污水地下渗滤系统生物代谢气体堵塞机理及其过程动力学

Subsurface wastewater infiltration system (SWIS) is considered to be a kind of self-adapted system, which consists of multi-habitats and multi-processes. Clogging phenomenon often occurs within the matrix, whose occurrence time and extent are affected by matrix composition, structure, biological process, influent quality and operation modes. Existing researches indicated that suspended solids and microbial developmental accounted for the occurrence of clogging. However, biological metabolic gases could adhere to the matrix surface through Van der Waals force and chemical bond force. Gas-curing effects were not considered in previous studies. Therefore, the existing results could not explain the following results: Although the influent suspended solids were removed mostly and intermittent operation mode was adopted, the permeability decreased dramatically in part of the system. Whether the biological metabolic gases are the main forces for matrix clogging and how the processes develop are still left to be revealed. Aiming at this problem, this project will consider the gases clogging process through simulation and in situ experimental methods. The types of clogging gases, their migratory paths and distribution characteristics could be clarified through scanning electron microscope technology, adsorptive functional groups determination, gas chromatography analysis, isotopic tracer method and isothermal adsorption enthalpy calculations. Furthermore, the clogging mechanisms and kinetic equations will be presented to improve the clogging theory of SWIS.

污水地下渗滤系统（SWIS）是以特殊调制土壤为基质的多生境、多过程自适应体系，其床体渗透性受基质组份、物理结构、生物过程、水质波动和运行条件等因素协同影响。已有研究认为颗粒物理性堵塞和微生物发育性堵塞是引起系统堵塞的根本原因，未考虑生物代谢气体因范德华力或化学键力等作用被固相吸附而诱发“气固化”堵塞，因此，不能解释为何进水悬浮物和干湿交替周期得到精确控制，而基质层局部渗透性仍锐减的现象。生物代谢气体究竟是不是以及如何导致基质堵塞，亟需通过相关微观机理和过程动力学研究加以阐明。本项目针对这一科学问题，拟通过模拟和原位实验手段，采用基质微观形貌分析、吸附功能基团定性、气相色谱检测、稳定同位素示踪、等温吸附焓计算等方法，辨识引发基质堵塞的生物代谢气体类型，探明生物代谢气体迁移路径及分布特征，揭示生物代谢气体堵塞机制，建立气体堵塞动力学方程，完善SWIS堵塞理论。

污水地下渗滤系统（SWIS）是以特殊调制土壤为基质的多生境、多过程自适应体系，其床体渗透性受多因素协同影响。已有研究认为物理性堵塞和生物发育性堵塞是引起系统堵塞的根本原因，未考虑生物代谢气体因范德华力或化学键力等作用被固相吸附而诱发的堵塞，因此，不能解释为何进水悬浮物和干湿交替周期得到精确控制，而基质层局部渗透性仍锐减的现象。本项目针对这一科学问题，结合模拟和原位实验手段，采用了高效气相-质谱检测、稳定同位素示踪、代谢组学分析、聚类分析、RDA分析等方法，辨识了SWIS生物代谢气体类型，探明了主要代谢气体在土层中的迁移规律、分布特征和影响因素；初步揭示了引发SWIS气体堵塞机制和过程动力学；完善了SWIS堵塞理论。主要研究结论如下：（1）散水层代谢气体以CO2和N2O为主，厌氧层以CH4和N2O为主，其占比随进水营养、进水方式、运行周期、系统深度等变化而存在差异。其中，N2O的产生是散水层硝化反应、饱和层反硝化反应和渗滤层共反硝化反应等生物过程共同作用的结果，基质硝态氮含量和反硝化强度是N2O释放速率的限制性因素，饱和厌氧区的N2O浓度始终最高，且在基质层垂直方向不均匀分布，是导致基质堵塞的关键原因；（2）N2O在基质层毛细孔道中的迁移过程和空间分布受水力负荷、碳氮比、污染负荷等因素影响显著；建立了基于UPLC-MS分析的微生物代谢组学模型，通过非靶向研究，识别了响应不同因素的潜在内源性代谢产物；（3）进水携带空气和N2O是诱发SWIS“孔喉”堵塞的主要气体类型。溶解氧穿透动力学获得的延迟因子表明渗滤区2％ - 20％的基质孔隙空间被气体占据，说明进水携带空气主要影响系统中部的渗透系数，诱发气体堵塞；而在散水层，在有控制地配水条件下，生物代谢气体堵塞不明显；（4）基于对流扩散方程，利用CXTFIT软件模拟示踪剂的穿透曲线，通过气体含量与运行时间的参数响应完善了气体堵塞的动力学方程，获得了不同曝气处理DO穿透曲线的模型模拟参数。