Enhancement of microbial electrochemical driven anaerobic ammonium oxidation in a bioelectrochemical-enhanced constructed wetland: Effect of applied voltage.

This study was conducted to explore enhancement of biological anode-dependent ammonium oxidation (bioanoammox) in a bioelectrochemical-enhanced constructed wetland (BECW) by an approach of regulating applied voltage, nitrogen transformation patterns and associated microbiological characteristics of the BECWs were then investigated at four different applied voltages during the advanced treatment of anaerobically-digested swine wastewater. The results showed that, application of different applied voltage could significantly affect start-up and operating performance of the BECW. As the applied voltage was 0.80 V, abundance and activities of the functional microbes (especially Nitrosomonas, Empedobacter, Geobacter, Candidatus Brocadia, and denitrifying bacteria) involved in bioanoammox significantly increased in the anode layer, resulting that the multi-path coupled nitrogen removal process based on bioanoammox was enhanced most effectively on this occasion. Correspondingly, the COD, TP, TN, NH4+-N, and NO3--N removal efficiencies of the apparatus, which start-up duration was 25 days, could respectively reach up to (77.01 ± 3.72)%, (94.46 ± 1.96)%, (87.16 ± 2.61)%, (82.87 ± 2.68)%, and (97.27 ± 1.44)% during the stable running phase, as well as the peak current density of (5.29 ± 2.42) A/m3 and the output power density of 883.51 mW/m3. It is concluded that microbial electrochemical driven anaerobic ammonium oxidation could become a primary route for nitrogen removal in the BECW with optimized microenvironment that developed as a result of the appropriate applied voltage.