Electrochemical and biochemical profiling of the enhanced hydrogenotrophic denitrification through cathode strengthening using bioelectrochemical system (BES)

To better the removal of nitrate pollutants accumulated in the environment economically and eco-friendly using bioelectrochemical system (BES). Biocathode strengthening by polarity reversal and PPy (Polypyrrole) modification for enhanced hydrogenotrophic denitrification were investigated. It was found that nitrate removal efficiency reached 95% during 6, 7, 8 and 11 days for PPy + inversion, PPy, polar inversion and the control groups, respectively. Besides, anodic COD removal for the PPy group reached 81.8% after three days, while it was only 67.4% for the control group. Coulombic efficiency of the four groups reached 57.5 (Control), 74.6 (Inversion), 75.8 (PPy) and 82.1% (PPy + inversion), respectively. Notably, an obviously enhancement of protein abundance could be observed at the PPy deposited biocathodes, indicating the advantage of PPy deposition for biofilm enriching in comparison with polar inversion. Through Illumina high throughput sequencing, it was found that the highest microbial abundances at the PPy + inversion strengthened biocathode mainly contain electro-consuming, denitrifying and hydrogenotrophic species as Proteiniphilum (93.1%), Fusibacter (87.2%), Aminiphilus (82.6%), Desulfovibrio (81.3%) and vadinBC27 wastewater-sludge group (80.8%). Finally, PICRUSt analysis indicated that the metabolic activities of hydrogenotrophic and electron transfer for the PPy + inversion group presented with the largest proportion comparing with three other groups. Therefore, cathode strengthening through surface medication and polar inversion could be a promising strategy for enhanced denitrification using BES.