Biological iron and manganese removal — cultivating naturally-occurring bacteria on a filter that oxidise Fe and Mn with little or no chemical.
Iron & Manganese Removal — in depth
Biological removal harnesses naturally-occurring iron- and manganese-oxidising bacteria. Operated in a narrow dissolved-oxygen and pH window on a filter, these bacteria oxidise Fe and Mn far faster than chemistry alone, with minimal chemicals, low sludge and excellent water quality — ideal for sustainable, large groundwater supplies once acclimatised.
What matters in practice
Naturally-occurring oxidisers.
Narrow oxygen window cultivated.
Low reagent and sludge.
Excellent for large supplies.
| Aspect | Biological | Chemical |
|---|---|---|
| Chemicals | Minimal | More |
| Sludge | Low | Higher |
| Start-up | Acclimatise | Immediate |
| Quality | Excellent | Good |
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Fundamentals, design drivers and practical guidance
Biological iron and manganese removal — cultivating naturally-occurring bacteria on a filter that oxidise Fe and Mn with little or no chemical.
Reynolds & Bauhm designs wellhead treatment around the specific groundwater chemistry — selecting aeration, oxidant dosing, catalytic or biological media and adsorption stages, and the monitoring that proves the barrier holds. We size filters on oxidation kinetics, not rules of thumb, so manganese in particular is fully removed.
Borehole and groundwater supplies are chemically reducing, often free of oxygen, and characteristically carry dissolved iron and manganese, sometimes arsenic, fluoride, ammonia or hydrogen sulphide. Because the raw water is clear at the wellhead and only discolours after contact with air, treatment is designed around controlled oxidation followed by filtration — converting dissolved metals into a filterable floc before they reach the distribution network.
Iron and manganese removal is governed by oxidation kinetics and pH. Iron oxidises readily by aeration above pH 7; manganese is far slower and usually needs a higher pH, a stronger oxidant, or a catalytic filter media that adsorbs and auto-catalyses the reaction. Where biological iron and manganese removal is used, naturally occurring bacteria perform the oxidation within the filter at lower chemical dose, producing a compact, backwashable bed.
What our engineers assess on every scope of this type
| Parameter | Typical basis | Why it matters |
|---|---|---|
| Monitoring | Wellhead + post-filter | Detects breakthrough before supply |
| Iron (Fe) | Aeration > pH 7 | Oxidises fast to filterable floc |
| Manganese (Mn) | High pH / oxidant / catalytic media | Slow kinetics; needs help |
| Arsenic | Oxidise then adsorb on Fe oxide | As(V) removes far better than As(III) |
| Fluoride | Activated alumina / bone char | Adsorption to meet drinking limit |
| Media | Catalytic or biological | Sets dose and backwash regime |
Common questions on borehole water treatment
Trivalent arsenic is first oxidised to the pentavalent form, which adsorbs strongly onto iron-oxide surfaces or dedicated media. The process is monitored for breakthrough so spent media is changed before the treated limit is exceeded.
Backwash is initiated on accumulated differential pressure, treated-water turbidity, or elapsed run-time — whichever comes first. This keeps the bed clean and the oxidised solids out of supply.
Yes — biological iron and manganese removal uses naturally occurring bacteria within the filter to oxidise the metals at reduced chemical dose, giving a compact, robust bed where the groundwater chemistry suits it.
Because dissolved iron (and manganese) are invisible in the reducing groundwater but oxidise on contact with air, forming coloured particulate. Biological Fe/Mn Removal is designed to oxidise and filter these metals deliberately, before the water reaches the network.
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