Numerical Simulation Of Typical Groundwater Contamination For Petrochemical Industry In Coastal Area

Due to the storage and transportation characters of petrochemical industry there is a high risk of contamination for the groundwater. In this paper a research was conducted for a petrochemical enterprise in Dalian City, Liaoning Province and the environmental risk was assessed for groundwater contamination. The research area involved in the entire petrochemical company as well the storage and transportation system.A site geological and hydrological survey for groundwater was conducted for the study area. Based on the measured data and the collected hydro-geological historical data the study got a comprehensive understanding of the aquifer structure, mastered the relationship between the recharge, runoff and drainage, and understood the dynamic characteristics of the groundwater as well established a numerical simulation model for groundwater. The model was calculated by Visual MODFLOW2011.1. The calculated water levels were compared with the observed ones from wells to reduce the model error through adjusting the model parameters, such as hydraulic conductivity.The paper predicted the risk of benzene leaching accident and oil separator seepage accident in sewage treatment plant which were the typical pollution risks for petrochemical industry. As for the benzene leaching accident the study constructed a non-aqueous phase liquid (NAPL) coupled model which researched on the migration process in vadose zone and aquifer using the software of HSSM and Visual MODFLOW. This study simulated the infiltration process of NAPL formed by petroleum pollution in vadose zone with Hydrocarbon Spill Screening Model (HSSM). With the penetrating time, concentration and the lens size as a boundary condition a modular finite-difference groundwater flow model was used to simulate the aquifer pollution migration. The solute transport model considered the factor of convection-diffusion migration and natural degradation and was soluted by MT3DMS. Depend on the specific coastal location of the study area a quantitative analysis of groundwater contamination risk and the adjacent sea area pollution was conducted. The results showed that benzene can migrate downward through the vadose zone and form lenses on top of the aquifer causing long-term pollution to the groundwater. The maximum exceeded the scope of the benzene was15684m2. The total amount of benzene transporting into the sea would up to3428kg in8.2a which would cause adverse effects on marine water quality and ecological environment.As for the oil separator seepage accident in sewage treatment plant a solute transport model was conducted. The results showed that the pollution plume would disappeared due to the result of convection-diffusion and degradation. So such pollution incident would not cause a long-term and irreversible impact for the groundwater.The study proposed the remediation measures for groundwater pollution based on the numerical simulation result of vadose zone and aquifer. The research methods and results can provide references for the study area groundwater pollution prevention as well as the risk assessment for petrochemical industry.