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关键词： Membrane bioreactor   artificial neural network   sensitivity analysis   permeability   membrane fouling  

摘要： Membrane bioreactor (MBR) has been widely employed for industrial effluent treatment, as its higher efficiency in removing pollutants makes effluent reuse more feasible. However, membrane fouling remains as a limiting factor for its greater diffusion. This work performed a sensitivity analysis study to investigate the effects of analytical and operating variables on membrane permeability. The case study is a MBR treating oil refinery effluents. After the identification and validation of a predictive neural model for permeability, sensitivity analysis methods based on both connection weights and variable disturbances were used to quantify and rank the variables influence. A comprehensive analysis showed that Suspended solids and Days between cleanings exerted greater effects on permeability, whereas sludge filterability and sludge temperature were less significant. In sequence, a specific analysis revealed distinct dynamics in MBR operation given different solids concentrations. For instance, from higher solids concentrations, among all the evaluated parameters, only COD presented low significance to the permeability. This evidence suggests that permeability is more susceptible to variations when operating with higher concentrations of Suspended solids. The global result of this study contributes to more efficient MBR operations since distinct relations with permeability imply different effects on membrane fouling.

关键词： Multi soil layering treatment (MSL)   digested swine wastewater (ADSW)   biosurfactant   ammonia removal   Pseudomonas frederiksbergensis  

摘要： A biosurfactant was harvested from anaerobically digested swine wastewater (ADSW) and employed to enhance ammonia removal in a comparative study using two multiple soil layer bioreactors (MSLs). Results showed that toxicity of the biosurfactant to microorganisms was negligible within the experimental concentration range. Optimal dose of the biosurfactant in MSLs to remove ammonia from ADSW was 0.1 CMC (Critical Micelle Concentration) under different hydraulic loading rate (HLR). For instance, when the HLR was adjusted as 80, 120, 160, and 200 L/(m(2)center dot d), the average ammonia removal efficiency in MSL without biosurfactant addition was appeared as 85.6%, 89.2%, 85.2% and 84.1%, respectively, after enhanced by 0.1 CMC of the biosurfactant under the same condition, the average ammonia removal efficiency was improved to 90.1%, 92.6%, 90.3%, and 87.4%, respectively. Inlet ammonia concentration obviously affected ammonia removal, the average ammonia removal efficiency increased rapidly to 93.0% and 89.1% in MSLs (with and without biosurfactant) along with the increasing inlet ammonia concentration from 800 mg/L to 1000 mg/L, and subsequently dropped to 78.9% and 79.7% with a further increase in the inlet ammonia concentration to 1400 mg/L. These results showed that the biosurfactant effectively enhanced ammonia removal by using MSL. Thus, the construction of MSL represented an effective means of reducing ammonia pollution caused by swine wastewater, and the use of biosurfactant was assuredly a promising and feasible option for enhancing the biological activity in MSL bioreactor.

关键词： Foaming   Soluble microbial products   Membrane bioreactor   Membrane fouling   Filamentous bacteria  

摘要： Though sludge foaming often occurs and thus causes serious membrane fouling in membrane bioreactors (MBRs), the fouling mechanisms related with the foaming phenomenon have not been well addressed, hindering better understanding and solving foaming problem. In this work, it was interestingly found that, the foulants during the foaming period possessed extremely high specific filtration resistance (SFR) (over 10(16) m kg(-1)) and strong adhesion ability to membrane surface. Chemical characterization showed that the proteins (178.57 mg/L) and polysaccharides (209.21 mg/L) in the foaming sample were about 6.4 times and 5.4 times of those in the supernatant sample, suggesting existence of a mechanism permitting continuous production of these foulants in the MBR during the foaming period. It was revealed that the fouling caused by foams was associated with gel layer filtration process, and the extremely high SFR can be interpreted by chemical potential change in the gel filtration process depicted in Flory-Huggins theory. Meanwhile, analyses by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed that the strong adhesion ability stemmed from the high interaction energy between the foaming foulants and membrane surface. In addition, 16S rDNA gene sequencing identified that the abundance of the foaming related bacteria species in the sludge suspension during the foaming period was more than 10 times of that during the non-foaming period. This study offered new mechanism insights into foaming fouling in MBRs. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： AnMBR   Food waste   High-solid   RIS model   Membrane fouling behavior  

摘要： A high-solid anaerobic membrane bioreactor (AnMBR) treating food waste was continuously operated to investigate AnMBR performance and membrane fouling behavior. The optimal methane yield of 0.57 +/- 0.08 L-CH4/g-VSin and organic loading rate (OLR) of 6.00 +/- 0.59 g-VS/L/d indicated that a high-rate methane fermentation of food waste was achieved by the AnMBR. The resistance-in-series (RIS) model was applied to delineate the resistances of different fouling fractions and elucidate fouling behavior under different filtration modes. The results showed that organic pore blocking was the dominant fouling at the low filtration to relaxation (F/R) ratio, accounting for 60% of the total resistance. By contrast, the cake layer governed the fouling when the F/R ratio became larger, accounting for 54% of the total resistance. To better understand membrane fouling behavior, the characteristics of cake sludge were investigated and compared with those of bulk sludge. Dissolved organic matter (DOM) analysis revealed that soluble microbial by-products played a comparably significant role as aromatic protein in membrane fouling in the high-solid AnMBR. This work provided a deep understanding of the membrane fouling behavior of a high-solid AnMBR in treating food waste and proposed the most appropriate membrane cleaning methods under different filtration modes, which is expected to contribute to the design, operation and further application of the high-solid AnMBR.

