Tangential flow filtration system

Equipment needed continuous centrifuge and tangential flow filtration system. Equipment needed expanded bed column for 4.5 liter resin. 

Figure 2. Simplified schematic of tangential flow filtration system.

This problem seems to be overcome by the tangential flow filtration system, specifically developed for a large sample size (1-2 m ) by Broman and coworkers in order to collect water from Baltic Sea, where the suspended particulate generally occurs at concentrations of 0.2-0.3 mg/L [10]. The system is made of a microporous poly(vinylidene difluoride) membrane, where the filtrate is separated from the retentate with a constant cutoff of 0.45 xm. A tangential flow of water sweeps the surface of the membrane so that the particles are kept in suspension avoiding membrane plugging. The retentate (liquid) each of volume 3-5 L is collected and centrifuged the supernatant and pellet are thereafter extracted and analyzed. 

Vandanjon, L., Rossignol, N., Jaouen, P., Robert, J.M., and Quemeneiu, F. (1999) Effects of shear on two microalgae species. Contribution of pumps and valves in tangential flow filtration systems. Biotechnoi Bioeng., 63,1-9. 

Kempken et al. [113] employed a rotating disc filter to harvest CHO cells, and observed that the filter could be operated at low transmembrane-pressure with high wall shear rates, leading to high filtrate flow rates, high product yields and minimum fouling. They concluded that their system offered a powerful alternative to conventional tangential flow filtration. 

All of the membrane processes utilize an engineering design known as "cross-flow" or "tangential flow" filtration. in this mechanism, the bulk solution flows over and parallel to the membrane surface, and because the system is pressurized, water is forced through the membrane. The turbulent flow of the bulk solution across the surface minimizes the accumulati.on of particulate matter on the membrane and facilitates the continuous operation of the system. 

The difference between conventional dead-end filtration and cross-flow filtration is the configuration of the system. For large-scale operations, only cross-flow filtration will be used. The membranes for miocrofiltration as well as ultrafiltration are commonly utilized in a variety of filtration devices. There are three basic types of tangential flow filtration devices plate and frame, hollow fiber, and spiral wound membranes. 

Filtration systems used for sterilization (membrane filters) can be used to separate cells from the supernatant but only for relatively small volumes as they do rapidly become clogged, and for this sort of volume centrifi ation is usually easier but not as efficient at removing small cell debris. Tangential flow filtration is used to reduce problems of filter blockage by continuous recirculation of the suspension across the membrane, and is recommended for larger volumes (several litres). Low volume systems are available from recognized filtration suppliers (e.g. Millipore, Sarstadt, Pall). Filtration systems have been reviewed (43). 

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