Cross Flow or Tangential Flow Filtration (TFF) Membrane Plants are used in Desalination, Brackish Groundwater Treatment, High Chloride Surface Water Treatment, Waste Water Treatment Plant Effluent Reuse, Biopharmaceutical, Food & Protein Applications for removal of undesired constituents and harvesting of desireable products. Cross flow membrane filtration technology has been used widely in industry globally. Filtration membranes can be polymeric or ceramic, depending upon the application. The principles of cross-flow filtration are used in reverse osmosis, nanofiltration, ultrafiltration and microfiltration. When purifying water, it can be very cost effective in comparison to the traditional evaporation methods. Techniques to improve performance of cross flow filtration include:
Backwashing: In backwashing, the transmembrane pressure is periodically inverted by the use of a secondary pump, so that permeate flows back into the feed, lifting the fouling layer.
Clean-in-place: Clean-in-place systems are typically used to remove fouling from membranes after extensive use. The CIP process may use detergents, reactive agents such as sodium hypochlorite and acids and alkalis such as citric acid and sodium hydroxide.
Concentration: The volume of the fluid is reduced by allowing permeate flow to occur. Solvent, solutes, and particles smaller than the membrane pore size pass through the membrane, while particles larger than the pore size are retained, and thereby concentrated. In bioprocessing applications, concentration may be followed by diafiltration.
Diafiltration: In order to effectively remove permeate components from the slurry, fresh solvent may be added to the feed to replace the permeate volume, at the same rate as the permeate flow rate, such that the volume in the system remains constant. This is analogous to the washing of filter cake to remove soluble components. Dilution and re-concentration is sometimes also referred to as "diafiltration."