Membrane-bioreactor configurations

Figure 14.1 Schematic illustration of the external membrane bioreactor configuration.

Figure 14.3 Schematic illustration of immersed membrane bioreactor configurations.

Le-Clech, P., Jefferson, B. and Judd, S.J. (2003) Impact of aeration, solids concentration and membrane characteristics on the hydraulic performance of a membrane bioreactor. Journal of Membrane Science, 218,117—129. Le-Clech, P., Jefferson, B. and Judd, S.J. (2005) Comparison of submerged and side-stream tubular membrane bioreactor configurations. Desalination, 173, 113-122. 

FIG. 22-45 Membrane bioreactor configurations for wastewater treatment, (a) With sidestream module (b) with submerged module. 

FIGURE 6.24 Membrane bioreactors configurations, (a) Internal outer-skin membranes and (b) outside membrane module. 

Le-Clech P, Jefferson B, and Judd SJ. A comparison of submerged and sidestream tubular membrane bioreactor configurations. Desalination 2005 173 113-122. 

Liquid-Liquid Extractive Membrane Bioreactor Configurations 133... 

Figure 20A Membrane bioreactor configurations. Reprinted with permission from Simate et al. (2011).

Various membrane bioreactor configurations have been described in the literature. Whatever the configuration, though, the main objective is to ensure the complete rejection of the enzyme in order to maintain the optimum level of efficiency inside the reacting volume. As described above, depending on the situation, enzyme molecules may be freely circulating on the retentate side, immobilized on the membrane surface itself, or inside the membranes... 

In the development of cell or enzyme-based processes, many process configurations exist, including batch, fed batch and continuous operation. In general, the conversion and the separation processes (downstream processing) are regarded as separate units, and most industrial processes are based on this approach. In the last decades, however, more attention is paid to the integration of conversion and separation, leading to the development of membrane bioreactors [49, 50], and some of these concepts have reached an industrial scale. The membranes used for this type of reactors are almost exclusively polymeric, as temperatures seldomly exceed 100 °C for obvious reasons. 

Membrane bioreactors can be classified into two main groups according to their configuration. The first group is commonly known as recirculated or external MBR and involves the recirculation of the solution through a membrane module that is outside the bioreactor. Both inner-skin and outer-skin membranes can be used in this... 

In recent years, membrane bioreactors, bioreactors combined with membrane separation unit have established themselves as an alternative configuration for traditional bioreactors. The important advantages offered by membrane bioreactors are the several different types of membrane modules, membrane structures, materials commercially available. Membrane bioreactors seem particularly suited to carry out complex enzymatic/microbial reactions and/or to separate, in situ, the product in order to increase the reaction efficiency. The membrane bioreactor is a new generation of the biochemical/chemical reactors that offer a wide variety of applications for producing new chemical compounds, for treatment of wastewater, and so on. 

The major market for membrane bioreactors is represented by wastewater treatment with the use of submerged modules configuration. These are considered among the best available technologies by the European Directives on Environment. Membrane bioreactors are also applied in food, red and white biotechnology. In these cases, the external loop configuration is used. 

FIGURE 46 Membrane bioreactor in a multiphasic configuration with reversible enzyme containment. 

Curcio S, Calabro V, Iorio G (2006) A theoretical and experimental analysis of a membrane bioreactor performance in recycle configuration. J Membr Sci 273 129-142... 

The most commonly utilized catalytic membrane reactor is the PBMR, in which the membrane provides only the separation function. The reaction function is provided (in catalytic applications) by a packed-bed of catalyst particles placed in the interior or exterior membrane volumes. In the CMR configuration the membrane provides simultaneously the separation and reaction functions. To accomplish this, one could use either an intrinsically catalytic membrane (e.g., zeolite or metallic membrane) or a membrane that has been made catalytic through activation, by introducing catalytic sites by either impregnation or ion exchange. This process concept is finding wider acceptance in the membrane bioreactor area, rather than with the high temperature catalytic reactors. In the latter case, the potential for the catalytic membrane to deactivate and, as a result, to require sub-... 

There are a number of membrane reactor systems, which have been studied experimentally, that fall outside the scope of this model, however, including reactors utilizing macroporous non-permselective membranes, multi-layer asymmetric membranes, etc. Models that have been developed to describe such reactors will be discussed throughout this chapter. In the membrane bioreactor literature, in particular, but also for some of the proposed large-scale catalytic membrane reactor systems (e.g., synthesis gas production) the experimental systems utilized are often very complex, in terms of their configuration, geometry, and, of course, reaction and transport characteristics. Completely effective models to describe these reactors have yet to be published, and the development of such models still remains an important technical challenge. 

The basic principles of bioconversion, bioreactors and biocatalysis are introduced, together with a description of the most important biocatalyst immobilization techniques. The mass transfer phenomena involved in membrane systems are discussed along with some representative configurations of membrane bioreactors, whose behaviour can be described using a simple mathematical approach. For all the aforementioned systems the most significant parameters have been defined to estimate the system performance. 

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