Simulating phosphorus precipitation in the form of vivianite in wastewater treatment plant with full plant model

• A methodology for full-plant model to predict vivianite formation is proposed. • Precipitation of siderite (FeCO 3 ) is implemented to well predict vivianite. • Kinetic rate of iron reduction is measured to predict vivianite accurately. Recovering vivianite (Fe 3 (PO 4 ) 2 ·8H 2 O) from wastewater treatment plants (WWTPs) has become a novel approach for phosphorus valorization. However, no modeling work has been conducted to study its formation process in full-scale WWTPs. This study investigated the influencing factors of vivianite precipitation within Viikinmäki WWTP by building a full plant model and evaluating the results with on-site measurements. Iron reduction rates were measured in sludge in different locations. The calibration process included the improvement of iron reduction and oxidation rates and the addition of a siderite (FeCO 3 ) precipitation model. The major parameters predicted for both the water line and sludge line agreed with measurements. Additionally, satisfactory results of important parameters were acquired for vivianite formation, namely pH, concentration of soluble sulfate, soluble phosphate, total phosphorus as well as vivianite quantities in sampling locations. Sensitivity analysis indicates that iron oxidation rate has a major influence on the effluent iron concentration while iron reduction rate and siderite precipitation constant are impactful for the vivianite quantity in the sludge line. The findings of this paper can be applied in the future to predict and improve vivianite recovery for WWTPs.