Membrane Cleaning, Compaction, and Chemical Degradation
This chapter provides an overview of the different strategies and chemicals used in membrane cleaning including the mechanisms by which they remove different foulants. Membrane compaction has been studied much less extensively for ultrafiltration and microfiltration membranes, since these membranes are generally operated at relatively low pressures. W. R. Bowen and R. A. Sabuni examined the use of pulsed electric fields for physical cleaning of cellulose nitrate microfiltration membranes. Chemical cleaners work by a number of different mechanisms, including displacement of the foulants from the membrane, solubilization of the foulants, and/or chemical modification of the foulants. Surfactants function as effective cleaning agents by displacing foulants from the membrane surface due to their strong surface adsorption, emulsifying oils, and solubilizing hydrophobic foulants by incorporating them into surfactant micelles. Enzymes are available that degrade proteins, starchs, fats and oils, and cellulose. Disinfection destroys all living pathogenic microorganisms, while sterilization also eliminates very highly resistant bacterial spores.