课程文献中心 更多>>

关键词： Trichloroethylene   Biodegradation   Airlift bioreactor   Carbon dioxide   Rhodococcus opacus   Artificial neural network  

摘要： This study evaluated the biological removal of trichloroethylene (TCE) by Rhodococcus opacus using airlift bioreactor under continuous operation mode. The effect of inlet TCE concentration in the range 0.12 -2.34 g m(-3) on TCE removal has studied for 55 days. During the continuous bioreactor operation, a maximum of 96% TCE removal was obtained for low inlet TCE concentration, whereas the highest elimination capacity was 151.2 g m(-3) h(-1) for the TCE loading rate of 175.0 g m(-3) h(-1). The carbon dioxide (CO2) concentration profile from the airlift bioreactor revealed that the degraded TCE has primarily converted to CO2 with a fraction of organic carbon utilized for bacterial growth. The artificial neural network (ANN) based model was able to successfully predict the performance of the bioreactor system using the Levenberg-Marquardt (LM) back propagation algorithm, and optimized biological topology is 3:12:1. The prediction accuracy of the model was high as the experimental data were in good agreement (R-2 = 0.9923) with the ANN predicted data. Overall, from the bioreactor experiments and its ANN modeling, the potential strength of R. opacus in TCE biodegradation is proved. (C) 2020 Elsevier Ltd. All rights reserved.

摘要： 58

摘要： 295

摘要： 421

关键词： fluid flow modeling   hemoglobin-based oxygen carrier   hollow fiber bioreactor   polymerized human hemoglobin   red blood cell substitute  

摘要： Hepatic hollow fiber (HF) bioreactors can be used to provide temporary support to patients experiencing liver failure. Before being connected to the patient's circulation, cells in the bioreactor must be exposed to a range of physiological O-2 concentrations as observed in the liver sinusoid to ensure proper performance. This zonation in cellular oxygenation promotes differences in hepatocyte phenotype and may better approximate the performance of a real liver within the bioreactor. Polymerized human hemoglobin (PolyhHb) locked in the tense quaternary state (T-state) has the potential to both supply and regulate O-2 transport to cultured hepatocytes in the bioreactor due to its low O-2 affinity. In this study, T-state PolyhHb production and purification processes were optimized to minimize the concentration of low-molecular-weight PolyhHb species in solution. Deconvolution of size-exclusion chromatography spectra was performed to calculate the distribution of polymeric Hb species in the final product. Fluid flow and mass transport within a single fiber of a hepatic HF bioreactor was computationally modeled with finite element methods to simulate the effects of employing T-state PolyhHb to facilitate O-2 transport in a hepatic bioreactor system. Optimal bioreactor performance was defined as having a combined hypoxic and hyperoxic volume fraction in the extracapillary space of less than 0.05 where multiple zones were observed. The Damkohler number and Sherwood number had strong inverse relationships at each cell density and fiber thickness combination. These results suggest that targeting a specific Damkohler number may be beneficial for optimal hepatic HF bioreactor operation.

关键词： Membrane bioreactor (MBR)   Fouling   Flat-sheet membrane   Membrane module   Membrane material   Extracellular polymeric substance (EPS)  

摘要： The relationship between fouling development in a continuous laboratory-scale membrane reactor (MBR/Lab) and the membrane material was investigated using flat-sheet membranes prepared from four materials (polyvinylidene difluoride (PVDF), polyethersulfone, chlorinated polyvinyl chloride, and polytetrafluoroethylene). Further, the characteristics of the suspension liquid in MBR/Lab were compared with those of samples from actual wastewater treatment plants. It was found that, in addition to the membrane material's own characteristics, the structural vulnerability of the membranes had a determining effect on fouling development. The PVDF membrane showed the highest transmembrane pressure during MBR operation and its surface experienced significant damage because of the shearing stress caused by aeration, resulting in the penetration of the membrane by the fouling compounds. The characteristics of suspension liquid in MBR/Lab were almost similar to those in the MBR at a night-soil treatment plant and the aeration tank of a sewage treatment plant.

摘要： 313

摘要： 49

关键词： Multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR)   Acidic 7-amino cephalosporanic acid (7-ACA) wastewater   Adsorption   Enzymatic activity  

摘要： In this study, a lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) was used for treating acidic 7-amino cephalosporanic acid (7-ACA) wastewater under different pHs (3.54-6.20) and hydraulic retention time (HRT) (48 h, 36 h, 24 h and 16 h). During about 200 days operation, under HRT of 48 h and pH condition about 6.0, the optimum average COD and BOD5 removal rates were reach to 84.4 +/- 2.1% and 94.9 +/- 0.8%, and the highest 7-ACA removal rate also observed as 77.6%. Biodegradation, membrane rejection, hydrolysis and sludge adsorption were the four main pathways of 7-ACA removal. With the increase of pH, biodegradation, membrane rejection and hydrolysis had significant positive impacts on 7-ACA removal, while adsorption had a negative impact. Moreover, mathematical models for 7-ACA removal rate and pH were calculated to guide the operation of Mt-ALMBR. Biodegradation was the main pathway to remove 7-ACA when pH was > 4.17.

摘要： 422