关键词： Packed-bed bioreactor   Perfusion culture   Galactosylated microfibrous scaffolds   Hepatocyte growth   Functionality maintenance  

摘要： Bioartificial liver (BAL) comprising a functional bioreactor represents a promising treatment, bridging patients with acute liver failure (ALF) to liver transplantation. In this research, a packed-bed (PB) bioreactor by utilizing galactosylated poly(ethylene terephthalate) microfibrous carrier (PET-Gal) was fabricated and evaluated in vitro. Human induced hepatocytes (hiHeps) were dynamically seeded into a PET-Gal loaded bioreactor and cultured for 10 days. During perfusion culture, the effects of bioreactor scaffold on hepatocyte seeding, growth and functionality (albumin secretion and urea production) were determined, compared with that of control with nonmodified PET carrier. Afterwards, drug metabolism and detoxification ability of hiHeps were measured. Results demonstrated that the seeding rate and proliferation fold within PET-Gal loaded bioreactor were significantly higher than that of control, resulting in a cell density of (8.17 +/- 0.52) x 10(7) cells/cm(3). In contrast to flattened morphology observed in the control, hiHeps cultured in PET-Gal based bioreactor displayed as three-dimensional (3D) cell aggregates with close cell-matrix and cell-cell interactions and high cell viability, leading to higher albumin secretion and urea production. Besides, there were high levels of phase I drug metabolism and ammonia elimination for PET-Gal cultured cells. Therefore, the PET-Gal based PB bioreactor fabricated herein supports high-density hepatocyte growth and meanwhile preserves hepatic functionality, showing great potential in BAL systems application.

关键词： WSe2   Few-layered   Chlorella-derived carbon   Dichalcogenides   Sodium/potassium-ion batteries  

摘要： Sodium/potassium-ion batteries (SIBs/PlBs) with high electrochemical performance are promising but there still remain daunting challenges to explore an anode material with appealing cycling stability and rate capability. In addition, the utilization of waste biomass arouses tremendous researches in energy storage applications. Herein, we elaborately coupling ultrathin few-layered WSe2 nanosheets with N, P-doped biochar by utilizing waste chlorella as adsorbent and reactor. It displays a prominent long-term cycling property (265 mAh g(-1) at 1 Ag-1 up to 1500 cycles) in SIBs, which is the best long-cycle performance ever reported for WSe2 . Paired with Na3V2(PO4)(3) cathode, full SIBs also exhibit superior capacity of 210 mAh g(-1) at 0.5 A g(-1) for 120 cycles. Notably, we also report WSe2-based anode material in PIBs, which delivers a high capacity of 333 mAh g(-1) at 0.1 A g(-1) for 100 cycles and superior cycling lifespan (155 mAh g(-1) at 1 Ag-1 up to 5300 cycles) as well as excellent rate properties. Additionally, the mechanism of the repeated process of sodiation/desodiation is revealed, by the deep characterization, such as ex-situ XRD/Raman, galvanostatic intermittent titration technique and CV measurements. (C) 2020 Elsevier Inc. All rights reserved.

关键词： Algal-sludge membrane bioreactor   Extracellular polymeric substances   Fouling   Microbial community  

摘要： In this study, a coupled system of algal-sludge and membrane bioreactor (AS-MBR) was established for fouling control, and meanwhile the performance of wastewater treatment was enhanced. Results indicated that the AS-MBR increased the COD, NH4+-N, TN and PO43- -P removal efficiencies from 91.7% to 95.9%, 90.8%-96.9%, 22.0% to 34.3% and 18.4%-32.6%, respectively. Further analysis suggested that in the AS-MBR, the total specific oxygen utilization rate (SOUR), the SOUR of ammonia oxidizing bacteria and the SOUR of nitrite oxidizing bacteria were 26.6%, 58.5% and 52.4% higher than the control, respectively, indicating the improvement of microbial activities in AS-MBR. Additionally, the membrane fouling rates in the AS-MBR were 52.6% and 32.2% lower than the control in the slow and rapid fouling processes, respectively. A further mechanism investigation demonstrated that the concentrations of extracellular polymeric substance (EPS) were decreased by 19.8% and 22.1% in the mixed liquid and the fouling layer, respectively, after the inoculation of algae, which was expected to have a positive effect on the higher permeability and longer operation cycle of the membrane in the AS-MBR. More regular floc morphology was observed for the fouling layer on the membrane of AS-MBR, with the polysaccharides and proteins forming large clusters and channels in the fouling layer that likely decreased the filtration resistance. Consequently, high-throughput sequencing analysis revealed that the microbial community in the AS-MBR had higher abundances of bacteria and algae related to nutrients and organic matters degradation, which was beneficial for the improvement of wastewater treatment and alleviation of membrane fouling. (C) 2020 Published by Elsevier Ltd.