BIRM vs. Pyrolox vs. Katalox Light: comparison of iron filtration media

BIRM, Pyrolox and Katalox Light: what they are and why it matters

If you have decided to address iron or manganese in water, sooner or later you will come across three names that appear in every professional comparison of filtration media: BIRM, Pyrolox and Katalox Light. At first glance, they look like three variants of the same thing – all are granular catalytic media, all oxidize and capture iron and manganese, and all require regular backwashing. In practice, however, the differences between them are fundamental, and choosing the wrong medium can mean that the filter simply does not work – despite being correctly sized, properly installed, and regularly backwashed.

In this article, we will examine the media in depth: from the physical and chemical nature of their operation, through the specific operating conditions each of them requires, to real-life scenarios where one medium fails and another excels. By the end, you will know exactly which medium belongs in your situation – or at least you will know which questions you need to answer before choosing a medium.

If you are just starting out and are not familiar with why iron in water is a problem and how to measure it in the first place, I recommend reading the article Iron and manganese in water: how to identify the problem and choose the right filter in our Knowledge Centre first. Here, I assume you already know the basics and we will go straight to the comparison of the media.

How catalytic filtration works – the basis for comparison

Before comparing, we must understand what all three media have in common. Iron in water occurs either as soluble ferrous Fe²⁺ (ferrous, "invisible", water looks clear) or as ferric Fe³⁺ (ferric, water is cloudy, rusty). Manganese behaves similarly: Mn²⁺ is soluble, Mn⁴⁺ is insoluble.

A catalytic filtration medium works on the principle of oxidation on the surface of the grain: soluble Fe²⁺ passes through a layer of media, oxidizes to Fe³⁺ on the catalytic surface, which immediately precipitates as ferric hydroxide and is captured between the media grains. The same mechanism applies to manganese. The medium therefore does not consume – it catalyzes the reaction. The captured oxides are periodically removed by backwashing.

The source of oxygen for oxidation can be threefold: dissolved oxygen directly from water, air injection before the filter (air injector, venturi), or chemical dosing (sodium chlorite, hydrogen peroxide, potassium permanganate – KMnO₄). And precisely in which source of oxygen each medium requires, the biggest practical differences lie.

BIRM – reliable classic with oxygen requirements

What is BIRM and how it works

BIRM (Burgess Iron Removal Medium) is a light, granular medium based on pumice (a volcanic rock) coated with manganese dioxide MnO₂. The surface catalyst accelerates the oxidation of Fe²⁺ to Fe³⁺, with dissolved oxygen from the water serving exclusively as the oxidizing agent. This is a key property and at the same time the biggest limitation of BIRM.

The medium has a low bulk density (about 0.7–0.8 g/cm³), making it an easily regenerable medium – backwashing takes place at relatively low flow rates (about 12–15 l/min for a 30 cm diameter vessel). The grain size is typically 0.3–1.6 mm effective size, with a Uniformity Coefficient under 1.7.

Operating conditions for BIRM – what must be met

Here comes the first major practical lesson: BIRM is very sensitive to the input parameters of the water. If they are not met, the medium simply does not work, no matter how large the filter is.

• pH: minimum 6.8 – ideally above 7.0. Below pH 6.5, BIRM loses its catalytic activity. This is the most common problem with groundwater from granite or peat, where pH is often 5.8–6.5.
• Dissolved oxygen (DO): at least 15 % molar excess relative to the Fe content. Rule of thumb: the O₂/Fe ratio must be at least 0.14 mg O₂ for every 1 mg Fe. If the water has 5 mg/l Fe, you need at least 0.7 mg/l O₂. Deep well water can have practically zero O₂ – in that case, BIRM will not work at all without pre-aeration.
• Hydrogen sulfide (H₂S): must not be present at all. H₂S poisons the catalytic surface faster than it can regenerate.
• Organic substances: total organic carbon (TOC) should be below 4–5 mg/l. Higher humic substance content will coat the grain surface and degrade performance.
• Oil, fats: absolute zero. One pass of oily water and BIRM is devalued for a long time.
• Chlorine: must not be present – it damages the catalytic surface. (Relevant mainly when connected to municipal water supply.)
• Manganese: BIRM can capture manganese, but only at pH above 8.0. At pH 7.0–7.5, the efficiency for manganese is minimal.
• Maximum iron content: the manufacturer (Clack) states a maximum of 10 mg/l for biologically unaffected water, in practice I recommend a limit of 8 mg/l with good other parameters.

