Assessment of Fate of Manganese in Oxide-Coated Filtration Systems

This study employed pilot-scale filters to examine the fate of Mn in MnOx(s)-coated filter media as a function of filter-applied pH and backwash conditions. A key operational issue for continuous efficient Mn(II) removal was maintenance of appropriate levels of free chlorine to ensure coated media regeneration. Neutral or slightly acidic pH promoted Mn(II) sorption and subsequent oxidation on MnOx(s)coated media. Alkaline influent pH (pH > 7) allowed some soluble Mn(II) oxidation by free chlorine prior to filtration, resulting in significant Mn removal by MnOx(s) particle filtration. Increased backwash rates removed greater amounts of MnOx(s) from the filter media. The combination of MnOx(s) accumulation on filter media during filtration and its partial removal during backwash maintained a net amount of MnOx(s) coating sufficient for catalyzing further soluble Mn(II) removal, yet it did not significantly alter the size of the media.