随着现代工农业生产对含氮废物的大量排放，硝酸盐氮在环境中的积累构成了潜在的公共健康危害，并对生态环境造成一定影响。然而，由于市政尾水和低污染自然水体中有机碳源的不足，制约了硝酸盐氮的有效去除。因此，寻求一种低碳氮比水体中硝酸盐氮的高效、经济和绿色去除方法具有十分重要的现实意义。

本研究以海绵铁（s-Fe⁰）代替普通零价铁，构建了海绵铁(s-Fe⁰)系统、海绵铁+生物炭(s-Fe⁰/BC)微电解系统、海绵铁+生物炭+锰砂(s-Fe⁰/BC/MS)增强型微电解系统三种硝酸盐氮的化学还原体系，并系统分析了三种体系中硝酸盐氮的去除和转化规律。其次，通过构建生物滤池的试验研究，重点考察了海绵铁、海绵铁+生物炭和海绵铁+生物炭+锰砂与微生物协同作用下对不同浓度和碳氮比的硝酸盐氮废水去除效果。最后，通过高通量测序分析了微生物的丰度差异性变化和种群群落演替。本研究的主要结论如下：

（1）海绵铁+生物炭微电解系统的形成以及锰砂的继续加入可有效提高硝酸盐氮的去除效果。其中，在海绵铁：生物炭（3:1）时硝酸盐氮的去除率为比单纯海绵铁系统提高53.9%，反应产物中氮气的占比提高了16.6%。当海绵铁：生物炭：锰砂（6:2:1）时硝酸盐氮的去除率和反应产物中氮气的占比分别比海绵铁+生物炭微电解系统提高了18.8%和12.5%。 除此之外，海绵铁+生物炭+锰砂增强型微电解系统可在广泛的初始pH条件下（2~12）具有相对稳定的硝酸盐氮去除率和氮气的转化率。

(2) 反应动力学研究表明：三种系统对硝酸盐氮的去除都比较符合准一级动力学方程，速率常数分别为0.00037 min^-1、0.00418 min^-1和0.00476 min^-1。扫描电镜（SEM）测试结果显示：生物炭和锰砂的加入提高了海绵铁表面的腐蚀程度。通过X射线光电子能谱（XPS）测试分析表明：锰砂的加入提高了海绵铁表面氧化物中Fe₃O₄的占比，从而减轻了海绵铁表面的钝化，增加了电子转移的速率。傅里叶红外光谱（FT-IR）测试分析表明：生物炭表面的含有大量羧基官能团，可以通过解离H⁺和形成酯基对反应体系的pH起到一定缓冲作用。

（3）反应器的启动阶段：不挂膜启动阶段，三组反应器的硝酸盐氮去除率均不断下降，表明单纯的利用零价铁或者铁碳微电解作用对硝酸盐氮化学还原不具有持久性。在碳氮比5:1条件下进行挂膜启动，稳定后三组反应器的硝酸盐氮几乎全被去除，总氮的去除率均在96%以上。反应器的运行阶段：反应器1（海绵铁+微生物耦合体系）在碳氮比3:1条件下总氮去除效果优于反应器2（海绵铁+生物炭+微生物耦合体系）和反应器3（海绵铁+生物炭+锰砂+微生物耦合体系）；然而在低碳氮比（1:1）和无外加有机碳源条件下反应器2和3的总氮去除效果更好。其中在高硝酸盐氮浓度（80 mg/L）和低碳氮比（1:1）条件下，反应器3的总氮去除效果明显优于另外两个反应器。对比三组反应器中COD的去除率与总氮的去除率的相关性，发现反应器1中总氮去除率与COD去除率相关性很高。相反，反应器2和3中总氮的去除率对COD的依赖性低于反应器1。另外，反应器3（海绵铁+生物炭+锰砂+微生物耦合系统）的沿程去除效果要明显优于反应器2（海绵铁+生物炭+微生物耦合系统）。

（4）微生物测试结果表明：铁碳微电解的形成可有效提高生物物种的丰富度，锰砂的加入提高了微生物物种的多样性。三组反应器的微生物群落结构存在一定差异性，且随着运行条件的改变，微生物群落结构不断发生演替。

With the massive discharge of nitrogen-containing wastes from modern industrial and agricultural production, the accumulation of nitrate nitrogen in the environment poses a potential public health hazard and has certain ecological impacts. However, the effective removal of nitrate nitrogen is constrained by the inadequacy of organic carbon sources in municipal tailwaters and low-pollution natural water bodies. Therefore, it is of great practical importance to seek an efficient, economical and green method for the removal of nitrate nitrogen from low carbon to nitrogen ratio water bodies.

