Water Problems — Manganese

Manganese is a mineral that naturally occurs in rocks and soil and may also be present due to underground pollution sources. Manganese is seldom found alone in a water supply. It is frequently found in iron-bearing waters but is rare than iron. Chemically it can be considered a close relative of iron since it occurs in much the same forms as iron. When manganese is present in water, it is as annoying as iron, perhaps even more so. In low concentrations, it produces extremely objectionable stains on everything with which it comes in contact. Deposits collect in pipelines, and tap water may contain black sediment and turbidity due to precipitated manganese. When fabrics are washed in manganese-bearing water, dark brown or black stains are formed due to the oxidation of the manganese.

The U.S. EPA Secondary Drinking Water Regulations recommend a limit of 0.05 mg/l manganese because of the staining which may be caused. For many industrial purposes, the manganese content should not exceed 0.01 to 0.02 mg/l. And in some cases, this is even considered excessive. In concentrations higher than 0.05 mg/l the manganese may become noticeable by impairing color, odor, or taste to the water. However, according to the EPA health effects are not a concern until concentrations are approximately 10 times higher. If it is unbearable, one could use water treatment technologies including cation exchange water softening, distillation, filtration, and reverse osmosis, which can be effective in removing manganese from water.

What health effects can manganese cause?

Manganese can be consumed from our diet and in our drinking water. Bathing and showering in manganese-containing water do not increase your exposure since manganese does not penetrate the skin and doesn’t get into the air. High exposure to manganese has been associated with toxicity to the nervous system, producing a syndrome that resembles Parkinsonism. Manganese is unlikely to produce other types of toxicity such as cancer or reproductive damage. Young children appear to absorb more manganese than older age groups but excrete less. This makes it particularly important for pregnant women and children to have clean drinking water.

Due to the fact that dissolved manganese oxidizes slower than iron, it is generally more difficult to be removed from the water. Pure elemental manganese metal is gray tinged with pink, brittle, and somewhat harder than iron which it resembles. Pure metal is not found in nature. However, this chemically active element is found in many compounds. Deposits occur in certain portions of the US as well as in other parts of the world.

Manganese is present most frequently as a manganous ion (Mn++) in water. Salts of man­ganese are generally more soluble in acid than in alkaline water. In this way, they are similar to iron. The manganous ion is usually introduced to water through the solubility of manganous bicarbonate.