Technical principle Circulating well (CW) technology is to repair the groundwater by creating three-dimensional circulation patterns in situ. This technology combines multiple techniques such as stripping, air injection, gas phase extraction, enhanced bioremediation and chemical oxidation in wells to promote the dissolution and migration of contaminants, aeration in wells to circulate groundwater, carry Volatile and semi-volatile organic matter dissolved in the groundwater enters the inner well and is removed by aeration. Groundwater circulation wells are designed to extract groundwater from an aquifer into a well from one run-off section of a double-mesh leak well and then from another run-off section so that an in-situ vertical groundwater circulation occurs in the aquifer surrounding the well The difference in pressure gradient between the two screens in the well is the driving force behind this circulation. 2. Conditions of use The main pollutants for groundwater circulation well technology are: halogenated volatile organic compounds, semi-volatile organic compounds, and fuels. Small modifications to the conventional circulation well can be used to treat other contaminants. Other pollutants that can be used in remediation processes in circulation wells include: non-halogenated volatile organic compounds, petroleum products and other components such as benzene, toluene, ethylbenzene and xylene; halogenated volatile organic compounds; semi-volatile organic Compounds; Pesticides and other minerals. Contaminants are required to be aqueous liquids; groundwater is naturally strong; areas less than 10-5 cm / s are not suitable for this area; shallow water will limit the efficiency of the technology; and the system should define good boundaries for groundwater contamination , Thus preventing the spread of pollutants. 3. Technology route After the site is polluted by organic matter, the following selection process is generally followed when judging whether the technology of groundwater circulation well is suitable: The flowchart shows whether the application of an organic pollutant site to circulating well technology mainly depends on the following two aspects: (1) the nature of pollutants Circulating well technology relies mainly on aeration in the well and in situ biodegradation in the treatment of organic pollutants. Therefore, the volatility and biodegradability of pollutants are important factors in assessing the applicability of the GCW repair technique. At the same time, it is necessary to consider Organisms in groundwater in the form of existence, when there is free state of organic matter, need to be removed in advance. (2) site hydrogeological conditions Circulating well in operation, in addition to the horizontal movement of groundwater, the most significant feature is the formation of the vertical flow of groundwater, so the hydraulic conductivity, porosity is an important parameter affecting the groundwater flow. 4. Technology costs The technology is all in the underground environment, eliminating the need for surface treatment facilities, saving repair costs. 5 advantages and disadvantages The technology of groundwater circulation well has more advantages than the technology of extraction and treatment: (1) The circulation well has the advantages of simple structure, convenient operation and maintenance; (2) Small disturbances to the site environment; (3) Groundwater is not pumped to the surface and a large amount of auxiliary facilities are saved, Vertical groundwater scouring may be used to deal with low permeability formation contamination. ⑤ Special well structure design can be used as a platform for other repair technologies.