Model Test Of Remediation Of MTBE Contaminated Soil With Surfactant And Thickener Combined With Air Sparging

At present,organic pollutants in soil are becoming more and more serious,among which volatile organic pollutants are an important part of organic pollutants.Existing studies have shown that air sparging can be used as an economical and effective technology for the remediation of volatile organic pollutants.However,due to the complexity of the site conditions and the characteristics of pollutants,the effect of air sparging remediation is poor.Therefore,it is of great engineering and scientific significance to explore a new method of enhanced air sparging remediation.In this paper,a self-developed two-dimensional model aeration system was used to carry out a model experiment of remediation of volatile organic pollutants with MTBE as a typical volatile organic pollutant.Explores the entire surfactant-enhanced air sparging,local surfactant-enhanced air sparging,local thickener-improved air sparging and local surfactant / thickener-common improved air sparging is feasible.In view of the above enhanced aeration method,systematic research has been carried out in the aspects of evolution of the influence zone shape,temporal and spatial evolutions of the MTBE concentration,MTBE removal efficiency,etc.,and the main results are obtained as follows:1)Through comparison between conventional air sparging test and entire surfactant-enhanced air sparging test,it is found that compared with conventional air sparging test,entire surfactant-enhanced air sparging test can achieve a higher removal efficiency of MTBE and a higher total removal rate of MTBE with a larger evolution of the influence zone shape and a higher effective air saturation,and can be used as an effective enhanced air sparging method.2)Based on the self-developed two-dimensional model air sparging system,the local surfactant-enhanced air sparging test was carried out.The results showed that the axial injection of surfactant solution resulted in the narrowest influence range,the largest effective air saturation,the best control ability of MTBE migration path and the highest total removal rate of MTBE.With the increase of the distance between the surfactant injection location and the axis of the model chamber,the influence range increased,the effective air phase saturation decreased,the control ability of the surfactant on the flow and the migration path of MTBE weakened,and the total removal rate of MTBE decreased gradually(the total removal rate of MTBE in the d=31.5cm test group was only 71%,Close to the conventional air sparging test).Therefore,in order to achieve the surfactant to guide the diffusion of airflow and MTBE and increase the total removal rate of MTBE,the injection position of surfactant should be as close as possible to the axis position.3)The results of the local thickener-improved air sparging test(air sparging barrier test and air sparging current limiting test)show that the influence range can be changed obviously when the thickener is injected at different positions.The injection of thickener near the central axis will greatly increase the aeration influence range and reduce the airflow channel density,with a larger contamination range of MTBE and a lower total removal rate of MTBE(70%).The injection of thickener on both sides of the central axis can limit the influence to a very narrow range near the central axis and greatly increase the airflow channel density,with a narrower contamination range of MTBE and a high MTBE total removal rate of up to 90%.4)Through the results of the local surfactant / thickener-common improved air sparging test(air sparging barrier-enhancement test and air sparging current limiting-enhancement test),it can be found that both thickener and surfactant can change the migration path of pollutants to the external environment,but the thickener effect is more obvious.When the thickener and surfactant cooperate,the enhancement effect of surfactant on the removal efficiency of MTBE(enhancing the passage of airflow and the diffusion migration of MTBE,and strengthening the pollutant flux on the dominant migration path)will be compatible on the basis of the blocking effect of thickener(the injection of thickener leads to the transfer of MTBE around the flow).