Metals in the Environment
Iron: Iron is the fourth most abundant element, by weight, in the earth's crust. Natural waters contain variable amounts of iron depending on the geological area and other chemical components of the waterway. Iron in groundwater is normally present in the ferrous or bivalent form [Fe++] which is soluble. It is easily oxidized to ferric iron [Fe+++] or insoluble iron upon exposure to air. This precipitate is orange-colored and often turns streams orange.
Environmental Impact: Iron is a trace element required by both plants and animals. It is a vital part of the oxygen transport mechanism in the blood (hemoglobin) of all vertebrate and some invertebrate animals. Ferrous Fe++ and ferric Fe+++ ions are the primary forms of concern in the aquatic environment. Other forms may be in either organic or inorganic wastewater streams. The ferrous form Fe++ can persist in water void of dissolved oxygen and usually originates from groundwater or mines that are pumped or drained. Iron in domestic water supply systems stains laundry and porcelain. It appears to be more of a nuisance than a potential health hazard. Taste thresholds of iron in water are 0.1 mg/L for ferrous iron and 0.2 mg/L ferric iron, giving a bitter or an astringent taste. Water to be used in industrial processes should contain less than 0.2 mg/L iron. Black or brown swamp waters may contain iron concentrations of several mg/L in the presence or absence of dissolved oxygen, but this iron form has little effect on aquatic life.
Criteria: The current aquatic life standard is less than 1.0 mg/L based on toxic effects. (It is one of the few for which the criteria is not calculated based on hardness.)
Aluminum and Water Quality
Aluminum: Aluminum is one of the most abundant elements in the earth's crust and occurs in many rocks and ores, but never as a pure metal. The presence of aluminum ions in streams may result from industrial wastes but is more likely to come from the wash water of drinking water treatment plants. Many aluminum salts are readily soluble; however, there are some that are very insoluble. Those that are insoluble will not exist long in surface water, but will precipitate and settle. Waters containing high concentrations of aluminum can become toxic to aquatic life if the pH is lowered (as in acid rain). For water wells, we have seen elevated levels of aluminum in the following cases: movement of grout materials for geothermal or groundsource heating and cooling systems, turbid waters and the aluminum is leached from the particle when the sample is preserved, leaching from cooking materials (pots, pans, and some cups), leached from piping caused by corrosion or microbiologically induced corrosion, corosion of a hotwater heater, and very low pH waters. The highest level we have ever detected was 80 mg/L in a leachate from a coal spoil pile and in well water it was 8 mg/L associated with corrosion and nuisance bacteria - Water was gray.
Criteria: Surfacewater - 0.75 mg/L . The secondary drinking water standard set for asethetic issues is 0.2 mg/L.
Water Research Center
...In Drinking Water