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关键词： Miniaturized bubble column (MBC)   Gas hold-up   Bubble size distribution   Hydrodynamic  

摘要： Miniaturized bubble columns (MBCs) have different hydrodynamics in comparison with the larger ones, but there is a lack of scientific data on MBCs. Hence, in this study, the effect of gas hold-up, flow regimes, bubble size distribution on volumetric oxygen mass transfer coefficient at different pore size spargers and gas flow rates in MBCs in the presence and absence of microorganisms were investigated. It was found that flow regime transition occurred around low gas flow rates of 1.18 and 0.85cm/s for small (16-40 mu m) and large (40-100 mu m) pore size spargers, respectively. Gas hold-up and K(L)a in MBC with small size sparger were higher than those with larger one, with an increasing effect in the presence of microorganisms. A comparison revealed that the wall effect on the flow regime and gas hold-up in MBCs was greater than bench-scale bubble columns. The K(L)a values significantly increased up to tenfold using small pore size sparger. In the MBC and stirred tank bioreactors, the maximum obtained cell concentrations were OD600 of 41.5 and 43.0, respectively. Furthermore, it was shown that in MBCs, higher K(L)a and lower turbulency could be achieved at the end of bubbly flow regime.

关键词： Bioenergy recovery   Co-substrate fermentation   Coffee processing wastewater   Waste activated sludge   Anaerobic membrane bioreactor  

摘要： A large amount of wastewater is generated in the processing of coffee from fruit to cup. Thermophilic high-solids co-digestion of coffee processing wastewater (CPW) and waste activated sludge (WAS) has been succeeded by anaerobic membrane bioreactor (AnMBR). Chemical oxygen demand (COD) removal efficiencies of 92 +/- 3% with an average methane yield of 0.28 LCH4/gCOD(removed) were achieved at a high solids content of 50 g/L in the AnMBR. The optimal digestion performance of 82.4% removal COD conversion to CH4 was achieved at hydraulic retention time (HRT) 10 d. Energy balance analysis revealed AnMBR has succeeded in energy positive at all the HRTs. The net energy potential (NEP) was determined to average 2.12-2.82 kJ/gCOD, amongst which the maximum NEP was achieved at HRT 15 d. These results indicated the high-solids co-digestion by AnMBR is a promising approach to maximize the bioenergy conversion from the co-substrate of CPW and WAS.

关键词： Acidithiobacillus   acidophiles   domestication   adaptation   consortia   targeted metagenomics   metagenome derived assembly  

摘要： Extreme acidophiles play central roles in the geochemical cycling of diverse elements in low pH environments. This has been harnessed in biotechnologies such as biomining, where microorganisms facilitate the recovery of economically important metals such as gold. By generating both extreme acidity and a chemical oxidant (ferric iron) many species of prokaryotes that thrive in low pH environments not only catalyze mineral dissolution but also trigger both community and individual level adaptive changes. These changes vary in extent and direction depending on the ore mineralogy, water availability and local climate. The use of indigenous versus introduced microbial consortia in biomining practices is still a matter of debate. Yet, indigenous microbial consortia colonizing sulfidic ores that have been domesticated, i.e., selected for their ability to survive under specific polyextreme conditions, are claimed to outperform un-adapted foreign consortia. Despite this, little is known on the domestication of acidic microbial communities and the changes elicited in their members. In this study, high resolution targeted metagenomic techniques were used to analyze the changes occurring in the community structure of local microbial consortia acclimated to growing under extreme acidic conditions and adapted to endure the conditions imposed by the target mineral during biooxidation of a gold concentrate in an airlift reactor over a period of 2 years. The results indicated that operative conditions evolving through biooxidation of the mineral concentrate exerted strong selective pressures that, early on, purge biodiversity in favor of a few Acidithiobacillus spp. over other iron oxidizing acidophiles. Metagenomic analysis of the domesticated consortium present at the end of the adaptation experiment enabled reconstruction of the RVS1 -MAG, a novel representative of Acidithiobacillus ferrooxidans from the Andacollo gold mineral district. Comparative genomic analysis performed with

