Removal of polysaccharide foulants from reverse osmosis feedwater using electroadsorptive cartridge filters

Abstract

ABSTRACT Fouling of reverse osmosis (RO) water filtration membranes is a common problem throughout the industry. Most membrane fouling has an organic component that is typically derived from planktonic transparent exopolymer particles (TEP). Polysaccharides are a major constituent of TEP that are produced both abiotically from organic colloid precursors and by a variety of organisms in marine and freshwaters. The microgel character of TEP makes them difficult to remove through conventional filtration other than by ultra filtration and RO membranes. However, removal of TEP by these membranes is also problematic. When the membrane surface is initially fouled with TEP, the TEP layer then acts as an attachment substrate for organism, colloids and other submicron particulates, further contributing to membrane clogging. We report on an innovative electroadsorptive, depth filter media that is shown to be effective in significantly reducing TEP from fresh water, sea water, and wastewater. This technology has significant potential to protect membranes from primary fouling due to both TEP and nanoparticle build-up. The electroadsorptive filter media removes TEP through a strong positive charge generated by nanofibers of the mineral boehmite and the torturous path created by the depth filter media itself. The filter media has a mean flow pore of about 0.7 microns and very high nanofiber surface area that produces a filter with low pressure drop but a high filtration efficiency and high loading capacity for TEP removal.