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

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-NH4+.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-NH4+.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.

Automated summary

Bioelectrochemical systems (BES) are a promising technology for nitrogen removal and recovery from wastewater with low energy consumption. In this study, a double chamber, flat plate BES reactor was connected to an air stripping system to recover ammonium from wastewater. Optimal conditions for ammonium recovery were found at an external voltage of +0.2 V and an air flow rate of 150 mL min(-1).