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排序方式: 共有109条查询结果,搜索用时 15 毫秒
51.
Biofouling in spiral wound membrane systems: Three-dimensional CFD model based evaluation of experimental data 总被引:1,自引:0,他引:1
J.S. Vrouwenvelder C. Picioreanu J.C. Kruithof M.C.M. van Loosdrecht 《Journal of membrane science》2010,346(1):71-85
A three-dimensional (3D) computational model describing fluid dynamics and biofouling of feed channels of spiral wound reverse osmosis and nanofiltration membrane systems was developed based on results from practice and experimental studies. In the model simulations the same feed spacer geometry as applied in practice and the experimental studies was used. The 3D mathematical model showed the same trends for (i) feed channel pressure drop, (ii) biomass accumulation, (iii) velocity distribution profile, resulting in regions of low and high liquid flow velocity also named channeling. The numerical model predicted a dominant biomass growth on the feed spacer, consistent with direct in situ observations on biofouling of spiral wound membrane modules and monitors using Magnetic Resonance Imaging (MRI). The model confirms experimental results that feed spacer fouling is more important than membrane fouling. The paper shows that mathematical modeling techniques have evolved to a stage that they can be used hand-in-hand with experiments to understand the processes involved in membrane fouling. 相似文献
52.
《印度化学会志》2021,98(6):100083
Microbe-influenced material damage is the result of contributions from different types of microbes and their physiological activity. This fact makes the understanding of microbial corrosion very difficult. Another interesting fact is that the biofilms formed by the bacterial action inhibit or promote the biocorrosion of metals depending on the local environmental conditions. A slight change in the living conditions such as nutrient composition, oxygen concentration, light, and temperature can alter the behavior of the microbial population from non-corrosive to aggressively corroding. The metabolic activity of certain bacterial strains and the biofilm produced by them helps to control biocorrosion. The use of bioengineered bacterial strains has also been found to offer promising results in biocorrosion control. The most widely practiced biocorrosion mitigation practices include the application of protective coatings and the use of biocides. Recently, incorporating the corrosion protective functional layers on the metal surface via polymerization reactions has gained importance. This review provides information on the type of microorganisms causing the biocorrosion, their mechanism of action, and the factors that influence the corrosion rate. The development and involvement of the biofilm in corrosion have also been discussed in detail. The techniques available for the control of biocorrosion have also been explored. 相似文献
53.
Monitoring the effect of chemicals on biological communities. The biofilm as an interface 总被引:1,自引:0,他引:1
Sabater S Guasch H Ricart M Romaní A Vidal G Klünder C Schmitt-Jansen M 《Analytical and bioanalytical chemistry》2007,387(4):1425-1434
Biofilms can be regarded as early warning systems for detection of the effects of toxicants on aquatic systems, because they
have been successfully used for detection of other environmental stressors (e.g. pH, salinity, organic pollution). A variety
of methods is used for detection of the effects of toxicants by use of biofilms. The methods range from structurally-based
to functionally-based, and from in vitro-based to systemic approaches. Physiological approaches may be appropriate for detection
of acute effects. Among these methods, photosynthesis is more related to the effect of toxicants affecting algal communities,
directly or indirectly, and extracellular enzyme activity is less specific. Selecting one or the other may depend on the suspected
direct effect of the toxicant. Integrated studies have revealed the relevance of toxicants to top-down or bottom-up regulation
of the biofilm community. Persistent or chronic effects should affect other biofilm indicators, for example growth or biomass-related
factors (e.g. chlorophyll), or community composition. Among these, community composition might better reflect the effects
of the toxicant(s), because this may cause a shift from a sensitive to a progressively tolerant community. Community composition-based
approaches do not usually adequately reflect cause–effect relationships and require complementary analysis of properties affected
in the short-term, for example physiological properties. The current array of methods available must be wisely combined to
disentangle the effects of chemicals on biofilms, and whether these effects are transient or persistent, to successfully translate
the chemical action of toxicants into the effect they might have on the river ecosystem. 相似文献
54.
自然水体生物膜胞外蛋白质吸附铅和镉的研究 总被引:6,自引:0,他引:6
本文通过长春市南湖水中生物膜优势菌种胞外蛋白吸附Pb2+和Cd2+的实验, 研究了胞外蛋白吸附重金属的规律. 相似文献
55.
Biofilm formation by foodborne pathogens on food processing surfaces has contributed to numerous disease outbreaks and food recalls. We evaluated the following strategies for elimination of mature biofilm formed by Staphylococcus aureus and Salmonella spp. on stainless steel surfaces: acidic electrolyzed water (AEW), ozone water (OW), or ultrasound (40 kHz) alone, and combinations of ultrasound and disinfectants. The dynamics of elimination by combinations were determined using the Weibull and biphasic models. Treatment with AEW alone reduced the number of biofilm cells by approximately 3.0 log cfu/cm2, whereas less than 0.8 log cfu/cm2 of cells reduction was observed in biofilm exposed to OW or ultrasound alone, even with treatment for 20 min. The combination of AEW and ultrasound produced an obvious synergistic effect on biofilm reduction, achieving approximately 4.8 log cfu/cm2 reduction in Salmonella spp. biofilm. Interestingly, the biphasic model was a better fit than the Weibull model for the elimination process of mature biofilm formed by both pathogens and subjected to a combination of ultrasound and AEW, as determined by smaller values of the statistical parameters RMSE and AIC, although both models could evaluate the dynamic processes. Our findings indicated that a combination of ultrasound and AEW could effectively reduce the biofilm formed by pathogens on food contact surfaces, and that the biphasic model could predict the number of residual cells after biofilm exposure to this intervention approach. 相似文献
56.
