Abstract
An investigation into the mechanism of fouling associated with the crossflow microfiltration of a model beer is proposed. This requires the development of a suitably representative model beer composed of dextrin, glucose, Bovine Serum Albumin (protein) and ethanol. Due to membrane cleaning limitations, the model beer solution operates at a one tenth concentration of the real product. Although other investigations have used model beers, this research is unique in the fact that it uses a carbohydrate based model beer to study the process of fouling when crossflowed through a reusable ceramic membrane. Since the parameter of concentration has become fixed, the effects of varying transmembrane pressure and crossflow velocity have been assessed. This was achieved through recording the flux decline and the quantitative results of permeate and retentate stream composition. Through data manipulation, the component retention in the retentate was calculated and a material balance produced to evaluate the amount of unaccounted for components. From these results, inferences will be made regarding the composition and behaviour of the membrane-fouling layer. This work will be verified by visualisation of the fouling membrane surfaces. The objectives of this research have been met; a successful model beer has been developed and the effects of crossflow filtration associated fouling investigated. The membrane foulant was visualised over set time periods using scanning electron microscopy. It was found that as the transmembrane pressure or crossflow velocity increased, the composition of the membrane foulant altered with protein predominating over dextrin. The development of this fouling layer prevented component passage which leads to component retention within the retentate. Visualisation of the early stages of fouling showed the membrane being covered in a gel-like layer, however, the pores remained uncovered. Over time, the gel fouling grows over the pores and a complete fouling layer results, actively reducing the flux and component permeation though the membrane.