR system for wastewater treatment. [ABSTRACT FROM AUTHOR]