In this study, three nitrate nitrogen chemical reduction systems were constructed with sponge iron (s-Fe⁰) instead of common zero-valent iron, sponge iron (s-Fe⁰) system, sponge iron + biochar (s-Fe⁰/BC) microelectrolysis system, and sponge iron + biochar + manganese sand (s-Fe⁰/BC/MS) enhanced microelectrolysis system, and the removal and transformation patterns of nitrate nitrogen in the three systems were systematically analyzed. Secondly, the pilot experimental study of constructing biofilter focused on the removal effects of sponge iron, sponge iron + biochar and sponge iron + biochar + manganese sand with microorganisms in synergy on nitrate nitrogen wastewater with different concentrations and carbon to nitrogen ratios. Finally, the differential changes in microbial abundance and population community succession were analyzed by high-throughput sequencing. The main findings of this study are as follows:

(1) The formation of the sponge iron + biochar microelectrolysis system and the continued addition of manganese sand can effectively improve the nitrate nitrogen removal effect. Among them, the removal rate of nitrate nitrogen at sponge iron: biochar (3:1) was 53.9% higher than that of the sponge iron system alone, and the proportion of nitrogen in the reaction products was increased by 16.6%. The removal rate of nitrate nitrogen and the proportion of nitrogen in the reaction products increased by 18.8% and 12.5%, respectively, when sponge iron:biochar:manganese sand (6:2:1) was used compared with the sponge iron+biochar microelectrolysis system. Besides, the sponge iron + biochar microelectrolysis system and the sponge iron + biochar + manganese sand enhanced microelectrolysis system could have relatively stable nitrate nitrogen removal rate and nitrogen conversion rate under a wide range of initial pH conditions (2~12).

(2) The reaction kinetics study showed that the removal of nitrate nitrogen by all three systems was more in line with the quasi primary kinetic equation with rate constants of 0.00037 (mg/L)/min, 0.00418 (mg/L)/min and 0.00476 (mg/L)/min, respectively. scanning electron microscopy (SEM) showed that the addition of biochar and manganese sand improved the corrosion of the sponge iron surface corrosion. The X-ray photoelectron spectroscopy (XPS) analysis showed that the addition of manganese sand increased the percentage of Fe₃O₄ in the oxide on the sponge iron surface, which reduced the passivation of the sponge iron surface and increased the rate of electron transfer. Fourier infrared spectroscopy (FT-IR) analysis showed that the surface of biochar contains a large number of carboxyl functional groups, which can play a role in buffering the pH of the reaction system by dissociating H⁺ and forming ester groups.

(3) Start-up phase of the reactor: The nitrate removal rate of all three groups of reactors decreased continuously during the start-up phase without membrane hanging, indicating that the chemical reduction of nitrate by using zero-valent iron or iron-carbon microelectrolysis alone was not sustainable. After stabilization, the nitrate nitrogen was almost completely removed from all three reactors, and the removal rate of total nitrogen was above 96%. During the operation phase of the reactors, reactor 1 (sponge iron + microbial coupling system) showed better total nitrogen removal than reactor 2 (sponge iron + biochar + microbial coupling system) and reactor 3 (sponge iron + biochar + manganese sand + microbial coupling system) at a carbon to nitrogen ratio of 3:1; however, reactors 2 and 3 showed better total nitrogen removal at low carbon to nitrogen ratio (1:1) and without additional organic carbon source. The total nitrogen removal in reactor 3 was significantly better than the other two reactors under the conditions of high nitrate nitrogen concentration (80 mg/L) and low carbon to nitrogen ratio (1:1). Comparing the correlation between the removal rate of COD and the removal rate of total nitrogen in the three groups of reactors, it was found that the correlation between the removal rate of total nitrogen and the removal rate of COD in reactor 1 was high. On the contrary, the dependence of total nitrogen removal rate on COD was lower in reactors 2 and 3 than in reactor 1. In addition, the along-range removal effect of reactor 3 (sponge iron + biochar + manganese sand + microbial coupling system) was significantly better than that of reactor 2 (sponge iron + biochar + microbial coupling system).

(4) The microbial test results showed that the formation of iron-carbon microelectrolysis could effectively increase the abundance of biological species, and the addition of manganese sand improved the diversity of microbial species. The microbial community structure of the three groups of reactors had some variability, and the microbial community structure evolved continuously with the change of operating conditions.

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