Evaluating the role of soluble aluminum in manganese removal via MnOx(s)-coated filtration media in drinking water treatment

Abstract

The Mn oxide (MnOx(s)) surfaces of water treatment filtration media are known to aid in the capture of dissolved Mn species, but the discovery of significant deposits of Al within these coatings (Tobiason et al., 2008) raised certain questions about the possible role of Al in soluble Mn removal and the formation of the MnOx(s) surface on the media. This phenomenon was addressed by conducting a series of bench-scale column studies that involved the application of solutions containing varying amounts of soluble Al and Mn to MnOx(s)-coated media. The experimental results confirmed that soluble Al was removed in significant amounts by adsorption onto the MnOx(s) media surface. The deposition of soluble Al onto the media surface did not have any significant effect on its ability to remove soluble Mn. Likewise, the relative amounts of Al incorporated into the media coating suggested that uptake of soluble Al alone cannot fully explain the levels of Al often found in real-world, MnOx(s)-coated filter media; instead, the incorporation of particulate forms of Al (routinely found in water treatment plant situations) must contribute to the formation of the MnOx(s) coatings on these media.