Which chemical is used to regenerate manganese greensand beds?

• A. Sodium hypochlorite
• B. Permanganate solution
• C. Hydrogen peroxide
• D. Chlorine gas

Answer: (B)

Regenerating manganese greensand beds relies on restoring the manganese dioxide coating that drives the oxidation process. The bed uses a MnO2-coated sand to oxidize contaminants like iron, manganese, and hydrogen sulfide from the water. Over time the coating becomes depleted and the bed loses its oxidizing power. Pushing a potassium permanganate solution through the bed reactivates it by oxidizing the reduced manganese on the surface back to MnO2 and depositing fresh MnO2 on the media, which restores its catalytic ability. Other chemicals listed are mainly used for disinfection or general oxidation and don’t rebuild the MnO2 coating, so they don’t regenerate the greensand bed.