Water tools
Iron and manganese removal: oxidant demand, alkalinity and sludge
Dissolved iron and manganese leave the water as ferric hydroxide and manganese dioxide once oxidised. Each oxidant has its own stoichiometry, acid release and sludge yield.
How it works
Each factor comes from the balanced reaction, for example iron with chlorine and with permanganate:
- oxidant required, mg per mg of metal
- moles of oxidant and metal in the balanced reaction
- molar masses of oxidant and metal, g/mol
- alkalinity consumed, mg CaCO₃ per mg of metal
- equivalents of acid released per mole of metal
- dry solids formed, mg per mg of metal
- moles and molar mass of each solid formed
Per mg of iron: oxygen 0.14, chlorine 0.64, chlorine dioxide 1.21, permanganate 0.94, ozone 0.43 mg; per mg of manganese: 0.29, 1.29, 2.46, 1.92 and 0.87 mg. The permanganate sludge factor includes the manganese dioxide the permanganate itself leaves. Complete-reaction figures for predesign: organically bound iron oxidises slowly, chlorine takes 15 to 30 minutes at pH 8 for iron and is not effective on manganese, permanganate and chlorine dioxide work within seconds.
Related reading
These calculators use standard published formulas and are provided for preliminary engineering guidance. Confirm against measured data and vendor projections before design. Model your full water matrix in Nepti or post your project to compare provider proposals.