Recovery of ammonium from domestic wastewater using microbial fuel cells

This study investigates the optimal conditions of microbial fuel cells (MFCs) for ammonium transport and chemical oxygen demand (COD) removal, and their potential for electricity generation. Batch experiments were conducted using external resistors of 1,500; 200; and 0 Ω, with synthetic domestic wastewater containing an initial NH4+ concentration of 20 mg N/L. Continuous flow experiments were also conducted to assess and compare the performance of MFC systems in terms of electricity generation, COD removal, and ammonium recovery. The results of the batch experiments showed that increasing the external resistance up to 1,500 Ω enhanced the concentration of NH4+ in the cathode chamber. Moreover, higher external resistance contributed to greater voltage stability. The continuous flow experiments revealed that electricity generation did not affect COD removal efficiency. The maximum COD removal efficiencies for the 1,500 Ω and control MFCs were 80.98 and 76.65%, respectively. The concentration of NH4+ in the cathode chamber of the 1,500 Ω MFC was higher than that of the control MFC. Struvite precipitation was used to recover ammonium from the cathode chamber in the continuous experiment. The crystallinity of the precipitate was confirmed by XRD analysis.