厌氧序批式反应器对低放含铀废水的处理及机理解析

The anaerobic bioreactors inoculated with anaerobic pure cultures or methanogenic anaerobic granular sludge have been successfully applied for the high-rate uranium removal from wastewater or groundwater. Those reported bioreactors removing uranium were mainly operated in continuous-flow column reactors. While there were several disadvantages for this operation mode, such as high concentration of additional carbon source and being prone to bias flow. Then, the anaerobic sequencing batch reactor (ASBR) was intended to be introduced into the field of uranium-containing wastewater treatment in this work. ASBR is spatially completely mixed, its characteristics of intermittent feeding and high biomass, leading to the resistance to shock loading and strong adaptability to outsides, and making it a potential biological technology for uranium removal from wastewater. Therefore, the present work focuses on the performance of ASBR, inoculated with methanogenic anaerobic granular sludge, treating uranium-containing wastewater, and inner mechanisms. The goal of this study is to investigate the kinetics of uranium forms, microbial activities, and microbial populations under different reactor operating parameters by advanced instruments, when the uranium-containing wastewater was treated by ASBR. Also the different uranium removal mechanisms for ASBR, with different carbon sources of ethanol or glycerol phosphate, were illustrated. Besides, the interaction between uranium forms, microbial activities and the ASBR operation situation, was also explored, in order to improve the system efficiency for uranium removal through process parameters' optimization. The present work will be beneficial to uranium removal from low-level uranium-bearing wastewater by ASBR.

以纯种厌氧微生物或厌氧颗粒污泥为接种源的厌氧生物反应器已被证明可对含铀废水或铀污染地下水进行高效处理。现已报道的除铀生物反应器主要以连续流柱式反应器方式运行，但是存在外加碳源浓度高、易发生偏流等缺点。为此本课题拟将厌氧序批式反应器（ASBR）引入含铀废水处理领域。ASBR空间上属于完全混合式，其间歇式进水和高生物量的特点，使其耐冲击负荷、适应性强，成为一项具有潜力的生物除铀技术。因此，本课题拟重点研究以厌氧颗粒污泥为接种源的ASBR工艺对低放含铀废水的处理及其除铀机理。拟充分运用先进的分析方法，考察不同反应器运行参数下ASBR处理含铀废水时铀形态、微生物活性、微生物种群结构等的动力学变化规律，揭示以乙醇或甘油磷酸酯为碳源时ASBR的不同除铀机制；探讨铀形态及微生物活性与ASBR运行状况之间的内在关系，优化工艺参数，提高系统除铀效率，为ASBR处理低放含铀废水提供理论基础和技术支持。

地下水体的铀放射性污染是核工业关注的环境问题之一。而利用微生物吸附、富集或还原矿化来去除地下水中铀放射性污染被认为非常有应用前景的生物修复技术技术之一。厌氧污泥作为接种源的反应器已证明可对该类污染进行有效的生物修复，但是在反应器运行、固定的铀长期稳定性以及除铀机制等方面还存在一些问题。针对上述问题，本课题主要开展了四个方面的研究内容，包括在硝酸盐、O2等物质存在时有效抵抗U(IV)重氧化，AnGS接种的厌氧序批式（ASBR）除铀系统运行，AnGS除铀过程中铀的种态和分布，ASBR的除铀机制。相较乙醇作为外加碳源的除铀体系，甘油磷酸酯作为外加碳源时，U(IV)沉淀的重氧化率降低80%以上。分别进行了以乙醇和甘油磷酸酯为碳源情况下AnGS接种的ASBR除铀系统的运行，实现含氧低放含铀废水的高效处理。开展了进水铀浓度、硝酸盐浓度、温度等对系统参数（如pH、溶解氧等）和铀在污泥中分布的影响研究，利用小瓶实验对各影响因素结束后微生物的铀还原活性进行了表征。在上述实验结果的基础上，对微生物除铀机制进行了更进一步的解析。污泥中U(IV)和U(VI)的含量在不同的影响参数下展现了不同的变化趋势。对不同机制在除铀中的贡献进行了定量表征，以8天的反应的结果看，胞外U(VI)的非还原性矿化对污泥中U的总去除量的贡献最高，为61.1±4.2%，而胞外还原性U(IV)沉淀、EPS固定和胞内U的累积的贡献分别为21.8±1.2%、8.8±1.1%和8.2 ±0.3%。综上所述，ASBR可以实现地下水中铀的有效去除，结合底物和运行参数的调整可以克服之前广泛报道的柱式反应器存在的一些问题，同时除铀机制的解析也更加深入。本课题研究结果可以为实现铀污染地下水的微生物修复系统或类似系统的高效稳定运行提供理论基础和技术指导。