Study On Remediation Of Oil Polluted Shallow Groundwater Using Surfactant-enhanced Air Sparing

As rapid economic development of human society, the expanding needs of economic and material, same as the demand for energy, has continued to increase. Therefore, the oil, as the most important energy, whose exploration and utilization are constantly expanding. At the same time, with the improper exploitation, the oil pipelines leaking and waste emissions and other issues that all seriously threatened the human health, ecological environment and social stability. Thus, study on remediation of the oil polluted the shallow groundwater has become a hot issue of environmental protection at the current domestic and foreign.Air Sparging ( AS) has proven to be the most effective means of remediation groundwater and unsaturated soils which have been contaminated with volatile organic compounds(VOCs)in all the polluted site remediation technologies. However, there are many drawbacks in the conventional Air Sparging, such as limited influencing area of air flow, low contaminant removal in heterogeneous medium, low removal efficiency. Therefore, how to take the appropriate means to strengthen the conventional Air Sparging, to improve its performances and the removal, all of which need urgent solution.According to domestic and foreign researches, a series of simulations were conducted to study:AS technology and its influencing factors(air flow rate, air injection mode);study on surfactant-enhanced air sparing(SEAS),including:surfactant selection,enhanced effect of contamination removal and its mechanisms concerned. (1)A one-dimensional column was installed to study Benzene and Naphthalene removal effect in groundwater with different influencing factors, the results showed that:â‘ Benzene and Naphthalene in gravelly, coarse sand, medium sand and silt showed a linear adsorption, the smaller size of the sand media particle, the greater absorption and sorption distribution coefficient Kd of the contaminations, so that, the adsorption effect is more significant, the application process of AS is more difficult.â‘¡With the increase of aeration, it can improve the contaminations removal efficiency. But, increasing the sparging, which has been the effect of a certain limit, will not improve removal of the contaminations, instead, the removal efficiency will decrease. Determined the optimum aeration is 300ml/min.â‘¢Removal of benzene and naphthalene in the continuous aeration is superior to in the intermittent pulse aeration. The continuous aeration is more suitable for the application of one-dimensional soil column. Therefore, the continuous aeration was used in the subsequent experiments.â‘£As a result of solubility and dissolution rate, naphthalene in the aeration process was trapped in solid form at the bottom of soil column and adsorption in the media. The removal of naphthalene was such different from benzene in AS process. In the AS application to removal such contaminations, it is more realistic to trying to accelerate the dissolution of the contaminations to the aqueous phase.(2)Surfactant selection is a problem which needs special consideration. Because of the specificity in groundwater, the issues, such as surfactant on the solubilization capacity of organic contaminations, the adsorption in medium and the ability to wash off the organic contaminations adsorbed in the media, need to be studied in order to choose the surfactant fit for subsurface and SEAS application. Four surfactants(Tween80, Tween20, SDBS, SDB)were compared, the results showed that:â‘ Compared the solubilization of the target contaminations in four contaminations, to benzene:Tween80>Tween20> SDB > SDBS; to naphthalene : Tween80 > Tween20 > SDB > SDBS.â‘¡ Compared the adsorption of four surfactant in medium:SDBS>Tween20>Tween80>SDB.â‘¢Compared the ability to wash off the organic contaminations adsorbed in the media, to benzene : Tween80 > Tween20 > SDBS; to naphthalene:SDBS>Tween80>Tween20. Because of the ideal properties in all aspects, Tween80 was choused to use in remediation and following experiments.(3)On the removal of benzene and naphthalene, the SEAS technology was compared with the conventional AS in the one-dimensional soil column, the results show that:â‘ For the volatile(Henry's constant larger)organic contamination benzene, the removal effects of the SEAS is not superior to AS. Therefore, the volatile organic contaminations are fit for AS.â‘¡For the semi-volatile(Henry's constant smaller)organic contamination naphthalene, compared with AS, the removal effects is significantly enhanced in the SEAS. Therefore, SEAS is more suitable for removing the semi-volatile or nonvolatile organic contaminations.â‘¢For the removal of the volatile organic contamination, the negative-non-mixed surfactant SEAS was better than the single one, but not significantly better than AS. For the removal of the semi-volatile or nonvolatile organic contaminations, the negative-non-mixed SEAS were not as well as the single one, meanwhile, the removal effect is also lower than AS.