With the rapid economic and social development in our country, the urbanization rate and the living standards of the people continue to improve, the amount of urban domestic waste is increasing day by day, and the amount of leachate is increasing year by year. Due to the limitation of economic and social development level and technical conditions, for a long period of time in the past, most of our country's domestic waste disposal methods were directly landfilled, and a large number of primary waste landfill facilities were built. The level of operation and management is not high, and the historical problem of leachate cannot be ignored.
Landfill leachate is formed after the garbage itself contains water, the moisture generated by the decomposition of organic matter, the surface precipitation, the water holding capacity in the cladding layer, and the groundwater flow into the landfill and other facilities during the collection, transportation, storage, and treatment of domestic garbage. A kind of waste water with complex pollutant composition, high concentration and great harm.
We were commissioned to carry out geophysical exploration for a domestic waste landfill project. At present, there is information that the landfill has been closed, but the leachate has continued to increase, and it is suspected that the leachate is leaking. The landfill area is now surveyed, to check out the reasons for the continuous increase of leachate by means of geophysical drilling, the location of possible leakage points is identified, and the situation of the site is investigated. The scope of the investigation is shown in the figure below.
According to the characteristics of pollutants in the survey area, the survey specifications, the development level and operability of instruments, and the successful application cases of related methods, the spontaneous potential method (SP), the charging method (CP) and the high-density resistivity method are selected as the main pollution detection methods in the survey area.
The overall workflow includes data collection and site surveys in the survey area, geophysical exploration, data analysis and interpretation, and delineation of polluted areas.
From the data results of this project, it can be concluded that the results of the SP gradient method and the CP method of the natural potential are combined. The results are shown in the figure below. From the result plan, it can be seen that there are 4 leakage areas on the site.
Figure 3 Plan view of the results of the SP method and the CP method
ERT results analysis
Figure 4 ERT-1 resistivity profile
Figure 5 ERT-5 resistivity profile
According to the high-density RES profile results, the distribution of resistivity in the field is clearly reflected.
ERT 3D Results
Comprehensively analyze the geophysical data in the survey area, and perform a 3D grid of the geophysical data. Through the 3D data, the shape, area and volume of the low-resistance anomaly layer can be clearly understood. According to the 2D resistivity profile and measurement results, the resistivity distribution law of the landfill is obvious. According to the field conditions and high-density results profile chromatogram, the relatively low-resistance anomaly is water-rich landfill.
The on-site work of this project includes the measurement of SP, CP method and high-density electrical measurement line.
1. From the results of SP and CP method:
There are 5 leakage areas on the site. Combined with the ERT survey line analysis, there is 1 damage to the bottom membrane on the north side.
2. From the results of the high-density survey line:
Groundwater enters the leachate regulation tank in the dam from the damaged part of the bottom membrane on the north side. From the results of the ERT survey line, it can be judged that there are dominant groundwater channels on the north side. Into the dam leachate regulation tank.