Ammonium Recovery From Agro-industrial Digestate Using Bioelectrochemical Systems

In this study the possibility to recover nitrogen from agro-industrial digestate using bioelectrochemical systems was investigated: two microbial electrolysis cells (MECs) were fed with both synthetic and real digestate (2.5 gNH4-N/L). Carbon felt and granular graphite (d > 2mm) were used as anodes in MEC-1 and MEC-2, respectively. As to synthetic wastewater, optimal nitrogen load (NL) was determined for MEC-1 and -2 (1.25 and 0.75 gNH4-N/d, respectively); MEC-1 showed better performance in terms of NH4-N removal efficiency (41±5%) and recovery rate (3.5±0.2 kgNH4-N/d/m3), compared with MEC- 2 (15±3% and 1.6±0.4 kgNH4-N/d/m3, respectively). At the optimal NL, lower NH4-N removal efficiencies and recovery rates were observed when real digestate was fed to MEC-1and -2, likely due to the higher complexity of the influent. Results are promising and may contribute in reducing the need for highly expensive and polluting processes for nitrogen synthesis