Development and optimization of a bioelectrochemical system for ammonium recovery from wastewater as fertilizer

Abstract

Bioelectrochemical systems (BES) have emerged as a potential technology for nitrogen removal and recovery from wastewaters with low energy consumption. In this work, a double chamber, flat plate BES reactor was connected to an air stripping system to recover ammonium from wastewater. The BES system was first operated under different electrochemical conditions working with synthetic wastewater. Applying an external voltage of +0.2 V and an air flow rate (for N stripping) of 150 mL min −1 proved to be the best scenario for ammonium recovery, in which 15.8 ± 1.6 g N–NH 4 + ·m −2 ·d −1 (vs. membrane surface area) were removed from wastewater (corresponding to 75.1 ± 3.8% of its original content) and 9.6 ± 1.9 g N–NH 4 + ·m −2 ·d −1 (vs. membrane surface area) were recovered (45.3 ± 7.5%) at a current density of 2.5 ± 0.2 A m −2 (vs. membrane surface area). The power consumption of the process (without considering aeration) was of 1.6 kWh per kg of removed nitrogen, which was lower than similar experiences reported in literature, making the proposed system quite appealing. Ammonia stripping yield was limited by catholyte pH and temperature, which were optimized along the experiment. Finally, tests with real blackwater as anolyte showed that the studied wastewater was not suitable for ammonium recovery in BES due to its low organic and nitrogen content. However, more concentrated blackwaters should also be tested to confirm this observation. Urine might also represent a valuable feedstock for ammonium bioelectrochemical recovery. • The proposed system allows nitrogen recovery as fertilizer at low energy consumption. • System performance is optimal under MEC operation as cations migration increases. • Tested BW is not suitable for recovery BES as it contained low organic content. • Stripping is a limiting step in recovery process, causing for not all removed nitrogen to be recovered. • Na + is the main cation competing with NH 4 + for charge transport across the CEM.