Model-guided nutrients recovery from real corn deep processing wastewater using endogenous magnesium in a fluidized...

This study evaluated a fluidized bed reactor (FBR) for treating corn deep processing wastewater (CDPW) to simultaneously recover nitrogen, phosphorus, and magnesium using only endogenous Mg²⁺ in the wastewater, without external magnesium addition. Increasing pH and reflux ratio (RR) enhanced TP and PO₄^3--P removal, whereas higher upflow velocity (Vup) reduced their removal; Mg/P ratio showed a positive but statistically insignificant effect. In contrast, NH₄⁺-N removal efficiency increased with pH and Vup and was only weakly affected by the Mg/P ratio and RR. Under optimized operating conditions, the FBR achieved removal efficiencies of 84.43-91.32% for PO₄^3--P, 8.96-11.22% for NH₄⁺-N, and 64.22-69.40% for Mg²⁺. A thermodynamic equilibrium model and a kinetic model were developed to evaluate FBR performance under fluctuating water quality; both reproduced the experimental data well, with the thermodynamic model slightly overestimating and the kinetic model slightly underestimating removal rates. Model validation confirmed their reliability in predicting nutrient removal within the above ranges. X-ray diffraction analysis showed that the main crystalline product was magnesium ammonium phosphate (MAP) with a purity of 91.5%, indicating that the recovered crystals can be directly used as fertilizer. Compared with Fenton treatment, MAP crystallization in the FBR exhibited lower overall treatment cost, reduced global warming potential, and decreased fossil resource consumption, demonstrating a more sustainable option for phosphorus recovery from CDPW.