Macrosolute fouling

With the majority of MF/UF processes based on the filtration of aqueous solutions, the unavoidable presence of dissolved solutes (salts, organic macromolecules of various nature and sizes) in the feed strongly affects the membrane performances. They can be directly responsible for membrane fouling through mechanisms like 

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Recent developments in LM module design, including rotational, vibrational membrane devices, pulsed-flow fluid management for polarization control, use of low-cost refractory monoliths as membrane supports, and use of electric potentials to minimize macrosolute polarization and fouling, may permit practical and economic application of membrane processes to liquid and gaseous streams which today are untreatable by such methods. 

Fouling (e.g., microbial adhesion, gel layer formation, and solute adhesion) at the membrane surface is a more complex phenomenon involving polarization, irreversible adsorption of macrosolutes or colloid particulates to, and/or gradual buildup of an adherent and coherent layer of solid material on, the membrane surface. It is amenable to mitigation by appropriate selection or surface treatment of the membrane surface (to minimize adsorption) by suitable fluid management or by employment of other forces to transport fouhng solutes. 

Hydrophobic membranes attracted a thicker irreversible adsorption layer than hydrophilic membranes [127, 128]. Hydrophilic membranes display low sorptivity for fouling macrosolutes such as proteins. In some situations, ionically charged membranes are more fouling-resistant than electroneutral membranes. The apparent high fouling-resistance of ceramic (alumina) membranes is worthy of special note, although the explanation of this... 

High Solids Feed by (Bubbled) Cross-Flow Filtration For applications, such as MBRs, the particulate solids content is relatively high [suspended solids (SS) up to 10-15 g/L] with additional colloids and macrosolutes. Under these conditions bubbled cross flow is essential to limit concentration polarization and subsequent fouling. 

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