Despite being the subject of peer reviewed research since the mid-1980s, the conservative nature of the wastewater treatment industry means that the commercial application of membrane aerated biofilm reactors has not realized the potential that the published research demonstrates. The early research demonstrated the ability of membrane aerated biofilm reactors to achieve good levels of pollutant removal from various types of wastewater, but also exposed several weaknesses of the technology (i.e. cost of membranes, control of biofilm thickness) which have prevented the concept of MABfRs being developed in viable wastewater treatment technologies. However, as membrane technology has developed, the cost of suitable membranes has fallen, prompting the research community to revisit the concept. This later batch of research has identified several niche applications where membrane supported biofilms can be used for effective removal of pollutants from water. Using the MABfR for the treatment of secondary effluent as a polishing step is another niche application which has been identified and is examined in this work; leading to the development of a patented treatment technology – the BioSettler.

Gas absorption rates were experimentally determined for a number of tworphase gas-liquid systems in co-current horizontal flow through circular tubes. Sparingly soluble gases were used in order to determine the liquid phase resistance to mass transfer. A series of experiments was designed to separate the effects of gas density, liquid-phase diffusivity, viscosity, surface tension, and tube diameter, on the mass transfer rates. The gas-liquid systems employed, in a single tube 1.757 cm. in diameter, were CO₂-water, He-water, CO₂-ethanol, and CO₂-ethylene glycol. Two additional tube sizes, 1.228 and 2.504.cm. in diameter were employed with the C02-water system to determine the effect of tube diameter. The gas and liquid flow rates used produced four different flow regions, bubble, plug, slug, and annular flow. The gas, and liquid, superficial velocities ranged from 0.1 to 40 fps, and 0.5 to 3.6 fps, respectively. Two correlations were developed for predicting mass transfer rates in two-phase flow. The first, based on a theory that each bubble represents a "mixing stage", is applicable to the bubble and plug regions of flow, and correlates the experimental' data for a wide range of liquid physical properties, as well as gas and liquid flow rates, with a probable error of approximately 15%. The second correlation, applicable to slug flow, empirically correlates the data for this region, over the same wide range of physical properties and flow rates, with a probable error of approximately 10%. The surface renewal or "penetration theory" mechanism of transfer is shown to be consistent with the experimental results obtained in the bubble and plug regions. In the slug region, on the other hand, evidence is available to indicate that another mechanism (probably that proposed by Kishinevskii), becomes increasingly important as the degree of turbulence increases. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

<p>Radiative cooling is an approach that utilizes the material reflectance in solar spectrum to reflect solar irradiation and emit the energy to deep space (2.7K) through the transparent portion in atmosphere (8-13μm). Therefore, radiative cooling is a passive cooling method that can generate a large reduction in energy consumption in the cooling sector. Scientists have been researching on the best solution for passive radiative cooling, including the utilization of multi-layer techniques with a metallic base layer. However, the current solutions are usually not cost effective and thus limited in the commercial applications. We initially started with the experiment on single-layer cooling paints embedded with TiO₂nanoparticles, and we were able to achieve a partial daytime radiative cooling effect of 60Wm^-2 Built upon our lab’s success of full-daytime sub-ambient cooling based on BaSO₄-acrylic paints, we experiment with colored cooling paints based on BaSO₄ nanoparticles instead of TiO₂ nanoparticles. Our results show much enhanced solar reflectance while matching the color, indicating the potential for colored cooling paints, although outdoor tests have not shown significant temperature drop compared to commercial colored paints yet. At the same time, we also explore creatures with shells in nature for possible solutions. Seashells are collected and the microstructures and radiative properties are characterized. The results provide insights into bio-inspired radiative cooling solutions.</p>

QC 20110616

This study was performed to increase knowledge of oxygen mass transfer (kLa) and mixing times in the scale-up of disposable bioreactors.Results of oxygen mass transfer studies showed kLa to increase with increasing agitation and aeration rates. By maintaining a scale-up constant such as gassed power to volume or shear, an almost constant kLa was achieved during scale-up from 50 to 2000 L. Using the scale-up constant Pg/V resulted in statistically higher kLa values at greater reactor volumes. Mixing times were revealed to be significantly affected by agitation, but not by the aeration rates tested. No pattern was recognized in the mixing time data over an increase in volume. Commonly used methods for predicting kLa upon scale-up were compared to experimental data. New coefficients were determined to fit the historic models to the parameters of this study, namely the unique geometry and low agitation and aeration rates used in the single-use systems. Each of the resulting four models was found to have average error rates from 16-23%. Although the error rates are not statistically different, the Moresi and Patete model was determined to be most conceptually accurate. The Moresi and Patete model found kLa to be more dependent on aeration than on the power input. This finding was consistent with the results of the experimental studies. The results of this study were for aeration rates (0.02-0.04 vvm) and agitation rates (Pg/V range of 2-20 W/m3) that are commonly used in single-use bioreactor systems.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography : leaves 81-83. / M.S.

<p> The rate of mass transfer from a series of bubbles, formed at constant frequency, rising through a quiescent liquid, was investigated at various times after bubble formation. The effect of surfactant on mass transfer was also studied. </p> <p> A decay from partially circulating to non-circulating conditions was found to occur in 7-8 seconds. The initial rate of mass ·transfer was appreciably reduced by the presence of surfactant. Mass transfer due to end effects was found to be 25-40% of the initial bubble mass. </p> / Thesis / Master of Engineering (ME)

A simplified model is developed to predict the heat and mass transfer between air and fallingilm liquid desiccant during dehumidification in a parallel-plate absorber. Compared to the second-order partial differential equations that describe fluid motion, first-order, non-coupled, ordinary differential equations are used to estimate the heat and mass transferred and explicit equations are derived from conservation principles to determine the exiting conditions of the absorber for different flow arrangements. The model uses a control volume approach that accounts for the change in desiccant film thickness and property values. The model agreed with a more complicated parallel flow model in literature. Using existing experimental data for a counterflow arrangement the model was validated over the range of input variables at the level of 8% for varying inlet desiccant flow rates and 10% for varying inlet air mass flow rates when an experimentally determined mass transfer coefficient was used in the model.

No description available.

As immiscible organic contaminants migrate through the subsurface environment, a significant portion of non-aqueous phase liquids (NAPL's) is trapped by capillary forces and remains in the subsurface as immobile blobs or ganglia. Residual saturations of NAPL on the order of 5-30 percent have been observed in saturated subsurface systems. The NAPL can partition into the aqueous phase and serve as a long-term source of groundwater contamination. NAPL-aqueous mass transfer rates impact the distribution and the rate of movement of the contaminant within the subsurface. The mass transfer coefficient is a function of many variables including aqueous phase velocity and NAPL-aqueous interfacial area. A one-dimensional column apparatus and experimental procedure was developed to study the nature of mass transfer between the aqueous phase (water), and a non-aqueous phase liquid (NAPL) in porous media. The NAPLs used in the experiments were composed of soluble and insoluble (inert) compounds. These experiments were designed to investigate the aqueous mass transfer of benzene, toluene, ethylbenzene, and xylene from and inert compound (soltrol or hexadecane). The results of this research indicate that the rate of NAPL-aqueous interphase mass transfer increases as a function of increasing aqueous phase velocity and percent NAPL saturation. Miller's equation was used to compare the model performance. Comparison of the experimental K values obtained by the literature was performed. The results indicated a satisfactory model performance. / Master of Science