Performance and microbial community of a novel non-aeration-based up-flow bioelectrochemical filter (UBEF) treating real domestic wastewater

Domestic wastewater treatment process via the activated sludge is complicated, energy-negative and potentially harmful. In this study, an up-flow bioelectrochemical filter reactor (UBEF) was designed without positive aeration in-priority for treating real domestic wastewater under different hydraulic retention times (HRTs). The removal of chemical oxygen demand (COD), ammonia and total nitrogen was attained at a high efficiency of 89%, 99% and 99% respectively, when HRT was set at h1 of ∼2.53 d. However, with the decreased of HRT from 2.53 to 0.28 d, the removal efficiency of nitrogen and COD decreased to 50% and 40% respectively, but the maximum power density increased from 3.01 to 98.90 mW/m3 with a low Coulombic efficiency of 0.25–1.51%. The results demonstrated that the UBEF can remove COD and ammonia from real domestic wastewater in an aeration-free energy sustainable process, although its power output was low. Moreover, the functional bacteria were detected using 16S rRNA gene-based pyrosequencing analysis, which showed that the microbial communities were different under varied HRT conditions. The Thauera-dominated consortium was inoculated in order to enhance the removal of pollutants and the generation of electricity from domestic wastewater, it was kept at a relative abundance when continuously feeding the real wastewater. In particular, nitrogen removing bacteria (NRB) including Nitrosomonas, Ignavibacterium, Thiobacillus, Dokdonella, Comamonas, Sterolibacterium and Flavobacterium were enriched on the anode and the cathode of the UBEF, which contributed to nitrogen removal by nitrification and denitrification. Therefore, this study demonstrated that the UBEF configuration had great potential applicability for energy sustainable wastewater treatment.