AWWA MTC69700

This powerpoint presentation begins by presenting the problem statement concerning nanofiltration: nanofiltration (NF) has an attractive capability of rejecting multivalent ions at a much lower pressure than that used for reverse osmosis (RO); NF productivity is generally hampered by multicomponent fouling caused by colloidal materials, dissolved organics, inorganic precipitates, and microorganisms accumulating on the membrane surface; and, foulant-foulant interactions cause much more complex fouling behaviors than those of individual fouling phenomena. The research goal was to develop an integrated model that has the ability to: describe combined fouling due to three different foulants; unify two-component fouling models such as cake-enhanced osmotic pressure and bi-dispersed colloidal fouling; and, include all the single-component fouling scenarios. The theory is presented and is broken down into singlet fouling, doublet fouling, triplet fouling, and equivalent flux. Presentation conclusions indicate the following: a novel theory was developed on the basis of the Happel's cell model to analyze the combined fouling of colloids, macromolecules, and solute ions; resistance of the combined fouling is much greater than each fouling of colloids-alone and macromolecules-alone cases; at the beginning of dead-end filtration, BSA gel layer undergoes remarkable structural compression with increasing volume fraction, while alginate and dextran do not; colloids and BSAs are not well mixed during the early stage of the filtration, causing theoretical under-prediction of the permeate flux; and, theoretical flux of combined fouling and the equivalent flux of the weak form provide the lower and upper bounds of the experimental flux of the triplet fouling; therefore, using measurement of individual fouling phenomena of colloids-alone and macromolecules-alone cases, the permeate flux of triplet fouling can be well estimated. Includes figures.