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A simultaneous partial nitrification, anammox and denitrification(SNAD) micro-aerobic system was constructed. The effects of different particle sizes of ZVI on the micro-aerobic system were investigated from the aspects of operation, microbial performance and community structure by adding 120 mg of zero-valent iron(ZVI) into the system. The results showed that the TIN removal rate of the system stabilized at 83.591% and the electron transport system activity(ETSA) was 1.48 times of the inoculated sludge under the domestication of ZVI with a partical size of 50 nm (50 nZVI), which was higher than the influence of other particle sizes of ZVI. The smaller the particle size, the more production of extracellular polymers promoted by ZVI, the more stable of the activated sludge structure. This was due to the fact that ZVI of smaller particle size was more easily adsorbed and utilized by microorganisms. The results of microbial community analysis showed that the smaller the particle size, the higher the diversity of the microbial community mediated by ZVI, and the more complex the community structure. ZVI mediation promoted the enrichment of microorganisms that were not sensitive to oxygen demand. Candidatus_Brocadia and Candidatus_Kuenenia, two kinds of AnAOB were the main bacteria detected in the samples with the highest abundance of 4.650% and 0.692% under the influence of 50 nZVI. Under nZVI, AnAOB acted together with two facultatively anaerobic denitrifying bacteria, Gemmobacter and norank_f_Comamonadaceae, which constituted the denitrification pathway of SNAD. In contrast, facultatively anaerobic denitrification was the main denitrification pathway mediated by mZVI.

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Abstract Pseudomonas putida KT2440 is emerging as a promising microbial host for biotechnological industry due to its broad range of substrate affinity and resilience to physicochemical stresses. Its natural tolerance towards aromatics and solvents qualifies this versatile microbe as promising candidate to produce next generation biofuels such as isobutanol. In this study, we scaled‐up the production of isobutanol with P. putida from shake flask to fed‐batch cultivation in a 30 L bioreactor. The design of a two‐stage bioprocess with separated growth and production resulted in 3.35 gisobutanol L–1. Flux analysis revealed that the NADPH expensive formation of isobutanol exceeded the cellular catabolic supply of NADPH finally causing growth retardation. Concomitantly, the cell counteracted to the redox imbalance by increased formation of 2‐ketogluconic thereby providing electrons for the respiratory ATP generation. Thus, P. putida partially uncoupled ATP formation from the availability of NADH. The quantitative analysis of intracellular pyridine nucleotides NAD(P)+ and NAD(P)H revealed elevated catabolic and anabolic reducing power during aerobic production of isobutanol. Additionally, the installation of micro‐aerobic conditions during production doubled the integral glucose‐to‐isobutanol conversion yield to 60 mgisobutanol gglucose–1 while preventing undesired carbon loss as 2‐ketogluconic acid.

Pseudomonas putida KT2440 is emerging as a promising microbial host for biotechnological industry due to its broad range of substrate affinity and resilience to physicochemical stresses. Its natural tolerance towards aromatics and solvents qualifies this versatile microbe as promising candidate to produce next generation biofuels such as isobutanol. In this study, we scaled‐up the production of isobutanol with P. putida from shake flask to fed‐batch cultivation in a 30 L bioreactor. The design of a two‐stage bioprocess with separated growth and production resulted in 3.35 gisobutanol L–1. Flux analysis revealed that the NADPH expensive formation of isobutanol exceeded the cellular catabolic supply of NADPH finally causing growth retardation. Concomitantly, the cell counteracted to the redox imbalance by increased formation of 2‐ketogluconic thereby providing electrons for the respiratory ATP generation. Thus, P. putida partially uncoupled ATP formation from the availability of NADH. The quantitative analysis of intracellular pyridine nucleotides NAD(P)+ and NAD(P)H revealed elevated catabolic and anabolic reducing power during aerobic production of isobutanol. Additionally, the installation of micro‐aerobic conditions during production doubled the integral glucose‐to‐isobutanol conversion yield to 60 mgisobutanol gglucose–1 while preventing undesired carbon loss as 2‐ketogluconic acid. [ABSTRACT FROM AUTHOR]

Low-frequency ultrasonics is a potential technology to reduce the hydrolysis phase period in anaerobic digestion process. In this study, the influence of combined low frequency ultrasonics and micro-aerobic (MA) pretreatment on sewage sludge solubilization, enzyme activity and anaerobic digestion were assessed. Initially, the effect of ultrasonic density (0.012, 0.014, 0.016, 0.018, 0.1, 0.12 and 0.14 W/mL) and irradiation time (1, 3, 5, 8, 9, 10 and 12 min) of 20 kHz frequency waves were investigated. Accordingly, the effect of micro-aerobic pretreatment (Air flow rate (AFR) = 0.1, 0.2, 0.3 and 0.5 VVM) within 20, 30, 40.48 and 60 h were examined. In addition, the effect of combined pretreatment on COD solubilization, lipase enzyme activation, ATP, percentage of live bacteria and methane gas production during the anaerobic process were examined. The results showed that the highest lipase activity (14.9 Umol/mL) was obtained under the effect of ultrasonic density of 0.1 W/ml within 9 min. The highest solubilization (65%) was observed under optimal micro-aerobic conditions: AFR = 0.2 (VVM) and micro-aerobic time: 40 h. Combined ultrasonic and micro-aerobic (US + MA) pretreatment increases the solubilization (70%), microbial activity (2080%) and lipase enzymatic activity (129%) compared to individual pretreatment. The Biogas production during anaerobic digestion pretreated with combined methods increased by 193% compared to the control, while the elevated values of biogas production in reactors pretreated by ultrasonic and micro-aerobic pretreatment alone were observed to be 101% and 165%, respectively. The net energy in reactor with the combined pre-treatment methods was calculated to be 1.26 kWh, while this value for control, pretreated ultrasonic and micro-aerobic reactors were obtained to be 0.56, 0.67 and 1.2 kWh, respectively.

