Dosing of iron salt solutions (Ferrous Chloride (FeCl₂), FeSO₄, Ferric Chloride (FeCl₃)) into wastewater to precipitate Hydrogen Sulphide (H₂S) as iron sulphide, preventing odour release from sewers and treatment works.
Coefficient of Variation (CoV) ≤0.05 at Hydrogen Sulphide (H₂S) monitoring point (minimum 5D downstream). Fe:S molar ratio must be ≥1.05:1 throughout the cross-section for complete Hydrogen Sulphide (H₂S) precipitation. Injection into acidic zone (pH <7) to prevent iron hydroxide precipitation before reaction.
Preferred MOC: FRP or 316SS for iron chloride service. PVDF injection quill for Ferrous Chloride (FeCl₂)/Ferric Chloride (FeCl₃). Avoid carbon steel (rapid corrosion in chloride solution).
Hydrogen Sulphide (H₂S) gas monitoring and ventilation mandatory in all enclosed installations (Hydrogen Sulphide (H₂S) is toxic at >10 ppm). Non-return valve on injection line to prevent sewer gas ingress. Injection in acidic pH zone (upstream of any caustic addition) to prevent iron hydroxide formation.