Economic membrane bioreactor

At various places throughout the first five chapters in the book we have, when it appeared relevant to the discussion, referenced studies which addressed issues pertaining to the economic/technical feasibility of membrane reactor processes. In this chapter we specifically focus our attention on these issues. In the discussion in this chapter we have, by necessity, drawn our information from published studies and reports. Several proprietary studies reportedly exist, carried out by a number of industrial companies, particularly during the last decade, which have evaluated the potential of membrane reactors for application in large-scale catalytic processes. By all accounts the conclusions reached in these proprietary reports mirror those found in the published literature. In the discussion which follows, we will first discuss catalytic and electrochemical reactors. We will then conclude with a discussion on membrane bioreactors. 

The initial membrane bioreactors cross-flowed the liquid phase through the membrane, which increased energy costs significantly. Currently viable membrane bioprocesses submerge the membrane in the liquid phase whereby the liquid flows parallel to the membrane matrices. This creates low pressure drops and makes the economic viability a reality. Current membrane reactors also tend to vary the volumetric membrane amount or carrier particles at 60-70% (Leiknes and Odegaard, 2007). 

Chapter 22 (Uragami, Chakraborty, Piemonte and Di Paola) presents a survey of membrane bioreactor appHcations in pharmaceutical, environmental and biomedical fields. The integration between the separation and the reaction units is demonstrated to highly improve the selectivity and productivity of bioreactors, especially when some factors (inhibition by products or reactants, contamination by xenobiotics) play a key role in the bioreactive systems. In Chapter 23 (Calabrb and lorio membrane bioreactors are described from an economical point of view. Most important rules and parameters have been preliminarily introduced. Some appUcations,... 

Abstract In this chapter, membrane bioreactors are described from an economic point of view. Economic analysis is a crucial stage in plant design, project and control and also requires an evaluation of the research, development and commercialization of the products and bioproducts. Such an analysis is focused here on membrane bioreactors and reactors, also taking into account the separation units such as micro-, ultra- and nano-flltration units that might be used as a downstream process or as pretreatment steps. The most important rules and parameters are first introduced. Some examples of application and case studies are also reported. 

Membrane bioreactors for wastewater treatment are another example of that, whereby capability, performance and water quality can be adopted as parameters together with the economic ones. 

Economics of membrane bioreactors (MBRs) for wastewater treatment... 

Tej ayadi S, Cheryan M, (1995), Lactic acid from cheese whey permeate. Productivity and economics of a continuous membrane bioreactor , Applied Microbiology and Biotechnology, 43(2), 242-248, DOI 10.1007/BF00172819. 

Biocatalytic resolution plays a major role in the industrial scale synthesis of a wide variety of optically pure amino acids. Tanabe uses an L-spe-cific aminoacylase for the manufacture of several L-amino acids, immobilized on DEAE-Sephadex. Degussa on the other hand, uses the free acylase in a membrane bioreactor. The process is highly efficient in enzyme use, and racemisation of the D-isomer is straightforward, thus providing good economics, and virtually no waste (Scheme 7.4). The process can be further refined by the use of racemase enzymes, which makes dynamic kinetic resolution feasible. 

Often the coupling of the membrane unit with the bioreactor results in significant synergy as in the study of O Brien et al. [6.15] on the application of PVMBR to ethanol production, which we discussed in Chapter 3. The required bioreactor volume for the PVMBR system was smaller than that of the conventional system by a factor of 12. Nevertheless, it turns out that the PVMBR-based process is still 25 % more expensive than the classical batch fermentation process in terms of capital costs despite the substantial reduction in the required reactor volume. This cost differential is not only due to the membrane costs, which are, themselves, substantial, but also due to the cost of the additional hardware associated with membrane operation. The application of MBR for the ethanol production by fermentation faces marginal economics, since ethanol is a relatively cheap commodity chemical. 

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