REMOVAL OF NANOPARTICLE FOULANTS FROM MF FILTRATE USING ELECTROPOSITIVE FILTER CARTRIDGES: ASSESSMENT OF IMPROVEMENTS IN PROCESS PERFORMANCE

摘要

Cartridge filters are integral components in membrane systems that are generally used as pretreatment and/or polishing processes to salt rejecting membrane processes like reverse osmosis (RO). These processes are used to remove particulate matter that may harm the RO pumping systems and lead to plugging/fouling of the spiral wound membrane elements. Cartridge filters may be constructed of a diverse array of materials and designed to have a range of mean pore sizes in order to target any number of particulate size fractions. In general conventional filtration, and specifically cartridge filtration, is often associated with mechanical removal mechanisms such as size exclusion or physical straining. While chemical interactions (van der Waals, electrostatic) also determine particle removal in conventional filtration processes they are not necessarily selected for when designing/selecting cartridge filters. One drawback that is associated with relying solely on size exclusion for removing contaminants from membrane processes streams is that those materials that are smaller than the mean pore size of the filter may be transported onto the downstream membranes, resulting in membrane fouling. Contaminants of particular concern for water reuse applications include organic macromolecules (natural organic matter, polysaccharides) and nanoparticles (manufactured, naturally occurring). While both of these material groups have been found to be particularly troublesome membrane foulants, nanoparticle foulants are receiving increasing attention from membrane scientists and engineers.