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关键词： Bioreactor   Hydrodynamic shear stress   Microfibrous scaffolds   Neurogenesis  

摘要： Microfibrous viscose-rayon scaffolds functionalized with poly-L-lysine and laminin were used to culture pheochromocytoma (PC12) cells in recirculation bioreactors under bulk laminar flow conditions. To determine the effects of continuous forced convective flow on cell viability, growth, and neurogenesis, the cultures were exposed to fluid-induced shear stresses of magnitude 2.7 x 10(-5) to 4.6 x 10(-3) Pa for up to 12 days. The results were compared with those obtained using static scaffold and static monolayer (2D) control cultures. Cell growth rates were 1.5- to 1.8-fold greater in the bioreactor scaffold cultures relative to the controls without flow. After treatment of the cells with nerve growth factor, development and extension of neurite networks and expression of several neural differentiation markers including beta 3-tubulin, shootin1, and EphA2 were also substantially enhanced in the presence of fluid convection. In the control cultures without fluid flow, cell growth and differentiation were greater in the static scaffold cultures than in the static 2D monolayers. This work demonstrates the significant beneficial effects of features of the physical culture environment, such as hydrodynamic conditions and cell attachment surface geometry, in regulating culture performance. Flow devices capable of supporting long-term cell culture while delivering controlled levels of hydrodynamic shear are a valuable practical tool for promoting nerve tissue development and regeneration in vitro.

关键词： Bioreactor   Oily sludge   Multiphase flow   Degradation kinetics   Parameters optimization  

摘要： In this paper, the degradation process of oily sludge in continuous aeration and stirred bioreactor was studied. The transient kinetics model for degradation of petroleum hydrocarbon by strain NY3 (pseudomonas aeruginosa) was established, by considering both the gas-liquid-solid multiphase flow model and the mass transfer reaction of microorganisms. By optimizing the key parameters such as stirring speed and aeration rate, the degradation rate of oily sludge can be improved. Based on the developed time-based model, the degradation rate of petroleum hydrocarbon can then be predicted. The experimental results showed the effectiveness of the proposed model, which can provide important theoretical support for the parameters optimization of the reactor and the degradation of petroleum pollutants.

关键词： Denitrification   Nitrogen removal   Old landfills   Landfill leachate   Biodegradable organic matter   COD/NO3--N ratio  

摘要： Old landfill leachate can be characterized by high ammonia nitrogen concentrations and limited biodegradable carbon availability. A promising and cost-effective option for ammonia nitrogen removal involves ex situ nitrification and in situ denitrification. This study aimed to investigate the denitrification capacity of old MSW in six landfill bioreactors with very low COD/NO3--N mass ratios that ranged between 0.12 and 3.99 g/g. In particular, this study is novel in that it tested COD/NO3--N mass ratios lower than previous studies. The experiment lasted 83 days. The results showed that denitrification occurred in all bioreactors and even at considerably low concentrations of biodegradable organic matter (BOD5 <= 9 mg O-2/L). In all but one case, when nitrate removal stopped at 55% due to the absence of leachate recirculation, nitrate removal was higher than 95%. The average nitrate removal rates (ANRRs), calculated under significantly different conditions, ranged from 33 to 135 mg NO3--N/L/d. The initial COD concentration and COD/NO3--N ratio did not appear to affect the ANRRs, which were influenced by the initial nitrate concentration and leachate recirculation. The maximum ANRR (135 mg NO3--N/L/d) was measured with the highest initial nitrate concentration (4491 mg NO3--N/L) and the lowest COD/NO3--N mass ratio (0.12 g COD/g NO3--N). The lowest ANRR (33 mg NO3--N/L/d) was calculated for a bioreactor with no leachate recirculation. Sulphate production observed in some bioreactors may suggest that, together with the heterotrophic pathway, autotrophic denitrification contributed to the removal of nitrate, especially in bioreactors with low COD/NO3--N mass ratio. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： AnMBRs   Colloidal particles   EPS   SMP   Fouling   Quorum quenching  

