Self-sustaining advanced wastewater purification and simultaneous in situ nutrient recovery in a novel bioelectrochemical system

Wastewater containing abundant organics and nutrient resources requires large energy input in conventional treatment technologies to reach the discharge standard and/or to recover nutrient resources. This study presents a self-sustaining advanced wastewater purification and in situ nutrient recovery process accomplished by a newly designed 10-liter-scale bioelectrochemical system containing membrane stack configuration, which was called an advanced microbial nutrient recovery cell (AMNRC). After subsequent treatments in the AMNRC's anode, cathode and stacked desalination chambers, all the removals of organics and nutrient in the domestic wastewater were achieved higher than 95%, which represented <24.9 mg/L of chemical oxygen demand, <14.2 mg/L of total nitrogen (TN), <6.5 mg/L of ammonium nitrogen (NH₄⁺-N), and <0.49 mg/L of total phosphorus (TP) were left in the final effluent. Three sequential treatment processes including anaerobic microbial degradation, aerobic microbial treatment, and electrical ion migration comprehensively facilitated the above removals. Meanwhile TN, NH₄⁺-N and TP were concentrated in the recovery solution by 260%, 150%, and 490%, respectively. Ammonium and phosphate were then recovered as struvite during crystallization. The AMNRC was proved as an energy neutral approach to efficiently purify wastewater and simultaneously recover nutrient, the treatment processes were driven by the energy extracted from wastewater itself.