Birm is a granular filtration media commonly used to remove dissolved iron and manganese from borehole and well water.
It offers a relatively economical treatment method because it does not require chemical regeneration. Instead, it uses the dissolved oxygen already present in the water to help oxidise iron and manganese into particles that can be removed through filtration.
However, Birm only performs effectively when the incoming water meets specific chemical conditions.
Water pH, dissolved oxygen, alkalinity and the presence of other contaminants all influence whether Birm is a suitable choice.
What Is Birm Filter Media?
Birm is a specialist catalytic filtration media manufactured by Clack Corporation.
It acts as a catalyst, accelerating the reaction between dissolved oxygen and soluble iron or manganese compounds.
The oxidation process converts these dissolved metals into insoluble particles that can be trapped within the filter bed.
The accumulated particles are subsequently removed during backwashing.
Unlike some other iron removal media, Birm does not require potassium permanganate or another chemical regenerant to restore its catalytic activity.
However, the water must contain sufficient dissolved oxygen to support the oxidation process.
How Does Birm Remove Iron?
Iron in borehole water is often present in its dissolved ferrous form (Fe²⁺).
At this stage, the water may appear perfectly clear.
When ferrous iron is oxidised, it converts into ferric iron (Fe³⁺), which forms insoluble iron compounds that can be removed by filtration.
Birm accelerates this oxidation reaction using dissolved oxygen present in the water.
The resulting iron precipitate becomes trapped in the media bed and is subsequently removed during backwashing.
This makes Birm particularly useful for clear groundwater containing dissolved iron, provided the necessary operating conditions are met.
Can Birm Remove Manganese?
Yes, Birm can also be used for manganese removal.
However, manganese is generally more difficult to oxidise than iron and requires a higher pH.
Clack recommends a pH of approximately 8.0–9.0 for effective manganese removal.
If the water contains both iron and manganese, Clack advises keeping the pH below approximately 8.5 to reduce the risk of forming difficult-to-filter colloidal iron.
Consequently, water containing both metals may require a relatively narrow operating pH range of approximately 8.0–8.5.
A water analysis should be used to determine whether Birm is an appropriate treatment method.
Water Quality Requirements for Birm
Birm is not suitable for every borehole or well water supply.
The following conditions are based on Clack's published technical guidance.
| Parameter | Operating requirement |
|---|---|
| pH for iron removal | Minimum 6.8 |
| pH for manganese removal | Preferably 8.0–9.0 |
| pH when iron and manganese coexist | Preferably below 8.5 |
| Dissolved oxygen for iron | At least 15% of the iron concentration |
| Dissolved oxygen for manganese | At least 29% of the manganese concentration |
| Organic matter | Generally below 4–5 mg/L |
| Hydrogen sulphide | Should not be present |
| Oil contamination | Should not be present |
| Polyphosphates | Should not be present |
Dissolved oxygen and metal concentrations should be compared using consistent units, normally mg/L.
Clack also specifies that alkalinity should exceed twice the combined sulphate and chloride concentration.
These requirements are important because unsuitable water chemistry can reduce the catalytic effectiveness of Birm.
Why Dissolved Oxygen Matters
Birm relies on dissolved oxygen to oxidise iron and manganese.
Some groundwater supplies contain very little oxygen, particularly where the water comes from deeper boreholes.
If the dissolved oxygen concentration is too low, Birm may not remove the metals effectively.
In these circumstances, aeration before the Birm filter may be necessary.
Ideally, dissolved oxygen should be measured directly at the water source under normal operating conditions, as sampling and exposure to air can alter the result.
What Happens If the pH Is Too Low?
Where the incoming water has a pH below 6.8, iron removal using Birm may be ineffective.
A pH correction stage can be installed upstream of the Birm filter to increase the pH.
Depending on the water chemistry, this may involve:
-
Calcium carbonate media such as Juraperle or Calcite
-
Magnesium oxide media such as Corosex
-
Chemical pH adjustment
The treatment must achieve a suitable pH for the contaminants being removed.
For manganese, simply raising the pH to 6.8 is unlikely to be sufficient.
Birm Service Flow Rates and Backwashing
Correct vessel sizing is essential for successful Birm filtration.
Two separate flow rates must be considered.
Service Flow Rate
The service flow rate is the amount of water passing through the filter during normal treatment.
If water passes through the media too quickly, there may be insufficient opportunity for oxidation and filtration.
This can result in iron or manganese passing through the system.
Backwash Flow Rate
Backwashing reverses the direction of water flow through the filter bed.
This expands and cleans the media, flushing accumulated iron and manganese precipitates to drain.
