There is little doubt when a water supply is contaminated with excessive iron or manganese -- the brown or black stains in sinks and laundry, rusty water coming from a faucet, and the obnoxious taste or odor are difficult to miss. While they are not considered to be health risks, treatments for iron and manganese can be very effective, but choosing the best option for any situation requires knowing which type of iron is present in the water. 

Types of Iron in Water Supplies

Iron can appear in several forms in a water supply, and knowing which form is present is essential to choosing the correct treatment. Fortunately, determining which form of iron is present in a water supply is not difficult.

• Water drawn from a faucet appears clear, but when allowed to stand develops black or rust-colored particles that settle to the bottom of a container. When this occurs it is likely that ferrous iron is present. This form reacts with air, chlorine, or other oxidants to form ferric iron. 
• Ferric iron is the second type of iron found commonly in water, seen in water that appears rusty, or has a red or yellow color, when drawn from a faucet. Ferric iron is insoluble in water, and settles quickly when allowed to stand in a container. 
• Appearance of a slimy brown or red film on plumbing fixtures (such as inside a toilet flush tank); or a gelatinous sludge in pipes, may indicate the presence of iron bacteria. These bacteria live in the water, and metabolize iron to live. In some cases, these bacteria even attack steel pipes to get the iron they need. 

Choosing the best treatment for iron or manganese removal depends not only on the form of the iron or manganese present, but also on how much of the contaminant is present, the hardness of the water, temperature variations, and the water's pH (acidity or alkalinity) level. Because of the complexity of the problem, a thorough water analysis and consulting with a water treatment professional is recommended.

Ferrous iron can effectively be treated by using a standard cation-exchange water softener. Iron is filtered from the water by the softener's resin bed, and is removed during regeneration of the softener. Special treatments for cleaning softener resins are commercially available if regeneration fails to completely remove the iron.

For more acidic or harder water, or if iron levels are very high, other measures may be necessary. These techniques often include oxidizing the iron to its insoluble ferric state (either by a special oxidizing filter medium, or by adding chlorine) , and filtering it from the water with an activated carbon filter. A special "iron filter" that performs both the oxidizing and filtering steps together may also be used. The activated carbon filter also removes any excess chlorine that may have been added to oxidize the ferrous iron. Other applications might include feeding soda-ash into the water, which reduces the acidity of the water, and greatly enhances iron and manganese oxidation and removal efficiency. 

Solving the problem of iron or manganese bacteria is usually accomplished through some sort of disinfection process such as chlorination, and then removing excess chlorine by an activated carbon filter. Diagnosing an iron or manganese bacteria problem is important, however, as they can plug or corrode pipes, and damage water softening equipment. 

One final technique used to remove iron and manganese is called chemical sequestration, in which the water is treated with organic compounds which allow the iron and manganese to pass through wate softening equipment. This method prevents the contaminants from oxidizing and coming out of solution. The harmless iron or manganese remains suspended in the water, but none of its staining effects are seen.

Consult a Professional

Choosing a treatment to solve an iron or manganese problem is often a complex decision, involving consideration of water test results, economic factors, and other water quality issues that need to be addressed in a water supply. We recommend consulting a water treatment professional - and even obtaining several opinions - before proceeding with any iron or manganese removal treatment plan.

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