Iron & Manganese Oxidant Dose Calculator
Sizing oxidation for iron and manganese removal? Enter raw-water Fe and Mn and get the theoretical oxidant demand — the stoichiometric minimum every groundwater plant design starts from.
| Component | Value |
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How the calculation works
Oxidizing dissolved Fe²⁺ to ferric hydroxide and Mn²⁺ to manganese dioxide consumes a fixed mass of oxidant per mass of metal. This calculator multiplies your raw-water metals by the standard stoichiometric ratios, then applies a safety factor for real-world conditions:
Chlorine demand (mg/L): (0.62 × Fe) + (1.27 × Mn)
Permanganate demand (mg/L): (0.94 × Fe) + (1.92 × Mn)
Design dose (mg/L): stoichiometric demand × safety factor
Feed rate (lb/day): 8.34 × flow (MGD) × design dose (mg/L)
Flows entered in gpm are converted first: MGD = gpm × 1440 ÷ 1,000,000.
Notes & limitations
- Stoichiometric minimum only. Actual oxidant demand runs higher when the water carries natural organic matter, ammonia, hydrogen sulfide, or other competing demand, when pH is low, or when contact time is short.
- Manganese oxidation by chlorine is slow below about pH 8. At lower pH, chlorine may need long contact time or a pH boost; potassium permanganate oxidizes manganese effectively across a wider pH range.
- Do not overdose permanganate. Excess KMnO₄ passes through filters and turns finished water pink. Stay near the stoichiometric need plus a modest margin.
- Verify with jar tests and pilot data. Confirm the calculated dose — and the actual residual — under your plant’s real pH, temperature, and contact time before setting chemical feed rates.
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