Search

Some microorganisms with the nitrification function can carry out nitrogen conversion under oxygen-limited conditions. In this study, a continuous-flow biofilm reactor was operated to investigate the removal of ammonium nitrogen (NH4-N) under microaerobic or anoxic conditions. After more than 100 days of long-term operation, the NH4-N removal rate and removal percentage reached 2.92 mg/(L·h) and 72.3%, respectively. In the batch experiments, NH4-N removal was achieved regardless of the presence or absence of nitrite. The main microorganisms relating to nitrogen metabolism in the system were Nitrospira, Nitrosomonas, Candidatus Kuenenia, and denitrifying bacteria. The metagenomics analysis indicated that these functional microorganisms constituted the main nitrogen metabolic network in the system, and microorganisms such as Rhodanobacter, Nitrosomonas, Defluvii, and Cyanobacteria had the possible capacity for oxygen production. Without organic carbon in the synthetic wastewater, heterotrophs including denitrifying bacteria might utilize organic carbon such as extracellular polymeric substances produced by autotrophs. The removal of NH4-N under oxygen-limited conditions might be achieved through interactions among nitrifying bacteria, anammox bacteria, and heterotrophs, which deserves further investigation. [ABSTRACT FROM AUTHOR]

Abstract Dye wastewater is one kind of refractory pollutant and it is commonly treated by the integrated anaerobic and aerobic process. A new integrated hydrolysis/acidification and multiple anoxic/aerobic (AO) process was proposed for the removal of color and nitrogen from azo dye wastewater. System performance, the degradation pathway of azo dye and nitrogen metabolic pathway were investigated with quadrupole-time-of-flight and metagenomic analyses. The proposed process removed color and nitrogen efficiently, with the removal percentages of 89.4% and 54.0%, respectively. A colorful intermediate C 16 H 11 N 3 O 7 S 2 during the degradation of azo dye was detected. Controlling a low dissolved oxygen concentration in the multiple AO process could enhance nitrogen removal. The detected bacteria possessing azoreductase for the azo dye degradation included Desulfovibrio aminophilus , Thermoanaerobacter , Lactococcus raffinolactis , Ruminiclostridium and Rhodopirellula. The nitrifying genes of amo and hao were mainly detected in Nitrosomonas , while the denitrifying genes were detected in Thauera, Candidatus Accumulibacte r and Rhodothermus marinus. Highlights • Hydrolysis/acidification and multiple AO process removed color and N effectively. • The color removal efficiency was enhanced under high COD concentrations. • Low DO in the multiple AO reactor induced high nitrogen removal. • A colorful intermediate was detected during RR2 degradation. • Microbial communities were analyzed by high throughput sequencing and metagenomics. [ABSTRACT FROM AUTHOR]

Abstract Long-term exposure of nitrifiers to high concentrations of free ammonia (FA) and free nitrous acid (FNA) may affect nitrifiers activity and nitrous oxide (N 2 O) emission. Two sequencing batch reactors (SBRs) were operated at influent ammonium nitrogen (NH 4 -N) concentrations of 800 mg/L (SBR H) and 335 mg/L (SBR L), respectively. The NH 4 -N removal rates in SBR H and SBR L were around 2.4 and 1.0 g/L/day with the nitritation efficiencies of 99.3% and 95.7%, respectively. In the simulated SBR cycle, the N 2 O emission factors were 1.61% in SBR H and 2.30% in SBR L. N 2 O emission was affected slightly by FA with the emission factor of 0.22%–0.65%, while N 2 O emission increased with increasing FNA concentrations with the emission factor of 0.22%–0.96%. The dominant ammonia oxidizing bacteria (AOB) were Nitrosomonas spp. in both reactors, and their relative proportions were 38.89% in SBR H and 13.36% in SBR L. Within the AOB genus, a species (i.e. , operational taxonomic unit [OTU] 76) that was phylogenetically identical to Nitrosomonas europaea accounted for 99.07% and 82.04% in SBR H and SBR L , respectively. Additionally, OTU 215, which was related to Nitrosomonas stercoris , accounted for 16.77% of the AOB in SBR L. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Conductive materials facilitate direct interspecies electron transfer between acidogens and methanogens during methane (CH4) production. Soluble microbial products (SMP) and extracellular polymeric substances (EPS) produced by microorganisms might act as the electron shuttle between microorganisms and conductive materials. In this study, effects of conductive ferroferric oxide (Fe3O4) on anaerobic treatment process and the production of SMP and EPS were investigated. The maximum CH4 production rate was enhanced by 23.3% with the dosage of Fe3O4. The concentrations of proteins, polysaccharides, and humic substances in tightly bound EPS (T-EPS) were promoted, suggesting that extracellular metabolisms were induced by conductive materials. Distribution of potential electron shuttles such as quinone-like substances, flavins, aromatic amino acids, and dipeptides in SMP and EPS phases were comprehensively investigated and these electron shuttles were significantly affected by Fe3O4. Dipeptides consisting of phenylalanine were widely detected in T-EPS of the Fe3O4 reactor, indicating a potential different extracellular electron exchange pattern with the addition of conductive materials. [ABSTRACT FROM AUTHOR]

