There are 5 different types of iron. This is important to us as what type of iron you have can affect how we treat your water.
Dissolved/Ferrous Iron
This type is most common in groundwater before it is exposed to air. It takes the form Fe2+. This water looks clear when discharged, but if left for example in a bucket it will turn brown. This cannot be filtered, but it can be removed by other means (e.g. cation exchange)
Oxidised/Ferric Iron (Rust)
This is common when the water has been exposed to air (e.g. in storage tanks). It takes the form Fe3+. This is a precipitate or suspended particles in the water, it is no longer dissolved. It can now be filtered. The water often has a red/brown appearance.
Colloidal Iron
Is in essence the same as Ferric iron (Also Fe3+), but the particles have formed at less than 1 micron in size, making them more difficult to filter. A coagulent may be needed
Organically Bound Iron
When tannins are also present in groundwater supplies, they can bind with ferrous iron, making it more difficult to remove. If softening is used it may need to be combined with tannin removal to be effective. Otherwise, oxidation and filtration can be used.
Bacterial Iron
There are several species of iron oxidising bacteria which can infect wells. These colonise the surface where water from an anaerobic environment meets the aerobic environment. These bacteria feed on soluble/ferrous iron and oxidise it to ferric iron Mucous is produced in the process and this often appears as a brown slime.Oily films may be observed on the water surface and a smell may be noted resembling fuel or sewage.
Iron bacteria are difficult to deal with once they are established. Shock treatment of wells with chlorine can be effective, however this may need to be repeated regularly. Otherwise continuous oxidation/filtration is an effective method of control.