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

Abstract

Struvite crystallization is a successful technique for simultaneously recovering PO43− and NH4+ from wastewater. However, recovering PO43− and NH4+ from low-concentration solutions is challenging. In this study, PO43−, NH4+, and NO3− were separated and concentrated from wastewater using bipolar membrane electrodialysis, PO43− and NH4+ can then be recovered as struvite. The separation and concentration of PO43− 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 PO43−, NH4+, and NO3− fits zero-order migration kinetics. The concentrated concentration of NH4+ and PO43− reached 805 mg/L and 339 mg/L, respectively, which demonstrates that BMED is capable of effectively concentrating and separating PO43− and NH4+. Therefore, BMED can be considered as a pretreatment method for recovering PO43− and NH4+ in the form of struvite from wastewater.