Novel bioelectrochemical processes focused on nitrogen in wastewater: Energy generation and resource recovery

The discharge of nitrogen into nature results in environmental degradation and public health problems. Conventional processes applied in wastewater treatment plants (WWTPs) for nitrogen removal have high energy demand and chemical consumption. Hence, this chapter addresses the recent research development about more sustainable approaches involving bioelectrochemical systems (BES) focused on nitrogen. Among the content are novel and meaningful insights towards the main factors controlling nitrogen oxidation, reduction, and separation/recovery; potential applications in WWTP; limiting factors; and contributions towards the circular economy principles. Despite there are limiting factors such as costly materials, lack of knowledge on microbial ecology, and low removal rates, the current generated in autotrophic nitrifying and denitrifying BES ranges from 1.2 to 1175 mA/m2 and 14 to 371 A/m3, respectively. This can potentially increase WWTPs self-sufficiency in terms of energy and external carbon. Alternatively, nitrogen can be recovered in BES (struvite, NH4HCO3 crystals or NH4OH), but improvements in ammonia separation across ion exchange membranes are necessary.