Iron and manganese in water usually come from rocks and soil in the Earth’s crust, dissolved by groundwater that is low in oxygen. When that water is pumped to the surface and exposed to air, the dissolved metals can oxidise, causing staining, metallic taste, deposits and filter clogging.
For wells, boreholes and other groundwater supplies, the problem may not be obvious at first. Water can look clear when it leaves the source, then change colour or leave deposits after standing.
This article explains what causes iron and manganese in water, the warning signs to look for, how to test for them and how oxidation-based treatment can remove them.
What causes iron and manganese in water?
Groundwater that is low in oxygen can dissolve iron and manganese from minerals in the Earth’s crust. This is why wells and boreholes are especially prone to these problems compared with many surface water supplies.
The type of iron matters. Dissolved ferrous iron can make water look clear at first. Once it meets oxygen, it oxidises into ferric iron and forms orange or brown particles.
Manganese behaves in a similar way, but is generally harder to oxidise and remove than iron. High iron levels can also support iron bacteria, which may produce slimy orange or brown deposits in wells, pipes and filters.
What are the warning signs?
Iron and manganese often reveal themselves through staining, colour changes, taste and deposits. The pattern can help indicate which metal is causing the problem.
| Sign | Likely cause |
| Orange or brown stains | High iron |
| Black or dark brown stains | Manganese |
| Metallic taste | Elevated iron levels |
| Clear water that turns orange after standing | Dissolved ferrous iron oxidising |
| Slimy orange deposits | Iron bacteria |
| Clogged filters, pipes or irrigation drippers | Iron, manganese or both |
By the time these problems are visible in tap water, oxidation and deposit formation may already be taking place throughout the system.
Is iron and manganese in drinking water a problem?
Iron in drinking water is usually more of a water quality and operational issue, while high levels of manganese can also raise health concerns over long-term exposure.
Iron can affect taste, colour and appearance and can contribute to staining and deposits in drinking water supplies. Manganese can cause similar nuisance problems, but high levels of manganese are more significant from a health perspective.
Under the EU Drinking Water Directive, the indicator values are 200 micrograms per litre (µg/L) for iron and 50 µg/L for manganese.
Public water systems are routinely monitored under regulatory frameworks. Private wells and smaller supplies may not be tested for manganese as consistently, so direct testing is important where staining, colour changes or deposits appear.
How do you test for iron and manganese?
A laboratory test can show actual iron and manganese concentrations and help distinguish a source-water problem from one occurring later in the system. Test both metals rather than assuming visible orange staining means iron is the only issue.
Retesting can also be useful after changes in pumping conditions, water level, treatment performance or source behaviour.
How does oxidation-based treatment work?
Oxidation-based water treatment converts dissolved iron and manganese into solid particles that can then be removed by filtration. This is the basic principle behind aeration, ozone treatment and chemical oxidation.
| Method | How it oxidises | Main consideration |
| Aeration | Introduces oxygen into the water | Effective for many iron problems, but manganese may be harder to oxidise |
| Chemical oxidants | Uses agents such as chlorine or permanganate | Requires chemical handling and dosing |
| Ozone | Provides strong oxidation | Can treat both iron and manganese before filtration |
After oxidation, sand, greensand or other filtration media remove the resulting particles.
Because manganese is generally more difficult to oxidise than iron, treatment conditions need to be matched to the actual water chemistry and concentrations.
Chemical-free oxidation with nanobubbles
Nanobubble systems can deliver oxygen or ozone efficiently into well water, helping improve gas transfer and oxidation before filtration. The bubbles remain suspended for longer than conventional larger bubbles, increasing contact between the gas and the dissolved contaminants.
PMnB Technologies, a European nanobubble water treatment company backed by Palgey Maim’s engineering heritage, uses oxygen and ozone nanobubbles for chemical-free oxidation of iron and manganese upstream of filtration.
In one PMnB well-water project in Mexico, wells were restored to operation at 144 m³/h (40 L/s) with effective iron and manganese removal and without chlorination.
For well owners, utilities and operators dealing with staining, filter fouling or difficult manganese removal, oxidation followed by filtration provides a practical route to improving water quality without relying on continuous chemical dosing.
Talk to an engineer about your well water.
