Balancing nitrate removal and energy utilization in pyrite-filled three-dimensional biofilm electrode reactor:...

This study aimed to optimize the intermittent electric field strategy to achieve high nitrate removal efficiency (NRE) with minimal energy consumption in a novel system coupling pyrite-based autotrophic denitrification with three-dimensional biofilm electrode reactor (P3DBER). The long-term operation demonstrated that medium (3:3 at 20 mA) power on versus off (on/off-ratio) significantly enhanced NRE (95.96 ± 1.46 %) while minimizing energy consumption (0.035 ± 0.002 kW·h/g NO₃^--N). The system displayed a more stable microbial community (77.30 % positive correlations) under low on/off-ratio (1:5-3:3) conditions, with Thiobacillus (5.68 %-28.47 %), Desulfovibrio (0.17 %-14.40 %), and Desulfomicrobium (0.21 %-13.28 %) as the predominant genera. Functional gene prediction indicated that traditional denitrification (47.95 ± 4.58 %) and dissimilatory nitrate reduction to ammonium (38.44 ± 3.18 %) were the primary nitrate reduction pathways. This study demonstrates that optimizing the on/off-ratio in P3DBER can balance NRE and energy efficiency, offering a promising strategy for designing high-performance and energy-saving wastewater treatment systems.