Manganese Removal with Pile Cloth Filtration
Precipitate dissolved manganese with permanganate, separate the manganese dioxide reliably — and keep the rinse water volume under control. With measured results from a full-scale field test.
Why Manganese Is a Filtration Problem
Dissolved manganese cannot be separated mechanically — no filter retains a dissolved substance. It must first be converted chemically into particulate form. From that point on, the quality of the solids separation alone decides how much manganese remains in the effluent.
This is precisely where many plants fail: precipitated manganese dioxide forms very fine, sometimes poorly flocculating particles. A filter medium that does not securely retain these particles simply lets them pass — the precipitation was then ineffective, the oxidant consumed, and the limit still not met.
The Process Chain
Oxidation and precipitation
Potassium permanganate (KMnO₄) is dosed into the raw water. Dissolved manganese is oxidised and precipitates as manganese dioxide (MnO₂, also known as “braunstein”) in fine, dark brown particulate form. A dissolved substance thereby becomes a separable solid.
Floc formation in the inlet
Dosing takes place under high turbulence — for example via a static mixer in the inlet pipe — so that the oxidant is distributed quickly and completely and the resulting particles reach a filterable size.
Separation on the pile cloth
The water passes through the submerged pile filter cloths of the disc or drum filter. The three-dimensional pile structure retains the manganese dioxide particles not only on the surface but within the fibre layer — surface and depth filtration in a single medium.
Suction cleaning
Once the differential water level is reached, a suction bar draws the deposited solids off the cloth surface. The fibres are lifted in the suction flow so that embedded particles are released and carried away counter-current. The remaining filter area stays in operation throughout.
Full-Scale Field Test: Measured Results
In an industrial process water circuit, a disc filter was operated with pile filter cloths. The influent contained 5 to 7 mg/l of dissolved manganese, precipitated via potassium permanganate. In two test phases, our pile filter cloths and a widely used 5 µm microfibre cloth from another supplier were compared under identical operating conditions.
| Parameter | Before filtration | After R+F pile cloth | After reference cloth |
|---|---|---|---|
| Total manganese | 5.65 mg/l | 1.65 mg/l | 6.04 mg/l |
| Manganese (dissolved) | 5.59 mg/l | 0.90 mg/l | 1.37 mg/l |
| Total iron | 1.86 mg/l | 0.59 mg/l | 1.71 mg/l |
The pile filter cloths reduced total manganese from 5.65 to 1.65 mg/l and dissolved manganese from 5.59 to 0.90 mg/l; total iron fell from 1.86 to 0.59 mg/l. The reference cloth measured 6.04 mg/l total manganese — above the inlet value — meaning the precipitated manganese dioxide particles were effectively not retained at all.
The side effect on iron is notable: the same filtration stage reduced the iron content by roughly two thirds without requiring a separate process step.
The Honest Trade-Off: Separation Performance vs. Rinse Water
High separation performance has a consequence that plant designs often do not anticipate: the more solids the cloth retains, the faster the differential water level builds up and the more frequently suction cleaning is triggered. In the field test described, this produced considerably larger rinse water volumes than originally designed for.
This is not an argument against fine media — it is a design parameter. Three levers are available: the choice of pile cloth construction (staple fibre, multifilament or microfibre, each with a different ratio of effluent value to cycle length), the available filter area, and the suction trigger setting. In practice we work with the operator to find the point where the target effluent value is reliably met without overloading the rinse water return.
The measured cycle lengths and backwash rates for all three constructions are documented in our performance data.
Typical Applications
- Industrial process water circuits with elevated manganese and iron content
- Groundwater and raw water treatment with an oxidation and precipitation stage
- Retrofitting existing disc or drum filters whose current cloths do not adequately retain manganese dioxide
- Plants that must separate metal hydroxides or oxidised metal compounds after chemical dosing
- Circuit water treatment where metal accumulation disrupts operation
The field test described is presented in deliberately anonymised form. We name neither the plant, operator or customer, nor any supplier or other manufacturer. The comparison covers only the behaviour of the filter media under identical operating conditions.
Manganese in Your Water?
Describe your load case — inlet concentration, oxidant, filter type and available filter area. We recommend the right pile cloth construction and can support a field test at your plant.