Iron and Water Quality

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.


Cadmium and Water Quality

Cadmium: Cadmium is a non-essential element and it diminishes plant growth. It is considered a potential carcinogen. It also has been shown to cause toxic effects to the kidneys, bone defects, high blood pressure, and reproductive effects.

Cadmium is widely distributed in the environment at low concentrations. It can be found in fairly high concentrations in sewage sludge. Primary industrial uses for cadmium are plating, battery manufacture, pigments, and plastics.

Criteria: The standard for domestic water supply is <0.01 mg/L. The allowable level for aquatic life is derived using a formula involving hardness. At a hardness of 100, 0.001 mg/L is considered protective.


Lead and water quality

Lead: The primary natural source of lead is in the mineral galena (lead sulfide). It also occurs as carbonate, as sulfate and in several other forms. The solubility of these minerals and also of lead oxides and other inorganic salts is low. Major modern day uses of lead are for batteries, pigments, and other metal products. In the past lead was used as an additive in gasoline and became dispersed throughout the environment in the air, soils, and waters as a result of automobile exhaust emissions. For years this was the primary source of lead in the environment. However, since the replacement of leaded gasoline with unleaded gasoline in the mid-1980's, lead from that source has virtually disappeared. Mining, smelting and other industrial emissions and combustion sources and solid waste incinerators are now the primary sources of lead. Another source of lead is paint chips and dust from buildings built before 1978 and from bridges and other metal structures.

Lead is not an essential element. In humans it can affect the kidneys, the blood and most importantly the nervous system and brain. Even low levels in the blood have been associated with high blood pressure and reproductive effects. It is stored in the bones.

Lead reaches water bodies either through urban runoff or discharges such as sewage treatment plants and industrial plants. It also my be transferred from the air to surface water through precipitation (rain or snow). Toxic to both plant and animal life, lead's toxicity depends on its solubility and this, in turn, depends on pH and is affected by hardness.

Criteria: The level considered protective for aquatic life at a hardness of 100 is less than 0.003 mg/L. Use as a domestic water source requires less than 0.05 mg/L. Drinking water must contain less than 0.015 mg/L.

Zinc and Water Quality

Zinc: Zinc is found naturally in many rock-forming minerals. Because of its use in the vulcanization of rubber, it is generally found at higher levels near highways. It also may be present in industrial discharges. It is used to galvanize steel, and is found in batteries, plastics, wood preservatives, antiseptics and in rat and mouse poison.

Zinc is an essential element in the diet. It is not considered very toxic to humans or other organisms.

Criteria: Criteria for aquatic life has been set at less than 0.106 mg/L based on hardness of 100 mg/L.

other Pages



Back to Main Watershed Page