In this study, the potential of using peroxide regenerated iron-sulfide control (PRI-SC®) for chemical phosphorus removal utilizing the existing iron sulfide found in wastewaters was investigated in batch tests and compared in full-scale facility-wide simulations to using iron salts. PRI-SC is a combination treatment that utilizes iron salts and hydrogen peroxide in a synergetic fashion, where hydrogen peroxide is used in regenerating the spent iron salt in situ in the form of iron sulfide, yielding ferric iron and colloidal sulfur. A simplified kinetic model was developed, calibrated, and integrated into a facility-wide model to simulate the process at the full-scale. Experimental results showed that dosing hydrogen peroxide, even at doses lower than the stoichiometrically required to oxidize iron sulfide, freed, and oxidized sulfide bound ferrous iron to ferric iron, which was consequently hydrolyzed and affected phosphorus removal. Higher dosing of hydrogen peroxide did not affect change in the speciation of sulfur remaining predominantly as elemental sulfur. Simulations showed that the application of PRI-SC with supplemental ferric iron dosing was able to cut the costs of chemicals addition up to 53% while maintaining a steady-state effluent phosphate concentration below 0.01 mg/L. PRACTITIONER POINTS: The kinetic model was used to optimize ferric iron and hydrogen peroxide dosing. The developed model can be integrated in existing wastewater process simulators. Dosing hydrogen peroxide effectively oxidized ferrous iron to ferric iron. The combination of hydrogen peroxide and iron salts can reduce the chemical addition cost by 53%.
Keywords: chemical phosphorus removal; hydrogen peroxide; kinetic model; physicochemical modeling.
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