摘要： Quorum quenching (QQ) has been applied as a promising membrane fouling control strategy for anaerobic membrane bioreactors (AnMBRs). Nevertheless, long-term operation of AnMBRs for real domestic wastewater (DWW) treatment needs to be systematically studied to evaluate comprehensive membrane fouling mechanisms and bioprocess performance. In this study, the impact of QQ on membrane fouling was investigated using a quorum quenching AnMBR (QQAnMBR) deploying a bead-entrapped facultative quorum quenching consortium (FQQ) to treat DWW. FQQ was shown to prolong membrane filtration operation by an average of 75%. Reduced proteins (p < 0.005) and carbohydrates (p < 0.005) in the extracellular polymeric substances (EPS) of mixed liquor (ML) were key differentiators that led to lower cake layer (CL) formation. Additionally, reduced biopolymers production (p < 0.05) in EPS improved sludge dewaterability. The findings suggested that QQ could alter fluorescent microbial metabolites of both EPS and CL as unveiled by excitation-emission matrix spectra pattern. Furthermore, colloidal particles (i.e., particles with size larger than 0.45 mm in ML supernatants) production was retarded by QQ, thereafter, also contributed to the reduced CL formation. Pore blockage was slightly increased by QQ, which might be attributed to pore blockage by large (similar to 230 nm) and small organic compounds (similar to 51 nm) in soluble microbial products (SMP). However, QQ had no significant impact on organic concentration of SMP, and QQ was not associated with particle size distribution of biomass. QQ performance was further affirmed through suppressed production of C4-HSL, 3-OXO-C6-HSL, and C6-HSL. The overall AHLs degradability of FQQ was well-maintained even after five membrane service cycles (total operation of 70 d). Moreover, QQ had no compromised impact on treatment performance (i.e., chemical oxygen demand (COD) removal and methane yield). Collectively, this study bridged the knowledge gap to

关键词： Water purification   Submerged membrane bioreactor   Ceramic membrane   Chitosan   Cellulose acetate   Activated carbon   Fouling reduction  

摘要： Purification of water is a critical and inevitable process at present to avoid the harmful effect of polluted water and to meet the need for safe drinking water to millions of people in the world. Several methods of water purification exist, but the combination of adsorption and filtration is found to be paramount in the water treatment process owing to the cost-effectiveness and efficacy of the process. The submerged ceramic membrane bioreactor, which includes both bioreactor and filtration system, is one of the most promising technologies effectively employed for water purification. The main hardship in using the membrane bioreactor system is the phenomena called fouling which decreases and gradually ceases the separation capacity of the membrane. The present work focuses on the reduction of fouling, thus increasing the efficacy of the membrane bioreactor system. The two green composite materials, chitosan beads with activated carbon (CH-AC) and cellulose acetate flakes with activated carbon (CA-AC), were used for the first time for reduction of fouling and found to be an excellent aid in the reduction of fouling. The composites synthesized were subjected to characterization using SEM, TEM and BET to study the physical properties of the composites. The optimum dosage of CH-AC and CA-AC for effective reduction of fouling was analysed. Thus, the present work imparts the novel, efficient, economical and eco-friendly solution for fouling reduction and also a significant improvement in the quality of effluent water.

标准号: T/HW 00018-2020

关键词： Anaerobic treatment   sludge digester   microbial community   dsrB gene   biogas  

摘要： An understanding of microbial communities present in anaerobic bioreactors can strongly facilitate the development of approaches to control undesirable microorganisms, such as sulfate-reducing bacteria (SRB), in the system. In this study, overall microbial communities present in anaerobic bioreactors from seven industrial wastewater treatment plants (including food, pulp and paper industries) were investigated using 16S rRNA gene amplicon sequencing (MiSeq, Illumina). The dominant methanogens identified in the anaerobic bioreactors treating industrial wastewater wereMethanobacteriumandMethanosaeta;Methanospirillumwas a predominant methanogen in the anaerobic sludge digester. Hydrogenotrophic and acetoclastic methanogens were detected at similar relative abundances in the anaerobic covered lagoons treating starch wastewater, whereas hydrogenotrophic methanogens were the predominant methanogens present in the sludge digester. SRB communities were further investigated using dsrB gene clone libraries. The results indicated the presence of SRB, such as unculturedDesulfobulbussp.,Syntrophobacter fumaroxidans,Syntrophorhabdussp. ***027, andDesulfovibrio fructosivarans ***-oxidizing SRB were the predominant SRB in all of the anaerobic bioreactors treating wastewater. In contrast, similar relative abundances of complete and incomplete-oxidizing SRB were observed in the sludge digester. The results of this study can further facilitate the development of SRB-controlling strategies to improve the efficiency of wastewater treatment.

