Synergetic cleaning procedure for a ceramic membrane fouled by beer microfiltration

Apart from considerations for hygienic operation, membrane cleaning is esse ntial to maintain consistent permeability and selectivity of membrane syste ms for clarifying beer and beverages where balanced fractionation of partic les/macromolecules is necessary. Experiments involved formulating and optim ising chemical cleaning methods for a ceramic microfiltration membrane, whi ch had been severely fouled during clarification of a commercial beer. The cleaning processes employed NaOH, HNO3, H2O2, and Ultrasil 11 as the chemic al cleaning agents. The cleaning ability and cleaning kinetics of the proce sses were evaluated in parallel with the study of the fouling mechanism, fo rmation and strength so as to elucidate the synergetic relationship between fouling and cleaning. A three-step cleaning mechanism was postulated. This led to the development of a fast and effective combined simultaneous caust ic cleaning and oxidation method (CSCCO), which was able to restore 87% of the original membrane's water permeability within 8 min. Analysis suggested the concept of a cleaning energy barrier E-c and a cleaning rate constant k(c0). This study confirmed the existence of a synergetic relationship betw een the prior fouling and optimum formulation of cleaner and optimal cleani ng condition. The study varied beer filtration conditions. Transmembrane pr essure (TMP) and crossflow velocity during fouling appeared to have a minim al effect on the membrane's subsequent cleanability, especially when the po werful CSCCO process was employed. The number of previous fouling/ cleaning cycles was influential. A complete removal of the residual fouling, formed on the virgin membrane's surface proved beyond the means of the harsh chem ical cleaning used under any conditions, The degree of residual fouling eve ntually reached a plateau and a level of 87% of the original water flux cou ld be restored repeatedly. (C) 1999 Elsevier Science B.V. All rights reserv ed.