Effect of dosing ferroferric oxide (Fe 3 O 4 ) on the anaerobic treatment of azo dye Reactive Red 2 (RR2) was investigated in two anaerobic sequencing batch reactors (ASBRs). System performance, dye degradation pathways, and microbial activities and structure were examined. The addition of Fe 3 O 4 significantly improved treatment efficiency, with the removal efficiency of RR2 increased by 116%, the maximum methane (CH 4 ) yield potential and the peak CH 4 production rate improved by 7.7% and 22.3%, and the lag phase shortened by 39.6%, respectively. The activity of the electron transport system was significantly enhanced by dosing Fe 3 O 4 , with the maximum value increased by 77% and conductivity of the anaerobic sludge increased by 178%. According to the proposed pathway for the degradation of RR2, the degradation products from complete cleavage of the N N bond in RR2 were obtained at the presence of Fe 3 O 4 , while were absent without Fe 3 O 4 . At high initial dye concentrations, the dosage of Fe 3 O 4 alleviated the inhibition to microbes by RR2, and high degradation rate and removal efficiency were maintained. The microbial community structure changed during the long-term acclimation with the dosage of Fe 3 O 4 . Paludibacter , Trichococcus and Methanosarcina were predominant and their relative abundances increased with the addition of Fe 3 O 4 . [ABSTRACT FROM AUTHOR]

Conductive materials can enhance direct interspecies electron transfer (DIET) during the anaerobic treatment of wastewater and provide ecological advantages for syntrophic methane (CH 4 ) production. The effects of ferroferric oxide (Fe 3 O 4 ) on the system performance and microbial communities were examined during the anaerobic treatment of synthetic wastewater with mixed organic carbon. The addition of Fe 3 O 4 did not enhance the relative abundance of methanogens, but increased the maximum CH 4 production rate by 15.4% and shortened the lag phase by 13.9%. Methanosarcina was the predominant methanogen contributing to DIET. Proteiniclasticum and Kosmotoga were dominant upon the addition of Fe 3 O 4 and were responsible for protein degradation. More extracellular proteins were produced and a filamentous morphology was observed upon the addition of Fe 3 O 4 . Short-term Fe 3 O 4 addition also improved the performance of the anaerobic treatment in the control reactor, and the Fe 3 O 4 rather than the microbial morphology was the more important factor enhancing DIET. [ABSTRACT FROM AUTHOR]

Aiming problems arising from the wind turbine with the frequency converter, this paper proposes a design for wind turbine based on differential speed regulation. The dynamic characteristics and parameter determination method of the structural components including differential gear train and speed regulating motor (SRM) were studied and the dynamic characteristic expression were obtained. The critical conditions about input power or output power for ring gear driven by SRM were researched. The way to determine the optimal structure parameters of SRM was put forward. The minimum peak power of SRM was regarded as the objective function while the transmission ratios of three gear sets which were placed in the different positions of overall structure scheme was optimized. A SIMULINK model of 1.5 MW wind turbine based on differential speed regulation was built and ran. The rotational speed, torque and power of the wind rotor, the SRM and the synchronous generator were obtained respectively. The simulation results can verify effectiveness of the theoretical analysis and parameter configuration. [ABSTRACT FROM AUTHOR]

