AWWA MTC64616

A major concern in the application of microfiltration membranes is the fouling of the membrane (that is, the irreversible blocking of pores by colloidal/particulate matter and by the macromolecules of natural organic matter). Research has demonstrated that pore size characteristics (maximum, minimum, and mean values of the major axis, minor axis, and aspect ratio) impact membrane performance (flux, rejection, and permeate particle size distribution). Recent investigations have examined the effect of uni-axial stretching of membranes on the performance properties and performance of microfiltration polymer membranes. Membranes made via phase inversion and track-etch (TE) methods have been investigated. These investigations included experimental studies that show stretching increased permeability beyond that caused by the reduction in thickness. The results also showed improved rejection capabilities for some membranes. The research included modeling the changes in the pore size characteristics caused by uni-axial stretching. The modeling of the deformation process, which is performed using finite element analysis, is discussed in this paper. Finite element analysis is used as there is not a closed-form solution of elliptical void growth that adequately takes into account interactions between pores. Specifically, this paper emphasizes the modeling of pore size and shape changes resulting from the stretching of TE membranes. TE membranes are used because of the simplistic geometries. While often described as circular straight through pores of a uniform size, TE membranes often have angled pores, creating elliptical pore openings. Models of the changes in track-etch membranes have been completed for a simplified 2-D system, where pores are circular and pass straight through the membrane, for a 2-D system with elliptical pores, and for a 3-D system that includes angled cylindrical pores. Includes figures.