潜流人工湿地中三卤甲烷微界面化学与生物共代谢耦合脱卤机制和调控

The trace contaminants in reclaimed water are usually of toxicity, which pose a threat to environmental safety and human healthy in wastewater reuse. Therefore, how to control these contaminants is of considerable engineering significance. Compared with other halogenated organic pollutants, trihalomethanes (THMs) are widely detected with highest concentration in wastewater treatment plant effluents, and are listed as priority pollutants in China in terms of their carcinogenesis and mutagenesis. Constructed wetland is a promising process to upgrade qualities of reclaimed water due to its high removal efficiency and small foot print. The removal of halogenated organic compounds in constructed wetlands has therefore been focused by recent academic studies. Based on the viewpoint of humus attached on substrates possessing micro-interfacial characteristics in subsurface-flow constructed wetlands, one of the aims of this study is to reveal the effects of sulfate reduction, transmembrane mass transfer and quinone-mediated electron transfer on THMs micro-interfacial chemical dehalogenation, and to identify the rate-limiting step in the system as well. Moreover, THMs can be dehalogenated by biological co-metabolism in subsurface-flow constructed wetlands. To increase the biological co-metabolic dehalogenation rates of THMs, the effects of water phase turbulence and interspecies hydrogen transfer on electron competition and electron shunt are investigated. Then, the coupled effect of micro-interfacial chemical and biological co-metabolic processes on THMs dehalogenation is studied. According to the mechanisms above, engineering regulation technologies are established. The results of this research are expected not only to clarify the coupled dehalogenation in complex systems, but also to introduce novel technical approaches to control ecological and healthy risks of reclaimed water.

再生水中含有微量有毒污染物，这些污染物在回用中产生的生态与健康风险是亟需解决的重要工程问题。在城镇污水处理厂尾水中，三卤甲烷被广泛检出，而且往往是浓度最高的卤代有机物，更因其致癌和致突变性，被列为我国优先控制污染物。人工湿地是污水深度处理的重要单元技术。如何发挥系统潜能，高效去除卤代有机物是人工湿地前沿研究的热点之一。本项目在识别潜流人工湿地系统腐殖质微界面特征的基础上，揭示基于硫酸盐还原、跨膜传质与醌基电子传递过程作用下的三卤甲烷微界面化学脱卤机制，识别反应体系的限速步骤；探明基于水相湍动与种间氢传递调控电子竞争与电子分流的作用机制，提高系统中三卤甲烷的生物共代谢脱卤速率；阐明潜流人工湿地中微界面化学与生物共代谢耦合脱卤的协同机制，建立系统对三卤甲烷高效脱卤的调控技术。研究结果不仅可以加深人们对复杂系统中卤代有机物耦合脱卤机制的认识，还能为保障污水回用的生态与健康安全提供新的技术途径。

城镇污水处理厂尾水中含有消毒副产物，这些消毒副产物的排放会对生态环境和人类健康构成威胁。人工湿地是污水再生回用的重要单元技术。本项目聚焦尾水再生回用中三卤甲烷等消毒副产物风险控制问题，在潜流人工湿地中开展了以下研究：(1)硫酸盐的去除效能和碳源竞争机制；(2)三卤甲烷等消毒副产物的去除效能及动力学；(3)三氯甲烷迁移转化归趋及去除机理；(4)水生植物与生物质碳源联合调控强化三卤甲烷去除新技术。主要结论如下：.(1)栽种植物对硫酸盐去除速率无明显影响，而投加生物质可显著提升硫酸盐去除速率。产甲烷菌在试验初期利用了湿地系统中大部分的有机碳源，而硫酸盐还原菌和反硝化细菌是试验末期消耗有机碳源最多的两类微生物，湿地系统内产甲烷菌与硫酸盐还原菌的COD消耗量的比值和mcrA与dsrA的基因拷贝数的比值之间呈显著的线性正相关。.(2)本研究选取的大多数消毒副产物（除三氯甲烷和1,1-二氯丙酮外）可在湿地中高效去除（去除效能>90%），且各系统之间无显著差异。各消毒副产物的去除遵循一级反应动力学，半衰期介于1.0~770.2h，且去除速率常数与水解常数具有明显正相关关系。.(3)吸附、植物吸收、生物降解和挥发是三氯甲烷在湿地系统中去除的重要途径。植物吸收的三氯甲烷大部分储存在根系部位，蒸腾作用和气相传输是植物对三氯甲烷吸收作用的主要驱动力。三氯甲烷在湿地基质上的吸附符合伪二级动力学方程和Freundlich等温吸附方程。三氯甲烷生物共代谢的主要功能微生物为硫酸盐还原菌和产甲烷菌。.(4)水生植物与生物质碳源可以有效提高三卤甲烷去除效能，其去除速率与硫酸盐还原速率呈正相关。据此研发了水生植物与生物质碳源联合调控技术，上述技术可以实现消毒副产物可持续高效去除。.上述研究结果加深了人们对复杂系统中消毒副产物去除及其作用机制的认识，据此研发的水生植物与生物质碳源联合调控技术为保障污水回用安全提供了新的技术途径。