硝酸盐可引起水体富营养化及水生态系统崩溃等问题，威胁人类用水安全，目前硝酸盐去除技术存在碳源依赖等困难，DNRA-Anammox耦合可同时去除低碳废水中的硝酸盐和氨氮，但也存在沉淀性能差（功能细菌随出水流失）和反硝化功能微生物竞争的问题。本论文着重研究功能微生物储留问题，利用试验小试、批式试验和宏基因测序，探究高低碳氮比（1#和2# C/N=7与3#和4# C/N=1）和两种附载状态（多孔填料SBBR和微孔滤袋MBBR）下DNRA-Anammox耦合性能以及与铁碳微电解双耦合的机理。在C/N=1进水不含氨氮时，因碳源不足DNRA将硝酸盐还原为氨氮的量极少，无法为Anammox提供足够的基质，故本论文进一步研究直接在进水中投加适量的氨氮（5#和6#）和利用铁碳填料提供电子促进硝酸盐还原为氨氮，为DNRA-Anammox耦合反应提供足够的基质和电子，探究C/N=1时投加氨氮对DNRA- Anammox菌富集的影响及C/N=1时铁碳微电解耦合DNRA-Anammox的效能和脱氮机理。主要研究结论如下：

（1）高低碳氮比四组反应器硝酸盐去除率为2# MBBR(100%)>1# SBBR(99.9%)>3# SBBR(9.57%) >4# MBBR (8.5%)，COD去除率为2# MBBR(92.55%)> 1#SBBR(84.14%)> 3# SBBR(78.7%) > 4# MBBR (76.77%)。结合反应速率结果可知，C/N=7相较于C/N=1，DNRA细菌有充足的有机物作为电子，进而能够为Anammox菌生长提供足够的亚硝酸盐和氨氮，更有利于污水中硝酸盐和COD的去除及生长代谢。

（2）C/N=1时投加氨氮的5# SBBR和6# MBBR反应器的硝酸盐去除率比相同条件下不添加氨氮的3# SBBR、4# MBBR反应器提高了13.45%和13.8%。外加氨氮使DNRA-Anammox生长和能量代谢不再依赖完全DNRA生成的氨氮，低碳氮比条件下有限的电子供体优先供给部分DNRA和反硝化生成亚硝酸盐，亚硝酸盐与外加氨氮进行Anammox过程，进一步提高硝酸盐的去除效率。

（3）7# Fe/C生物滤池运行初期硝酸盐和COD去除率为100%远远大于3# SBBR、4# MBBR。纯铁碳微电解填料通过化学还原将硝酸盐还原为氮气的效率为13.48%，同时还能提供电子还原硝酸盐为亚硝酸盐（11.47mg/L）和氨氮（4.16 mg/L），为Anammox提供基质提高硝酸盐的去除效率。随着铁碳微电解的进行和微生物的生长，导致铁碳微电解减弱，硝酸盐去除率有所降低。对铁碳填料进行XPS、SEM发现Fe/C填料中零价铁含量降低和钝化以及铁碳填料表面生物膜的形成，降低铁碳微电解效率，提高耦合效果。

（4）与DNRA过程密切相关的nirB、nirD和nrfA、nrfH功能基因相对丰度之和2# MBBR (0.2253%)>1# SBBR（0.2208%）>3# SBBR (0.1619%)>5# SBBR（0.1593%）>4# MBBR ( 0.1574%)>7# Fe/C（0.1442%）>6# MBBR(0.1068%)，与Anammox过程密切相关的hzs和hdh功能基因相对丰度之和1# SBBR（0.007%）<2# MBBR (0.008%)<4# MBBR (0.011%)<3# SBBR(0.014%)<7# Fe/C ( 0.015%)<5# SBBR(0.0169%)<6# MBBR(0.0173%)。C/N=7更有利于DNRA菌的富集，C/N=1更有利于Anammox菌的富集。在低COD/NO₃^-下投加氨氮有利于Anammox菌的培养。在7# Fe/C滤池中铁碳微电解系统通过还原硝酸盐为氨氮和亚硝酸盐，为Anammox菌提供基质，促进了Anammox菌培养。

（5）从基因丰度角度，高碳氮比条件下，附载方式为微孔滤袋更有利于DNRA-Ana mmox相关细菌的富集。低碳氮比条件下，附载方式为多孔填料更有利于DNRA- Anammox相关细菌的富集。低碳氮比条件下投加氨氮，附载方式为多孔填料更有利于DNRA相关细菌的富集，附载方式为微孔滤袋更有利于Anammox相关细菌的富集。

