"Cyclic crystallization mode" reduces the iron source dosage in the recovery of vivianite form municipal wastewater

Vivianite is a high-value product for phosphorus (P) recovery from municipal wastewater. To obtain vivianite with higher crystallization ratio and larger particle size, excessive iron source was often dosed during the crystallization process, which not only increases the cost of reagents but also leads to excessive iron concentration in the effluent. In this study, by analyzing the influence of pH and Fe/P ratio on the saturation index value, a "cyclic crystallization mode" was proposed to reduce the iron source dosage in fluidized bed crystallization process to realize the phosphorus recovery from municipal wastewater. With which, the iron dosage was reduced by 20 %, the d50 was increased by 94 %, and the hydraulic retention time was reduced by 0.5 h. This study provides theoretical basis and method to reduce the iron source cost in the vivianite crystallization technology for the recovery of phosphorus.