Dissolved iron in groundwater (Maryland's Coastal Plain province) typically originates from dissolution of iron oxyhydroxide sediment-grain coatings and authigenic iron-bearing minerals such as goethite, limonite, and iron hydroxide produced from weathereing of glauconite (iron-aluminum silicate). The reaction of iron in groundwater is complex and depends on the amount of iron-bearing minerals in the sediment, the Eh (reduction-oxidation potential) of the water, the pH,and the availability of other ions that can bond with iron. Also, aqueous iron chemistry can be affected greatly by both iron-reducing and iron-oxidizing microorganisms.
The Secondary Maximum Contaminant Level for iron in drinking water is 0.3 milligrams per liter (US Environmental Protection Agency). Concentrations greater than this value can stain clothing and plumbing fixtures and can impart a metallic taste to water. Removal of iron is generally accomplished by a combination of increasing the pH of the water through the addition of a strong base (for example chlorine and permanganate, MnO-4), and passing the water through a sand or activated charcoal filter. Cation exchange can also be used to remove small quantities of iron.
[Source of data in table: "A User's Guide for the Artesian Aquifers of the Maryland Coastal Plain--Part Two:Aquifer Characteristics" (H. Hansen, 1972; Maryland Geological Survey)]