In practice, BIRM works excellently where the well water has: pH above 7.0, sufficient oxygen (aerated water, surface well), no H₂S, iron content up to 6–8 mg/l and minimal organic load. Typical application: a drilled well up to 30 m in a limestone environment, alkaline water, Fe 2–5 mg/l, no odor. Our product Water filter for iron and manganese HydroTreat BIRM 0.8 m³/h is a classic example of such a solution for households with consumption for 4–5 people.

Advantages and disadvantages of BIRM in short

• ✅ The cheapest medium of the three (the price per liter is significantly lower than Pyrolox or Katalox)
• ✅ Easy to handle, simple backwash at low flow rates
• ✅ Long service life under proper conditions (8–12 years)
• ✅ Does not require chemical regeneration additives
• ❌ Very sensitive to pH and oxygen content
• ❌ Does not work on manganese at normal pH
• ❌ Destroyed by H₂S, organics, oil
• ❌ Requires pre-aeration for anoxic water

Pyrolox – a heavy player with real catalytic power

What is Pyrolox

Pyrolox is natural manganese dioxide (MnO₂) in granular form, with MnO₂ content typically above 75 %. Unlike BIRM, it is not a coated carrier, but a massive catalyst grain. The bulk density of Pyrolox is 1.5–1.8 g/cm³ – roughly two to three times heavier than BIRM. And that is the first major practical complication.

The catalytic mechanism of Pyrolox is different from BIRM: MnO₂ can also function as a direct oxidant (reaction MnO₂ + Fe²⁺ → MnO + Fe³⁺), and the "used" catalyst is regenerated by oxidation with air or KMnO₄. In practice, Pyrolox is most commonly operated with continuous air injection or with periodic KMnO₄ dosing.

Operating conditions of Pyrolox

• pH: 6.5–9.0 – Pyrolox is more tolerant to lower pH than BIRM. It can operate at pH 6.5–6.8, where BIRM fails.
• Iron content: it can handle significantly higher levels – realistically up to 20–25 mg/l with proper sizing and aeration.
• Manganese: very good efficiency on Mn²⁺ even at pH 7.0–7.5, which is an advantage over BIRM.
• Air injection: strongly recommended, or alternatively KMnO₄ dosing for regeneration of the catalytic surface.
• H₂S: tolerates low concentrations (up to ~1 mg/l), higher concentrations require prior degassing.
• Backwash: this is a problem. Due to its high density, Pyrolox requires a backwash flow of 30–40 l/min for a 30 cm diameter (some sources mention up to 50 l/min). That is 2–3× more than BIRM. If you do not have sufficient flow from the source, the medium will not be properly backwashed, the iron oxide clusters will not be released, and the filter will gradually clog.

When to use Pyrolox and when not to

Pyrolox makes sense where BIRM is insufficient – that is, at high iron content (over 8 mg/l), in the presence of manganese, or at lower pH where BIRM does not work. It is a medium for more demanding conditions. However, due to its high weight, you must be sure that your well or water treatment plant can provide enough pressure and flow for backwash. If you have a well with a yield of 0.5 m³/h and require a backwash flow of 2 m³/h – Pyrolox will stop working before you even notice.

From long-term experience: I have seen Pyrolox fail most often with customers using shallow wells (8–15 m) and weaker pumps, who bought it themselves online without consulting. The filter worked for the first month, then started to release iron – because the backwash never happened properly.

Katalox Light – a modern compromise with excellent parameters

What is Katalox Light and how it differs

Katalox Light is a medium of the newer generation, developed by the German company Weco. It is a light carrier (zeolite-like material) with a high MnO₂ content on the surface – up to 10 % MnO₂ by weight. The bulk density is around 0.85–1.0 g/cm³, so it is slightly heavier than BIRM, but significantly lighter than Pyrolox. This combination – high catalytic MnO₂ content on a light carrier – is the key to its success.

Katalox Light works efficiently with dissolved oxygen from water (similar to BIRM), but thanks to the higher content of active MnO₂, it can also oxidize manganese at lower pH and handle higher Fe concentrations. It does not necessarily require chemical regeneration – air injection or just sufficient aeration of the water before the filter is sufficient.

