Bioreactors plug-flow reactor

A tubular bioreactor design with operational may lead to a CSTR, having sufficient recycle ratio for plug flow that behave like chemostat. The recirculation plug flow reactor is better than a chemostat, with maximum productivity at C, 3 g-m 3. Combination of plug flow with CSTR which behave like chemostat was obtained from the illustration minimised curve with maximum rate at CSf = 3 g-m-3. 

Industrial hazardous wastewater can be treated aerobically in suspended biomass stirred-tank bioreactors, plug-flow bioreactors, rotating-disc contactors, packed-bed fixed-biofilm reactors (or biofilters), fluidized bed reactors, diffused aeration tanks, airlift bioreactors, jet bioreactors, membrane bioreactors, and upflow bed reactors [28,30]. 

The bioreactor has been introduced in general terms in the previous section. In this section the basic bioreactor concepts, i.e., the batch, the fed-batch, the continuous-flow stirred-tank reactor (CSTR), the cascade of CSTRs and the plug-flow reactor, will be described. 

In the ideal plug-flow reactor (Figure 11.16) the continuous phase flows as a plug through the reactor i.e., there is no mixing or, in other words, no axial dispersion. Consequently, if a compound is consumed or produced, a concentration gradient will exist in the direction of flow. The mass balance is therefore first set up over an infinite small slice perpendicular to the direction of the flow with volume dV of the bioreactor. Assuming steady state and F =Fq=F, Equation (11.5) then is reduced to ... 

The treatment of PAH-contaminated soil in a reactor environment is basically limited to the use of soil slurry reactors. Conversely, many different bioreactor designs exist for the treatment of water contaminated with PAHs. As reviewed by Grady (1989) and Grady Lim (1980), these include fixed film reactors, plug flow reactors, and a variety of gas-phase systems, to name a few. Given the depth and magnitude of such a topic, for the purposes of this review discussions will be limited to a generic overview of reactor applications for PAH bioremediation. 

Figure 10.2.1 Plug flow reactor simulation using NSTAGEs of CSTRs for solution. [From Analysis of a Continuous, Aerobic Fixed-Film Bioreactor. I.. Stcady-.Siaio Bclia ior. by Y. Park.. VI. F. Davis and D. -. Wallis, Biotech. 26 11984) 457. copyright...

A continuous bioreactor type plug flow reactor (PFR) with immobilized cell of Saccharomyces cerevisiae in spherical particle was used in the work to take into account the variations of concentrations at the reactor length and inside spherical particle. 

Several bioreactor designs are used to produce bioproducts, and include, but are not limited to batch reactors, fed-batch reactors, continuous cultivation reactors, plug flow reactors, recycle bioreactor systems, immobilized cell reactors, biofilm reactors, packed bed reactors, fluidized-bed reactors, and dialysis cultivation reactors (Williams 2002). These reactor types can contain either mixed or pure cultures, and can stimulate heterotrophic and/or phototrophic cellular functions depending on the specific reactor design. Additionally, these reactor schemes can be used to produce products directly, or to harvest biomass or other products for downstream processes. Due to the complex nature of bioreactors, particularly anaerobic digesters, the use of metagenomics is helpful to understand the physiology of such systems. 

When the substrate concentration S is much greater than Km, Eqs. (12) and (13) reduce to the same form. In this case, the continuous flow stirred reactor and the plug flow device achieve similar conversion values in a given time. In contrast, when S Km, the reaction rate becomes first order in the substrate concentration (see Eq. (9)), and the plug flow reactor provides higher conversion values in comparison with the well-mixed continuous flow device. In the latter bioreactor, all the enzyme would be exposed to the same low concentration of the substrate which is not useful except when the reaction is inhibited by the substrate. 

Cells in suspension Plug flow reactor with hydrodynamic stirring with or without static mixing elements in tube or flat-bed bioreactor Continuous... 

Large-scale bioreactors can be described, as discussed above, in terms of aggregates of model reactors like the ideal stirred-tank and the ideal plug-flow reactor. These are low-dimensional compartment models that are easy to use, but they... 

We wish to compare the performance of two reactor types plug flow versus CSTR with a substrate concentration of Csf = 60g-m 3 and a biomass yield of Y = 0.1. In a plug flow bioreactor with volume of 1 m3 and volumetric flow rate of 2.5 m -li what would be the recycle ratio for maximum qx compared with corresponding results and rate models proposed for the chemostat ... 

The various types of plug flow bioreactors were recently surveyed by Moser (1985a). They utilize surface aeration by means of a variety of rotating brushes, rotors, cone aerators, or gas or fluid jets such as are found in biological waste water treatment plants. Beyond all mechanically driven systems, reactors can also be both aerated and mixed pneumatically, or one pump can serve for both mixing and hydrodynamic stirring. 

Steady-state flow reactors, with a constant supply of reactants and continuous removal of products, can be operated as both a continuous stirred-tank bioreactor (CSTB) and as a plug flow bioreactor (PFB). It is possible to have different configurations of the membrane bioreactor where the biocatalyst is immobilized in the fractionated membrane support (Katoh and Yoshida, 2010). In Fig. 1.6 the scheme of a CSMB in which the biocatalyst is immobilized on the surface of the membrane beads is presented. The biocatalyst immobilized in the porous structure of a fractioned membrane can also be operated in CSMB. For example, two configurations are shown in Fig. 1.7 (a) for flat-sheet and (b) for spherical porous structures, respectively. Such structures could also be adopted for PFB, where a bed of membrane support with the immobilized biocatalyst could be utilized, in either a fixed or fluid configuration. 

On the other hand, for the ideal tubular reactor with a plug-flow-like profile (PER), the material balance has to be made over a differential element of volume, dV = Adz, where A is the cross-sectional area of the bioreactor and dz is a differential thickness of the bioreactor (Figure 7.4). The material balance thus becomes... 

Beeause F is the volume processed in time f in a continuous flow bioreactor and Vl is the corresponding volume in a batch reactor, a comparison of Eqs. (11) and (13) shows that batch and plug flow (i.e., packed bed) bioreactors containing the same amount of enzyme will achieve equal conversions in a given time. This is a general conclusion, irrespective of the reaction kinetics. A continues flow packed bed enzyme bioreactor may be advantageous relative to batch reactor, as the unproductive time for batch preparation could be eliminated in the continuous flow unit. However, the batch reactor may have other important advantages such as the ease of pH control in a well-mixed device. 

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