Abstract Utilization of algicidal bacteria as a biological agent have been receiving significant interest for controlling harmful algal blooms. While various algicidal bacterial strains have been identified, limited studies have explored the influence of bacterial culture conditions on its algicidal activity. Here, the effect of oxygen on the algicidal activity of a novel bacterium JK12, against a model diatom, Phaeodactylum tricornutum (P. tricornutum) was studied. Strain JK12 showed high algicidal activity against P. tricornutum and was identified as Pseudomonas chlororaphis (P. chlororaphis) by 16S ribosomal RNA gene analysis. JK12 culture supernatant exhibited strong algicidal activity while washed JK12 cells showed no obvious activity, indicating that JK12 indirectly attacks algae by secreting extracellular algicidal metabolites. Micro-aerobic culture condition dramatically enhanced the algicidal activity of JK12 by 50%, compared to that cultured under aerobic condition in 24 h. Extracellular metabolomic profiling of JK12 using gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry analysis revealed significantly higher amounts of allantoic acid, urocanic acid, cytidine 2′,3′-cyclic phosphate, uridine 2′,3′-cyclic phosphate, and chlorinated tryptophan in the micro-aerobic culture. This is the first report to demonstrate the important role of oxygen on the algicidal activity of a non-pathogenic strain P. chlororaphis. In addition, the metabolomics analysis provided insights into the algicidal mechanism of P. chlororaphis.

A recently discovered thermophilic bacterium, Geobacillus thermoglucosidasius M10EXG, ferments a range of C5 (e.g., xylose) and C6 sugars (e.g., glucose) and is tolerant to high ethanol concentrations (10percent, v/v). We have investigated the central metabolism of this bacterium using both in vitro enzyme assays and 13C-based flux analysis to provide insights into the physiological properties of this extremophile and explore its metabolism for bio-ethanol or other bioprocess applications. Our findings show that glucose metabolism in G. thermoglucosidasius M10EXG proceeds via glycolysis, the pentose phosphate pathway, and the TCA cycle; the Entner?Doudoroff pathway and transhydrogenase activity were not detected. Anaplerotic reactions (including the glyoxylate shunt, pyruvate carboxylase, and phosphoenolpyruvate carboxykinase) were active, but fluxes through those pathways could not be accurately determined using amino acid labeling. When growth conditions were switched from aerobic to micro-aerobic conditions, fluxes (based on a normalized glucose uptake rate of 100 units (g DCW)-1 h-1) through the TCA cycle and oxidative pentose phosphate pathway were reduced from 64+-3 to 25+-2 and from 30+-2 to 19+-2, respectively. The carbon flux under micro-aerobic growth was directed formate. Under fully anerobic conditions, G. thermoglucosidasius M10EXG used a mixed acid fermentation process and exhibited a maximum ethanol yield of 0.38+-0.07 mol mol-1 glucose. In silico flux balance modeling demonstrates that lactate and acetate production from G. thermoglucosidasius M10EXG reduces the maximum ethanol yield by approximately threefold, thus indicating that both pathways should be modified to maximize ethanol production.

Abstract H 2 S can be produced under aerobic conditions, which goes against the traditional view of an obligatory anaerobic metabolism process. In this research, the sulfate-reduction behavior at the micro-aerobic solid–liquid interface in a landfill was investigated. H 2 S emission from mineralized waste from the landfill material could be enhanced when exposed to O 2. The highest H 2 S concentration of 56.54 mg·m−3, observed at an O 2 concentration of 2%, was 4.5 times higher than the highest concentration of H 2 S recorded under anaerobic conditions. The presence of leachate influenced protection of the anaerobic sulfate-reducing bacteria against O 2 , allowing the bacteria to survive and even undergo significant sulfate reduction under micro-aerobic conditions. The sulfate concentration could be maintained at a high level because of possible oxidation–reduction cycling under micro-aerobic conditions and the risk of H 2 S emission was always high. This research provides a theoretical basis for controlling the release of H 2 S within landfills. Graphical abstract Unlabelled Image Highlights • H 2 S emission from mineralized waste was enhanced under micro-aerobic conditions. • Leachate influenced protection of the sulfate-reducing bacteria against O 2. • High H 2 S emission risk as the sulfate accumulation under 2% and 5% O 2 concentration [ABSTRACT FROM AUTHOR]

Abstract Micro-aerobic condition has proven to be effective in enhancing sulfide oxidation to elemental sulfur (S0) during integrated simultaneous desulfurization and denitrification process (ISDD). In this study we investigated and compared the performance and microbial community of ISDD process operating under initially anoxic, then micro-aerobic and finally switch back to anoxic condition. For all the three tested scenarios, comparable bioreactor performance in terms of sulfate (95.0 ± 4.4%, 90.6 ± 3.8%, 89.8 ± 3.5%) and nitrate (∼100%) removal was achieved. However, a shift of ISDD bioreactor from micro-aerobic to anoxic environment clearly increased the S0 production (30.6%), relative to that at initial anoxic condition (14.2%). Further anoxic bioreactor operation with different influent nitrate concentrations also obtained satisfactory performance particularly in terms of S0 production. Microbial community analysis results showed that functional microorganisms selectively enriched at micro-aerobic condition, particularly sulfide-oxidizing bacteria (SOB), could also function well and enhance S0 production when bioreactor switching from micro-aerobic to anoxic environment. We proposed that micro-aerobic strategy could function as a bio-selector and provide a new idea in functional microorganisms selectively enrichment for wastewater treatment. Highlights • Performance of ISDD process shifting from micro-aerobic to anoxic was explored. • Satisfactory reactor performance was achieved after operating condition switchover. • Selectively enriched microbe function well when switching back to anoxic. • Micro-aerobic strategy could function as a bio-selector for microbe enrichment. [ABSTRACT FROM AUTHOR]

