In Situ Chemical Oxidation Of Gasoline Contamination Groundwater By Persulfate:A Box-column Experimental Study

Persulfate(S₂O₈^2-)was widely used in the remediation of organic contaminated groundwater,but persulfate is a strong oxidant.The use of oxidation would cause changes in groundwater chemical indicators and affect microbial activity,which is not conducive to subsequent biodegradation.It is important to find a fast and efficient oxidation method and how to recognize the transition characteristics of oxidation to biodegradation.In order to reveal the effect of persulfate oxidation on the BTEX contaminated groundwater in gasoline under dynamic water flow conditions,and to characterize the conversion of chemical oxidation to biodegradation.In this project,sodium sulphate was used as the oxidant to establish an in situ remediation of the BTEX contaminated groundwater in the box-column system.The in situ persulfate oxidation was carried out on the contaminated area and the contaminated area.The following conclusions were obtained by the persulfate oxidation in the gasoline contamination process:?1?In the absence of ethanol,although the natural attenuation effect existed in the system,the BTEX concentration in the source region is always maintained at a high level,and the natural attenuation is insufficient to degradation of high concentration BTEX;in the presence of ethanol,it would increase the solubility of BTEX in groundwater;under dynamic water flow conditions,ethanol will have less effect on the natural attenuation of BTEX,and the ethanol in the system will migrate and disappear quickly.?2?In the case of PS/BTEX molar ratio of 10,20,50,the degradation rate of BTEX will increase with the increase of PS/BTEX molar ratio,When PS/BTEX in molar ratio of 50,a large of PS would remain in the downgradient,which will adversely affect the groundwater environment in the downgradient.When PS/BTEX in molar ratio of 20,the residual amount of PS was less and the oxidation effect is the best,so the PS/BTEX molar ratio is 20;The concentration of benzene had a large attenuation coefficient.Persulfate oxidation could quickly remove benzene which was difficult to biodegrade,which was beneficial to the subsequent biodegradation of other components of BTEX,which greatly reduces the difficulty of biodegradation.The following conclusions were obtained by the persulfate oxidation treatment during the gasoline leakage process:?4?When the gasoline leaks,the excessive persulfate PS does have a good preventive effect and oxidation effect,which can effectively reduce the release of BTEX components into the groundwater environment,greatly reducing the BTEX of the pollution source area.Pollution can fundamentally curb the increase in pollution.?5?The presence of ethanol does not hinder PS oxidation of BTEX,has little effect on PS oxidation of BTEX,and is quickly depleted;under dynamic water flow conditions,PS does not react with ethanol.By analyzing the water chemistry indicators,the following conclusions are drawn:?6?In the system,the change of DO,NO₃^-,pH and ORP can identify the conversion of persulfate oxidation to biodegradation,which were ideal transition indicators.At the same time,the residual amount of PS oxidation by product SO₄^2-can reflect the severity of oxidation.During the oxidation,changes in water chemistry(DO,NO_3-,pH,and ORP)identified a short-term inhibition of biological effects,and as the oxidative strength decreased,these indicators gradually returned to their initial levels,indicating biological effects begin to recover.