Removal and Recovery of Ammonium and Phosphate from Wastewater Using a Redox Flow Deionization Cell (RFDC)

Abstract

Ammonium (N) and phosphate (P) are key nutrients used in different applications, particularly in fertilizers for food production. They are present at different levels in domestic and industrial wastewater, discharging of which without removing these nutrients can cause serious harm to the environment. This work studies the use of redox flow deionization cells (RFDCs) as a new method for N and P removal, demonstrating their merits of high energy efficiency, continuous operation, and deionization in the ion removal channel and meanwhile concentrating ions in the ion concentration channel. The effects of wastewater concentration and applied cell voltage on the RFDC performances, including average salt removal rate, ion removal efficiency, and electrical energy consumption, were investigated with N removal and P removal experiments. The influences of coexisting ions (Na+, Cl–) on N and P removal were also examined. The findings show that regardless of the presence of coexisting ions, N and P can be rapidly and completely removed from the deionization stream and in the meantime concentrated in the ion concentration stream. This study demonstrates RFDCs as an effective, efficient strategy for N and P removal together with their recovery, suggesting a great potential of this new technology in wastewater treatment.