Abstract The process performance of a full-scale sludge process reduction activated sludge (SPRAS) system in long-term operation were investigated by inserting a micro-aerobic tank and a clarifier before conventional activated sludge process. The full-scale SPRAS for industrial park wastewater treatment achieved efficient pollutants removal and a low observed sludge yield of 0.074 g SS/g COD. Batch tests showed that influent feeding into the micro-aerobic tank favored sludge reduction, and obtained a sludge decay constant of 0.168 d−1. The SPRAS enriched slow growers and hydrolytic bacteria for sludge reduction, showed high simultaneous nitrification and denitrification efficiency in the micro-aerobic tank with abundant denitrifying bacteria, and improved sludge settleability by enriching floc-forming bacteria. Process configuration of the SPRAS was beneficial to enhance maintenance metabolism, cyclic micro-aerobic and anaerobic uncoupling, and lysis-cryptic growth for sludge reduction. Techno-economic analysis showed that the SPRAS greatly reduced sludge production with small footprint and low cost. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • DO effect on sludge reduction was studied by side-stream reactor (SSR) coupled MBR. • Anaerobic and micro-aerobic SSR-MBR obtained higher nitrogen removal than aerobic. • Micro-aerobic SSR-MBR had higher sludge reduction (61.1%) than anaerobic and aerobic. • Anaerobic SSR favored hydrolysis and fermentation, and aerobic enriched slow growers. • Micro-aerobic SSR benefited hydrolytic, fermentative and slow-growing bacteria. Abstract An anoxic/oxic membrane bioreactor (MBR) and three side-stream reactor (SSR) coupled membrane bioreactors were operated in parallel to investigate effects of dissolved oxygen (DO) level in SSR on sludge reduction and microbial community structure of SSR-MBRs. The four MBRs were equally efficient in COD and ammonium nitrogen removal. The anaerobic and micro-aerobic SSR favored nitrogen removal through denitrification, simultaneous nitrification and denitrification and autochthonous substrate release as carbon source. The micro-aerobic SSR achieved greatly higher sludge reduction efficiency (61.1%) than anaerobic (37.3%) and aerobic SSR (7.9%). Micro-aerobic SSR obtained the highest endogenous decay constant (0.035 d−1) compared to anaerobic (0.023 d−1) and aerobic SSR (0.015 d−1). High-throughput sequencing results revealed that anaerobic SSR enriched hydrolytic and fermentative bacteria, aerobic environment favored the growth of slow-growing bacteria, and micro-aerobic SSR stimulated biological activities of both anaerobic and aerobic bacteria. [ABSTRACT FROM AUTHOR]

A micro-aerobic side-stream reactor (MSSR) was inserted in returned sludge line of a membrane bioreactor (MBR) for sludge reduction. Three MSSR coupled MBRs (M-MBRs) and an anoxic/oxic MBR (AO-MBR) were operated in parallel to investigate effects of micro-aerobic condition and hydraulic retention time (HRT) of MSSR (HRT M ) on process performance. M-MBRs and AO-MBR were equally effective in COD and NH 4 -N removal. Rising HRT M from 3.3 to 6.7 h increased sludge reduction from 10.8% to 47.5%, and promoted dissolved organic matters release and utilization by enriching hydrolytic, fermentative and predatory bacteria. M-MBR at HRT M of 3.3 h obtained the highest nitrogen removal, and enriched denitrifiers ( Thauera and Hyphomicrobium ) in the MSSR. The highest relative abundance of polyphosphate-accumulating organisms was observed in M-MBR at HRT M of 5.0 h, which achieved the highest phosphorus removal. Prolonging HRT M to 6.7 h improved sludge dewaterability by enriching floc-formation bacteria ( Nannocystis ) and inhibiting filamentous bacteria ( Candidatus_Alysiosphaera ). [ABSTRACT FROM AUTHOR]

This study evaluated performance of an upflow membraneless microbial electrolysis cell (MEC) with flow-through electrodes for wastewater treatment. First, methane production and COD removal were evaluated in continuous flow experiments carried out using synthetic and municipal wastewater. A 29–75% increase in methane production was observed under bioelectrochemical conditions as compared to an anaerobic control. Next, simultaneous removal of COD and nitrogen was studied under microaerobic conditions created by continuous air injection to the anodic compartment of the MEC. While the presence of oxygen decreased Coulombic efficiency due to aerobic degradation of COD, enhanced ammonium removal with near zero nitrite and nitrate effluent concentrations was observed. Evidence of direct ammonium oxidation at the anode as well as nitrite and nitrate reduction at the cathode was obtained by comparing performances of MECs operated under anaerobic and microaerobic conditions with the control reactor operated at zero applied voltage. [ABSTRACT FROM AUTHOR]

