Year : 2015
Author : Dimitrios C.Sioutopoulos, Anastasios J.Karabelas
Development of polysaccharide fouling layers during dead-end membrane ultrafiltration is an inherent problem in water treatment and similar separation processes.Despite its practical significance, ultrafiltration membrane fouling under constant permeate flux J has received inadequate attention. Therefore,constant-flux experiments,with typical alginate model-solutions covering the flux range of practical interest (i.e.10–100L/m2 h), are employed to obtain new insights in to fouling layer characteristics. The specific resistance α, as the most representative fouling-layer property,is used for data interpretation.The behavior of resistance α, with increasing permeate volume,confirms that the segel-type layers are strongly affected by flux J and generally compressible.Layer compressibility is evident beyond an initial phase of membrane coverage by alginates.The initial resistance αi, corresponding to thin developing layers and relatively small pressure-drop across thelayer/“cake” ΔPc, is independent of ΔPc, approximately linearly increasing with J. For all data-sets,variation of resistance α with ΔPc is well correlated by a generalized expression involving(in additiont o αi) two parameters, n and Pa, considered to represent layer/cake compressibility index and reference pressure,respectively; these parameters also increase(and are fairly well correlated) with J. The usefulness of these data is demonstrated in elucidating issues such as”critical flux” for this filtration mode.