Iron and manganese occur naturally in water, especially groundwater. Neither of the elements causes adverse heath effects; they are, in fact, essential to the human diet. However, water containing excessive amounts of iron and manganese can stain clothes, discolor plumbing fixtures, and sometimes add a "rusty" taste and look to the water.

The US Environmental Protection Agency and the Safe Drinking Water Act (SDWA) has established a secondary (aesthetic) standard Maximum Contaminant Level (MCL) for iron in drinking water of 0.3 parts per million (ppm); for manganese it is 0.05 ppm. At present, the US Environmental Protection Agency (EPA) has not set health standards for either iron or manganese in drinking water, therefore, stated MCLs are not enforceable. However, a health based standard for manganese is possible. Manganese may affect neurological and muscle function in humans. The Department of Environmental Services (DES) Health Risk Assessment Program has adopted an interim health based standard for manganese of 0.84 mg/L.

How iron and manganese are removed depends on the type and concentration, and this helps determine the best procedure and treatment system to use. Iron and manganese can be present in water in one of three basic forms: dissolved, particulate and colloidal. The predominance of one form over another is dependent on the water's pH. The two most common treatment methods are removal by oxidation/filtration and adsorbing onto ion exchange resins.

Oxidation involves the introduction of an oxidizing agent which chemically reacts with the iron or manganese to form an insoluble particle which can then be physically filtered out through a media bed.

Oxidation can be carried out one of the following methods:

• aeration - blowing/spraying air through the water
• addition of dissolved chemical oxidants - chlorine, chlorine dioxide and potassium permanganate (KMnO4)
• adsorption - greensand media and activated carbon

The process of oxidation followed by filtration is fairly easy and is often the treatment of choice. The use of ion exchange resins for the removal of iron and manganese has limited application due to the requirement that the contaminants be in dissolved form and at very low levels. This is due to the tendency of oxygen to react with the iron and managanes and therefore, increase the potential for plugging and buildup on the resin surface. Iron fouling is a common, and sometimes, irreversible problem with ion exchange treatment.

Treatment technologies for Iron and Manganese Removal from Groundwater:

Aeration
Activated Carbon
Media Filtration
Chemical Oxidation
Ion Exchange