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As a substitute for bisphenol A (BPA), the potential toxicity and endocrine disruption of bisphenol S (BPS) have gradually attracted wide attention. Exploring methods to degrade BPS is of great significance. Microbial fuel cells (MFCs) have been extensively used for the removal of contaminants and have demonstrated excellent performances. In this paper, an efficient strategy of micro-aeration to the anode chamber of MFC was conducted to boost the biodegradation of BPS without inhibiting the current generation. The removal efficiency of BPS by MFC under the micro-aerobic condition was 36.35%, which was 1.8 times higher than that of the control group. The introduction of trace oxygen had a neglectable effect on the maximum power density of the system. This work not only enhanced the biodegradation of BPS in MFCs by a simple strategy but also showed that commonly thought of anaerobic MFCs could enrich more functional bacteria (Lentimicrobium , Chryseobacterium and Gordonia) under the micro-aerobic condition in terms of endocrine disruptors removal. Therefore, this paper can provide a reference for the methods of enhancing the BPS removal performance by MFC. • BPS degradation can be enhanced under micro-aerobic condition in MFCs. • Micro-aeration has negligible impact on MFCs' power production performance. • Microbial diversity variations are account for efficient BPS removal in R MO. [ABSTRACT FROM AUTHOR]

• Micro-aerobic enhanced SRE of short HRT side-stream process significantly. • AAMOM 4 achieved 30.41% SRE and maintained carbon and nitrogen removal efficiency. • Micro-aerobic in MSR accelerated the hydrolysis of POM and promoted denitrification. • Micro-aerobic in SSR increased cell lysis and ATP dissipation. • Hydrolytic, slow growing, predatory and fermentation bacteria cooperated to raise SRE. Side-stream reactor (SSR), as an in-situ sludge reduction process with high sludge reduction efficiency (SRE) and less negative impact on effluent, has been widely researched. In order to reduce cost and promote large-scale application, the anaerobic/anoxic/micro-aerobic/oxic bioreactor coupled with micro-aerobic SSR (AAMOM) was used to investigate nutrient removal and SRE under short hydraulic retention time (HRT) of SSR. When HRT of SSR was 4 h, AAMOM system achieved 30.41% SRE, while maintaining carbon and nitrogen removal efficiency. Micro-aerobic in mainstream accelerated the hydrolysis of particulate organic matter (POM) and promoted denitrification. Micro-aerobic in side-stream increased cell lysis and ATP dissipation, thus increasing SRE. Microbial community structure indicated that the cooperative interactions among hydrolytic, slow growing, predatory and fermentation bacteria played key roles in improving SRE. This study confirmed that SSR coupled micro-aerobic was a promising and practical process, which could benefit nitrogen removal and sludge reduction in municipal wastewater treatment plants. [ABSTRACT FROM AUTHOR]

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

The engineering applications of mainstream anaerobic ammonium oxidation (anammox) have raised increasing attention due to its energy-efficient, however, the organics-mediated microbial dynamics and mixotrophic metabolisms in anammox consortia under micro-aerobic conditions are still elusive. Here, the response of the anammox process to sodium acetate and glucose at a C/N ratio ranging from 0 to 0.5 was investigated under micro-aerobic conditions, respectively. Results showed that the additional glucose could promote the nitrogen removal efficiency (NRE) and nitrogen removal rate (NRR) of anammox processes at a low C/N ratio (0.3), representing 84.00% and 0.53 N kg·m−3·d−1. The introduced organics could regulate the diversity of the microbial community and simplify the microbial relationship in anammox consortia. Anammox could not benefit from the introduced sodium acetate, while glucose could effectively enhance the anammox activity and microbial interactions in anammox consortia. Glucose might also stimulate the mixotrophic mechanism of Ca. Kuenenia, further promotes the proliferation of anammox sludge under micro-aerobic conditions. This study reveals that glucose could positively mediate microbial interactions and mixotrophic metabolism in anammox consortia under micro-aerobic conditions, which raises a new horizon for the proliferation of anammox sludge for mainstream engineering applications. [Display omitted] • Glucose (C/N = 0.3) group's nitrogen removal rate was 1.35 times higher than control. • The additional organics simplified microbial diversity. • Glucose (C/N < 0.5) enhanced the microbial interactions in anammox consortia. • Glucose stimulated the mixotrophic anammox and proliferation of anammox sludge. [ABSTRACT FROM AUTHOR]

Dynamic experiments were carried out in two reactors with anaerobic sludge as the seed sludge under low dissolved oxygen concentration (lower than 1.0 mg/L) condition, one reactor with magnetic particle and the dosage being 4 g/L determined by the static experiments and the other as the blank control. The synthetic glucose solution was used to culture the micro-aerobic sludge. The results indicated that the reactor with magnetic particles had a higher chemical oxygen demand removal efficiency and mixed liquid suspended sludge than the blank in which no magnetic particles existed. The sludge under the influence of weak magnetic field had better settling property with the average value of sludge volumetric index (SVI) lower than 100 mL/g, while in the reactor without magnetic particles, the sludge had a loose structure, poor setting property, and a SVI value higher than 200 mL/g. The influence of the weak magnetic field on the flocculation capability of the sludge was investigated through the testing of the indexes such as the total dose of extracellular polymers, the ratio of protein and polysaccharides, flocculating ability, relative hydrophobicity, and surface charge. The results showed that the existence of magnetic particles had greatly increased flocculating performance of the sludge. [ABSTRACT FROM PUBLISHER]