Nitrate can cause problems such as eutrophication of water bodies and collapse of water ecosystems, threatening human water security, and the current nitrate removal technology has difficulties such as carbon source dependence, DNRA-Anammox coupling can remove nitrate and ammonia nitrogen in low-carbon wastewater at the same time, but there are also problems of poor precipitation performance (loss of functional bacteria with effluent) and competition of denitrifying functional microorganisms. In this study, we focused on the storage of functional microorganisms, and used batch experiments and macro-whole gene sequencing to explore the coupling performance of DNRA-Anammox and the mechanism of DNRA-Anammox coupling with iron-carbon microelectrolysis under high and low C/N (1# and 2# C/N=7 and 3# and 4# C/N=1) and two attached states (porous packing SBBR and microporous filter bag MBBR). When the influent water of C/N=1 does not contain ammonia nitrogen, the amount of nitrate reduced to ammonia nitrogen by DNRA is very small due to insufficient carbon source, which cannot provide sufficient matrix for Anammox, so this paper further studies further studies on the direct addition of appropriate amount of ammonia nitrogen (5# and 6#) in the influent water and the use of iron-carbon filler to provide electrons to promote the reduction of nitrate to ammonia nitrogen, so as to provide sufficient matrix and electrons for the DNRA-Anammox coupling reaction, and explore the effect of ammonia nitrogen addition on DNRA- when C/N=1 is added, the effect of ammonia nitrogen on DNRA- Effect of Anammox enrichment and the efficiency and denitrification mechanism of iron-carbon microelectrolytic coupling of DNRA-Anammox at C/N=1. The main conclusions of the study are as follows:

(1) Nitrate removal rates in the four reactors with high/low C/N were: 2# MBBR (100%) > 1# SBBR (99.9%) > 3# SBBR (9.57%) > 4# MBBR (8.5%). COD removal rates were: 2# MBBR (92.55%) > 1# SBBR (84.14%) > 3# SBBR (78.7%) > 4# MBBR (76.77%). Combined with reaction rate results, it shows that at C/N=7 compared to C/N=1, DNRA bacteria have sufficient organic matter as an electron donor, enabling them to provide adequate nitrite and ammonia nitrogen for Anammox bacteria growth. This is more favorable for the removal of nitrate and COD from wastewater and for microbial growth and metabolism.

(2) At C/N=1, the nitrate removal rates of reactors 5# SBBR and 6# MBBR (with added ammonia) were 13.45% and 13.8% higher, respectively, than reactors 3# SBBR and 4# MBBR (without added ammonia) under the same conditions. The external ammonia supply meant DNRA-Anammox growth and energy metabolism no longer relied solely on ammonia generated by DNRA. The limited electron donor under low C/N conditions was prioritized for partial DNRA and denitrification to produce nitrite. This nitrite then combined with the externally added ammonia for the Anammox process, further improving nitrate removal efficiency.

(3) At the initial stage of operation, reactor 7# Fe/C biofilter achieved nitrate and COD removal rates of 100%, far exceeding those of reactors 3# SBBR and 4# MBBR. Pure Fe/C micro-electrolysis carriers chemically reduced nitrate to nitrogen gas with an efficiency of 13.48%. Simultaneously, they provided electrons to reduce nitrate to nitrite (11.47 mg/L) and ammonia nitrogen (4.16 mg/L), supplying substrate for Anammox and thereby enhancing nitrate removal efficiency. As the Fe/C micro-electrolysis proceeded and microorganisms grew, the micro-electrolysis weakened, leading to a decrease in nitrate removal rate. XPS and SEM analysis of the Fe/C carriers revealed a reduction and passivation of zero-valent iron (ZVI) content and biofilm formation on the carrier surface, which reduced Fe/C micro-electrolysis efficiency but improved the coupling effect.

(4) The summed relative abundance of functional genes closely related to the DNRA process (nirB, nirD, nrfA, nrfH) was: 2# MBBR (0.2253%) > 1# SBBR (0.2208%) > 3# SBBR (0.1619%) > 5# SBBR (0.1593%) > 4# MBBR (0.1574%) > 7# Fe/C (0.1442%) > 6# MBBR (0.1068%). The summed relative abundance of functional genes closely related to the Anammox process (hzs, hdh) was: 1# SBBR (0.007%) < 2# MBBR (0.008%) < 4# MBBR (0.011%) < 3# SBBR (0.014%) < 7# Fe/C (0.015%) < 5# SBBR (0.0169%) < 6# MBBR (0.0173%). C/N=7 favors the enrichment of DNRA bacteria, while C/N=1 favors the enrichment of Anammox bacteria. Adding ammonia nitrogen under low COD/NO₃⁻ conditions is beneficial for cultivating Anammox bacteria. In the 7# Fe/C filter, the Fe/C micro-electrolysis system, by reducing nitrate to ammonia nitrogen and nitrite, provided substrate for Anammox bacteria, promoting their cultivation.

(5) From the perspective of gene abundance, under the condition of high C/N, the loading mode of microporous filter bags is more conducive to the enrichment of DNRA-Ana mmox-related bacteria. Under the condition of low C/N, the porous packing method was more conducive to the enrichment of DNRA-Anammox-related bacteria. Under the condition of low C/N, the addition of ammonia nitrogen and the attachment method of porous packing were more conducive to the enrichment of DNRA-related bacteria, and the attachment method of microporous filter bags was more conducive to the enrichment of Anammox-related bacteria.