Iron is one of the most abundant elements in the earth's crust. It is an essential nutrient for life. Ironically (oops! no pun intended.) it is the cause of most of our water quality complaints, i.e. rusty water. If you are having problems with rusty water, see Private Filtration later in this document.
We use iron to protect and convey our water from well to tap, often in direct contact with the water. However, almost all of the iron that we occasionally see coloring our tap water has been in the water long before touching any man-made structure. Iron has been significantly present in the drinking water of all creatures since they began to walk on the face of the earth.
There is no maximum contaminate level for iron. A level above 0.3 ppm can cause staining on porcelain and in laundry. We have levels of iron between 0.9 and 1.6 ppm (ihtr) in fresh raw water from our wells. That level will fluctuate wildly in our distribution system depending on flow rate pattern, temperature, and distance from production.
Iron begins as natural deposits in soils and rock and some organic matter. As rainwater falls, it picks up oxygen and carbon dioxide from the air and organic matter from the ground. The water percolates though the soil where bacteria use the oxygen in the water to metabolize the organic matter. As the oxygen is depleted, other bacteria use oxidized iron in the soil to further metabolize the organic matter. These actions cause the water to become more acidic and the iron to become more soluble. As the water percolates deeper, the organic matter is depleted and the bacteria die. Deeper yet, the water picks up calcium and magnesium from limestone formations. This serves to neutralize the acids and limit the iron concentration. This is the stage when our wells will collect the water.
The iron in our well water is colorless before chlorination. As air or chlorine contacts the iron in the water the iron will oxidize to its trivalent state. Iron in this state is strongly colored and insoluble (rust). We therefore treat the water with a chemical to sequester the iron prior to chlorination. This prevents the strong color and precipitation. This treatment is temporary, however, decaying with time and elevated temperatures. As the treatment decays, the iron will change color and drop out of solution. Often this occurs during low flow rates inside a water main, coating the inside with rust. When the flow rate increases, it picks up the rust and carries it wherever the water is going.
Chemical preparations are commonly available to treat rust stains. They work by making the iron soluble again. Sulfites and bisulfites are their common ingredients. Check your local grocery or hardware store. Back to Contents
Edited 03/20/2004