Operating conditions of Katalox Light

• pH: 6.0–10.0 – the widest tolerance range of all three media. It works even at pH 6.0–6.5, where BIRM fails and Pyrolox operates only with chemical assistance.
• Iron content: up to 30 mg/l (the manufacturer states even higher, but realistically for households, 15–20 mg/l is a practical limit with proper sizing).
• Manganese: excellent efficiency on Mn²⁺ at pH above 6.5 – better than BIRM, comparable to Pyrolox.
• H₂S: can handle up to ~2 mg/l, which is better than BIRM, but at higher concentrations, a degasser must be used prior.
• Backwash: requires a flow of about 18–22 l/min for a 300 mm diameter – significantly less than Pyrolox, slightly more than BIRM. Most domestic wells can handle this.
• Air injection: recommended for maximum performance, but not a necessary condition as with Pyrolox.
• Organic substances: tolerates slightly higher TOC than BIRM (up to ~8 mg/l), but here too, high organic load reduces performance.

Lifespan and regeneration of Katalox Light

The manufacturer states a media lifespan of 8–10 years under normal conditions. The media is not consumed, but it gradually wears out mechanically and the catalytic surface may become partially clogged. Regular backwashing (automated using a timer-controlled head) is sufficient maintenance in most cases. Periodic dosing of KMnO₄ (once every 6–12 months) is recommended as a regeneration of the catalytic surface in case of significant clogging.

For those interested in how to properly set the backwash frequency and how long the media will last, I recommend the article Maintenance and regeneration of filter media: how long do they last and when to replace in our Knowledge Center.

Direct comparison: BIRM vs. Pyrolox vs. Katalox Light

Let's now put the gathered information side by side in a clear table. For most customers, this is the most valuable part of the article.

Parameter	BIRM	Pyrolox	Katalox Light
Min. pH	6.8	6.5	6.0
Max. Fe (mg/l)	8–10	20–25	15–30
Manganese	Poor (pH>8)	Good	Excellent
H₂S tolerance	None	<1 mg/l	<2 mg/l
Backwash flow (Ø300mm)	12–15 l/min	35–45 l/min	18–22 l/min
Bulk density	~0.75 g/cm³	~1.65 g/cm³	~0.9 g/cm³
Chemicals required?	No	Recommended	Optional
Media cost (relative)	Low (1×)	Medium (2–3×)	Medium (2.5–3×)
Media lifespan	8–12 years	8–12 years	8–10 years

Decision scenarios from practice – which medium for which case

Scenario 1: Typical borehole water, Fe 3 mg/l, pH 7.3, no odor

This is the "golden standard" for BIRM. The water has sufficient pH, the Fe content is within a comfortable range, and there are no complications. BIRM will work reliably, inexpensively, and without the need for chemical dosing. If you are looking for a simple, low-maintenance solution and have exactly this type of water, BIRM is the right choice. For example, a solution like Iron and manganese water filter HydroTreat BIRM is ideally sized for a household of 3–5 people.

Scenario 2: Shallow well in a peat area, pH 6.2, Fe 2 mg/l, Mn 0.3 mg/l

The acidic environment of a peat area, with low pH – BIRM will not help at all here. Pyrolox would work, but the yield of shallow wells in such areas is usually low and backwashing would be problematic. Katalox Light is the clear choice here: it can handle pH 6.2, captures manganese, and backwashing is feasible even in a low-yield well. With pre-aerated air injection, the performance will be excellent.

Scenario 3: Deep artesian well, Fe 18 mg/l, Mn 0.5 mg/l, pH 7.1, yield 3 m³/h

High Fe content, presence of manganese, but excellent yield. Here the choice is between Pyrolox and Katalox Light. Pyrolox can handle such a load very well and the well yield allows for backwashing. Katalox Light can also handle these parameters, but the volume of media and tanks will need to be properly oversized. In this case, I would choose Pyrolox as the primary medium if sufficient backwash flow is available, or alternatively a combination of Pyrolox + BIRM layers (so-called dual-media filtration).

Scenario 4: Family house, Fe 5 mg/l, Mn 0.2 mg/l, H₂S ~0.5 mg/l, pH 7.0

The presence of hydrogen sulfide (rotten egg smell) rules out BIRM. The pH is in the range where both Pyrolox and Katalox Light work. Both can handle H₂S up to 0.5 mg/l, but I would recommend pre-aeration (a small aeration tank or venturi with air injection). Katalox Light with air injection is an excellent solution here – flexible, manageable backwashing, covers Fe, Mn, and mild H₂S.

