【作者】 路莹；

【导师】 迟宝明； 杜新强；

【作者基本信息】 吉林大学 ， 地下水科学与工程， 2009， 硕士

【摘要】 平谷作为北京市4个应急水源地之一,合理开发当地雨洪资源可为缓解北京等地水资源紧张的现状起到重要作用。地下水人工回灌方式是雨洪资源利用的重要途径,具有很好的应用前景。但是该方法仍存在许多关键问题有待突破,其中堵塞问题是制约雨洪资源地下回灌技术发展和推广的最重要因素之一。因此,开展地下回灌过程中堵塞的研究,对于预防与控制堵塞的发生、发展,保证人工回灌系统正常运行,以实现高效、安全回灌具有重要的理论及现实意义。本文针对平谷地区实施雨洪水地下回灌过程中可能发生的主要堵塞类型开展相关研究。采用室内土柱实验与计算机模拟等方法,分析了悬浮物堵塞的发展规律,并预测了研究区不同回灌条件下悬浮物堵塞的发展过程;将水质渗滤实验结果与Phreeqc模拟相结合,对矿物沉淀化学堵塞的发展进行了评价;运用微生物生长模型计算了研究区不同雨洪水可能引起的生物堵塞程度;基于以上研究,综合评价了研究区实施雨洪水地下回灌可能产生的堵塞风险,并提出了堵塞预防与治理措施的建议。更多还原

【Abstract】 Pinggu district, as one of the four emergency water sources in Beijing, is facing a series of issues, such as a prolonged drought, serious shortage of water resources and a continually widening gap between the water supply and its actual demand. Stormwater Harvest has both a good prospect for the development and an applicative value to alleviate water resources tension of Beijing. Groundwater Artificial Recharge (GAR) has been proved to be a promising method for regulating and storing stormwater in underground space. However, Clogging Problem was recorded to cause many recharge systems out of use in GARs all over the world. Thus, it is necessary to analyze and evaluate the degree of clogging before GAR construction in the study area, which will be of great theoretical and practical significance to maintain the stormwater GAR systems stable and safe.This thesis focuses on the possible clogging problem that may occur during groundwater recharge with stormwater in Pinggu. Several methods were combined in this study, such as field investigation and observation, lab experiments, computer modeling, and etc. The main work includes analysis of possible clogging types, modeling of the clogging process due to suspended solids, calculation of the precipitation in chemical reactions, and bioclogging evaluation. Based on the above research, discussions on integrated clogging were furthered, and some prevention and redevelopment techniques were recommended as well. Finally, such conclusions were draw as follows:(1) Analysis of groundwater recharge conditions, including the recharge sites, recharge water quality, and etc, represents that possible clogging is induced by suspended solid, chemical precipitation and biological organisms.(2) To reveal the development of suspended solids clogging, a lab column experiment was conducted. In this experiment, hydraulic conductivity of the porous media increased at the beginning, followed with steady decline. The range of clogging influence is the area of 52cm below the surface, of which the section between 0cm and 10cm clogged heavily. Moreover, the clogging rate fell with depth, so the fastest rate appeared in the layer of the upper 1cm. While for the whole sand column, the clogging rate is less than any clogging layers.(3) The mathematic model for suspended solid clogging was derived from the theories of groundwater dynamics, suspended solids migration and etc. Comsol software was applied to solve this model. Then, the comparison figures of the simulations with the experimental data illustrated modelled results had a reasonably good agreement with the observation data within the process of experiment.(4) Clogging extention under five fixed conditions was simulated by the above model respectively. From the modeled results, we discussed the the effects of concentration of SS in recharge water and the depth of water table on clogging development. First, specific discharge will fall down to less than half of the initial value when recharging with the max concentration of SS, 273mg/L. Second, the infiltration rates between two degrees of groundwater table with 10m interval, were narrow, only 5% difference after continuously recharge of 30d.(5) Another column experiment was carried out to simulate the water chemical evolution in vadose zone. The experimental data represented that total dissolved solid (TDS) and saturated index (SI) of recharge water increased during infiltration. Whereas, the TDS and SI of the outflows decreased with time, and went towards those values of the inflows.(6) Based on the results of filtration experiments, Phreeqc was introduced to calculate three typical calcium precipitations after outflow mixed with groundwater in different times. The calculated results shows CaSO4 will precipitate from water, with the max mass of 0.97mol per liter water at the beginning.(7) Bioclogging degree assessment employed microorganism growth theory and the quality relationship between the amount of biofilm and hydraulic conductivity of porous media. We evaluated Water Recourses at 8 sites, of which water in Xiyu Reservoir has the worst effect, and it can reduce the permeability of surface media down to 97.8 percent of the virgin at most. Overall, the degree of bioclogging is little in the study area. (8) Integrated analysis was made from three aspects, including clogging area, evolution and degree. Suspended solid clogging was proved to be the major type of concern. Consequently, preventive and redevelopment measures should be taken in terms of water quality and engineering. However, there is no effective technique to redevelop the recharge system at prevent.更多还原