The automotive industry is undergoing a transformational period where more and more new energy vehicles (NEVs) are being produced and delivered to the market. Accordingly, some new challenges arise during the manufacturing process for car companies. Since the mixed-model assembly line has been widely used, how to integrate the NEVs into the existing assembly system that was designed for the production of gasoline cars is a key issue. A practical approach assigning a specific workforce to handle NEV assembly work is applied at the BMW assembly shop. This work studies this new production pattern and focuses on the design of the assembly system under this pattern. This work aims to develop a method for minimizing the production cost of NEV assembly. Thus, an exact algorithm for hierarchically solving the assembly line balancing problem and vehicle model sequencing problem is proposed. Mixed integer programming mathematical models that describe these two problems are formulated for the first time. Three new benchmark problems and one industry case that include the NEV models are created to evaluate the effectiveness of the proposed method. Results of numerical tests demonstrate that the developed algorithm can quickly generate reconfiguration solutions of the assembly line for various model mix scenarios and production rates. High flexibility of the manufacturing system can be obtained using the proposed approach. [ABSTRACT FROM AUTHOR]

During anaerobic digestion, methanogenic activities and pathways can be affected by intermediates. Here, the effects of intermediates acetate, propionate, and ethanol on methanogenesis were investigated. Four anaerobic sequencing batch reactors were acclimated with propionate (ASBR_P), ethanol/propionate (ASBR_EP), acetate/propionate (ASBR_AP), and ethanol/acetate/propionate (ASBR_EAP). Ethanol was the easiest one to be biodegraded, thereby enhancing the maximum methane production rate and shortening the lag phase, while the longest acclimation time and lowest methane production rate were observed in ASBR_P. Different microbial communities and syntrophic patterns existed in four reactors. Desulfovibrio and Geobacter were the dominant ethanol-oxidizing bacteria in ASBR_EP and ASBR_EAP, respectively. Both Desulfovibrio and Geobacter possessed the potential of extracellular electron transfer, which might be the advantage of ethanol dosage for enhancing methanogenesis through direct interspecies electron transfer. Methanosarcina was enriched in ASBR_P and ASBR_AP, while Methanosaeta in ASBR_EP and ASBR_EAP. Genes responsible for acetoclastic methanogenesis were significantly enriched in ASBR_EAP, possibly resulting in the highest methanogenic activity from acetate. Results from this study will advance the optimization of practical anaerobic systems, which can be achieved by regulating the intermediates with different fermenting pathways. • Organics affected methanogenic activity and microbial community significantly. • Ethanol could enhance the CH 4 production rate and reduce the lag phase efficiently. • Types of VFAs affected the enriched ethanol oxidizing Desulfovibrio and Geobacter. • Ethanol might affect VFA degradation by influencing the acclimated microorganisms. • The contribution of ethanol to methanogenesis should be evaluated comprehensively. [ABSTRACT FROM AUTHOR]

• This study clarified the co-occurrence network of syntrophs and methanogens. • Diverse quorum sensing genes were detected in all anaerobic sludge samples. • Two quorum sensing signals are suggested to impact the regulation of type IV pili. • Environmental factors significantly affected the syntrophic patterns. Interspecies electron transfer plays an important role in syntrophic methanogenesis. Direct interspecies electron transfer (DIET) between syntrophic oxidizers and methanogens via conductive pili has been only confirmed in some specific co-cultures. This study examined potential syntrophic cooperation via type IV pili and quorum sensing between widespread syntrophic bacteria and methanogens through a metagenomic analysis of 12 anaerobic sludge samples. We found that Methanosaeta and Methanosarcina , which are reported to have DIET ability, were dominant in most methanogenic samples. Putative conductive pili genes were found in some typical syntrophic bacteria, which has rarely been reported previously. The existence of diverse quorum-sensing genes suggested that various quorum-sensing systems might participate in the communication of anaerobic microorganisms. Specifically, the diffusible signal factor and 3′-5′ cyclic diguanosine monophosphate related genes were mainly assigned to syntrophic bacteria. These results suggest that the combined regulation of these signals might be responsible for the biosynthesis of type IV pili and affect syntrophic interaction during methanogenesis. These novel results provide fresh evidence to support the widespread existence of DIET in anaerobic methanogenic systems; therefore, regulating the quorum-sensing system may promote syntrophic interaction. [ABSTRACT FROM AUTHOR]

The detection of acyl homoserine lactones (AHLs) in activated sludge is essential for clarifying their function in wastewater treatment processes. An LC–MS/MS method was developed for the detection of AHLs in both the aqueous and solid phases of activated sludge. In addition, the effects of proteases and extracellular polymeric substances (EPS) on the detection of AHLs were evaluated by adding protease inhibitors and extracting EPS, respectively. Recoveries of each AHL were improved by adding 50 μL of protease inhibitor, and recoveries were also improved from 0 to 56.9% to 24.2%–105.8% by EPS extraction. Applying the developed method to determine the type and concentration of AHLs showed that C 4 -HSL, C 6 -HSL, C 8 -HSL and 3-oxo-C 8 -HSL were widely detected in a suspended activated sludge system. The dominant AHL was C 8 -HSL, with a highest concentration of 304.3 ng/L. C 4 -HSL was mainly distributed in the aqueous phase, whereas C 6 -HSL, C 8 -HSL and 3-oxo-C 8 -HSL were preferentially distributed in the sludge phase. [ABSTRACT FROM AUTHOR]

