Membrane bioreactor values

The value AP can change in the axial direction in the hollow fiber (AP is the pressure drop in the membrane matrix due to the momentum transfer, the velocity through the membrane is u0 , where e is the membrane porosity). Kelsey etal. [11] have solved the equation system in all three cases, namely for closed-shell operation, partial ultrafiltration and complete ultrafiltration and have plotted the dimensionless axial and radial velocities as well as the flow streamlines. Typical axial and radial velocity profiles are shown in the hollow-fiber membrane bioreactor at several axial positions in Figure 14.8 plotted by Kelsey etal. [ 11]. This figure illustrates clearly the change of the relative values of both the axial and the radial velocity [V=vL/(u0Ro), U=u/u0 where uc is the inlet centerline axial velocity]. 

Figure 19.4 Protein secretion (shade bars) and urea synthesis (full bars) of human hepatocytes cultured in the galactosylated membrane bioreactor for 21 days. The values are the mean of six experiments standard deviation.

A cost analysis of an extractive membrane bioreactor (EMB) for wastewater treatment has been reported by Freitas dos Santos and Lo Biundo [6.24]. The EMB studied was similar with those reported in Chapter 4. Calculations were carried out for a feed flowrate of 1 m h of wastewater polluted with dichloromethane at a concentration of 1 g l A minimum pollutant removal rate of 99 % and 8000 h of operation per year were considered. As expected, the analysis indicated that the costs are strongly dependent on the pollutant flow entering the bioreactor to be transformed. Two key parameters, namely the total membrane area required and the external mass transfer coefficient, were studied. The results show that the costs and membrane area decrease significantly as the mass transfer coefficient increases from 0.5 x 10 to 2.0 x 10 m-s (these values are typical for large units, while laboratory measured values harbor around 5x10 m-s [624]). Using a mass transfer coefficient of 1.0 x 10 m s the authors calculated the costs and the membrane area required for different wastewater flowrates. These results are shown in Fig. 6.3. 

Microbial contamination is mainly caused by the presence of the microorganisms used in the biological process and can be eliminated by using ultra/microfiltration membrane bioreactors. The membrane effectively retains the microbial culture inside the reactor so that it may be operated under low hydraulic residence time. It has been previously demonstrated that the membrane bioreactor ensures a high nitrate removal rate (up to 7.7 Kg NO /m reactor-day) and a residual concentration of nitrate and nitrite, in the treated water, below the maximum admissible values (Barreiros et al., 1998). 

PBR, FBR, and ALR are widely used for the production of both high-value and low-value bioproducts, as well as for waste treatment. Membrane bioreactors, in contrast, are more suitable for the production of high-value bioproducts or complete immobUization of cells, which cannot be achieved by using other types of bioreactors. In addition to the application in biomanufacturing, cell immobihzation holds great promise for future applications, spanning from microbial biosensors to microbial biofilms, cell microarrays, and cell therapy. 

The membrane bioreactor (MBR) is a viable process for the treatment and reuse of wastewater at the municipal scale. The market value of MBR technology was estimated to be approximately US 217 million in 2005, rising at an average annual growth rate of between 9.5 and 12%, and is estimated to reach US 500 million by 2013 (Judd, 2011). During this time the capacity of MBRs has expanded from a typical 10 000 mVday to over 100 000 m /day, including an installation in Shiyan, Hubei province in China commissioned in 2009 with a capacity of 120 000 m /day (Judd, 2011). 

Zhu D, Zhu Y, Cai H, Gao G, Gao C, Li B. Method for treating leather waste to produce coUagen with high added value by using enzyme bioreactor and membrane separator (Shenzhen Xianke Environment Protection Co., Ltd, People s Republic of China). Patent Priority CAN 145 194650 AN 2006 754551 (in Chinese). 

EP = Product values - Costs of raw materials, bioreactors, membrane systems, utilities. 

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