Study On Numerical Simulation Of Groundwater Environment Effect Of A Chemical Plant In Hebei Province

With the rapid development of social economy,the demand for groundwater in industrial and agricultural production is increasing.As an important part of the national economy,the petrochemical industry produces a large amount of pollutants in the production process,and the concentration of pollutants is generally high,and the composition is complicated.If not properly treated,it will cause serious pollution to groundwater and seriously threaten human health.Therefore,before the establishment of the chemical plant,it is necessary to conduct groundwater environmental impact assessment and prediction based on the hydrogeological conditions of the proposed plant area.Through the establishment of groundwater numerical model,the possible pollutant leakage under different working conditions can be simulated and predicted for the scope of groundwater pollution,so as to provide a basis for the environmental protection of groundwater in the proposed factory and surrounding areas.Based on a chemical plant in Hebei province as the research object,this paper analyzes the development and utilization of groundwater on the basis of collecting the data of natural geography,geology and hydrogeology,and evaluates the current situation of groundwater quality.On the basis of defining the geological conditions and environmental characteristics,the hydrogeological concept model is established.GMS is used to establish groundwater flow and groundwater solute transport simulation models,and the model is discrete in time and space.The model identification period is 5 months,and the verification period is 3 months.By repeatedly adjusting the parameters,the measured flow field and the simulated flow field fit better,and a mathematical model with higher accuracy can be obtained.Based on the analysis of the pollution production characteristics of the proposed chemical plant's process flow,COD_Mn,petroleum,benzene,and xylene are selected as the pollution factors.According to the requirements of environmental capacity on different factors,the concentration change of each characteristic pollution factor and the possible pollution range were simulated and predicted under normal and accident conditions Through the above research,the following conclusions are mainly drawn:1.To monitor the water quality of the proposed chemical plant,a total of 17 water quality sampling points?including 10 phreatic and 7 quaternary confined water?are set up in the study area,and the monitoring time is April 2014?dry season?,August?high water season?,and December?normal water period?,and supplementary monitoring was conducted in July 2015and January 2017.By analyzing the above water quality data,the mainly anions of groundwater in the study area are mainly HCO₃^-,and the cations are mainly Na⁺and Ca²⁺.The dissolved total solids,fluoride,total hardness,iron and manganese content of individual monitoring points exceeded the standard.The quality of confined water is better than phreatic water,and the characteristic pollutant petroleum in this study was not detected.Benzene,toluene,and xylene were detected at individual monitoring points during the wet and normal water periods,but were not detected during the dry season,and neither was detected during the two supplementary monitoring sessions.2.The hydrogeological conceptual model was established,and the boundary conditions were generalized into flow boundary and water-proof boundary.The conceptual model of groundwater system is generalized into a heterogeneous and isotropic,spatial three-dimensional structure,and unsteady groundwater flow system.Use pumping and seepage tests to calculate hydrogeological parameters.Through historical data analysis and collection of water resources development and utilization data,Regional groundwater system recharge item mainly include rainfall infiltration,agricultural irrigation infiltration,canal infiltration and lateral replenishment,and the main excretion items include lateral discharge,evaporative discharge,artificial mining and leakage.The recharge and excretion of the groundwater and confined aquifer in the study area were calculated respectively,and the water equilibrium analysis was carried out.3.Based on the hydrogeological concept model,the numerical simulation model of underground water flow and solute transport were established.The model was identified and verified by the estimation-correction method,and he simulation model after repeated adjustments basically meets the accuracy requirements.4.The simulation model was used to predict the concentration change and possible migration range of pollution factors after 1,5,10 and 20 years of operation under normal and accident conditions Under the normal working condition of conventional designed buried pipeline leakage,the influence range of pollution after 20 years of xylene leakage is462470.57m²,and the maximum migration distance is 1013.87m.Under accident conditions,the pollution influence range of para-xylene in phreatic 20 years later is 573723.48m²,and the maximum transport distance is 1078.66m.During the 20-year operation of the chemical plant,no matter whether anti-seepage measures were taken,there was no excessive groundwater pollution area,which did not affect the groundwater environmental protection goals.However,the scope of the pollution of each pollutant will exceed the plant area within 2-5 years,and strict groundwater pollution prevention and control measures must be taken.