Scenario 5: Garden cottage, seasonal operation, Fe 4 mg/l, pH 7.5, consumption 0.3 m³/day

Low consumption, seasonal operation – here you need to be careful about seasonal media standstill. BIRM can biologically colonize and reduce performance if left without backwashing for long periods. Katalox Light is somewhat more resistant to seasonal standstill. But with such a low flow rate (0.3 m³/day), we are talking about a very small tank – BIRM with an automatically controlled head with weekly backwashing is sufficient and more economical. I always recommend performing a manual backwash before the first use when starting up seasonally.

Media combinations and additional technologies

In real installations, media are often combined or supplemented with additional technologies. Here are the most common combinations from practice:

• BIRM + manganese greensand (lower layer): when the primary issue is Fe, but manganese is also present and the pH is not sufficient for pure BIRM to handle Mn. Layered filtration in one tank.
• Katalox Light + UV lamp: if the water contains Fe and biological contamination (coliform bacteria from the well). Katalox Light removes Fe and Mn, UV lamp Viqua S463RL ensures disinfection. This is a complete solution for well water, where you want drinking water without any compromises. More about UV disinfection can be found in the article UV water disinfection: when a filter is not enough and you need a UV lamp.
• Iron filter + water softener: if you have hard water with Fe, the iron filter should precede the water softener – otherwise, the resin in the softener will quickly clog with iron. Automation is key – for example, automatically controlled water softener head 1" HYS-1 can be used for the softener installed after the filter. More about this combination can be found in the article Water softening vs. filtration: what is the difference and what do you need.
• Aeration + catalytic filter: for water with low O₂ (deep artesian well). A simple aeration tank or venturi with air injection is installed before the filter. This dramatically increases the oxygen content and makes BIRM or Katalox Light work more efficiently.

If you are at the beginning of the decision-making process and are unsure which combination of technologies is right for you, I recommend reading the article How to choose a water filter for the household: a complete guide in our Knowledge Center. And if you are solving the sizing of the device according to household consumption, take a look at What filter flow do I need: calculating capacity according to household consumption.

Practical notes on installation and operation

Media bed height and expansion space

Regardless of which medium you choose, one important rule applies: the media layer (bed) must have enough free space above it for expansion during backwash. BIRM expands by 40–50 % during backwash, Katalox Light by 30–40 %, and Pyrolox by 25–35 %. If the tank is filled to the brim with media, backwash cannot properly stir and release the captured oxides – the filter will gradually clog.

Typical rule: the media layer should occupy a maximum of 55–60 % of the tank’s bed height. The rest is expansion space. If you are unsure about the calculation, read Installation of a household water filter: procedure, tools, and most common mistakes.

Backwash frequency

For BIRM: with Fe content up to 3 mg/l, backwash every 3–5 days at a flow of 0.5–1 m³/day is sufficient. With Fe 5–8 mg/l, daily backwash is recommended. For Katalox Light and Pyrolox: daily or every-day backwash is standard for medium and high Fe content.

Automation using an electronic head with a timer is practically necessary for catalytic filtration – manual triggering of backwash is always neglected sooner or later in practice. Setting backwash to nighttime hours (2:00–4:00) minimizes the impact on daily water consumption.

Initial start-up and media conditioning

New filtration media require a conditioning period. BIRM and Katalox Light will develop a full catalytic surface within 2–4 weeks. During this period, the filter performance may be lower and the water may be slightly cloudy. Pyrolox releases MnO₂ dust during the first start-up – new media must be thoroughly rinsed for 30–60 minutes at maximum backwash flow until the water runs clear before putting it into operation.

What makes a filter ineffective – most common mistakes from practice

Over the years of practice, I have seen filters fail for various reasons. Most common:

• BIRM installed on water with pH 6.5 – result: zero. The customer thinks the filter is broken.
• Pyrolox in tanks without sufficient backwash flow – the media clogs within 3–6 months.
• Katalox Light without any pre-aeration in anoxic water from a deep well – partial results, not full capacity.
• Too small expansion spaces – no media can be rinsed.
• Skipping water analysis – the customer buys media based on price, not on water parameters.

More on problem diagnostics can be found in the article Common water filter faults and how to fix them.

Economics: purchase and operating costs

Price plays a big role in customer decisions, but it should be evaluated correctly. The price of the media is only one item of the total costs – it is important to consider:

• Media price: BIRM ≈ 1×, Pyrolox ≈ 2.5–3×, Katalox Light ≈ 2.5–3× (BIRM price as a base)
• Required media volume: for the same Fe load requirements, you need less Katalox Light than BIRM (higher catalytic activity = smaller volume). The difference can be 20–30 %.
• Backwash operating costs: Pyrolox consumes 2–3× more

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