Anaerobic digestion (AD) is widely used for conversion of waste materials into biogas, but inhibition of methane production caused by overloading can be a major problem. The micro-aerobic microbial community MC1 was used to successfully culture methanogens, Methanosarcina acetivorans C2A and Methanosaeta thermophila NBRC 101360. The maximum 16S rRNA gene concentrations of Methanosarcina acetivorans C2A and Methanosaeta thermophila NBRC101360 were 1.06 × 106 and 1.35 × 103 copies/mL, respectively. The five key bacteria in MC1 were quantified to assess the effect of inoculation on the abundances of the bacteria in the mixed culture. The original MC1 total 16S rRNA gene concentration was 1.93 × 108 copies/mL, and the total 16S rRNA gene concentration had increased to 4.79 × 109 copies/mL on day 9 (p < 0.05). The proportions of the key strains in MC1+MST had changed by day 9. Cells were harvested and used to bioaugment and increase the pH values of the high- and medium-temperature anaerobic systems. After bioaugmentation, thermophilic AD recovered well. The cumulative amounts of gas produced were 44.78% and 28.28% higher in the MC1+MST and MC1 groups, respectively, than the sterilized control. The MC1+MST group gave better results than the chemical addition control group (CaCO 3). There was no clear effect of bioaugmentation in mesophilic AD. When compared with traditional pure culture of methanogens as inoculants, methanogen cultivation in MC1 was simple and there was no need to separate and purify the target strains. This simplified methanogenic bioaugmentation agent was useful to study the mechanism of bioaugmentation for the recovery from low pH inhibition, showing the potential for practical application. [Display omitted] • MC1 provided the necessary conditions for growth of acetoclastic methanogens. • Compared with MC1, the proportions of the key strains changed in MC1+MST. • MC1-grown methanogens accelerated the recovery of the AD process. • By augmented MC1+MST, biogas production increased by 44.78%. • MC1 provided a simple procedure for cultivating bioaugmentation seeds. [ABSTRACT FROM AUTHOR]

The microbial communities (Bacteria and Archaea) established in an anaerobic fluidized bed reactor used to treat synthetic vinasse (betaine, glucose, acetate, propionate, and butyrate) were characterized by denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis. This study was focused on the competitive and syntrophic interactions between the different microbial groups at varying influent substrate to sulfate ratios of 8, 4, and 2 and anaerobic or micro-aerobic conditions. Acetogens detected along the anaerobic phases at substrate to sulfate ratios of 8 and 4 seemed to be mainly involved in the fermentation of glucose and betaine, but they were substituted by other sugar or betaine degraders after oxygen application. Typical fatty acid degraders that grow in syntrophy with methanogens were not detected during the entire reactor run. Likely, sugar and betaine degraders outnumbered them in the DGGE analysis. The detected sulfate-reducing bacteria (SRB) belonged to the hydrogen-utilizing Desulfovibrio. The introduction of oxygen led to the formation of elemental sulfur (S) and probably other sulfur compounds by sulfide-oxidizing bacteria (γ- Proteobacteria). It is likely that the sulfur intermediates produced from sulfide oxidation were used by SRB and other microorganisms as electron acceptors, as was supported by the detection of the sulfur respiring Wolinella succinogenes. Within the Archaea population, members of Methanomethylovorans and Methanosaeta were detected throughout the entire reactor operation. Hydrogenotrophic methanogens mainly belonging to the genus Methanobacterium were detected at the highest substrate to sulfate ratio but rapidly disappeared by increasing the sulfate concentration. [ABSTRACT FROM AUTHOR]

Abstract: In order to provide a new method for the treatment of printing and dyeing wastewater, the experiment studies how to treat dyeing-printing wastewater by IC reactor, refluent tank (10L), self-regulating control valve making of medical infusion, air flow meter which the basic units of (mL/min), dissolved oxygen instrument, aerator pumps (3.5W) and aeration equipment under the micro-aerobic condition; The prophase experiment is that wastewater was flocculated. The step is: first, PH of the printing and dyeing wastewater would be changed to 7.5 or so,then, wastewater and flocculants (10% PAC flocculants and 0.05% PAM coagulant aids) were mixed and the mixing ratio of was 400 to 1.at last, the decolorizing ratio was stable at 46% approximately; after the biodegradability of dyeing wastewater improving, under the dissolved oxygen -0.3 ∼ 0.5mg/L (ms) condition, the printing and dyeing wastewater (my) was diluted by domestic sewage which mixing ratio is 7 to3.Then added the printing and dyeing wastewater gradually,and held the increase ratio of influent COD load as 7% and mixed water COD load steadily as 25%. When the influent load reached 4655.1mg/L or so, dissolved oxygen was 0.3 ∼ 0.5mg/L, HRT was 6h, the reactor worked best,this moment, the removal rate of COD could reach 85.8%; when the micro-oxygen granular sludge can deal with printing and dyeing wastewater effectively, under the appropriate influent load, compared the influence of two micro-oxygen conditions of the dissolved oxygen concentration 0.5 ∼ 0.8 (mg/L) and 0.8 ∼ 1.0 (mg/L) on system performance to that of the higher concentration of dissolved oxygen 1.0 ∼ 1.2(mg/L) in the runback water; In order to create a good living environment for granular sludge, during the experiment, inoculation sludge, pH of influent and effluent,influent load operation, HRT are controlled strictly, as a result, it is discovered that the temperature change affects the decolorization. At about 15°C, the decolorization rate is very low, only about 12.7 percent, however, when the temperature at around 25°C, the decolorizing rate increases rapidly, about 75.8%; at around 35°C, the decolorizing rate tends to maintained slowly at around 80.7 percent. [Copyright &y& Elsevier]