Syntrophic methanogenesis can be improved by the addition of conductive materials. In this study, conductive carbon fibers (CFs) were applied to efficiently enrich syntrophic microorganisms with potential direct interspecies electron transfer (DIET) ability and promote methanogenic activity. With ethanol as the substrate, CFs shortened the acclimation time remarkably. The maximum methane production rate and the ethanol degradation rate of suspended biomass were increased by 40% and 68%, respectively, even when CFs were subsequently removed. However, with acetate and propionate as the mixed substrate, CFs decreased the methanogenic activity. In the reactor fed with ethanol, CFs increased the relative abundance of Geobacter , Desulfovibrio , and methanogens by 57%, 39%, and 63%, respectively. Methanosaeta possessed most methane production genes and might involve in DIET. Furthermore, CFs increased the relative abundance of ethanol-degradation genes assigned to Geobacter , Desulfovibrio and Pelobacter , suggesting the promoted ethanol-degradation. The triggered electron transport system activity and acetoclastic methanogenesis also explained the accelerated effects on ethanol-degradation by long-term acclimation with CFs. Notably, the dominance of Geobacter and Methanosaeta combined with the increased electron transfer constant in the CFs-amended ethanol reactor indicated the potential role of DIET after the removal of CFs, which deserved further clarification. Unlabelled Image • Carbon fibers could enrich ethanol-oxidizing Geobacter and Desulfovibrio. • Methanogenesis from ethanol was improved even when carbon fibers were removed. • Acetoclastic methanogenesis was triggered by carbon fibers in ethanol reactors. • The promotion of carbon fibers was strongly affected by organic substrates. [ABSTRACT FROM AUTHOR]

Direct interspecies electron transfer (DIET) is a new electron-transfer strategy for enhanced propionate degradation. Ethanol can enrich the DIET species of Geobacter and conductive ferroferric oxide (Fe 3 O 4) can promote DIET. Therefore, coupled effects of ethanol and Fe 3 O 4 on propionate degradation were investigated. The maximum CH 4 production rate was increased by 81.4% by adding Fe 3 O 4 when simultaneously fed with ethanol and propionate, while the improvement could not be observed without ethanol. The sludge conductivity and the electron transfer system activity by adding Fe 3 O 4 were increased by 2.66 and 2.73 times, respectively. Besides, the relative abundance of functional microbes such as Geobacter , Syntrophobacter , Smithella , and Methanosaeta , and their functional genes were increased by the supplement of Fe 3 O 4. The improvement of propionate degradation by adding Fe 3 O 4 was largely attributed to the co-existence of ethanol degradation. The DIET between Geobacter and Methanosaeta might provide more energies or rapidly consume the oxidation products to promote the propionate degradation. Unlabelled Image • CH 4 production was enhanced by dosing Fe 3 O 4 with organics of ethanol and propionate. • Fe 3 O 4 increased the sludge conductivity and electron transfer system activity. • Fe 3 O 4 promoted the relative abundance of functional microbes and their genes. • DIET might promote the degradation of propionate by providing more energies. [ABSTRACT FROM AUTHOR]

Wastewater management has experienced different stages, including pollutant removal, resource recovery, and water nexus. Within these stages, anaerobic ammonia oxidation-based biotechnology can be incorporated for nitrogen removal, which can help achieve sustainable wastewater management, such as reclamation and ecologization of wastewater. Here, the physiology, metabolism, reaction kinetics and microbial interactions of anammox bacteria are discussed, and strategies to start-up the anammox system are presented. Anammox bacteria are slow growers with a high doubling time and a low reaction rate. Although most anammox bacteria grow autotrophically, some types can grow mixotrophically. The reaction stoichiometric coefficients can be affected by loading rates and other biological reactions. Microbial interactions also contribute to enhanced biological nitrogen removal and promote activities of anammox bacteria. The start-up of the anammox process is the key aspect for its practical application, which can be realized through seed selection, system stimulation, and biomass concentration enhancement.