微生物作用下排水系统含有机质沉积物的起动输移理论研究

The performance of sewer networks has important consequences from an environmental and social point of view. Poor functioning can result in flood risk and pollution at a large scale. Sediment deposits forming in sewer trunks might severely compromise the sewer line by affecting the flow field, reducing cross-sectional areas, and increasing roughness coefficients. The sewer sediment management is significant to improve the safety and efficiency of sewer system. However, the sewer sediment contain high organic content. In my and others previous studies, it was found that the influence of microbial activities on sediment erosion and transport was significantly. The traditional sediment transport theory and formula were still used in the development of sediment removal technology, which disagreed with the transport rules of the sediment with high organic content and microbial activities. Therefore, the application plans to study the microscopic mechanism of the impaction of microbial activities on sediment erosion and transport through apparatus experiments with cylinders and channels and micro-observation with LCSM and SEM. On this basis, the incipient motion rule of sewer sediment with microbial activities was studied and the distinguishing method for incipient motion was developed. Moreover, the transportation and re-precipitation of suspended solid after eroded will be also investigated. In this way, two phase objectives of incipient motion condition and precipitation probability model can be accomplished. At last, the theory of sediment erosion and transport under the condition of content organic and microbial activities can be developed. The research results of the application will rich the current theory of sediment transport, and will be very helpful for the development of sewer sediment removal technology. The research results has academic guidance meaning for the self-cleansing design and sediment management in urban sewer system.

管道沉积物是导致城市排水系统失效的主要功能性病害之一，加强沉积物管理对提升排水系统安全性具有重要意义。但排水系统沉积物富含有机质，相关文献及申请人预研究均证实，微生物作用下含有机质沉积物的运动规律与传统泥沙运动理论存在较大差异。因此，本项目拟通过圆筒、明渠等装置实验和激光共聚焦显微镜、扫描电镜等微观分析技术，研究微生物对含有机质沉积物运动影响的宏观规律和微观机理，揭示微生物作用的影响机制和定量表征；在此基础上，研究微生物作用下含有机质沉积物的起动条件，探索起动判别的统一希尔兹方法，分析微生物作用后悬浮颗粒输移（再沉淀）的运动规律，完成“微生物作用下含有机质沉积物起动条件”及“起动后颗粒输移裹挟阈值与再沉淀概率模型”两个阶段目标，从而建立微生物作用下含有机质沉积物起动—输移（再沉淀）的运动理论。研究成果将丰富现有泥沙运动理论，为城市排水系统沉积物管理技术的发展和管养水平的提升奠定理论基础。

管道沉积物是导致城市排水系统失效的主要功能性病害之一，加强沉积物管理对提升排水系统安全性具有重要意义。但排水系统沉积物富含有机质，相关文献及申请人预研究均证实，微生物作用下含有机质沉积物的运动规律与传统泥沙运动理论存在较大差异。因此，本项目通过圆筒、明渠等装置实验和激光共聚焦显微镜、扫描电镜等微观分析技术，开展了微生物作用下含有机质沉积物微观特性与宏观起动输移规律的研究，主要研究结果如下：.（1）通过广泛调研排水管道沉积物，排水系统沉积物中值粒径范围在0.026mm~0.449mm，有机质含量为2.67%~12.02%，真密度为0.43 g/cm3~1.563 g/cm3。.（2）微生物作用对含有机质沉积物起动规律的影响包括两方面：第一，微生物生长产生的生物膜不仅使沉积物表面更为光滑，而且能增加颗粒间多糖类物质，含量在40-140ug/g，增加了沉积物生物粘性联结作用。第二，微生物活动消耗有机颗粒、产生气体，使试样内部空隙变大、整体膨胀。其中相对于厌氧、在好氧条件下生物活动的影响更为明显。.（3）通过不同G值下的圆筒试验表明，有机质含量和培养时间对沉积物粘结力有重要影响：相同工况下，随着沉积物有机质含量的增高，沉积物的无机颗粒粘结力降低；随着培养时间的增加，沉积物的无机颗粒粘结力呈现为先增大后减小的变化规律，与EPS多糖含量的变化规律一致。.（4）定量分析生物膜的增强效果，提出了包含有因生物膜产生而增强的生物粘性系数Az和因内部空蚀膨胀而削弱的生物削弱系数Ax的生物综合影响系数A’，从而得到了考虑了微生物综合影响的希尔兹曲线，同时，提出了考虑微生物作用下生物粘性力影响的起动概率，建立了希尔兹数θ和起动概率P的关系。 .（5）通过长直管道中溃坝流作用下沉积物悬浮与再沉淀分布形态研究表明，随着冲刷次数增加，整个沉积床变薄并向后推进，在距离闸门5倍无量纲距离之前，冲蚀率急剧的下降，之后，冲蚀率缓慢下降并逐渐趋稳，提出了沉积物冲蚀率与储水水位、下游距闸门距离的经验公式。.项目成果丰富了泥沙起动理论，为排水系统沉积物管理提供了理论支撑，对城市排水系统提质增效具有工程应用价值与理论指导意义。