关键词： Copper resistant   Electroplating wastewater   MBR   Ochrobactrum   Protein  

摘要： It is necessary to study the mechanism of resistance to heavy metals in microbiological processes. In this study, Ochrobactrum MT180101 was used as the microbial source of an membrane bioreactor to investigate its degradation efficiency for electroplating wastewater and the copper-resistant mechanism. Meanwhile, excitation emission matrix-parallel factor, scanning electron microscope, atomic force microscope, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and proteome analyses were applied to explain the comprehensive mechanism of the Ochrobactrum MT180101 resisting heavy metal toxicity. The results indicated that the Ochrobactrum MT180101 resisted heavy metal toxicity with the following pathways: i) binding metal cations on cell wall surfaces, fi) generating microbial products such as protein to chelate and stabilize the metal cations, iii) bio-transporting heavy metals from the intramembrane to the outer membrane by means of intracellular transport, and iv) reducing heavy metals through enzyme-mediated biotransformation. The results ensure that Ochrobactrum MT180101 was a copper-resistant bacterium that can be used in the pretreatment or deep treatment of electroplating wastewater.

关键词： Alternanthera sessilis   bioremediation   domestic sewage treatment   SHEFROL (R)  

摘要： In a first-ever report on this subject, it is shown that a common amphibious plant joyweed (Alternanthera sessilis) can be used in rapid and efficient treatment of biodegradable wastewaters, typified by domestic sewage. The plant was effective when used indoors under artificial lighting, as well as outdoors. It enabled treatment of sewage, varying widely in strength (from 300 mg/L to 1800 mg/L in chemical oxygen demand), to the extent of 78.9-83.9%. It was also able to remove biological oxygen demand, suspended solids, phosphorous, nitrogen, and the heavy metal copper to the extent of 87%, 93%, 45%, and 43%, respectively. Over 99% of total coliforms, faecal coliforms, and faecal streptococci were also removed. The treatment was very swiftly achieved, at a hydraulic retention time of just 6 h, in the "sheet flow root level" (SHEFROL (R)) bioreactor developed earlier by us and of which a patent claim has been registered. The findings indicate that A. sessilis has the potential to affect primary, secondary, and tertiary treatment of domestic sewage along with significant pathogen removal in a single process step when used in SHEFROL (R) bioreactors.

关键词： Aeration   MBR   Flat sheet membrane   CFD   Wall shear stress  

摘要： The aeration rates in the membrane bioreactor is an important management-point that can reduce the maintenance costs and the membrane fouling by changing the reactor flow patterns and the shear stresses in the vicinity of the membrane surface. In the present study, COMSOL, a finite element analysis (FEA) program was used to analyze the velocity distribution, the shear stresses between the membranes and the baffle, and the shear stresses between the membranes in a system in which two flat membrane modules are installed within a bench-scale submerged flat membrane reactor for aeration at the bottom. The diameters and velocities of the bubbles that develop the velocities within the reactor were measured through image analysis and the results were applied to numerical analysis. The shear stresses between the membrane and the baffle showed relatively high values ranging from 0 Pa to 0.1 Pa at the 1/3 point from the bottom of the membrane module and showed high shear stresses in some of the top part of the membrane module too. However, the shear stresses between the membranes were formed to be lower than the shear stresses between the membranes and the baffle. This is disadvantageous to the reduction of fouling on the surfaces of the membranes where permeation fluxes exist. (C) 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

关键词： Separation science   Energy   Fluxes   Filtration   Membranes  

摘要： The limitation of the membrane bioreactors treating municipal wastewater to manage peak flux conditions have often led to conservative design, which negatively impacts on capital and operating costs. This paper discusses the effectiveness of an alternative operation mode, tested under various peaking conditions and different experimental unit sizes. In this mode, the initiation of the backwashing is regulated by a transmembrane set-point value, which determines the degree of membrane fouling permitted. At low peaking factor, results showed a suitable fouling control, comparable to that obtained with the conventional temporized mode, but with higher process productivity (14-16%). During the long-term tests, this control mode demonstrated its capability to achieve a sustainable operation at high peaking fluxes (J(p) = 70 L/h m(2)) and peak periods of 6 h.