Abstract: The degradation characteristic of micro-organisms in the aerobic granular sludge system is different from that in the aerobic granular sludge system or anaerobic granular sludge system. At the beginning, the concentration of inflow water keeps the COD influent concentration in the end of cultivation of anaerobic granular sludge: 3418mg / L stably, the volume load of reactor: 33.4kgCOD/ (m3•d), HRT:7h, the main flow velocity of water: 2L/h, back-flow influent velocity: 0.6L / h, the concentration of dissolved oxygen in refluent tank: 0.3 ∼ 0.5mg/L .The influent pH after 37 days, pH of influent is controlled 6.5above. The COD removal rate, the reducing of HRT takes 0.5h space; when the COD removal ratio is stable, the improving velocity of back-flow water takes 0.2L/h space and HRT keeps 7h. When the influent organic load upgraded 385.7g COD / d eventually after 8 times improvement, the experimentation is accomplished, at the same time, the HRT reached 5h, the refluent flux was 1.4L/h and removal rate of COD was 84.7%. It is also found that the anaerobic granular sludge disintegrated seriously in the test, particle size showed a narrowing trend and a large number of fragments fell and suspended in reactor. As a result, the SS concentration of out-flow water fluctuated largely throughout the experimentation. [Copyright &y& Elsevier]

Abstract: Depending on the availability of oxygen, Escherichia coli is able to switch between aerobic respiratory metabolism and anaerobic mixed acid fermentation. An important, yet understudied, metabolic mode is the micro-aerobic metabolism at intermediate oxygen availabilities. The relationship between oxygen input, physiology and gene expression of E. coli MG1655 and two isogenic mutants lacking succinate dehydrogenase (SDH) and fumarate reductase (FRD) activities was analyzed at different aerobiosis levels. Growth rate and cell yield were very similar to the parent strain. By-product formation was altered in the sdhC mutant to higher acetic acid and glutamate production in batch cultures. In continuous cultures with defined oxygen input gene expression analysis revealed a dependency of many catabolic genes to aerobiosis. Acetate excretion was still detectable under aerobic conditions in the sdhC mutant; the frdA mutant lacked anaerobic succinate excretion. Anaerobic repression of the sdh operon was diminished in the frdA strain, possibly to allow SDH to partially replace FRD. The experiments illustrate the remarkable adaptability of E. coli physiology—to compensate for the absence of important metabolic genes by altering carbon flux and/or gene expression such that there are only minor changes in growth capability across the aerobiosis range. [Copyright &y& Elsevier]

Abstract: This study demonstrates enhanced methane production from wastewater in laboratory-scale anaerobic reactors equipped with electrodes for water electrolysis. The electrodes were installed in the reactor sludge bed and a voltage of 2.8–3.5V was applied resulting in a continuous supply of oxygen and hydrogen. The oxygen created micro-aerobic conditions, which facilitated hydrolysis of synthetic wastewater and reduced the release of hydrogen sulfide to the biogas. A portion of the hydrogen produced electrolytically escaped to the biogas improving its combustion properties, while another part was converted to methane by hydrogenotrophic methanogens, increasing the net methane production. The presence of oxygen in the biogas was minimized by limiting the applied voltage. At a volumetric energy consumption of 0.2–0.3Wh/LR, successful treatment of both low and high strength synthetic wastewaters was demonstrated. Methane production was increased by 10–25% and reactor stability was improved in comparison to a conventional anaerobic reactor. [Copyright &y& Elsevier]

Abstract: The denitrifying sulfide removal (DSR) process with bio-granules comprising both heterotrophic and autotrophic denitrifiers can simultaneously convert nitrate, sulfide and acetate into di-nitrogen gas, elementary sulfur and carbon dioxide, respectively, at high loading rates. This study determines the reaction rate of sulfide oxidized into sulfur, as well as the reduction of nitrate to nitrite, would be enhanced under a micro-aerobic condition. The presence of limited oxygen mitigated the inhibition effects of sulfide on denitrifier activities, and enhanced the performance of DSR granules. The advantages and disadvantages of applying the micro-aerobic condition to the DSR process are discussed. [Copyright &y& Elsevier]

Abstract: The biological denitrifying sulfide reaction (DSR) frequently proceeds in anaerobic environments since excess oxygen inhibits the activity of the denitrifiers. This study isolated a consortium H7, comprising two strains, Penibacillus sp. and Aneurinibacillus aneurinilyticus. It indicated that the DSR performance with the H7 in a mixotrophic medium is significantly enhanced at high sulfide concentrations. The H7 was inhibited by adding >200mgl−1 of S2− under anaerobic conditions. However, when 280mg −1 of S2− was added, H7 could still degrade some of the sulfide, nitrate and acetate under micro-aerobic conditions. Micro-aerobic conditions stimulated the activity of sulfide oxidase and increased the removal rate of highly concentrated sulfide, reducing the inhibition of sulfide on denitrifiers and improving DSR performance. [Copyright &y& Elsevier]

H2S removal from biogas produced in anaerobic digestion of sludge through the introduction of oxygen under micro-aerobic conditions is studied. Research was carried out in two pilot plant reactors (working volume, 200 L each) treating sludge from WWTP with HRT of 20 days. Mixing was provided via sludge or biogas recirculation. Introduction of very low oxygen flow (0.013-0.024 L/Lreactor d) successfully removed H2S content in biogas with an efficiency above 99%. Reactor performance during micro-aerobic operation in terms of biogas production, methane yield and COD removal were not affected by the amount of oxygen supplied, remaining stable and similar to the anaerobic behaviour. Sludge recirculation (∼50 L/h) and biogas recirculation (∼3.5 L/min) as mixing methods were found not significant in H2S removal from biogas while biogas recirculation reduced by 10 times dissolved sulphide concentration compared to sludge recirculation. [ABSTRACT FROM AUTHOR]

