Water Clarification and Media Filtration: Iron and Manganese Reduction


Iron and Manganese reduction

Iron and Manganese along with turbidity are the most common quality issues in water supplies. The recommended limits of 0.3 mg/l for Fe and 0.05 mg/l for Mn are the approximate concentrations above which iron and Manganese cause problems like taste/odour, laundry stains, and blockages.

Iron can be found in water as dissolved Fe2+ (ferrous) or as precipitate Fe3+ (ferric).  In the same way, Manganese can be found dissolved as Mn2+ or insoluble as Mn3+ or Mn4+.

Dissolved Iron and Manganese cannot be filtered easily and the common practice is to oxidise all Fe2+ and Mn2+ to Fe3+ and Mn3+ and then remove the precipitate flocks by filtration.

Fe and Mn can be oxidised using aeration, chlorine dosing or any other oxidation agent but reaction times are, in general, high (5 to 30 min). These reaction times can be accelerated by means of a catalytic media like Greensand or DMI-65, with which Fe and Mn are oxidised and precipitated by contact with the catalytic media.

Based on the water analysis, lay-out and other factors we recommend the next two alternatives:

Pre-oxitation and standard media filtration

Iron and Manganese are oxidised for a minimum of 30 min and then solids are removed on a non specialised filter, typically in dual-media with 500 mm of 1.1 mm GAC and 500 mm of 0.6 mm filter sand.  Filtration rate shall be a maximum of 12m/h.


In-line oxidation and filtration with catalytic media

An oxidising agent is dosed in line and Greensand or DMI-65 are used as catalytic and filtrating media.


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*(1) All data for information only and subject to change based on actual water analysis and final design parameters


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