Nitrogen removal from wastewater using membrane aerated microbial fuel cell techniques

Nitrogen removal mainly relies on sequential nitrification and denitrification in wastewater treatment. Microbial fuel cells (MFCs) are innovative wastewater treatment techniques for pollution control and energy generation. In this study, bench-scale wastewater treatment systems using membrane-aerated MFC (MAMFC) and diffuser-aerated MFC (DAMFC) techniques were constructed for simultaneous removal of carbonaceous and nitrogenous pollutants and electricity production from wastewater. During 210 days of continuous flow operation, when the dissolved oxygen (DO) in the cathodic compartment was kept at 2 mg/L, both reactors demonstrated high COD removal (>99%) and high ammonia removal (>99%) but low nitrogen removal (<20%). When a lower DO (0.5 mg/L) was maintained after day 121, both the MFC-based reactors still had excellent COD removal (>97%). However, the nitrogen removal of MAMFC (52%) was 2-fold higher than that of DAMFC (24%), indicating an enhanced performance of denitrification after DO reduction in the cathodic compartment of the MAMFC. Meanwhile, terminal restriction fragment length polymorphism (T-RFLP) analysis of ammonia-oxidizing bacteria (AOB) population in the MAMFC indicated the diversity of AOB with equally important Nitrosospira and Nitrosomonas species present in the cathodic biofilm after DO reduction. The average voltage output in the MAMFC was significantly higher than that in DAMFC under both DO conditions. The results suggest that MAMFC systems have the potential for wastewater treatment with improved nitrogen removal and electricity production.