The backwash flow must be sufficient to expand the bed without carrying excessive media into the drain.
A system may have sufficient water flow for normal household use but insufficient flow to backwash the filter correctly.
This is particularly important when selecting a system for a borehole pump.
Example Birm System Flow Rates
The following examples illustrate service and backwash requirements for selected GAPS Birm systems.
| Vessel size | Service flow | Backwash flow |
|---|---|---|
| 10" × 54" | 0.6 m³/hr | 1.1 m³/hr |
| 13" × 54" | 1.0 m³/hr | 2.0 m³/hr |
| 14" × 65" | 1.2 m³/hr | 2.3 m³/hr |
| 16" × 65" | 1.6 m³/hr | 3.4 m³/hr |
These are examples from specific system designs. Actual requirements depend on the vessel, media bed, control valve and operating conditions.
The available backwash flow should always be confirmed before selecting a filter.
Does Birm Require Regeneration?
No.
Birm does not need regeneration with salt, potassium permanganate or another chemical regenerant.
Its catalytic properties allow oxidation to continue as long as the water chemistry remains suitable.
However, regular backwashing is essential to remove accumulated contaminants.
If backwashing is inadequate, the media can become fouled, increasing pressure loss and reducing treatment performance.
What Can Cause Birm to Stop Working?
Several factors can affect Birm performance.
Insufficient Dissolved Oxygen
Without adequate oxygen, the oxidation process cannot proceed effectively.
Incorrect pH
Low pH can prevent effective iron removal, while manganese typically requires a higher pH.
Hydrogen Sulphide
Hydrogen sulphide can interfere with Birm and should be addressed using an alternative treatment arrangement.
Chlorine and Chemical Oxidants
Chlorination can reduce Birm's catalytic activity.
Clack advises that chemicals introduced into water contacting Birm should be checked for compatibility.
Polyphosphates
Polyphosphates can coat the media and interfere with its operation.
Organic Fouling
Excessive organic matter may reduce treatment performance.
Water containing iron bacteria, heavy biological deposits or other fouling contaminants may require additional pretreatment.
Birm vs Other Iron Removal Media
Birm is one of several media available for iron and manganese removal.
| Media | Main advantages | Important considerations |
|---|---|---|
| Birm | Economical, relatively lightweight, no chemical regeneration | Requires suitable pH and dissolved oxygen; unsuitable for hydrogen sulphide |
| Filox-R | High manganese dioxide content; suitable for demanding iron and manganese applications | Requires substantial backwash flow and appropriate oxidation conditions |
| Pyrolox | Dense manganese dioxide media used for iron, manganese and hydrogen sulphide treatment | Heavy media with significant backwashing requirements |
| Crystal-Right CR100 | Can reduce dissolved iron, manganese and hardness; may also raise low pH | Uses ion exchange and requires salt regeneration; feedwater conditions must be suitable |
There is no single media that is best for every application.
For example, Birm may be a sensible choice where dissolved iron is present, the pH is suitable and sufficient oxygen is available.
Where the water contains hydrogen sulphide, has inadequate oxygen or presents more challenging treatment conditions, an alternative approach may be required.
How Long Does Birm Media Last?
Birm can provide a long service life when properly operated.
The media is not consumed during the normal oxidation process.
However, its lifespan depends on:
-
Incoming water quality
-
Correct pH and dissolved oxygen
-
Backwashing frequency and effectiveness
-
Chemical compatibility
-
Sediment and biological fouling
-
Physical loss or degradation of media
Periodic testing of treated water is recommended to confirm that the system continues to perform effectively.
Is Birm Suitable for Drinking Water?
Birm can form part of a drinking water treatment system, provided the product and installation are suitable for the intended application.
However, removing iron and manganese does not necessarily make water microbiologically safe.
Private borehole and well supplies should be assessed for other potential contaminants, including bacteria.
Where microbiological contamination is present, additional treatment such as appropriately designed UV disinfection may be required.
Birm Filtration Systems from GAPS Water Treatment
GAPS Water Treatment supplies Birm filtration media and automatic backwashing systems for domestic, commercial and industrial applications.
Our range includes systems fitted with Clack, Fleck and Autotrol control valves.
If you are unsure whether Birm is suitable, email sales@gapswater.co.uk with your water analysis, required service flow and available backwash flow.
Ideally, the water analysis should include iron, manganese, pH, dissolved oxygen, alkalinity, sulphate and chloride.
Our team can help you determine whether Birm is an appropriate choice or whether an alternative treatment method should be considered.
Powered by Discount Bot