OPTIMIZING TREATMENT THROUGH FE AND MN FRACTIONATION

A series of filtration steps was used to separate iron (Fe) and mangan ese (Mn) into soluble, colloidal, and particulate fractions. Two case studies demonstrate how fractionation data can improve understanding o f the origins and removal of Fe and Mn. The Mn species present in one water source were shown to be regulated by a biogeochemical cycle in w hich the natural oxidation and reduction of Mn appeared to be microbia lly mediated. Mn removal was improved by adjusting the application of potassium permanganate to account for this cycle. A groundwater treatm ent plant was suffering from high postfilter Fe and Mn concentrations. Fractionation data identified the problem as inadequate solids captur e, not oxidant dosage, allowing a quick solution. The unexpected oxida tion of Mn with chlorine (Cl-2) was attributed to Fe oxide surface cat alysis. Without adequate particle removal (no coagulant added), applyi ng Cl-2 on top of the filters exhibited superior removal to adding Cl- 2 before a detention basin.