关键词： Bioreactor   disc degeneration   intervertebral disc   organ culture   mechanical loading  

摘要： Low back pain is the leading cause of disability worldwide and in many patients the source of pain can be attributed to pathological changes within the intervertebral disc (IVD). As present treatment options fail to address the underlying biological problem, novel therapies are currently subject to intense research. The physiologic IVD microenvironment features a highly complex interaction of biochemical and mechanical factors influencing cell metabolism and extracellular matrix turnover and is therefore difficult to simulate for research purposes on IVD pathology. The first whole organ culture models were not able to sufficiently replicate human in vivo conditions as mechanical loading, the predominant way of IVD nutrient supply and waste exchange, remained disregarded. To mimic the unique IVD niche more realistically, whole organ culture bioreactors have been developed, allowing for dynamic loading of IVDs and nutrient exchange. Recent advancements on bioreactor systems have facilitated whole organ culture of various IVDs for extended periods. IVD organ culture bioreactors have the potential to bridge the gap between in vitro and in vivo systems and thus may give valuable insights on IVD pathology and/or potential novel treatment approaches if the respective model is adjusted according to a well-defined research question. In this review, we outline the potential of currently utilized IVD bioreactor systems and present suggestions for further developments to more reliably investigate IVD biology and novel treatment approaches.

关键词： MBR   mathematical modelling   calibration   validation   wastewater treatment  

摘要： A mathematical model to simulate the biological processes occurring in a membrane bioreactor (MBR) is presented. The model accounts for different MBR technical features by introducing specific permeability parameters for the applied membrane system. The model considers for the heterotrophic storage process and the formation of soluble microbial products. The introduction of an inhibition coefficient influencing the anoxic kinetics enables the model to simulate the particular operating conditions of the plant, such as a high or low dissolved oxygen concentration in the denitrification tank. The model was applied at the MBR wastewater treatment plant of Vila Nova do Ceira (Portugal) which uses a classic pre-denitrification cycle. Data for calibration and validation were sampled at the same wastewater treatment plant. Calibration was achieved by varying the kinetic parameters of the model to match the simulation results to the experimental data. The values of the kinetic parameters were similar to those found in the literature. The validation was performed by two different methodologies to analyse the model response to diverse operating conditions, and to evaluate the resilience of the MBR. Calibration and validation results were evaluated with mean average error, root mean square error and fractional mean bias as performance indexes. In most cases, these indexes confirmed the high accuracy of the model. Overall, the results of the calibration and validation steps enriched the proposed model by providing an effective biological description of the processes characterizing the MBR. Thus, the model is a reliable tool for the management and designing of MBR.

关键词： Cometabolic biodegradation   p-Nitrophenol   Molecular weight   Microbial structure   Soluble microbial products  

摘要： The system performance, sludge property and microbial community shift were evaluated in a nitrifying sludge (NS) bioreactor for simultaneous treating p-Nitrophenol (PNP) and high ammonia wastewater. After long-term acclimation for 80 days, the removal efficiencies of PNP and NH4+-N reached to 99.9% and 99.5%, respectively. Meanwhile, the effluent PNP gradually decreased from 7.9 to 0.1 mg/L by acclimation of sludge. The particle size of NS increased from 115.2 mu m to 226.3 mu m accompanied by the decreased zeta potential as a self-protection strategy. The presence of PNP exposure altered the effluent soluble microbial products (SMP) fluorescent components and molecular composition. The increase in the relative abundance of Thauera, Nitrospiraceae and Nitrosomonas indicated the nitrification and denitrification capacities of NS increased, which maybe the PNP cometabolic biodegradation effect. Moreover, Ignavibacteria and Aeromonas were responsible as the dominant bacteria for degrading PNP in the nitrifying system.