Cultivation of aerobic granular sludge coupled with built-in biochemical cycle galvanic-cells driven by dual selective pressure and its denitrification characteristics.

Dual selective pressure was applied as the driving condition to cultivate an enhanced aerobic granular sludge (AGS) with Fe(0)-based biochemical cycle galvanic-cells (BCGC) as the core. The BCGC-AGS coupled micro-electrolysis with synergistic autotrophic-heterotrophic denitrification to enhance nitrogen removal. COD and total nitrogen removal of 91.8% and 95.9% were achieved, respectively. The formation of circulation channel between Fe3+ and Fe2+ provided a solid foundation for the biochemical cycle of galvanic-cells with low consumption. The existence of micro-electrolysis selective pressure in BCGC-AGS was also confirmed. Facultative aerobic bacteria Methylocystis and Azospirillum were the most abundant genera. Facultative iron redox bacteria and autotrophic denitrifying bacteria Geobacter, Thiobacillus, Aquabacterium, Thauera and Azospirillum showed high abundance, affirming the success culture of EAGS system. Load shock test verified BCGC-AGS possessed excellent load shock resistance. Obtaining the advantages of fast-cultivation, high-efficiency and low galvanic-cells consumption, BCGC-AGS showed significant potential for practical application.