氯代有机污染物在“新型分步耦合型固定化微生物反应墙”的降解过程和代谢机制

The microorganism has been used for building the bio-augmented permeable reactive barriers (Bio-PRBs) for remediation of the chlorinated organics (1,1,1-TCA, 2,4-DCP) contaminated groundwater. The microorganism coupled with the traditional metal PRBs is proved to be an effective strategy for improving the performance of Bio-PRBs significantly. However, the vicious biological clogging and chemical ion clogging affect the long-term running of the Bio-PRBs system. In this study, a “sequential coupling of bio-augmented permeable reactive barriers” developed by us independently will be employed. The new Bio-PRBs contains the microorganism reactive barrier 1 and the metal reactive barrier 2, which will be constructed respectively. The inorganic ions and chlorinated organics will be prevented and significantly degraded in two different barriers by activating and immobilizing the microorganism in barrier 1, so as to alleviate the clogging and improve the performance of Bio-PRBs system. This study aims at investigating the effects of microorganism activation and immobilization and ion transport and transformation on the performance of Bio-PRBs. Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Scanning Electron Microscopy (SEM) would be utilized to reveal the formation and mechanism of microbial membrane and ion precipitation in different microregions. High-Throughput Sequencing combined with Gas Chromatography-Mass Spectrometer (GC-MS) would be utilized to observe the relationship between metabolic and methanation of chlorinated organics and the relevant functional bacteria and archaea. The morphology and spatial distribution of chlorinated organics in Bio-PRBs would be in-situ analyzed by Diffusive Gradients in Thin-Films (DGT) and high energy spectroscopy. A multi-process coupling reaction model based on convection, dispersion, adsorption, chemical reaction and biological degradation would be constructed for describing and predicting the chlorinated organics transport and transformation in the heterogeneous Bio-PRBs system. This study aims at providing theoretical and model support for the development of new Bio-PRBs process.

利用微生物构建微生物反应墙(Bio-PRBs)修复氯代有机物污染的地下水已有一些探索，证明微生物与金属反应墙的耦合可显著提升其性能，但微生物和离子沉淀的淤堵影响系统长期运行。本研究拟设计一种分步耦合型固定化Bio-PRBs，分别构建微生物层和金属填料层，通过微生物固定和活性激活，实现无机离子和氯代有机物的分段阻控和深度处理，缓解淤堵。研究微生物和无机离子对Bio-PRBs性能影响；利用飞行时间二次离子质谱、扫描电镜揭示微生物膜和离子沉淀在不同微区形成和作用机制；利用高通量测序、气-质联用色谱探明功能细菌、古菌与氯代有机物的代谢和能源化关联机制；运用有机物梯度扩散薄膜技术和高能光谱学原位分析氯代有机物在Bio-PRBs中赋存形态、空间分布变化；构建有机物在Bio-PRBs非均质体系基于对流、弥散、吸附、化学反应和生物降解多过程耦合反应模型，为发展新型Bio-PRBs工艺提供理论和模型支撑。

一些研究表明微生物与金属反应墙（PRBs）耦合可显著提升其降解氯代有机物效果，但微生物淤堵、活性低等影响PRBs系统长期运行。本研究研发一种分步耦合型固定化微生物反应墙（Bio-PRBs），构建微生物反应层和金属填料层，通过微生物活性激活和固定同时避免淤堵，实现Bio-PRBs性能显著提升。研究典型植物源花生壳PS生物炭和动物源牛粪DM生物炭激活微生物性能，验证PS高效激活作用及在实际土壤构建Bio-PRBs效果；研发零价铁（ZVI@CA）和生物炭固定化微生物（BC&Cell@CA）凝胶小球；探索ZVI@CA和BC&Cell@CA界面交互行为和机制；验证ZVI@CA+ BC&Cell@CA垂向Bio-PRBs反应柱修复2,4,6-TCP污染地下水性能；解析零价铁-微生物交互作用下功能微生物多样性和丰度；构建对流-弥散-吸附（线性）-微生物降解和对流-弥散-两点吸附（线性+动力学）-化学反应-微生物降解2种多过程反应模型；矫正后模型可准确反演2,4-DCP和2,4,6-TCP迁移行为及预测其时空演化规律。结果显示相比DM生物炭，PS生物炭和微生物耦合在批实验和实际土层应用中均具有最好去除2,4-DCP能力及阻滞土壤2,4-DCP迁移性能。联合BC&Cell@CA和ZVI@CA两种修复材料提升了修复2,4,6-TCP污染地下水性能79%，同时污染物反应速率提升175%；ZVI@CA显著提升BC&Cell@CA小球内部功能微生物硫酸盐还原菌Desulfitobacterium丰度（0.08% 提高到18.62%）加速了其对2,4,6-TCP共代谢作用，同时Desulfitobacterium释放电子中间体还原Fe（III）铁氧化物, 最终Fe2+和铁基小球表面存在的Fe3O4全部转化为针铁矿(α-FeOOH); 模型结果表明BC&Cell@CA和ZVI@CA化学-微生物强化显著降低弥散度 a (0.53 cm降低到0.20 cm)，增加了线性分配系数Kd (2.20 cm3∙mg-1增加到19.00 cm3∙mg-1)、反应速率 λ (2.40 day-1增加到3.60 day-1)和2,4,6-TCP一阶动力学吸附占比(30%升高到80%)。构建Bio-PRBs多过程耦合反应模型，验证该新型Bio-PRBs性能；以上为发展新型Bio-PRBs提供理论和模型支撑。