Removing Iron and Manganese from Water: Testing and Treatment Options

Iron and manganese are commonly found in groundwater, particularly in borehole and private water supplies. Although they occur naturally, elevated concentrations can cause staining, discoloured water, unpleasant tastes and problems with plumbing and water treatment equipment.

Removing these metals successfully depends on more than simply installing a filter. The form of the iron or manganese, water pH, dissolved oxygen, flow rate and available backwash capacity all influence which treatment method will work.

This guide explains how to identify iron and manganese problems, the treatment options available and what to consider before selecting a system.

How Do Iron and Manganese Affect Water?

Iron and manganese often occur together, but they can produce different symptoms.

Problem	Typical signs
Iron	Orange, reddish-brown or rusty staining
Manganese	Black or dark brown deposits and staining
Dissolved iron	Water initially appears clear but turns brown after exposure to air
Oxidised iron	Visible rust-coloured particles or sediment
Possible iron bacteria	Orange-brown slime, gelatinous deposits and recurring fouling

These signs are useful indicators, but they cannot establish the exact concentrations or forms present.

A rotten-egg smell may indicate hydrogen sulphide, which is a separate water-quality problem that can occur alongside iron and manganese.

UK Drinking Water Standards

The UK national drinking-water standards are:

• Iron: 0.2 mg/L (200 µg/L)

• Manganese: 0.05 mg/L (50 µg/L)

These values primarily address water quality, including appearance, staining and treatment performance. Elevated manganese can also raise health concerns, particularly with prolonged exposure at sufficiently high concentrations.

For a borehole or private supply, meeting the iron and manganese standards alone does not establish that the water is suitable for drinking. Microbiological quality and other chemical parameters must also be assessed.

Source: Drinking Water Inspectorate – Drinking Water Standards.

Why Is Water Testing Important?

Before choosing an iron or manganese removal system, a suitable water analysis is essential.

Ideally, the analysis should include:

• Total iron and manganese concentrations

• Dissolved iron and manganese, where relevant

• pH

• Turbidity

• Hardness and alkalinity

• Dissolved oxygen, particularly when considering Birm

• Organic matter or colour where contamination is suspected

• Hydrogen sulphide where odours are present

The required service flow rate and available backwash flow are equally important when sizing a system.

Dissolved vs Oxidised Iron

Iron may occur in two main forms:

Dissolved ferrous iron (Fe²⁺) is often invisible in freshly drawn water. When exposed to oxygen, it can oxidise into insoluble ferric compounds, producing the familiar orange-brown deposits.

Oxidised ferric iron (Fe³⁺) is already present as particles or suspended solids. These may be removed by appropriately sized sediment or multimedia filters.

This distinction matters because an ordinary sediment cartridge cannot reliably remove dissolved ferrous iron.

Manganese can also occur in dissolved and oxidised forms. Dissolved manganese is generally more difficult to oxidise than iron and often requires higher pH or additional treatment.

Methods for Removing Iron and Manganese

1. Sediment and Multimedia Filtration

If iron is already oxidised and present as suspended particles, mechanical filtration may be suitable.

Options include:

• Sediment cartridges

• Bag filtration

• Multimedia filters

• Backwashing sediment media such as Turbidex

Backwashing filters are often preferable where significant quantities of iron sediment are present because accumulated solids can be flushed to drain.

However, mechanical filtration alone will not reliably remove dissolved iron or manganese.

Where necessary, the water must first undergo oxidation so the dissolved metals can be converted into filterable particles.

2. Birm Filtration

Birm filtration systems use catalytic media to assist the oxidation of dissolved iron, allowing the resulting particles to be captured and removed through backwashing.

Birm can be an economical treatment method because it does not normally require chemical regeneration.

However, its performance depends heavily on feedwater conditions.

Important considerations include:

• A minimum pH of approximately 6.8 for iron removal

• Adequate dissolved oxygen

• Suitable alkalinity and water chemistry

• Absence of hydrogen sulphide and oil

• Compatibility with any chemicals present in the water

For manganese removal, Clack recommends a pH of approximately 8.0–9.0 for best results. Where iron is also present, additional pH restrictions apply.

Chlorine and certain treatment chemicals can interfere with Birm's catalytic activity.

Birm should only be selected after confirming the water chemistry and ensuring the system can provide the required service and backwash flow rates.

3. Filox-R and Pyrolox Filtration

Filox-R and Pyrolox are manganese dioxide-based filter media used for iron and manganese reduction.

Both can be effective in suitably designed backwashing filtration systems.

Filox-R iron and manganese removal systems use high-manganese-dioxide-content media to assist oxidation and filtration.

Pyrolox filtration systems use naturally occurring manganese dioxide media and can also be considered where hydrogen sulphide is present.

These media offer useful treatment options, but they are considerably denser than Birm.

Consequently, the available backwash flow rate is particularly important. Insufficient backwashing can allow accumulated deposits to remain within the bed, reducing performance and potentially causing fouling.

Manganese removal may also require a higher operating pH than iron removal.

For heavily contaminated water, additional aeration, chemical oxidation or contact time may be necessary.