Ultrasonic treatment has been shown to have a favorable effect on the regeneration of spent biological activated carbon (BAC) from drinking water treatment plants. In this study, the use of ultrasound as a regeneration method had a significant effect on the recovery of spent BAC after 7.5 years of use; it effectively increased the iodine value from 300 mg/g to 600 mg/g and restored the specific surface area and pore volume of BAC. Ultrasound effectively changed the structure of the biofilm inside and on the surfaces of BAC particles, on the basis of confocal laser scanning microscopy (CLSM) images. The thickness of the surface biofilm attached to BAC reached an “active” level (about 100 μm) at the regeneration frequency of 40 kHz. The dehydrogenase activity significantly improved from 4.50 mg TF/g BAC to 9.13 mg TF/g BAC, and the content of adenosine-triphosphate (ATP) in regenerated BAC was maintained at a high level (2.501 × 10−6g ATP/g BAC), thus allowing the development of microbial growth. The production of soluble microbial products (SMPs) from regenerated BAC decreased during the reuse process. The removal efficiency of DOC, CODMn, NH4+ and NO3– control increased by approximately 78%, 71%, 50% and 20%, respectively. 相似文献
57.
Af?in Y. ?etinkaya Emre O?uz K?ro?lu Neslihan Manav Demir Derya Y?lmaz Baysoy Bestamin ?zkaya Mehmet ?akmak?? 《催化学报》2015,(7):1068-1076
Electricity production from brewery wastewater using dual-chamber microbial fuel cells (MFCs) with a tin-coated copper mesh in the anode was investigated by changing the hydraulic retention time (HRT). The MFCs were fed with wastewater samples from the inlet (inflow, MFC-1) and outlet (outflow, MFC-2) of an anaerobic digester of a brewery wastewater treatment plant. Both chemical oxygen demand removal and current density were improved by decreasing HRT. The best MFC performance was with an HRT of 0.5 d. The maximum power densities of 8.001 and 1.843 μW/cm2 were obtained from reactors MFC-1 and MFC-2, respectively. Microbial diversity at different condi-tions was studied using PCR-DGGE profiling of 16S rRNA fragments of the microorganisms from the biofilm on the anode electrode. The MFC reactor had mainlyGeobacter,Shewanella, andClostridium species, and some bacteria were easily washed out at lower HRTs. The fouling characteristics of the MFC Nafion membrane and the resulting degradation of MFC performance were examined. The ion exchange capacity, conductivity, and diffusivity of the membrane decreased significantly after foul-ing. The morphology of the Nafion membrane and MFC degradation were studied using scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectroscopy. 相似文献
58.
A steady-state mathematical model has been developed to predict axial-concentration profiles of a pollutant in an extractive-membrane bioreactor (EMB). Typically, the previous models describe the pollutant concentration profiles in the membrane-attached biofilms in a direction perpendicular to the membrane. In contrast, the model presented in this work describes not only the radial profiles, but also the axial profiles along the membrane length. Biofilms of Xanthobacter autotrophicus GJ10 were grown on the surface of silicone rubber tubes. A diffusion-reaction model was employed to describe the diffusion and reaction in the biofilm in the radial direction. Membrane tubes were modelled as a series of mixed tanks to allow the prediction of axial concentrations. The model predictions were verified by experimental data from a range of operating conditions. These included different dissolved oxygen concentrations in biomedium and different wastewater flowrates. Finally, the rate-limiting step in the reactor was determined to be the mass-transfer resistance of the pollutant in the biofilm. 相似文献
59.
Recent decades have revealed that many bacterial species are capable of communicating with each other, and this observation
has been largely responsible for a paradigm shift in microbiology. Whereas it was previously believed that bacteria lived
as individual cells, it is now acknowledged that bacteria preferentially live in communities in the form of primitive organisms
in which the behavior of individual cells is coordinated by cell–cell communication, known as quorum sensing (QS). Bacteria
use QS for regulation of the processes involved in their interaction with each other, their environment, and, particularly,
higher organisms We have focused on Pseudomonas aeruginosa, an opportunistic pathogen producing more than 30 QS-regulated virulence factors. P. aeruginosa causes several types of nosocomial infection, and lung infection in cystic fibrosis (CF) patients. We review the role of
QS in the protective mechanisms of P. aeruginosa and show how disruption of the QS can be used as an approach to control this cunning aggressor. 相似文献
60.
Quantitative and morphological analysis of biofilm formation on self-assembled monolayers 总被引:1,自引:0,他引:1
Ploux L Beckendorff S Nardin M Neunlist S 《Colloids and surfaces. B, Biointerfaces》2007,57(2):174-181
In spite of intensive studies over the past two decades, the influence of surface properties on bacterial adhesion and biofilm formation remains unclear, particularly on late steps. In order to contribute to the elucidation of this point, we compared the impact of two different substrates on the formation of bacterial biofilm, by analysing bacterial amount and biofilm structure on hydrophilic and hydrophobic surfaces. The surfaces were constituted by NH2- and CH3-terminated self-assembled monolayers (SAMs) on silicon wafers, allowing to consider only the surface chemistry influence because wafers low roughness. A strain of Escherichia coli K12, able to produce biofilm on abiotic surfaces, was grown with culture durations varying from 4 h to 336 h on both types of substrates. The amount of adhered bacteria was determined after detachment by both photometry at 630 nm and direct counting under light microscope, while the spatial distribution of adhered bacteria was observed by fluorescence microscopy. A general view of our results suggests a little influence of the surface chemistry on adherent bacteria amount, but a clear impact on dynamics of biofilm growth as well as on biofilm structure. This work points out how surface chemistry of substrates can influence the bacterial adhesion and the biofilm formation. 相似文献