Abstract:

To achieve the successful process regulation and steady operation, gradually increasing the $\mathrm{NO}_2^{-}$ concentration with a proportion of ladder accumulation in the continuous flow reactor is of significance. In this study, we investigated the long-term effects and reaction mechanisms of $\mathrm{NO}_2^{-}$ on the interactions between Anammox bacteria (AnAOB) and sulfur-oxidizing bacteria (SOB) in an autotrophic denitrification (AuDen)-Anammox system, as well as the nitrogen removal performance and microbial community response on the coupled system. An anaerobic biological fluidized bed (AFBR) with an effective volume of 2.5 L was operated for 140 days and the statistical results indicated that, compared with the control group ($\mathrm{NO}_2^{-}$=0), the nitrogen removal efficiency (NRE) and the contribution of Anammox to total nitrogen (TN) removal both significantly improved with the increase in $\mathrm{NO}_2^{-}$ concentrations, while the ratio of actual/theoretical of $\mathrm{SO}_4^{2-}$ markedly decreased. It can be concluded that $\mathrm{NO}_2^{-}$ enhanced the synergy between AnAOB and SOB, thus improving the TN removal capacity of the coupled system. Under a constant TN content, the NRE improved from 80.3%±3.2% to 88.1%±3.4% and the contribution of Anammox to TN improved from 81.7%±2.4% to 92.5%±2.3% in the environment with accumulated $\mathrm{NO}_2^{-}$. The high throughput gene sequencing results of the above process showed that the relative abundance of major functional microorganisms, including Thiobacillus, Candidatus kuenenia and Desulfurivibrio, remained steady or increased with the increase in $\mathrm{NO}_2^{-}$ concentrations. Furthermore, the relative abundance of hydrolytic bacteria, such as SM1A02, 1013-28-CG33, and SC-I-84, increased while the relative abundance of other functional microorganisms decreased. These indicated that the environment with accumulated $\mathrm{NO}_2^{-}$ could optimize the structure and function of the coupled community. Canonical correlation analysis (CCA) showed that the $\mathrm{NO}_2^{-}$ concentration was negatively correlated with the abundance of Ca. kuenenia (P=0.539) while positively correlated with the abundance of Thiobacillus (P=0.00533). Moreover, the accumulated $\mathrm{NO}_2^{-}$ was positively correlated with the TN removal (P=0.00767) in Anammox and AuDen process. Overall, the concentration-induction-adaption mechanism of $\mathrm{NO}_2^{-}$ in the Anammox and AuDen coupled system demonstrated that the environment determines the structure and function of the microbial community; in turn, the microbial populations adapt to and influence the environment through structural adjustment.

Key words: anammox, autotrophic denitrification, nitrite, synergy, microbial community

摘要：

在连续流反应器中，逐步增加$\mathrm{NO}_2^{-}$的浓度，构造阶梯积累比例，对过程调控与稳态运行具有积极意义。考察了耦合系统的脱氮性能和微生物群落的响应特征，探究$\mathrm{NO}_2^{-}$对厌氧氨氧化（Anammox）耦合自养反硝化（AuDen）系统中厌氧氨氧化菌（AnAOB）和硫自养反硝化菌（SOB）相互作用的长期影响及反应机制。有效容积为2.50 L的厌氧生物流化床（AFBR）连续140 d的运行结果表明，与对照组（$\mathrm{NO}_2^{-}$=0）相比，随着所积累$\mathrm{NO}_2^{-}$浓度的增加，耦合系统的脱氮效率（NRE）及Anammox对总氮（TN）去除的贡献百分比显著提高，$\mathrm{SO}_4^{2-}$的实际产生值/理论值明显减小，这说明了所积累的$\mathrm{NO}_2^{-}$能够促进AnAOB与SOB之间的协同，提高了耦合系统TN的去除能力。在氮含量相同的情形下，存在$\mathrm{NO}_2^{-}$积累的环境能够使系统脱氮效率从80.3%±3.2%提高至88.1%±3.4%，Anammox对TN去除的贡献从81.7%±2.4%提高至92.5%±2.3%。上述过程的高通量测序结果显示，随着$\mathrm{NO}_2^{-}$浓度的增加，主要功能微生物（Thiobacillus、Candidatus kuenenia及Desulfurivibrio等）的相对丰度维持稳定或上升，水解菌（SM1A02、1013-28-CG33、SC-I-84等）的相对丰度也上升，而其他功能微生物的相对丰度下降，证明了存在$\mathrm{NO}_2^{-}$积累的水质环境能够优化耦合群落的结构和功能。典型相关性分析（CCA）表明，$\mathrm{NO}_2^{-}$浓度与Ca. kuenenia的丰度（P=0.539）呈负相关，而与Thiobacillus的丰度（P=0.00533）呈正相关，所积累的$\mathrm{NO}_2^{-}$与Anammox、AuDen对总氮去除的贡献均为正相关关系（P=0.00767）。总体而言，所发现的$\mathrm{NO}_2^{-}$在Anammox+AuDen耦合反应体系中的浓度-诱导-适应机制，演绎了如下规律：环境决定了微生物种群的结构与功能，相反，微生物种群也会通过结构调整来适应及影响它们的环境。

关键词: 厌氧氨氧化, 自养反硝化, 亚硝酸盐, 协同, 微生物群落