Separation and Concentration of Nitrogen and Phosphorus in a Bipolar Membrane Electrodialysis System

Struvite crystallization is a successful technique for simultaneously recovering PO(4)(3−) and NH(4)(+) from wastewater. However, recovering PO(4)(3−) and NH(4)(+) from low-concentration solutions is challenging. In this study, PO(4)(3−), NH(4)(+), and NO(3)(−) were separated and concentrated from wastewater using bipolar membrane electrodialysis, PO(4)(3−) and NH(4)(+) can then be recovered as struvite. The separation and concentration of PO(4)(3−) and NH(4)(+) are clearly impacted by current density, according to experimental findings. The extent of separation and migration rate increased with increasing current density. The chemical oxygen demand of the feedwater has no discernible impact on the separation and recovery of ions. The migration of PO(4)(3−), NH(4)(+), and NO(3)(−) fits zero-order migration kinetics. The concentrated concentration of NH(4)(+) and PO(4)(3−) reached 805 mg/L and 339 mg/L, respectively, which demonstrates that BMED is capable of effectively concentrating and separating PO(4)(3−) and NH(4)(+). Therefore, BMED can be considered as a pretreatment method for recovering PO(4)(3−) and NH(4)(+) in the form of struvite from wastewater.