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The Metropolitan Water District of Southern California carried out a study to evaluatemanganese (Mn) desorption from filter media during biological filtration startup. Mncontamination of the filter media was a byproduct of prior use of ferric chloride (FeClsub3/sub), whichcontains Mn, for coagulation and free chlorine exposure. During pilot- and full-scale testingat pH 6.5, FeClsub3/sub coagulation (without chlorine) released soluble Mn at nearly four times thelevel released by aluminum sulfate (alum; 105 g/L for FeClsub3/sub and 27 g/L for alum). Pilot-scaleexperiments demonstrated that Mn was present in the filter column in three valence states[Mn(II), Mn(III), and Mn(IV)]. Mn(II) in the filter influent was from the FeClsub3/sub. Mn on theanthracite media was hypothesized to be Mn(II)/Mn(IV) and first physically displaced by ferriciron, aluminum, and hydrogen, and then catalytically oxidized to Mn(IV) by silica sand. Includes 39 references, tables, figures.

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Edition: Vol. 98 - No. 5 Published: 05/01/2006 Number of Pages: 12 File Size: 1 file , 370 KB