What are Iron and Manganese?
Iron and manganese are two of the most common contaminants present in groundwater wells. These two metals have many similar chemical properties and are often removed in the same treatment processes.
What happens to iron and manganese when they enter the environment?
Natural ore deposits of iron and manganese bearing minerals yield these metals to groundwater. When drawn from the tap dissolved iron and manganese will often be invisible to the eye but detectable by taste. Both iron and manganese undergo oxidation when exposed to the air in which they become visible as a colored sediment which can settle out in the glass. Iron can also be added to the water from a rusting plumbing system or from corrosion of pumps, water meters, fittings or an unlined pressure tank.
How might I be exposed to iron and manganese?
Neither of these metals are considered to be toxic, but are listed by the Alaska Department of Environmental Conservation (ADEC) as secondary (aesthetic) parameters, affecting the appearance and palatability of the water.
Iron produces the familiar rust ring in bathtub fixtures and sinks and orange or yellow stains on clothing, while manganese produces black stains. ADEC limits the amount of iron to 0.3 ppm and manganese to 0.05 ppm in public water supplies.
In low concentrations iron and manganese can be removed by water softeners. At higher levels the softener media may become permanently fouled with iron, so an iron filter with greensand media and potassium permanganate as a regenerant is used. Potassium permanganate is either added as a continuous feed ahead of the iron filter or in the backwash cycle to recharge the media and restore its treatment capacity.
High concentrations of iron or manganese can also be treated by aeration, converting the dissolved iron and manganese to a precipitate form such as described above. The precipitate is removed by a sediment or sand filter. Frequent replacement of the cartridge style filters or backwashing of the sand filters is required to maintain the flow of water through the treatment system.
Several methods are available for testing iron and manganese, with the most accurate being atomic absorption spectrophotometry. Northern Testing Laboratories uses Perkin Elmer Atomic Absorption equipment for the analysis of iron and manganese. NTL's detection limits are in the ppb level for these metals. Because of the very low detection level they can attain, it is recommended that you collect the samples in one of their specially prepared acid washed bottles. To determine the concentration of iron and manganese in the well water, it is highly recommend sampling as near the well as possible. Collecting a sample from a cold water tap in the house would determine the amount of iron or manganese in your finished drinking water supply after treatment such as softeners or reverse osmosis units.