Study On BTEX Migration In Aquifer

Progress of modern civilization along with the continuous oil products consumption,However, during its mining, transport, storage and processing of the process usually triggered a series of serious pollution problems. BTEX, as common petroleum components cause soil and groundwater pollution around the whole world. Because of its toxicity and the " carcinogenicity-mutagenicity-teratogenicity " feature will do a direct injury to people's health . For this kind of groundwater pollution, People often take certain measures to control and manage the polluted sites. As, chemical oxidation and microbial remediation are popular measures. Because of their expensive handling charges, ineffective long-term effects of treatment or long management cycle, it is difficult for them to enter the practical application. So, study how BTEX migrate in the aquifer is of great significance for the effective control over their groundwater pollution problems.I study BTEX migration in contaminated aquifer and the differences between different components in my thesis. Also, study the natural attenuation of BTEX with column experiment, which explained the different migrations between different components. During the quantitative research, I find the role of volatilization and biodegradation in the process of BTEX natural attenuation. Specific studies and findings are as follows:(1)Simulate BTEX migration in contaminated aquifer and the differences between different components, findings are as follows:1) In the BTEX pollution plume along the direction of hydraulic gradient, the distribution of different components is different. The range of benzene pollution plume is 70.79cm, toluene distribute to 23.07cm, ethyl-benzene distribute to 25.78cm,xylene distribute to26.69cm. With benzene, toluene, ethyl-benzene and xylene in aquifer suffered different natural attenuations.2) In the aquifer, BTEX mostly migrate to both horizontal sides and seldom in the vertical direction. BTEX pollution plume mainly distributed in the shallow aquifer, and near the line of ground water the highest pollutants concentrations appear.3) After the aquifer contaminated by BTEX, the redox conditions of the plume have changed. Accompanied with the growth of reducibility in the plume, redox-sensitive target such as Fe2 +, S2-, NO2- appear.(2) Volatilization and biodegradation are the most important mechanisms of BTEX migration. In this paper, two sets of static and dynamic experiments are designed for quantitative research of the mechanisms of BTEX natural attenuation. Static experiments are used to determine the concentration of biology inhibitor, Dynamic simulation of column experiments are used to study the role of volatilization and biodegradation during BTEX migration.1) By adding inhibitors to control biological activity of microorganisms, so we can study the contribution of biodegradation. I determine HgCl2 as the biological inhibitor in this experiment. From Table 3.5 we can see that as a biological inhibitor HgCl2 has played a very good inhibition in groundwater. Before the concentration of HgCl2 research 500mg / L, biological activity decreased all the time, until the concentration of HgCl2 research 500mg / L biological activity decreased at 0.019, and then basically unchanged. As a result, select 500mg / L as the biological inhibitor concentration.2) By the compare of column 1 and column 2, study the mechanism of BTEX volatilization. During the process of BTEX migration, the volatilization indeed played a role in the promotion of attenuation, and the volatilization mechanism in accordance with the dynamic equation of the attenuation level. Benzene, toluene, ethyl-benzene respectively, the volatilization rate coefficients are 0.0024, 0.0018 and 0.0009. Also from the BTEX volatile attenuation level dynamic equations, we can see that the higher the concentration of BTEX is in groundwater, the faster the rate of volatilization.3 ) During the migration in aquifer, BTEX can be used by micro-organisms, and then be attenuated, and in accordance with the attenuation level dynamics. Benzene, toluene, ethyl-benzene, inter-, para-xylene and o-xylene, respectively biological decay rate coefficients are 0.0007,0.0068,0.0009,0.0014, and no significant role is found in the biological removal of o-xylene. It illustrate that in aquifer, indigenous micro-organisms most likely to use toluene, then is para-xylene.As China is a developing country, there are very serious problems of groundwater pollution, at the same time facing scarce investigations and studies in the field of groundwater pollution, with excessive gap to the level of foreign issues in related technical studies. There is an urgent need for a large number of studies to be carried out in order to study the migration mechanisms of pollutants in groundwater. In particular, different aspects of the mechanisms during pollutants migration. In this way we can further clarify the driving force of pollutants transformation. Combination of its own transformation mechanisms and then start low cost and effective treatment technology research.I study BTEX migration in contaminated aquifer and the different mechanisms between different components in my thesis. And determine the ratio of biodegradation and volatilization to the role of the BTEX migration. Provide a reliable theoretical basis for practical engineering applications in the field of BTEX contaminants control and restoration in groundwater. Provide important practical significance for the control and restoration of contaminated sites, especially BTEX aquifer pollution problems.