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It has been hypothesized that a set of simple tests can be used to characterize("fingerprint") source feed waters and membranes such that integrating feed solution andmembrane properties can lead to optimal membrane selection and operation. Knowledge of source water characteristics is important because it can aid in theproper selection of a membrane that best resists fouling and exhibits good flux recoveryafter cleaning to optimize the operation of membrane treatment facilities. Developing afingerprinting technique to gain knowledge of source water characteristics and applying itto a predictive model was the focus of this research.Flow Field Flow Fractionation (Fl-FFF) is one of several such tests that canprovide "fingerprint" information about source water quality that can be integrated withknown membrane properties and correlated to flux decline in cross-flow membranefiltration. Flow FFF is typically used to separate solutes based on size and iscommonly described as a single-phase chromatographic technique. The flux decline potential of a solution is related to the concentration of thesolutes contained in the mixture at the membrane surface, their potential for forming aboundary layer or cake-like mass at that concentration, and their potential for irreversiblyadhering to the membrane material at the surface and/or within pores. An ideal model topredict membrane flux should be based on first principles. However, such models are nottractable for the complex mixtures that are real world water supplies. Means to"collapse" the behavior of a complex mixture into a single "effective" medium orcomponent would greatly simplify the task of predicting membrane filtrationperformance.Several of the qualitative relationships that define a solution's potential forcausing flux decline relate to a variety of the physico-chemical properties of the solutes.Since many of the same properties govern the Fl-FFF methodology, it may be a usefultool for defining the physico-chemical properties of an effective medium that is beingfiltered, and results can thus be interpreted in terms of the parameters in a flux declinemodel.The general approach for this research was to perform Flow FFF measurementson combinations of silica colloids (dp = 74 nm) and whey protein (MWavg = 25,500 Da)under different cross field velocities and solution ionic strength conditions. Theexperimentally obtained retention ratios and hydrodynamic conditions were used toprovide input parameters to an advection-dispersion transport model solved for the Fl-FFF system. The residence time distributions (RTDs) were transformed to a residencediameter distribution function (RDDF). A moment analysis of experimental ("real") vs.model ("ideal") RDDFs was used to quantify differences. Includes 7 references, tables, figures.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 20File Size: 1 file , 930 KB