Using Microfiltration

Clarification Using Microfiltration Crossflow filtration (microfiltration includes crossflow filtration as one mode of operation in Membrane Separation Processes, which appears earlier in this section) relies on the retention of particles by a membrane. The driving force for separation is pressure across a semipermeable membrane, while a tangential flow of the feed stream par lel to the membrane surface inhibits solids settling on and within the membrane matrix (Datar and Rosen, loc. cit.). 

Hoffman, W., Kiesner, C., Clawin-Radecker, I., Martin, D., Etnhoff, K., Lorenzen, P. C., Meisel, H., Hammer, P., Suhren, G., and Teufel, P. (2006). Processing of extended shelf-life milk using microfiltration. Int. ]. Dairy Technol. 59, 229-235. 

Membrane processes. Conventional filtration processes can separate particles down to a size of around 10 xm. If smaller particles need to be separated, a porous polymer membrane can be used. Microfiltration retains particles down to a size of around 0.05 xm. A pressure difference across the membrane of up to 4 bar is used. The two most commonly used arrangements are spiral wound and hollow fiber, as discussed in Chapter 8. 

A useful microfiltration apparatus, which prevents re-introduction of dust into filtered solution through contact with laboratory air, has been described by Levine et al. so and is shown in Fig. 12. The liquid is placed in the upper chamber and the lid closed. Filtration into the LS cell and recycling back into the upper chamber are carried out and repeated several times by manipulation of the stopcocks. Finally the filled cell is sealed and placed in the LS photometer. A rather similar device has been reported by Casassa and Berry32. ... 

The cells and cell lysates (fragments of disrupted cells) can be separated from the soluble components by using microfiltration (Chapter 8) with membranes. This separation method offers following advantages ... 

Cold sterilization of beer using microfiltration was introduced on a commercial scale in 1963. The process was not generally accepted at that time, but has recently become more common. Sterilization of beer and wine is much less stringent than pharmaceutical sterilization. The main objective is to remove yeast cells, which are quite large, so the product is clear and bright. Bacterial removal is also desirable a 106 reduction in bacteria is equivalent to the best depth filters. The industry has found that 1-p.m filters can remove essentially all the yeast as well as provide a 106 reduction in the common bacteria found in beer and wine. Because the cost structure of beer and wine production is very different from that... 

Zhu, B.T., Cliford, D.A., Chellam, S. (2005). Comparison of electrocoagulation and chemical coagulation pretreatment for enhanced virus removal using microfiltration membranes. Water Res. 39, 3098-3108. 

In summary, we have described an anaerobic process for singlecell protein from crude carbohydrates. The inhibitory by-products are simultaneously converted into methane. Mass transfer limitations can be avoided by using microfiltration rather than dialysis. Further study of the kinetics and improvements in yield will be necessary in order to make an economic comparison with other processes for single-cell protein. 

The organics are extensively characterised by IHSS (Averett et al (1989)). As a third orgamc, 5000L of surface water from the Mooney Mooney Dam (Brisbane Water National Park, NSW, Australia) were concentrated using microfiltration (MF) and reverse osmosis (RO) and freeze dried. The procedure is described in Appendix 1. Aldrich HA, a commercially available product (Sigma Aldrich, Australia) was used for comparison in some experiments. This HA is not from a aqueous source, but nevertheless frequently used in the literamre. 

The concentration of NOM from Moonej Mooney Dam in the Brisbane Water National Park (NSW, Australia) using microfiltration (MF), reverse osmosis (ROJ and freev e drying is described. Characterisation of the product is shown in Chapter 4. 

Nevertheless, several etiological applications have been developed, using microfiltration membranes with average pore diameters between 0.1... 

M. Mierzejewski, D. Guendert, Industrial appHcations using microfiltration as RO pretreatment, Ultrapure Water 21 (7) (2004) 29-35. 

Figure 2 shows an existing industrial flowsheet for the manufacture of the product and figure 3 shows the optimal flowsheet as generated by the synthesis software. The basic structure of the two flowsheets is the same but Jacaranda suggested the cell concentration step uses microfiltration instead of a centrifuge which is certainly a feasible option. Results for an intracellular product also produced similar flowsheets to those used in practice (Steffens et al 2000a). 

Sun, J., Hu, Y., Bi, Z. Cao, Y Improved performance of air-cathode single-chamber microbial fuel-cell for wastewater treatment using microfiltration membranes and multiple sludge inoculation. J. Power Sources 187 (2009a), pp. 41 -419. 

Figure 19. Device structure for nanoLEDs using microfiltration membranes.

Fruit juice processing is a major use for membrane filters, particularly for clarification (using microfiltration or ultrafiltration), concentration (using reverse osmosis) and deacidification (using electrodialysis). The clarification of apple juice by ultrafiltration is now an important process, whether making clear juice or natural (i.e. cloudy) ones. 

---