Groundwater circulation wells enhance the directional delivery of persulfate in low-permeability aquifers
In situ chemical remediation technology has many problems in groundwater environment,such as difficult injection,slow diffusion speed,limited diffusion range and unclear diffusion direction,etc.,to a great extent,it has limited its effectiveness in actual restoration projects.Groundwater circulating wells(GCW),as a kind of artificial hydraulic control technology,have potential in the remediation efficiency of coupling enhanced in situ chemical injection technology.One-dimensional sand column experiment,two-dimensional sandbox experiment and numerical simulation were used to investigate the delivery process of GCW-driven reagent.Persulfate(PS)was selected as the repairing agent,the effects of the concentration of GCW reinforcements and the process parameters of circulating wells(circulation mode and flow rate)and low permeability media(kaolinite and illite)on the migration of GCW reinforcements were studied.The results showed that the forward circulation mode was beneficial to the uniform distribution of PS and can significantly increase the delivery rate of PS,while the reverse circulation mode can make PS relatively concentrated near the circulation wells.However,the higher the circulating velocity,the greater the variation of PS concentration distribution and the instability of the repair process.The higher the initial concentration,the greater the effective diffusion coefficient,which was more conducive to the diffusion of persulfate from high concentration to low concentration.GCW can form a hydraulic gradient with orthogonal to the low permeability zone to weaken the obstruction of PS delivery.The research results provide a new solution for in situ high-efficiency remediation of contaminated low permeability areas.
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