多途径电子传递强化厌氧氨氧化脱氮除Cr(VI)的机理研究

Aquatic heavy metal and ammonium pollutions have become a serious risk for the ecological environment in China. Anaerobic ammonium oxidation (ANAMMOX) is a promising discovery in the fields of microbiology and environmental science and engineering. It is not only significant natural process contributing to the global biogeochemical nitrogen cycle, but also can be exploited for the treatment of ammonium-rich wastewater. However, the performance of ANAMMOX process would be easily suffered from the toxicity of Cr(VI) coexisted in wastewater, mainly due to the extremely slow growth rate of the autotrophic ANAMMOX bacteria. Based on the characteristics of the electron transfer in the ANAMMOX system coupled with Cr(VI) reduction, a novel idea regarding multiple electron transfers is initially proposed in the present study in order to realize simultaneous and enhanced nitrogen removal and Cr(VI) reduction. In the present study, the inhibition characteristics of Cr(VI) on ANAMMOX will be first investigated to illustrate the mechanism of Cr(VI) toxicity on ANAMMOX bacteria. Secondly, the intracellular electron transfer pathways inside the coupled ANAMMOX sludge system will be illuminated for Cr(VI) bioreduction. Finally, new extracellular electron transfer pathways will be designed to enhance the simultaneous removal of nitrogen and Cr(VI) from wastewater. The major objectives of the present study are to clarify the intracellular as well as extracellular electron transfer mechanisms for Cr(VI) reduction in ANAMMOX sludge system, and thus to explain the synergistic removal mechanism of nitrogen and Cr(VI). Therefore, the theoretical basis for enhanced removal of nitrogen under Cr(VI) stress as well as the simultaneous removal of Cr(VI) from the recalcitrant wastewater would be provided after accomplishing the project.

水体重金属氨氮污染是当前我国水生态环境面临的重大风险。厌氧氨氧化是微生物与环境领域的重大发现，除对全球氮素循环贡献巨大外，在高浓度含氮废水处理中也备受关注。但厌氧氨氧化菌为自养型细菌，生长缓慢，极易遭受重金属Cr（VI）的抑制，致使工艺脱氮效能降低。本项目基于厌氧氨氧化系统Cr（VI）还原过程的电子传递特征，提出多途径电子传递强化厌氧氨氧化协同脱氮除Cr（VI）的新思路。研究Cr（VI）对厌氧氨氧化的作用特性，揭示其作用机理；研究厌氧氨氧化系统胞内电子传递特性，揭示系统内Cr（VI）生物还原的胞内电子传递途径与机理；设计胞外电子传递新途径，揭示厌氧氨氧化协同强化脱氮除Cr（VI）机理。本项目旨在搞清厌氧氨氧化系统Cr（VI）还原的胞内、胞外多途径电子传递特征，揭示厌氧氨氧化脱氮除Cr（VI）机理，为重金属氨氮废水高效处理及工艺推广应用提供科学依据。

水体重金属氨氮污染是当前我国水生态环境面临的重大风险。厌氧氨氧化是微生物与环境领域的重大发现，除对全球氮素循环贡献巨大外，在高浓度含氮废水处理中也备受关注。但厌氧氨氧化菌为自养型细菌，生长缓慢，极易遭受重金属Cr(VI)的抑制，致使工艺脱氮效能降低。本项目基于厌氧氨氧化系统Cr(VI)还原过程的电子传递特征，提出多途径电子传递强化厌氧氨氧化协同脱氮除Cr(VI)的新思路，为重金属氨氮废水高效处理及工艺推广应用提供科学依据。取得如下成果：.（1）系统比较了Cr(III)和Cr(VI)对厌氧氨氧化的短期影响特性，并开展了Cr(VI)对厌氧氨氧化的抑制动力学研究。2 mg/L的Cr(III)可微弱促进厌氧氨氧化，促进率为8.9%。Cr(VI)对厌氧氨氧化的半抑制浓度为10.91 mg/L。Cr(VI)对Anammox基质转化动力学的影响符合Haldane方程，Cr(VI)对于Anammox的抑制呈现非竞争抑制特征。.（2）揭示了Cr(VI)在厌氧氨氧化污泥中的迁移分布行为，探索了Cr(VI)抑制厌氧氨氧化活性的机理。污泥对Cr(VI)的截留作用较弱，但仍然有部分Cr(VI)扩散到EPS中，最终进入污泥内部。截留到污泥中的Cr(VI)则全部被污泥水解产生小分子有机物、EPS中PN和PS和血红素共同催化还原成Cr(III)。.（3）研究了中间产物（羟胺和羟胺）强化厌氧氨氧化同步脱氮除Cr(VI)的调控机制。联氨的解毒机制可能包括体内ROS相关修复酶CAT/SOD/POD酶的应激反应、促进细胞色素C与Cr(VI)反应、通过促进脱氮过程关键酶的表达促进电子传递系统的活性、联氨与六价铬发生化学反应，从而减轻了铬对厌氧氨氧化的毒性。长期运行中，NH2OH的添加使EPS、厌氧氨氧化活性和血红素含量恢复效果均优于对照组。.（4）研究了胞外电子传递途径（蒽醌类电子穿梭体和半导体黄铁矿）强化厌氧氨氧化同步脱氮除Cr(VI)的调控机制。蒽醌类电子穿梭体及其负载物通过上调BC1复合体和细胞色素C产生系统分泌细胞色素C- naxl，提高电子传递的整体活性，缓解其抑制作用。黄铁矿通过增强底物扩散和电子传递、刺激EPS分泌和提高代谢水平来缓解Cr(VI)对厌氧氨氧化过程性能的影响。