高炉碱矿渣纳米铁强化微生物脱盐电池型人工湿地的脱氮除磷机制

Water environment of bay was threatened by eutrophication. Purifying performance by traditional biological method was limited because of salty ions interference. Microbial desalination cells combined with constructed wetlands (MDC-CWs) was able to eliminate nitrogen and phosphorus by traditional nitrification-denitrification and chemical denitrification, accompanied with desalination and electronic production. However, the application of MDC-CWs was limited by shortage of carbon source and low performance of phosphorus removal. In this study, alkaline blast-furnace slag with high absorption and nano zero valent iron (nZVI) with high activity were synthesized as new materials to improve the nitrogen and phosphorus removal performance in MDC-CWs. The improved pollutants removal performance was enhanced by adding this new material in MDC-CWs with salt-tolerant and electronic microorganism, ion exchange interface, and aerobic - anoxic -anaerobic environment. On the one hand, the improvement of nitrogen and phosphorus removal performance was accomplished by denitrification driven by iron and adsorption by alkaline slag. On the other hand, anion and cation spontaneously moved to cathode and anode by exchange membrane because of electronic potential, which was produced by salt-tolerant and electrogenic microorganisms. The bio-electrochemical removal and desalting mechanism to treat wastewater of the bay in MDC-CWs was elucidated by the variation of nitrogen, phosphorus and iron, migration of salt ions and the condition of microbe. In addition, the influencing factors of improvement performance to treat wastewater of the bay in MDC-CWs were investigated, and it is an option to provide technical reserve and scientific basis for eutrophication mitigation as well.

富营养化威胁海湾水环境，传统生物法存在盐离子胁迫难发挥功效。微生物脱盐电池-人工湿地（MDC-CWs）具有脱氮除磷禀赋并同步脱盐产电，但仍受碳源不足和除磷性能不佳的制约。本课题利用粒化高炉碱矿渣和高活性纳米铁，制备负载材料。通过MDC-CWs对碱矿渣纳米铁脱氮除磷实验，揭示其脱氮除磷效应。利用MDC-CWs特有的耐盐产电微生物、离子交换界面和好氧-兼氧-厌氧环境，强化修复性能。一方面，铁盐和碱矿渣实现了系统反硝化脱氮和吸附沉淀除磷的改善；另一方面，耐盐产电微生物的电子输出产生电势差，促进阴阳离子自发经交换膜移动至阴阳电极，实现脱盐产电。通过碱矿渣纳米铁强化MDC-CWs对海湾水体净化过程中氮、磷、铁形态转化、盐离子的迁移及微生物群落特征分析，阐明脱氮除磷产电脱盐机制。进一步探索影响碱矿渣纳米铁强化MDC-CWs修复海湾水体的关键因素，为缓解水体富营养化威胁提供技术储备和科学依据。

富营养化威胁水环境安全、限制水资源循环利用。海湾由于其所处地理位置，氮、磷营养盐所引起的富营养化威胁海湾水环境。而传统生物法存在盐离子胁迫难发挥功效。微生物脱盐型人工湿地（MDC-CWs）具备脱氮禀赋，但仍受到碳源不足和除磷效率低的制约。研究一种既能有效利用MDC-CWs修复海湾水体的功能，又能实现高效安全修复的方法，将对缓解海湾水体富营养化潜在威胁具有重要意义。粒化高炉碱矿渣和铁盐是强化MDC-CWs脱氮除磷性能的一种手段。利用铁盐激发的反硝化（生物反硝化、化学反硝化）脱氮性能、并发挥碱矿渣的吸附除磷禀赋，构建高效MDC-CWs将是缓解海湾水体潜在富营养化形势的重要选项。将纳米铁负载于碱矿渣上可缓解纳米材料出水流失，降低成本。在MDC-CWs运行过程中，碱矿渣纳米铁可利用复合系统特有耐盐产电微生物的电子输出、交换膜的离子迁移界面及天然存在的好氧-兼氧-厌氧环境，协同发挥生物反硝化、化学反硝化及厌氧铁氧化的优势，及碱矿渣的吸附和铁磷沉淀性能，构建高效脱氮除磷的MDC-CWs。通过试验，发现粒化高炉碱矿渣负载纳米铁作为外加碳源可有效强化低碳氮比时复合系统的去污能力。当C/N为0时，添加粒化高炉碱矿渣负载纳米铁材料的装置比未添加的装置出水TN去除率有明显提高，随HRT（4天）变化分别增加了13.84 %、12.52 %、9.58 %和7.42 %，但随着盐度的增加，强化的程度有所减弱，这与铁离子在人工湿地的缓释速度和利用速率有关。通过分析复合型人工湿地中的反硝化作用发现，粒化高炉碱矿渣负载纳米铁材料的存在一方面可以作为外加碳源为微生物分解有机物的过程提供能量，另一方面材料中含有的Fe0可以在被氧化前会与污水中的硝氮发生反应生成氨氮，而氨氮因为亚硝化型硝化反应后，剩余量被细菌利用与硝氮进行厌氧氨氧化反应，表现为系统中出水得亚硝氮浓度增加。此外，碱矿渣纳米铁强化MDC-CWs的运行效果也将进一步实现其产电脱盐功能的同步。因此，对MDC-CWs中碱矿渣纳米铁修复海湾水体的研究的具有重要的现实意义和科学价值。