Bench scale experimentation was completed to assess the potential of using a short residence time pretreatment reactor upstream of aerobic digestion to enhance the destruction of pathogens. The impact of aeration, temperature, hydraulic residence time (HRT), solids concentration, and feeding frequency on the pretreatment process was investigated. Subsequent testing evaluated pathogen destruction resulting from the operation of selected pretreatment conditions in a staged configuration with conventional aerobic digesters. Either highly oxidative or highly reductive conditions were observed to be most effective in reducing the concentrations of E. coli. and Salmonella spp. in the pretreatment reactor. When operated in series with the aerobic digesters, the more highly reducing conditions in pretreatment were found to enhance die-off of the microorganisms in subsequent aerobic digestion compared to the control. [ABSTRACT FROM AUTHOR]

Coupled granules are self-immobilized aggregates of microorganisms under micro aerobic conditions, which have the dissolved oxygen (DO) level of 0.6 mg.L-1. The effects of DO concentration on pentachlorophenol (PCP) reduction and its microbial community were investigated in a coupled anaerobic and aerobic reactor. Both the diversity and the dynamicity of the Eubacteria and Archaea community, which were responsible for PCP degradation, were evaluated by means of amplification by polymerase chain reaction (PCR) and separation using the denaturing gradient gel electrophoresis (DGGE) technique. The results demonstrated a major shift in the Eubacteria and Archaea community as the mixed aerobic and anaerobic seeding sludge (1:1 by volume) developed into coupled granules and finally acclimated with PCP throughout the experiment period within 60 days. The numbers of the Eubacteria population decreased from 20, 16 to 11; Shannon diversity index decreased from 2.75, 2.53 to 2.10. In contrast, the number of the Archaea population increased from 12, 14 to 18; and Shannon diversity index increased from 1.87, 1.88 to 2.43. Phylogenetic analysis based on 16SrDNA genes showed the dominance Sphingomonas, Desulfobulbus, Proteobacteria, Actinobacterium, Methanogenic and some uncultured bacteria in the PCP-degrading coupled granules. Microorganism community construction of coupled granules was also deduced. [ABSTRACT FROM AUTHOR]

Sulphide generated during anaerobic treatment of S-containing wastewaters represents an environmental problem. Adding limited amounts of oxygen or nitrate (or nitrite) to biologically (or chemically) oxidise sulphide forms a simple process-level strategy to control this problem. This short review evaluates the feasibility and limitations of this strategy on the basis of the results of bioreactor studies. [ABSTRACT FROM AUTHOR]

To investigate the inorganic nitrogen conversion in reactors that were operated under aerobic and micro-aerobic conditions and to identify populations that became acclimated in the reactors under those oxygen conditions, we operated two reactors with 72 h of hydraulic retention time and an artificial medium containing ammonium- and nitrite-nitrogen without any organic compound. We determined the concentration of inorganic nitrogen in samples from the reactors and the microbial community structure in the reactors by using PCR-DGGE of the partial 16S rRNA gene. The results showed that nitrification to nitrate fully progressed in the aerobic reactor within 24 h, but we could not find any obvious reaction in the micro-aerobic reactor. In a view of microbial community structure, the total number of microorganisms composing the communities in the reactors was dramatically decreased compared to those of the initial inoculated sludge that originated from the Jang-lim sewage treatment plant in Busan, Republic of Korea because of the limited nutrients present. One Nitrospira sp. was clearly detected under both aerobic (as DO > 2 mg l-1) and micro-aerobic (as DO < 0.7 mg l-1) conditions while no AOB-like bacterium was exactly matched among main bands. By the results, nitrite-oxidizing bacteria may be more tolerant to variations in oxygen, or the occupation of ammonia-oxidizing bacteria as dominant groups may have been inhibited by substrate starvation and high concentrations of nitrite-N in influent. [ABSTRACT FROM AUTHOR]

Abstract: A whole-core injection method was used to determine depth-related rates of microbial mineralization of 14C-phenanthrene added to both contaminated and clean marine sediments of Puget Sound, WA. For 26-day incubations under micro-aerobic conditions, conversions of 14C-phenanthrene to 14CO2 in heavily PAH-contaminated sediments from two sites in Eagle Harbor were much higher (up to 30%) than those in clean sediments from nearby Blakely Harbor (<3%). The averaged 14C-phenanthrene degradation rates in the surface sediment horizons (0–3cm) were more rapid (2–3 times) than in the deeper sediment horizons examined (>6cm), especially in the most PAH polluted EH9 site. Differences in mineralization were associated with properties of the sediments as a function of sediment depth, including grain-size distribution, PAH concentration, total organic matter and total bacterial abundance. When strictly anaerobic incubations (in N2/H2/CO2 atmosphere) were used, the phenanthrene biodegradation rates at all sediment depths were two times slower than under micro-aerobic conditions, with methanogenesis observed after 24 days. The main rate-limiting factor for phenanthrene degradation under anaerobic conditions appeared to be the availability of suitable electron acceptors. Addition of calcium sulfate enhanced the first order rate coefficient (k 1 increased from 0.003 to 0.006day−1), whereas addition of soluble nitrate, even at very low concentration (<0.5mM), inhibited mineralization. Long-term storage of heavily polluted Eagle Harbor sediment as intact cores under micro-aerobic conditions also appeared to enhance anaerobic biodegradation rates (k 1 up to 0.11day−1). [Copyright &y& Elsevier]

