Drinking Water Questions and Answers

Do you have questions about your private drinking water supply?  How about wellhead protection including the management of your private sewage treatment system?  Send your questions using the Ask An Expert feature on this web site.  University of Nebraska - Lincoln Extension Water Quality Educator Sharon Skipton will address your questions.

May, 2012 Consumer Question Of The Month

Q: We have high levels of dissolved iron and manganese in our water. How can it be managed?

A: The four most commonly applied methods for treating water containing dissolved iron and manganese, are: ion exchange water softeners, oxidizing filters, aeration (pressure type) followed by filtration, and chemical oxidation followed by filtration. All four methods can be successful if performance criteria are met. An individual should work with a reliable, competent water treatment dealer to select the best treatment method for a given situation.

Conventional water softeners are sometimes effective for removing dissolved iron and manganese concentrations of 5 mg/L or less from water. Iron and manganese removal is accomplished in the same way as calcium and magnesium (hardness) removal in water by an exchange process. Iron and manganese are exchanged with sodium on the ion exchange resin.

An oxidizing filter, which both oxidizes and filters iron and manganese in one unit, is the most widely used option for managing moderate levels of dissolved iron and manganese at combined concentrations up to 15 mg/L. An oxidizing filter typically contains a filter media of natural manganese greensand or manufactured zeolite coated with manganese oxide. The filter media is periodically treated with potassium permanganate to form a coating that oxidizes the dissolved iron and manganese so each form precipitates. This precipitated iron and manganese is filtered out by the manganese greensand because it also acts as a filtering media.

High levels of dissolved iron and manganese at combined concentrations up to 5 to 10 mg/L can be treated with an aeration (mixing with air) followed by a filtration system. In this system, air is sucked in and mixed with the passing stream of water to oxidize the iron and manganese into particles. The air-saturated water then enters the precipitator/aerator vessel, usually a pressure-type aerator for domestic use, where air is separated from the water. The water then flows through a filter, which uses various filter media to filter out oxidized particles of iron and manganese. More time and oxygen are required for treating manganese compared to iron with this type of system.

High levels of dissolved or oxidized iron and manganese greater than 10 mg/L can be treated by chemical oxidation followed by a sand trap filter to remove the precipitated particles. This treatment is particularly useful when iron is combined with organic matter or when iron bacteria are present. In this method, the water is treated with an oxidizing agent such as ozone, chlorine, or potassium permanganate to convert any dissolved iron and manganese into solid, oxidized forms that can then be filtered through a sand trap filter. Significant retention or contact time is required to allow oxidation to take place. For this reason, a storage tank may be needed. If chlorine is used as the oxidizing agent, it may be necessary to install an activated carbon filter to remove taste and odor from residual chlorine left in water after oxidation.