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

Struvite crystallization is a successful technique for simultaneously recovering PO₄^3- and NH₄⁺ from wastewater. However, recovering PO₄^3- and NH₄⁺ from low-concentration solutions is challenging. In this study, PO₄^3-, NH₄⁺, and NO₃^- were separated and concentrated from wastewater using bipolar membrane electrodialysis, PO₄^3- and NH₄⁺ can then be recovered as struvite. The separation and concentration of PO₄^3- and NH₄⁺ 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 PO₄^3-, NH₄⁺, and NO₃^- fits zero-order migration kinetics. The concentrated concentration of NH₄⁺ and PO₄^3- reached 805 mg/L and 339 mg/L, respectively, which demonstrates that BMED is capable of effectively concentrating and separating PO₄^3- and NH₄⁺. Therefore, BMED can be considered as a pretreatment method for recovering PO₄^3- and NH₄⁺ in the form of struvite from wastewater.