Crossflow Filtration

Sometimes referred to as Tangential Flow Filtration, Crossflow Filtration is used mostly in the sub-micron range, it’s most common uses are in the range of Microfiltration, Ultrafiltration, and Nanofiltration. Crossflow is used most often, in situations that require the filtration of very large volumes of fluid, or the separation of very high concentrations of solids.

As the system pore size, or molecular weight cut-off decreases, the operating pressure of the system increases. Microfiltration systems can operate in the 20 – 40 PSI range, while some Ultrafiltration and Nanofiltration systems will require often require pressures far greater than 100 PSI.

The feed stream forms a “Recirculation-loop”, where the feed stream passes across the membrane sheet surface, or more commonly through the center lumen of a membrane tube.

In a typical tubular microfiltration application, a fluid, such as chemically pre-treated wastewater, flows through the tubular modules at high velocity, sufficient to maintain turbulent flow. At typical operating pressures of 20 – 80 psi, the “Permeate Stream” is forced through the pores of the membrane, while suspended particulates remain in the “Retentate Stream”. The turbulent flow on the membrane surface prevents the build-up of particles on the inner surface of the tube, providing high flux and prolonged filter life.

This turbulent crossflow performance and large bore tubular design, may eliminate the need for some prefiltration steps and should routinely handle high solids levels. These types of systems are usually used to process very large volumes of liquids.

Typical applications would include:

Biological or biopharmaceutical processing
Concentration of fruit juices and extracts
Food and beverage processing
Desalination of brackish water or seawater
Purification of rinse water in electroplating tanks
Municipal or industrial water and wastewater purification

Cross-flow filtration can concentrate solids and semi-solids very effectively because membrane selection is designed to keep the solids retained on the membrane surface rather than in the filter matrix. Cross-flow filtration can concentrate solids and semi-solids very effectively because membrane selection is designed to keep the solids retained on the membrane surface rather than in the filter matrix.

Remember, when the fluid volumes or the solids levels are high, consider Crossflow Filtration as a viable option.

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