Most of this is from the World Health Organization. Iron is the second most abundant metal in the earth�s crust. Elemental iron is rarely found in nature since the iron ions readily combine with oxygen and sulphur compounds to form oxides, hydroxides, carbonates and sulfides; most common in nature are oxides. Anaerobic ground water may contain iron (+II) up to several mg/l (ppm) without having any discoloration or turbidity when pumped directly from a well.
Iron in well water of 200mg/L is very, very high and could be an error. World health organization says iron can be as high as 50 mg/L in anaerobic well water, but usually concentration in the oxygen devoid well water is 0.5 to 10 mg/L. Median iron in surface waters is 0.7mg/L.
When water with dissolved iron is exposed to air a precipitate is formed Fe(OH)3 that is yellowish or ochre. The reddish precipitate is ferric oxide Fe203. Both precipitates can form gels or flocs that are detrimental to fish and aquatic life because they coat eggs and gills. Trout and pike have died at iron concentrations of 1-2mg/L (USEPA Quality Criteria for Water). Variability of natural waters with alkalinity, pH, hardness, and temperature and presence of ligands will change the valence and state of solubility, thus affecting iron�s toxicity.
Last edited by Bill Cody; 05/04/12 08:43 PM.
