Experiments on the particle deposition characteristics of artificial groundwater recharge：Based on influence of recharge water temperature and particle charge
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Abstract:
Artificial recharge of groundwater is a technology that injects excess surface water, rain flood or reclaimed water into the ground through surface infiltration or artificial recharge wells, so as to effectively recharge groundwater and raise the groundwater level. The physical clogging dominated by particle clogging is the main factor restricting the large-scale popularization and application of groundwater artificial recharge project. The particle deposition process in the pores of the media controls the particle clogging phenomenon of the whole media. At present, the research on the internal relationship, mutual transformation and cross-scale coupling between the two processes is limited. The movement and deposition of particles in the pores of the media are the microscopic mechanism of particle clogging. The important factor affecting the movement state of particles in the pores of the media is the pore water flow field. The recharge head is the decisive factor to determine the flow velocity and flow field distribution. The temperature will change the dynamic viscosity and density of the water, which will affect the flow field, change the fluid drag force on the particles and affect the particle deposition. The pH and ionic strength of recharge water affect the particle deposition by affecting the charge of the particles in the water.A physical experimental system of particle clogging in one-dimensional sand column groundwater recharge with fixed head was built, and two media were used for comparative experiments. Combined with physical experiments and Computed Tomography, a numerical model that can describe the particle deposition process in the pores of porous media is constructed, and the numerical model is corrected and verified by physical experiment data and CT scan results. The recharge temperature is selected as the thermodynamic factor, the recharge particle charge is selected as the electrochemical factor, and the recharge head is selected as the engineering factor, and the three are included in one groundwater recharge particle clogging evaluation system. The numerical simulation of multi-physical scenarios with μm-level accuracy was carried out to research the effects of hydraulic factors, thermodynamic factors, and electrochemical factors on the deposition of groundwater recharge particles. According to the combination of the upper limit, the lower limit and the intermediate value of each influencing factor, multiple physical scenarios are set up.The influence weight value of the recharge head on the particle deposition of the two media is 0.144 3, the influence weight value of the recharge temperature is 0.648 8, and the weight value of the recharge particle charge is 0.206 9. There are many data fluctuations in the numerical simulation process, which indicates that the internal flow field and particle motion process of the media are extremely complex and changeable, and a theoretical explanation is proposed. The recharge head is used as a control group to analyze the influence of thermodynamic factors and electrochemical factors on particle clogging and particle deposition in groundwater recharge compared with conventional engineering factors. The range of values is small. In the practice of groundwater artificial recharge engineering, the engineering factors such as recharge head and particle concentration of recharge water still have the greatest impact on particle clogging. The recharge temperature has the highest weight only in engineering scenarios involving extreme water temperature recharge such as groundwater source heat pump.In the case of large variation of recharge temperature, the highest weight factor affecting particle deposition in quartz sand media and glass bead media is recharge temperature, followed by recharge head, and recharge particle charge is the factor with the lowest weight. In the engineering scenarios involving extreme recharge temperature such as ground source heat pump, it is necessary to consider the recharge temperature as an important factor affecting the groundwater recharge clogging. At the same time, the influence of water temperature on the occurrence and development of particle clogging can not be ignored in ordinary projects that do not involve extreme recharge temperature. The influence of electrochemical factors on particle deposition and particle clogging in the process of artificial recharge of groundwater is low. When considering the physical clogging of groundwater recharge such as particle clogging, the electrochemical factors such as ionic strength and pH of recharge water can be selectively ignored.
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