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 raised several questions about the MnOx(s) surface. A series of experiments and analyses were performed to examine the presence of Al within MnOx(s) coatings formed on water treatment filtration media. It was hypothesized that the presence of Al within the MnOx(s) coatings might have an impact on the capture of Mn by the MnOx(s) surface. A 2008 study of oxide coated filtration media found that Mn and Al are present in nearly equimolar quantities within the oxide coatings. This led to questions of how and why the Al became incorporated into the surface. This phenomenon was analyzed by conducting a series of bench-scale column studies, treatment plant data collection, and analysis of the MnOx(s) surface utilizing an electron microscope. The results confirm that Al deposits onto the MnOx(s) media surface by two separate mechanisms; adsorption of dissolved Al species and the deposition of colloidal and particulate Al(OH)3(s) precipitate species onto the surface. Analysis of the MnOx(s) coating with by electron microscopy shows a heterogeneous surface composed of a mix of crystalline Mn oxides existing alongside amorphous Al(OH)3(s) species. The deposition of Al onto the media surface does not have any significant effect on the removal of soluble Mn, but the potential impact that Al might have on the capture of other dissolved species should be explored further.