Iron and Manganese

Most water contains some iron and manganese which naturally leaches from rocks and soils. Found naturally in soils, rocks, plants, and most water supplies, these minerals are essential to human health. Excess amounts in drinking water can cause discolored water, rusty-brown stains or black specs on fixtures and laundry. Excess amounts may also affect the taste of beverages and can build up deposits in pipes, heaters or pressure tanks.

Drinking Water Standard and Health Risks

Iron and manganese in the amounts found in most drinking waters are not harmful to health. The secondary drinking water standards of 0.3 milligram per liter for iron and 0.05 milligram per liter for manganese are set to indicate problems of taste, staining, and cloudiness.

Manganese is one of a small group of chemicals (including iron, copper and a few others) that reaches an undesirable level due to taste, odor, or color before it becomes a health hazard. For this reason, health-based guidelines for these chemicals are usually not available. Instead, secondary or "aesthetic" MCLs have been promulgated by the U.S. EPA. These "SMCLs" are not formally adopted by the state and thus are not legally enforceable. However, exceeding the SMCL usually means that the water is undesirable for human consumption. The SMCL for manganese is 0.05 mg/l.

The existence of an SMCL for a chemical does not preclude that chemical being present in water at a level that would be a health concern if consumed. Consumption of water containing large amounts of manganese has been documented to cause adverse health effects in a few cases. Because of the large amounts of wells being found in the state with high manganese levels, and because some people apparently consume water containing levels much higher than the SMCL, it was determined that a guideline for protection of public health was necessary in addition to the existing SMCL.

The Department of Health and Human Services has determined that a reasonable guideline for manganese would be about 0.8 mg/l.

Possible Source of Contamination

In some places iron occurs in high concentrations naturally because of the type of rocks and soils the water comes in contact with. If the water is acidic, ground water can also pick up additional iron from contact with well casing, pump, and piping. The more acidic the water, the more it will dissolve metal from the surface it contacts.

High iron in ground water also can be caused by landfill leachate or a leaking petroleum tank.

Correcting The Problem

Iron and manganese can be removed by any one of a number of methods. Contact a water treatment specialist. They are listed in the yellow pages under "Water Treatment".