关键词： Wave bioreactor   Computation Fluid Dynamics (CFD)   Volume of fluid (VOF)   Hydrodynamic   Resonance  

摘要： Culture of mammalian or human cells in Wave bioreactor is widely used for cell expansion or for biologics manufacturing. Wave bioreactor cultivation of sensitive cells such as stem cells, immune cells or anchorage-dependent cells, is recognized as an attractive option for culture in suspension or adherently on microcarriers. A systematic optimization of the mixing, oxygen transfer rate and shear stress, most favorable for the cells requires a deep understanding of the hydrodynamics inside the Wave bioreactor bag, i.e. cellbag. Numerical simulation by Computation Fluid Dynamics (CFD), is considered as an inexpensive and efficient tool for predicting the fluid behavior in many fields. In the present study, we perform numerical simulations by Ansys-FLUENT to characterize the flow conditions in a 10 L cellbag. The numerical simulations are carried out to investigate the fluid structures for nine different operating conditions of rocking speed and angle. The influence of these operating parameters on the mixing and the shear stress induced by the liquid motion are studied. We find that the mixing and shear stress increase with the cellbag angle from 4 degrees to 7 degrees but that increasing rocking speeds are not systematically associated with increasing mixing and shear stress. It is concluded that a resonance phenomenon is responsible for the fact that the lowest studied rocking speed, 15 rpm, generates the highest fluid velocity, mixing and shear stress compared to the higher speeds of 22 and 30 rpm. (C) 2018 The Authors. Published by Elsevier Ltd.

关键词： baker's yeast   fouling   landfill leachate   membrane bioreactor   recalcitrant compounds  

摘要： In this study, commercial baker's yeast (Saccharomyces cerevisiae) was employed as a novel inoculum for a membrane bioreactor (MBRy). It was applied to landfill leachate (LFL) treatment to remove recalcitrant organic compounds as well as for the assimilation of recalcitrant compounds, since yeasts have a high ability to break such compounds down. The MBR was inoculated with 10 g L-1 of commercial baker's yeast and was operated at a hydraulic retention time of 48 h and pH of 3.5. The specific air demand based on the membrane area (SADm) was maintained at 0.6 m(3) h(-1) m(-2). The MBRy achieved chemical oxygen demand (COD), color, NH3, and humic substances removal of 68, 79, 68, and 50%, respectively. Furthermore, the MBRy showed lower fouling potential, which can be attributed to the low extracellular polymeric substances production, as the formation of a cake layer was the major mechanism of membrane fouling. The work demonstrated that novel MBR is a promising technology for treating recalcitrant landfill leachate.

关键词： Bioffim/activated sludge membrane bioreactor   Hydrolyzed polyacrylamide   Biodegradation   Membrane fouling and cleaning   Extracelluar polymeric substances   Microbial function  

摘要： This study deeply investigated the overall performance, nitrogen transformation, membrane fouling and cleaning, extracelluar polymeric substances (EPS) and microbial function in a biofilm/activated sludge membrane bioreactor (BF-AS-MBR) for treating actual hydrolyzed polyacrylamide (HPAM)-containing oilfield wastewater. The removal efficiencies of HPAM, COD, viscosity, TOC and TN achieved 97.5%, 98.5%, 74.8%, 98.5% and 96.2%, respectively. Nitrogen transformation revealed nitratation became the main reaction in the process of aerobic amide group bioconversion and surpassed denitrification, nitritation and ammonification in BF-AS-MBR system. Scanning electron microscopy (SEM) showed the morphology of new, contaminated and washed membranes. The membrane permeability was recovered to 92% and 87% after the first and second cleaning, respectively. Tryptophan protein-like, aromatic protein-like, simple aromatic protein-like and fulvic acid-like organics presented in loosely bound EPS (LB-EPS) of sludge. Polysaccharide-like and tyrosine protein-like organics presented in tightly bound EPS (TB-EPS) of sludge. Tryptophan protein-like organics existed solely in TB-EPS of cake sludge, and played an essential role in membrane fouling. HPAM-degrading microorganisms and nitrifiers were deeply discussed to explore its correlations with HPAM removal, EPS and membrane fouling. The viscosities of HPAM solution re-prepared with different effluent were compared, and the order was: supernatant after biodegradation < effluent after membrane filtration approximate to clean water. This study offered a technical support and theoretical foundation for treating actual HPAM-containing oilfield wastewater, and improved water reuse.