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Iron - Manganese• Iron Iron, which makes up 5% of the earth's crust, is a common water contaminant. It can be difficult to remove because it may change valence states - that is, change from the water-soluble ferrous state (Fe2+) to the insoluble ferric state (Fe3+). When oxygen or an oxidizing agent is introduced, ferrous iron becomes ferric which is insoluble and so precipitates, leading to a rusty (red-brown) appearance in water. This change can occur when deep well water is pumped into a distribution system where it adsorbs oxygen. Ferric iron can create havoc with valves, piping, water treatment equipment, and water-using devices. Certain bacteria can further complicate iron problems. Organisms such as Crenothrix, Sphaerotilus and Gallionella use iron as an energy source. These iron-reducing bacteria eventually form a rusty, gelatinous sludge that can plug a water pipe. When diagnosing an iron problem, it is very important to determine whether or not such bacteria are present. • Manganese Although manganese behaves like iron, much lower concentrations can cause water system problems. However, manganese does not occur as frequently as iron. Manganese forms a dark, almost black, precipitate. |
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