Factors Influencing Iron Reduction–Induced Phosphorus Precipitation

Abstract

Abstract

An iron-amended anaerobic sequencing batch reactor, fed with synthetic sewage, was used to evaluate the factors influencing iron reduction–induced phosphorus precipitation from a simulated septic system. Results revealed that soluble phosphate could be effectively removed from the reactor when the added amorphous ferric oxyhydroxide (α-FeOOH) was increased from a molar ratio of 1.5 to 3. Whereas cycle time, substrate concentration, and temperature did not have a noticeable effect on iron reduction and the subsequent phosphorus removal, agitation was found to be an important factor, enabling better contact between α-FeOOH and the microorganisms during phosphorus removal. Precipitates collected from the reactor were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Results demonstrated that the precipitate was mainly vivianite [Fe₃(PO₄)₂·8H₂O], which suggests that phosphorus was removed through iron reduction–induced precipitation. This paper provides insights into phosphorus removal from septic sewage using a novel approach.