Nitrate (NO₃⁻) accumulation in effluent decreases the biological nitrogen performance of anammox process for wastewater treatment. Redox-active biochar has been demonstrated as an effective additive to improve microbial NO₃⁻ reduction via redox cycling of the surface functional groups. However, their redox reactivity toward anammox consortia remains unknown. In this study, we investigated the effects of corn stover-derived biochars with different particle sizes (10-30 μm (SP), 200-500 μm (MP) and 2-5 mm (LP)) on nitrogen removal performance of anammox reactors under continuous operation with varying nitrogen loading rates over the long term. The average nitrogen removal efficiencies of anammox reactors amended with SP-, MP- and LP-biochar were 97.9%, 97.5% and 87.9%, respectively, which were significantly higher than that of the control (80.5%). Effluent NO₃⁻ concentration was reduced by 40.7-45.2% with presence of biochar as compared to the control, which may be attributed to microbial interaction with Chloroflexi-affiliated heterotrophic denitrifying bacteria. The electrochemical analysis of the sludge extracellular polymeric substances (EPS) based on cyclic voltammetry and electrochemical impedance spectrum revealed that the extent of biochar to increase the electron-transport ability of EPS decreased with the biochar particle size (SP > MP > LP). Furthermore, SP-biochar outperformed LP-biochar for promoting the proliferation of anammox bacteria Candidatus Brocadia and increasing the abundance of anammox-associated functional genes (hzsA, hdh, nirS and napA) in the sludge. Together, these findings showed the stimulatory effect of redox-active biochar for anammox consortia and the particle size-dependence, which may potentially assist in operating anammox processes with high nitrogen removal performance.

硝酸盐（NO ₃ ^- ）的流出物的积累降低了废水处理厌氧氨氧化过程的生物脱氮性能。氧化还原活性生物炭已被证明是改善微生物NO _3-的有效添加剂^。通过表面官能团的氧化还原循环进行还原。然而，它们对厌氧菌团的氧化还原反应性仍然未知。在这项研究中，我们研究了不同粒径（10-30μm（SP），200-500μm（MP）和2-5 mm（LP））的玉米秸秆生物炭对厌氧氨氧化反应器脱氮性能的影响。在长期运行的情况下，氮气负荷率会长期变化。用SP-，MP-和LP-生物炭改良的厌氧氨氧化反应器的平均脱氮效率分别为97.9％，97.5％和87.9％，显着高于对照（80.5％）。NO ₃出水^-与对照相比，在存在生物炭的情况下，其浓度降低了40.7-45.2％，这可能归因于与绿屈挠菌相关的异养反硝化细菌的微生物相互作用。基于循环伏安法和电化学阻抗谱的污泥细胞外聚合物质（EPS）的电化学分析表明，生物炭增加EPS的电子传输能力的程度随生物炭粒径的增加而降低（SP> MP> LP）。此外，SP-生物炭优于LP-生物炭促进厌氧氨氧化菌增殖暂定Brocadia和增加厌氧氨氧化相关功能基因（的丰度HZS A，HDH，NIR S和拉毛A）在污泥中。总之，这些发现表明氧化还原活性生物炭对厌氧菌团的刺激作用和颗粒大小依赖性，这可能有助于以高脱氮性能运行厌氧菌过程。