Ammonium removal and recovery from real digestate wastewater by a modified operational method of membrane capacitive deionization unit

Abstract

In this study, an extensive examination of ammonium removal and recovery from highly concentrated digestate wastewater was systematically performed. The treatability and ammonium recovery potential of the real digestate wastewater was assessed by enhanced Flowed Channel Membrane Capacitive Deionization (fcMCDI), which was introduced in our previous study. The fcMCDI cell was found efficient to remove ammonium ions from a synthetic mixture of glucose and Ca2+ and Na+ ions, which are the major components of the anaerobic digestate liquid. Specific ammonium removal performance of the system was investigated in the presence of other ions. In a single cycle experiment, the process was able to remove the Mg2+, Ca2+, K+ and NH4+ ions from real digestate wastewater at percentages of 90.4%, 85%, 67.9% and 54.4%, respectively. A comparison of the conventional MCDI operation with an increased voltage application method with the fcMCDI cell was presented. Ammonium was successfully recovered in the form of ammonia gas by increasing the cell's working voltage, and simultaneous deionization of the other ions in the digestate wastewater was achieved. The obtained ammonium removal efficiencies were 89% and 67% with synthetic and real digestate wastewater, respectively. The results demonstrated that the enhanced MCDI technology holds a great potential to be an energy-efficient process for ammonium removal and recovery while also removing other contaminants effectively from highly concentrated wastewater sources. (C) 2019 Elsevier Ltd. All rights reserved.