Optical and Acoustic Methods for in situ Characterization of Membrane Fouling

Optical and Acoustic Methods for in situ Characterization of Membrane Fouling  

Nowadays, ultrafiltration (UF) or microfiltration (MF) membrane processes are widely used because of their ability to remove particles, colloidal species and microorganisms from different liquids feeds. However a limitation inherent in the process is membrane fouling due to the deposition of suspended matter during filtration. Therefore the understanding of formation and transport properties of particle deposits responsible for membrane fouling is a necessary step to optimize membrane processes. Thus it is necessary to obtain local information in order to analyze and model the basic mechanisms involved in deposit formation and then to further predict the process operation. Besides, it is also useful to control the deposit formation and to plan preventive or curative actions with a controlled efficiency. Nonetheless, local parameters such as cake thickness and porosity are hardly reachable with conventional techniques. 

The only way to obtain local information about the deposit stmcture at a given time during filtration is to use in situ and real-time measurement with a non-invasive method, that is to say a method which does not disturb the process and cake build-up during filtration or removal during hydraulic cleanings. 

Over the past years, a number of non-invasive techniques have been used to observe in situ membrane processes but few are adapted to confined geometry like inside/out hollow fibers [1, 2]. Most of the time, one characterization method only provides one kind of information about the deposit thickness or images or a structural parameter. This chapter focuses on the development and validation of two characterization methods to obtain complementary information (thickness and porosity) about the local structure of the deposit. 

Two characterization methods have been developed. The approach is to use those two methods in a complementary way to obtain a complete characterization of 

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