Groundwater containing iron and manganese can cause discolored water, laundry and plumbing fixtures, and in return can lead to consumer complaints. It's your job to find out the best way to prevent these problems and keep your customers happy.

Some treatment methods that have been known to be effective are oxidation/filtration, ion exchange and sequestration. First, you need to find the source of the problem and where it occurs before you can properly choose what method to use.

Different methods of treatment

There are a few different methods to explore before deciding which one is the best for your customer's iron and manganese problem.

For example, oxidation needs to happen before iron and manganese can even be filtered. This process involves transferring electrons to the oxidizing agent. Ferrous iron (Fe⁺²) oxidizes to form ferric iron (Fe⁺³) forming the insoluble iron hydroxide complex Fe(OH)₃ and manganese is oxidized from (Mn⁺²) to (Mn⁺⁴) forming (MnO₂).

"Effective oxidants used to help facilitate this conversion include chlorine, chlorine dioxide, permanganate and ozone," says Greg Gilles, vice president and principal of AdEdge Technologies Inc. "Aeration has also been used for years in both small and large water systems, but the kinetics of iron conversion are relatively slow compared to chemical oxidants and require more time, large contact vessels and other ancillary equipment for effective iron removal."

The chemical oxidants mentioned above aid in the oxidation/filtration process to convert iron and manganese from their ferrous and manganous form to their ferric and manganic forms where they can be subsequently filtered with various types of media and removed from the filters with regular backwashing. Some of these media are inert or non-reactive, while others such as those containing MnO₂ are catalyticm, which improves the efficiency of the process. This is a very common and effective treatment option for community and non transient, non-community systems.

Moreover, a home water softener can be used to treat low or moderate levels of dissolved iron and manganese. Water that has not been exposed to oxygen will allow the resins to remove the metals from the water.

However, the debate over using water softeners is that if the iron and manganese in the water become exposed to oxygen, they can clog up the softener, which will lead to poor performance, regular cleaning and costly repairs.

The method of sequestration starts at the pump intake when chemicals are added to the groundwater before it comes in contact with air or chlorine. This solution is one that can control the effects of iron and manganese but will not remove them.

"Where iron is very low (typically less than 1.0 mg/L), sequestering agents, which use polyphosphates to combine with the dissolved ferrous iron can effectively keep the iron in solution by combining with the iron to prevent it from forming filterable precipitants and depositing," explains Gilles.

This works by delaying the oxidation of iron and manganese by adding any three of the polyphosphates (pyrophosphate, tripolyphosphate or metaphosphate) to the metals, and this will also prevent sludge buildup in the pipes.

Sequestration can leave a slightly metallic taste in your customer's water, but it will prevent discoloration of the water and staining of plumbing fixtures.

Dealers should not rush into recommending an iron and manganese solution without exploring the customer's conditions, needs and problem water. A water quality test at the beginning of the process can lead to easier implementation and also help solidify the relationship.

Consider all factors. "pH is often overlooked in iron removal, " concludes Gilles. "pH should be above 6.8 and preferably in the range of 7.5 to 8.5 for optimal removal."