The focus of this study was on sulfate-rich wastewater treatment in a novel anaerobic / micro-aerobic bioreactor system. The system was composed of an upward-flow anaerobic sludge blanket (UASB) reactor and a floated bed micro-aerobic reactor, which was packed with elastic porous carriers and was controlled in a situation of dissolved oxygen below 0.5 mg l-1. The floated bed micro-aerobic reactor was developed for accumulating a higher amount of biomass in carriers with a short hydraulic retention time (HRT) for biological oxidation of hydrogen sulfide to elemental sulfur. During long-term steady state operation, experimental results showed that an average of 70±6% of sulfate was transformed to hydrogen sulfide in UASB reactor. Moreover, the overwhelming majority of sulfide was oxidized to elemental sulfur and sulfate in micro-aerobic reactor; and the recirculation of effluent to UASB reactor reduced effectively the degree of inhibition caused by sulfate-rich wastewater. In UASB reactor, chemical oxygen demand (COD) removal efficiency increased with COD loading, in contrast, the performance of sulfate removal decreased with the increase in sulfate loading in a range of 1.0-1.75 kg SO42- m-3 d-1. In micro-aerobic reactor, sulfide was removed almost completely under the operation of HRT 2.8 h. Furthermore, experimental results of continuous operations revealed that oxidation-reduction potential (ORP) was an adequate parameter for controlling biological oxidation of sulfide. When ORP was regulated in a lower range of -250 to -300 mV, the amount of regenerated sulfate was reduced significantly in micro-aerobic reactor. [ABSTRACT FROM AUTHOR]

The integrated autotrophic and heterotrophic denitrification (IAHD) process, which can simultaneously degrade sulfide, nitrate, and organic carbon with nitrate as a solo electron acceptor, has gained increasing attention as a key unit in industrial wastewater treatment. Micro-aerobic technology, which introduces trace oxygen as an additional electron acceptor, has been demonstrated as an effective strategy for enhancing the IAHD performance. This study focus on the electronic balance calculation of the IAHD process and reveals for the first time that the IAHD process can efficient proceed with an insufficient supply of electron acceptors (nitrate) under micro-aerobic conditions. In the IAHD batch tests, the highest sulfide, nitrate, and acetate removal efficiencies and rates were obtained with an electronic deletion rate peak at 55.1%. Further sulfide oxidizing batch tests demonstrated that the electronic deletion rates were 18.7% and 38.2% under oxygen contents of 5 mL and 10 mL, respectively, in the biological sulfide oxidizing process. Illumina sequencing was used to analyze the microbial community structure in the sulfide oxidation process and indicated Thiobacillus , Thauera , Mangroviflexus , and Erysipelothrix dominated in all community compositions, in which the relative abundance of Thiobacillus increased with an increase in the electronic deletion rate. This study reveals a potential linkage between the electronic gap and the enhanced IAHD performance, which proves new insights into the simultaneous sulfur, nitrogen, and organic carbon removal process.

Utilization of algicidal bacteria as a biological agent have been receiving significant interest for controlling harmful algal blooms. While various algicidal bacterial strains have been identified, limited studies have explored the influence of bacterial culture conditions on its algicidal activity. Here, the effect of oxygen on the algicidal activity of a novel bacterium JK12, against a model diatom, Phaeodactylum tricornutum (P. tricornutum) was studied. Strain JK12 showed high algicidal activity against P. tricornutum and was identified as Pseudomonas chlororaphis (P. chlororaphis) by 16S ribosomal RNA gene analysis. JK12 culture supernatant exhibited strong algicidal activity while washed JK12 cells showed no obvious activity, indicating that JK12 indirectly attacks algae by secreting extracellular algicidal metabolites. Micro-aerobic culture condition dramatically enhanced the algicidal activity of JK12 by 50%, compared to that cultured under aerobic condition in 24 h. Extracellular metabolomic profiling of JK12 using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry analysis revealed significantly higher amounts of allantoic acid, urocanic acid, cytidine 2′,3′-cyclic phosphate, uridine 2′,3′-cyclic phosphate, and chlorinated tryptophan in the micro-aerobic culture. This is the first report to demonstrate the important role of oxygen on the algicidal activity of a non-pathogenic strain P. chlororaphis. In addition, the metabolomics analysis provided insights into the algicidal mechanism of P. chlororaphis. [ABSTRACT FROM AUTHOR]

The concentration of ammonia nitrogen is relatively high during autothermal thermophilic micro-aerobic digestion (ATMAD), which could significantly affect the sludge stabilization. This paper aims to investigate the impacts of ammonia nitrogen on ATMAD process, batch experiments were carried out with dosage of certain amount of NH 4 HCO 3 into digestion system. The total ammonia nitrogen (TAN) was considered as a suitable indicator to characterize the ammonia inhibition. As the TAN reached to approximately 1000 mg L -1 , the sludge digester presented a relatively low removal of volatile solids, due to adverse effects of ammonia nitrogen on sludge digestion. Three pathways that closely related to ammonia inhibition were investigated in this research. Digestion system could be inhibited by high TAN due to K + deficiency of the cells and the decline of Mg 2+ in the cytoplasm, and the accumulations of reactive oxygen species lead to oxidative stress for the microbes. Ammonia inhibition can be mitigated by the increase of oxidative enzyme., (Copyright © 2018 Elsevier Ltd. All rights reserved.)