Neither media should be selected solely on a quoted maximum iron concentration. Actual performance depends on the complete water analysis and system design.

4. Low-Fouling Water Softeners

A water softener is primarily designed to remove calcium and magnesium hardness through ion exchange.

However, suitable resin may also remove relatively small quantities of dissolved iron and manganese.

Low-fouling water softeners can be useful where:

• Iron and manganese concentrations are relatively low

• The metals are predominantly dissolved

• Hardness removal is also required

• Water chemistry falls within the resin manufacturer's operating limits

The main limitation is fouling.

When dissolved iron oxidises into insoluble particles, deposits can accumulate on the resin and interfere with ion exchange and regeneration.

This is why low-fouling resin is not necessarily a replacement for dedicated iron filtration.

In some applications, a softener may be installed after an iron removal filter to provide additional polishing.

Softener capacity and regeneration settings must account for the additional iron and manganese loading where the manufacturer permits this use.

5. Crystal-Right and Specialist Multi-Function Media

Certain specialist media can address several water-quality problems within one system.

For example, Crystal-Right CR100 systems may be suitable for selected applications involving hardness, iron and manganese.

These systems use salt regeneration and must be selected according to the specific media's operating conditions.

They can offer a practical alternative where more than one treatment objective is involved, but they are not universally suitable for high iron or manganese concentrations.

What If the Water Has a Low pH?

Low pH can significantly affect iron and manganese removal.

Although iron may oxidise relatively readily under suitable conditions, dissolved manganese is often much more difficult to remove at lower pH values.

Depending on the water analysis, pH correction may be required before filtration.

This can involve media such as Juraperle or FloMag, or another appropriately designed pH adjustment system.

The target pH should be selected for the downstream treatment media and the overall water chemistry.

Excessively high pH is not automatically better and can introduce other treatment problems, including precipitation and scaling.

What About Iron Bacteria?

Orange or reddish-brown slime within filter housings, toilet cisterns and pipework may indicate iron-related bacterial growth.

However, slime alone is not proof of iron bacteria, and further investigation may be necessary.

Iron bacteria and related organisms can produce deposits that:

• Restrict pipework and filters

• Increase maintenance requirements

• Interfere with treatment media

• Cause persistent staining and odours

Replacing a filter cartridge will not necessarily resolve established bacterial growth within a borehole or plumbing system.

Depending on the source and severity, treatment may involve professional cleaning, disinfection and ongoing management of the water supply.

UV disinfection is not a substitute for removing existing slime or biofilm from a system. It also requires suitable pretreatment to prevent particles and deposits from affecting performance.

A full microbiological assessment is important where water is intended for drinking.

Choosing the Right Treatment System

The most appropriate treatment depends on the actual water quality and operating conditions.

Water-quality issue	Treatment approaches to consider
Oxidised iron sediment	Sediment or backwashing multimedia filtration
Dissolved iron with suitable oxygen and pH	Birm or catalytic filtration
Iron and manganese requiring more intensive treatment	Filox-R, Pyrolox or another appropriately designed oxidation/filtration system
Low-level dissolved metals with hardness	Suitable low-fouling ion exchange resin
Combined hardness and selected iron/manganese problems	Specialist media such as Crystal-Right
Low pH	pH correction before treatment, where required
Significant organic contamination or bacterial slime	Additional investigation and treatment stages

For some private supplies, a complete treatment arrangement might involve:

1. Sediment prefiltration where required

2. pH correction or oxidation, according to the analysis

3. Backwashing iron and manganese filtration

4. Fine cartridge filtration where appropriate

5. UV disinfection where microbiological treatment is required

This is an illustrative arrangement rather than a universal installation design. The order and selection of treatment stages must follow the water analysis.

Remember the Backwash Requirements

One of the most important considerations when specifying backwashing iron and manganese filters is the difference between service flow and backwash flow.

A filter may operate at a modest service flow rate but need a substantially greater flow during backwashing.

The borehole pump, pressure system, control valve, drain line and pipework must all support the required backwash rate.

Choosing a vessel based only on its nominal service flow can result in inadequate cleaning of the media bed.

This is especially important with dense manganese dioxide media such as Filox-R and Pyrolox.

Confirming Treatment Performance

Once a system has been installed and commissioned, treated-water testing is essential.

A suitable monitoring programme should check iron and manganese after treatment and periodically thereafter, particularly as filters approach their scheduled backwash or regeneration.

If the source is used for drinking, the wider microbiological and chemical safety of the supply must also be confirmed.

Clear-looking water is not proof that dissolved iron, manganese or other contaminants have been adequately removed.

Need Help Selecting an Iron and Manganese Filter?

At GAPS Water Treatment, we supply filtration equipment, specialist media and complete water treatment systems for domestic, commercial and private water supplies.

To help us identify suitable equipment, please email your water analysis together with:

• Required service flow rate

• Available backwash flow rate

• Available water pressure

• Details of existing treatment equipment

• Any known problems with staining, sediment or odours

Email: sales@gapswater.co.uk

We can then review the information and advise on suitable treatment options and equipment.