The presence of stains, particulates and metallic taste often make it obvious that iron and manganese are present in a water supply even without water testing.

The concentration will determine the most practical and economical water treatment options to solve the problem. In addition to the concentration, it is also important to determine the form of the iron and manganese.

Ion exchange

• Conventional water softeners are sometimes effective for removing iron and small amounts of manganese.
• Softeners are generally only recommended when the water pH is greater than 6.7, the water hardness is between 3 and 20 grains per gallon (50 to 350 mg/L) and the dissolved iron concentration is less than 5 mg /L. Oxidized forms of iron and manganese will foul the softener resin.
• If oxidized iron and/or manganese are present in the raw water, filtration should be used for removal.

Manganese greensand filters

• In manganese greensand filters, the filter media is treated with potassium permanganate to form a coating that oxidizes the dissolved iron and manganese and then filters them out of the water.
• Because these units combine oxidation and filtration, they can be used to treat raw water with dissolved and/or oxidized iron and manganese.
• Manganese greensand filters require significant maintenance including frequent regen.eration with a potassium permanganate solution as it is consumed during oxidation of the dissolved metals.
• In addition, these units require regular backwashing to remove the oxidized iron and manganese particles.

Birm filters

• Birm filters are similar to manganese greensand but they do not require regen.eration because they utilize oxygen present in the raw water to oxidize the metals.
• As a result, the raw water must contain a certain amount of dissolved oxygen and the pH should be at least 6.8 for iron removal and 7.5 for manganese removal.
• Even under ideal conditions, manganese removal efficiency is highly variable with birm filters. Birm filters do require backwashing to remove accumulated oxidized metal particles.

Oxidation followed by filtration

• When combined levels of iron and manganese exceed 10 mg/L, the most effective treatment involves oxidation followed by filtration.
• In this process, a chemical is added to convert any dissolved iron and manganese into the solid, oxidized forms that can then be easily filtered from the water. Chlorine is most commonly used as the oxidant although potassium permanganate and hydrogen peroxide can also be used.
• A small chemical feed pump is used to feed the chlorine (usually sodium hypochlorite) solution into the water upstream from a mixing tank or coil of plastic pipe. The mixing tank or pipe coil is necessary to provide contact time for the iron and manganese precipitates to form.
• Significant system maintenance is required with these units. Solution tanks must be routinely refilled and mechanical filters need to be backwashed to remove accumulated iron and manganese particles.